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Final Electrical Specifications
LTC4100 Smart Battery Charger Controller
FEATURES
s s
DESCRIPTIO
July 2003
s s s
s s s s s s s s s s
Single Chip Smart Battery Charger Controller 100% Compliant (Rev. 1.1) SMBus Support allows for Operation with or without Host SMBus Accelerator Improves SMBus Timing Wide Output Voltage Range: 6.4V to 26V Hardware Interrupt and SMBAlert Response Eliminate Interrupt Polling High Efficiency Synchronous Buck Charger 0.5V Dropout Voltage; Maximum Duty Cycle > 98% AC Adapter Current Limit Maximizes Charge Rate 0.8% Voltage Accuracy; 5% Current Accuracy Up to 4A Charging Current Capability 10-Bit DAC for Charge Current Programming 11-Bit DAC for Charger Voltage Programming User-Selectable Overvoltage and Overcurrent Limits High Noise Immunity SafetySignal Sensor Small 24-Pin Narrow (0.209") SSOP Package
The LTC(R)4100 Smart Battery Charger is a single chip charging solution that dramatically simplifies construction of an SBS compliant system. The LTC4100 implements a Level 2 charger function whereby the charger can be programmed by the battery or by the host. A SafetySignal on the battery being charged is monitored for temperature, connectivity and battery type information. The SMBus interface remains alive when the AC power adapter is removed and responds to all SMBus activity directed to it, including SafetySignal status (via the ChargerStatus command). The charger also provides an interrupt to the host whenever a status change is detected (e.g., battery removal, AC adapter connection). Charging current and voltage are restricted to chemistry specific limits for improved system safety and reliability. Limits are programmable by two external resistors. Additionally, the maximum average current from the AC adapter is programmable to avoid overloading the adapter when simultaneously supplying load current and charging current. When supplying system load current, charging current is automatically reduced to prevent adapter overload.*
APPLICATIO S
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Portable Instruments and Computers Data Storage Systems and Battery Backup Servers
, LTC and LT are registered trademarks of Linear Technology Corporation. *U.S. Patent No. 5,723,970
TYPICAL APPLICATIO
DCIN 3V TO 5.5V
13.7k 1.21k 17 11 CHGEN ACP 6 10 7 9 8 15 16 13 1.13k 10k 54.9k 0.082F 14 20 LTC4100 VDD DCDIV CHGEN ACP SMBALERT SCL SDA THB THA ILIM VLIM IDC
0.1F
DCIN INFET CLP CLN TGATE BGATE PGND CSP BAT VSET ITH GND
5 4 24 23 1 3 2 21 22 18 19 12 6.04k
0.1F 5k
0.033
20F 10H
0.01F 0.0015F 0.12F SafetySignal 0.1F
SMBALERT# SMBCLK SMBDAT
Figure 1. 4A Smart Battery Charger
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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0.025 SMART BATTERY 20F 100 SMBCLK SMBDAT
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4100 TA01
1
LTC4100
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW TGATE PGND BGATE INFET DCIN CHGEN SMBALERT SDA SCL 1 2 3 4 5 6 7 8 9 24 CLP 23 CLN 22 BAT 21 CSP 20 IDC 19 ITH 18 VSET 17 VDD 16 THA 15 THB 14 VLIM 13 ILIM
Voltage from VDD to GND ................................ 7V/-0.3V Voltage from CHGEN, DCDIV, SDA, SCL and SMBALERT to GND .............................. 7V/-0.3V Voltage from DCIN, CLP, CLN to GND ........... 32V/-0.3V PGND wrt. GND .................................................... 0.3V CSP, BAT to GND .............................................. 28V/-5V Operating Ambient Temperature Range (Note 4) ........................................................... - 40C to 85C Junction Temperature Range ............... - 40C to 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC4100EG
ACP 10 DCDIV 11 GND 12
TJMAX = 125C, JA = 90C/W
G PACKAGE 24-LEAD PLASTIC SSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL IDCIN VTOL ITOL VDD Shutdown Battery Leakage Current UVLO Undervoltage Lockout Threshold VDD Power-Fail DCIN Current in Shutdown Current Sense Amplifier, CA1 Input Bias Current into BAT Pin CMSL CMSH CA1/I1 Input Common Mode Low CA1/I1 Input Common Mode High PARAMETER DCIN Operating Range DCIN Operating Current Charge Voltage Accuracy Charge Current Accuracy (Note 3) VDD Operating Voltage
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 20V, VDD = 3.3V, VBAT = 12V unless otherwise noted. (Note 4)
CONDITIONS
q
MIN 6
TYP 3
MAX 28 5 0.8 1 3 5 5.5
UNITS V mA % % % % V A V V mA A V
Charging (Note 2)
q
-0.8 -1 -3 -5 3 15 4.2 4.7 2 11.66
VCSP - VBAT Target = 102.3mV IDAC = 0xFFFF 0V VDCIN 32V DCIN = 0V, VCLP = VCLN = VCSP = VBAT DCIN Rising, VBAT = 0V Part Held in Reset Until this VDD Present VCHGEN = 0V
q q
q q q
30 5.5 3 3
q
0 VCLN-0.2
VDCIN 28V
q
2
U
V
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WW
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LTC4100
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 20V, VDD = 3.3V, VBAT = 12V unless otherwise noted. (Note 4)
SYMBOL ITMAX ITREV PARAMETER Maximum Current Sense Threshold (VCSP-VBAT) Reverse Current Threshold (VCSP-VBAT) Transconductance Source Current Sink Current Current Limit Amplifier Transconductance VCLP ICLP Current Limit Threshold CLP Input Bias Current Transconductance Sink Current OVSD Overvoltage Shutdown Threshold as a Percent of Programmed Charger Voltage DCIN DetectionThreshold (VDCIN-VCLP) Forward Regulation Voltage (VDCIN-VCLP) Reverse Voltage Turn-Off Voltage (VDCIN-VCLP) INFET "ON" Clamping Voltage (VDCIN-VINFET) INFET "OFF" Clamping Voltage (VDCIN-VINFET) Oscillator fOSC fMIN DCMAX Regulator Switching Frequency Regulator Switching Frequency in Drop Out Regulator Maximum Duty Cycle VTGATE High (VCLN-VTGATE) VBGATE High VTGATE Low (VCLN-VTGATE) VBGATE Low TGTR TGTF BGTR BGTF TGATE Transition Time TGATE Rise Time TGATE Fall Time BGATE Transition Time BGATE Rise Time BGATE Fall Time VTGATE at Shutdown (VCLN-VTGATE) VBGATE at Shutdown Duty Cycle 98% VCSP = VBAT ITGATE = -1mA IBGATE = -1mA ITGATE = 1mA IBGATE = 1mA CLOAD = 3000pF, 10% to 90% CLOAD = 3000pF, 10% to 90% CLOAD = 3000pF, 10% to 90% CLOAD = 3000pF, 10% to 90% ITGATE = -1A ITGATE = 1A 50 50 40 40 5.6 5.6 255 20 98 300 25 99 50 10 10 50 110 100 90 80 100 100 345 kHz kHz % mV V V mV ns ns ns ns mV mV IINFET = 1A IINFET = -25A DCIN Voltage Ramping Up from VCLP-0.05V Measured at ITH, VITH = 1.4V
q q
ELECTRICAL CHARACTERISTICS
Current Comparators ICMP and IREV
CONDITIONS VITH = 2.4V
q
MIN 140
TYP 165 - 30 1
MAX 200
UNITS mV mV mmho A A mmho
Current Sense Amplifier, CA2 Measured at ITH, VITH = 1.4V Measured at ITH, VITH = 1.4V -40 40 1.5 93 100 100 1 36 102 107 110 107
mV nA mmho A %
Voltage Error Amplifier, EA
Input P-Channel FET Driver (INFET)
q q q q
0.0
0.17 25
0.25 50 6.5 0.25
V mV mV V V
-60 5
-25 5.8
Gate Drivers (TGATE, BGATE)
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LTC4100
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 20V, VDD = 3.3V, VBAT = 12V unless otherwise noted. (Note 4)
SYMBOL VACP PARAMETER DCDIV Threshold DCDIV Hysteresis DCDIV Input Bias Current ACP VOH ACP VOL DCDIV to ACP Delay SafetySignal Decoder SafetySignal Trip (RES_COLD/RES_OR) SafetySignal Trip (RES_IDEAL/RES_COLD) SafetySignal Trip (RES_HOT/RES_IDEAL) SafetySignal Trip (RES_UR/RES_HOT) Time Between SafetySignal Measurements DACs Charging Current Resolution Charging Current Granularity Guaranteed Monotonic Above IMAX/16 RLIMIT = 0 RLIMIT = 10k 1% RLIMIT = 33k 1% RLIMIT = Open (or Short to VDD) All Values of RILIM All Values of RVLIM RLIMIT = 0 (0-1A) Charging Current = 0x03FF (0x0400 Note 7) RLIMIT = 10k 1%, (0-2A) Charging Current = 0x07FE (0x0800 Note 7) RLIMIT = 33k 1% (0-3A) Charging Current = 0x0BFC (0x0C00 Note 7) RLIMIT = 0pen (or Short to VDD) (0-4A) Charging Current = 0x0FFC (0x1000 Note 7) Charging Voltage Resolution Charging Voltage Granularity Guaranteed Monotonic (2.9V VBAT 28V) 97.3 97.3 72.3 97.3 11 16 10 1 2 4 4 80 (NOTE 5) 107.3 107.3 82.3 107.3 Bits mA mA mA mA mA mV mV mV mV Bits mV RTHA = 1130 1%, CTH = 1nF (Note 6) RTHB = 54.9 1% RTHA = 1130 1%, CTH = 1nF (Note 6) RTHB = 54.9 1% RTHA = 1130 1%, CTH = 1nF (Note 6) RTHB = 54.9 1% RTHA = 1130 1%, CTH = 1nF (Note 6) RTHB = 54.9 1% DCDIV = 1.3V DCDIV = 1V
q q q q
ELECTRICAL CHARACTERISTICS
AC Present Comparator
CONDITIONS VDCDIV Rising from 1V to 1.4V VDCDIV = 1.2V IACP = -2mA IACP = 1mA VDCDIV = 1.3V
q
MIN 1.14 -1 2
TYP 1.20 25
MAX 1.26 1 0.5 10
UNITS V mV A V V s k k k ms ms
95 28.5 2.85 425
100 30 3 500 32
105 31.5 3.15 575
250
Wake-Up Charging Current (IWAKE-UP) Charging Current Limit CSP - BAT
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LTC4100
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 20V, VDD = 3.3V, VBAT = 12V unless otherwise noted. (Note 4)
SYMBOL PARAMETER Charging Voltage Limit CONDITIONS RVLIM = 0 Charging Voltage = 0x2260 (Note 7) RVLIM = 10k 1% Charging Voltage = 0x3330 (Note 7) RVLIM = 33k 1% Charging Voltage = 0x4400 (Note 7) RVLIM = 100k 1% Charging Voltage = 0x5400 DCIN 22V (Note 7) RVLIM = 0pen (or Short to VDD) Charging Voltage = 0x6D60 DCIN 29V (Note 7) Logic Levels VIL VIH VOL IIL IIH VOL VOL VIL VIH SCL/SDA Input Low Voltage SCL/SDA Input High Voltage SDA Output Low Voltage SCL/SDA Input Current SCL/SDA Input Current SMBALERT Output Low Voltage SMBALERT Output Pull-Up Current CHGEN Output Low Voltage CHGEN Output Pull-Up Current CHGEN Input Low Voltage CHGEN Input High Voltage Power-On Reset Duration tHIGH tLOW tR tF tSU:STA tHD:STA tHD:DAT tTIMEOUT SCL Serial Clock High Period SCL Serial Clock Low Period SDA/SCL Rise Time SDA/SCL Fall Time Start Condition Setup Time StartCondition Hold Time SDA to SCL Falling-Edge Hold Time, Slave Clocking in Data Time Between Receiving Valid ChargingCurrent() and ChargingVoltage() Commands VDD = 3V VDD = 5.5V VDD Ramp from 0V to >3V in <5s IPULL-UP = 350A, CLOAD = 250pF, RPU = 9.31k IPULL-UP = 350A, CLOAD = 250pF, RPU = 9.31k CLOAD = 250pF, RPU = 9.31k CLOAD = 250pF, RPU = 9.31k
q q q q q q q q q q
ELECTRICAL CHARACTERISTICS
MIN 8.730 12.999 17.269 21.538 27.781
TYP 8.800 13.104 17.408 21.712 28.006
MAX 8.870 13.209 17.547 21.886 28.231
UNITS V V V V V
0.8 2.1 0.4 -1 -1 1 1 0.5 -17.5 -10 -10 -3.5 0.4 -17.5 -3.5 0.9 2.5 3.9 100 4 4.7 15000 1000 300 4.7 4 300 140 175 210
V V V A A V A V A V V V V s s s ns ns s s ns sec
IPULL-UP = 350A VSDA, VSCL = VIL VSDA, VSCL = VIH IPULL-UP = 500A VSMBALERT = VOL IOL = 100A VCHGEN = VOL
q
q
q
q q
SMBus Timing (Refer to System Management Bus Specification, Revision 1.1, Section 2.1 for Timing Diagrams)
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: See Test Circuit. Note 3: Does not include tolerance of current sense resistor. Note 4: The LTC4100E is guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 5: Current accuracy dependent upon circuit compensation and sense resistor. Note 6: CTH is defined as the sum of capacitance on THA, THB and SafetySignal. Note 7: The corresponding overrange bit will be set when a HEX value greater than or equal to this value is used.
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LTC4100
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TGATE (Pin 1): Drives the Top External P-MOSFET of the Battery Charger Buck Converter. PGND (Pin 2): High Current Ground Return for BGATE Driver. BGATE (Pin 3): Drives the Bottom External N-MOSFET of the Battery Charger Buck Converter. INFET (Pin 4): Drives the Gate of the External Input P-MOSFET. DCIN (Pin 5): External DC Power Source Input. CHGEN (Pin 6): Digital Bidirectional Pin to Enable Charger Function. This pin is connected as a wired AND bus. The following events will cause the POWER_FAIL bit in the ChargerStatus register to become set: 1. An external device pulling the CHGEN signal to within 0.9V to GND; 2. The AC adapter voltage is not above the battery voltage. SMBALERT (Pin 7): Active Low Interrupt Output to Host (referred to as the SMBALERT# signal in the SMBus Revision 1.1 specification). Signals host that there has been a change of status in the charger registers and that the host should read the LTC4100 status registers to determine if any action on its part is required. This signal can be connected to the optional SMBALERT# line of the SMBus. Open drain with weak current source pull-up to VDD (with Schottky to allow it to be pulled to 5V externally). SDA (Pin 8): SMBus Data Signal from Main (host-controlled) SMBus. External pull-up resistor is required. SCL (Pin 9): SMBus Clock Signal from Main (host-controlled) SMBus. External pull-up resistor is required. ACP (Pin 10): This Output Indicates the Value of the DCDIV Comparator. It can be used to indicate whether AC is present or not. DCDIV (Pin 11): Supply Divider Input. This is a high impedance comparator input with a 1.2V threshold (rising edge) and hysteresis. GND (Pin 12): Ground for Digital and Analog Circuitry. ILIM (Pin 13): An external resistor is connected between this pin and GND. The value of the external resistor programs the range and resolution of the programmed charger current. VLIM (Pin 14): An external resistor is connected between this pin and GND. The value of the external resistor programs the range and resolution of the charging voltage. THB (Pin 15): SafetySignal Force/Sense Pin to Smart Battery. See description of operation for more detail. The maximum allowed combined capacitance on THA, THB and SafetySignal is 1nF (see Figure 4). A series resistor 54.9k needs to be connected between this pin and the battery's SafetySignal for this circuit to work correctly. THA (Pin 16): SafetySignal Force/Sense Pin to Smart Battery. See description of operation for more detail. The maximum allowed combined capacitance on THA, THB and SafetySignal is 1nF (see Figure 4). A series resistor 1130 needs to be connected between this pin and the battery's SafetySignal for this circuit to work correctly. VDD (Pin 17): Power Supply Input for the LTC4100 Digital Circuitry. Bypass this pin with 0.1F. Typically between 3.3V and 5VDC. VSET (Pin 18): Tap Point of the Programmable Resistor Divider, which Provides Battery Voltage Feedback to the Charger. ITH (Pin 19): Control Signal of the Inner Loop of the Current Mode PWM. Higher ITH corresponds to higher charging current in normal operation. A 0.0015F capacitor to GND filters out PWM ripple. Typical full-scale output current is 40A. Nominal voltage range for this pin is 0V to 3V. IDC (Pin 20): Bypass to GND with a 0.082F Capacitor. CSP (Pin 21): Current Amplifier CA1 Input. This pin and the BAT pin measure the voltage across the sense resistor, RSENSE, to provide the instantaneous current signals required for both peak and average current mode operation. BAT (Pin 22): Battery Sense Input and the Negative Reference for the Current Sense Resistor. A bypass capacitor of at least 10F is required.
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LTC4100
PI FU CTIO S
CLN (Pin 23): Negative Input to the Input Current Limiting Circuit Block. If no current limit function is desired, connect this pin to CLP. The threshold is set at 100mV below the voltage at the CLP pin. When used to limit supply current, a filter is needed to filter out the switching noise. CLP (Pin 24): Positive Input to the Input Current Limiting Circuit Block. This pin also serves as a power supply for the IC. Bypass to ground with a 1F capacitor.
BLOCK DIAGRA
100 VBAT
0.01F VSET 0.1F GND 12 DCIN 1.28V 0V OSCILLATOR WATCHDOG DETECT tON 20F 1.19V CLP 18 11-BIT VDAC
- + EA
gm = 1m
L1 SW Q2
TGATE
1 PWM LOGIC 3 2 23 24 5 5.8V 4
Q
S R
D1
Q3
BGATE PGND CLN
RCL
CLP DCIN INFET
+ CL1 -
gm = 1m
Q1 VIN
CLP CHGEN 6 VDD 10A SMBALERT 7 SMBus INTERFACE AND CONTROL LIMIT DECODER THERMISTER INTERFACE 1.2V
SDA 8 SCL 9 THA 16 THB 15
Figure 2.
TEST CIRCUIT
LTC4100 - + 1.19V + - EA
VTOL =
ITH +
VDAC CSP BAT VSET LT1055
0.6V
4100 TC01
gm = 1.5m
100mV
-
W
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- + - CA1 + 22 BAT RSENSE 3k 21 9k /5 BUFFERED ITH CSP SW 20F
VBAT
+ -
ICMP IREV - + - + 1.19V 19 ITH 10-BIT IDAC 10 ACP DCDIV 11 20 IDC 17mV
VIN
17 VDD
13 14
ILIM VLIM RVLIM RILIM
VBAT - VVDAC * 100 VVDAC FOR VVDAC = 17.56V(0x44A0) DCIN = 21V
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LTC4100
OPERATIO
Overview (Refer to Block Diagram) The LTC4100 is composed of a battery charger section, a charger controller, a 10-bit DAC to control charger current, an 11-bit DAC to control charger voltage, a SafetySignal decoder, limit decoder and an SMBus controller block. If no battery is present, the SafetySignal decoder indicates a RES_OR condition and charging is disabled by the charger controller (CHGEN = Low). Charging will also be disabled if DCDIV is low, or the SafetySignal is decoded as RES_HOT. If a battery is inserted and AC power is connected, the battery will be charged with an 80mA "wakeup" current. The wake-up current is discontinued after tTIMEOUT if the SafetySignal is decoded as RES_UR or RES_C0LD, and the battery or host doesn't transmit charging commands. The SMBus interface and control block receives ChargingCurrent() and ChargingVoltage() commands via the SMBus. If ChargingCurrent() and ChargingVoltage() command pairs are received within a tTIMEOUT interval, the values are stored in the current and voltage DACs and the charger controller asserts the CHGEN line if the decoded SafetySignal value will allow charging to commence. ChargingCurrent() and ChargingVoltage() values are compared against limits programmed by the limit decoder block; if the commands exceed the programmed limits these limits are substituted and overrange flags are set. The charger controller will assert SMBALERT whenever a status change is detected, namely: AC_PRESENT, BATTERY_PRESENT, ALARM_INHIBITED, or V DD power-fail. The host may query the charger, via the SMBus, to obtain ChargerStatus() information. SMBALERT will be deasserted upon a successful read of ChargerStatus() or a successful Alert Response Address (ARA) request. Battery Charger Controller The LTC4100 charger controller uses a constant off-time, current mode step-down architecture. During normal operation, the top MOSFET is turned on each cycle when the oscillator sets the SR latch and turned off when the main current comparator ICMP resets the SR latch. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current trips the current
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comparator IREV, or the beginning of the next cycle. The oscillator uses the equation,
tOFF = (VDCIN - VBAT ) (VDCIN * fOSC )
to set the bottom MOSFET on time. The result is quasiconstant frequency operation: the converter frequency remains nearly constant over a wide range of output voltages. This activity is diagrammed in Figure 3.
OFF TGATE ON ON BGATE OFF INDUCTOR CURRENT
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tOFF TRIP POINT SET BY ITH VOLTAGE
Figure 3.
The peak inductor current, at which ICMP resets the SR latch, is controlled by the voltage on ITH. ITH is in turn controlled by several loops, depending upon the situation at hand. The average current control loop converts the voltage between CSP and BAT to a representative current. Error amp CA2 compares this current against the desired current programmed by the IDAC at the IDC pin and adjusts ITH for the desired voltage across RSENSE. The voltage at BAT is divided down by an internal resistor divider set by the VDAC and is used by error amp EA to decrease ITH if the divider voltage is above the 1.19V reference. The amplifier CL1 monitors and limits the input current, normally from the AC adapter, to a preset level (100mV/ RCL). At input current limit, CL1 will decrease the ITH voltage to reduce charging current. An overvoltage comparator, OV, guards against transient overshoots (>7%). In this case, the top MOSFET is turned off until the overvoltage condition is cleared. This feature is useful for batteries that "load dump" themselves by opening their protection switch to perform functions such as calibration or pulse mode charging.
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LTC4100
OPERATIO
PWM Watchdog Timer There is a watchdog timer that observes the activity on the TGATE pin. If TGATE stops switching for more than 40s, the watchdog activates and turns off the top MOSFET for about 400ns. The watchdog engages to prevent very low frequency operation in dropout - a potential source of audible noise when using ceramic input and output capacitors. Charger Start-Up When the charger is enabled, it will not begin switching until the ITH voltage exceeds a threshold that assures initial current will be positive. This threshold is 5% to 15% of the maximum programmed current. After the charger begins switching, the various loops will control the current at a level that is higher or lower than the initial current. The duration of this transient condition depends upon the loop compensation, but is typically less than 1ms. SMBus Interface All communications over the SMBus are interpreted by the SMBus interface block. The SMBus interface is an SMBus slave device. All internal LTC4100 registers may be updated and accessed through the SMBus interface, and charger controller as required. The SMBus protocol is a derivative of the I2CTM bus (Reference "I 2C-Bus and How to Use It, V1.0" by Philips, and "System Management Bus Specification", Version 1.1, from the SBS Implementers Forum, for a complete description of the bus protocol requirements.) All data is clocked into the shift register on the rising edge of SCL. All data is clocked out of the shift register on the falling edge of SCL. Detection of an SMBus Stop condition, or power-on reset via the VDD power-fail, will reset the SMBus interface to an initial state at any time. The LTC4100 command set is interpreted by the SMBus interface and passed onto the charger controller block as control signals or updates to internal registers.
I2C is a trademark of Philips Electronics N.V. *http://www. SBS-FORUM.org
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Description of Supported Battery Charger Functions The functions are described as follows (see Table 1 also): FunctionName() 'hnn (command code) Description: A brief description of the function. Purpose: The purpose of the function, and an example where appropriate. * SMBus Protocol: Refer to Section 5 of the Smart Battery Charger specification for more details. Input, Output or Input/Output: A description of the data supplied to or returned by the function. ChargerSpecInfo() ('h11) Description: The SMBus Host uses this command to read the LTC4100's extended status bits. Purpose: Allows the System Host to determine the specification revision the charger supports as well as other extended status information. * SMBus Protocol: Read Word. Output: The CHARGER_SPEC indicates that the LTC4100 supports Version 1.1 of the Smart Battery Charger Specification. The SELECTOR_SUPPORT indicates that the LTC4100 does not support the optional Smart Battery Selector Commands. ChargerMode() ('h12) Description: The SMBus Host uses this command to set the various charger modes. The default values are set to allow a Smart Battery and the LTC4100 to work in concert without requiring an SMBus Host. Purpose: Allows the SMBus Host to configure the charger and change the default modes. This is a write only function, but the value of the "mode" bit, INHIBIT_CHARGE may be determined using the ChargerStatus() function. * SMBus Protocol: Write Word. Input: The INHIBIT_CHARGE bit allows charging to be inhibited without changing the ChargingCurrent() and ChargingVoltage() values. The charging may be resumed by clearing this bit. This bit is automatically cleared when power is re-applied or when a battery is re-inserted.
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LTC4100
OPERATIO
Table 1: Summary of Supported Charger Functions
SMBus Address 7'b0001_001 Command Code 8'h11 Data Type Info Reserved
Function ChargerSpecInfo()
SELECTOR_SUPPORT
ENABLE_POLLING POLLING_ENABLED
ChargerMode()
7'b0001_001
8'h12
Control Reserved
Write ChargerStatus() 7'b0001_001 8'h13
Permitted Values
BATTERY_PRESENT ALARM_INHIBITED
Ignored
1/0 1/0
CURRENT_NOTREG VOLTAGE_NOTREG
Ign 1/0
CHARGE_INHIBITED
Status
AC_PRESENT
Read ChargingCurrent() Write ChargingVoltage() Write AlarmWarning() 7'b0001_001 8'h16 7'b0001_001 8'h15 7'b0001_001 8'h14
Return Values Value Permitted Values Value Permitted Values
1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0
0
LEVEL:3/LEVEL:2
CURRENT_OR
VOLTAGE_OR
POWER_FAIL
RES_COLD
RES_HOT
RES_UR
RES_OR
1
0
0
0
1/0
CHARGING_CURRENT[15:0] Unsigned integer representing current in mA CHARGING_VOLTAGE[15:0] Unsigned integer representing voltage in mV
TERMINATE_DISCHARGE_ALARM REMAINING_CAPACITY_ALARM
TERMINATE_CHARGE_ALARM
Control
OVER_CHARGED_ALARM
REMAINING_TIME_ALARM
OVER_TEMP_ALARM
FULLY DISCHARGED
RESERVED_ALARM
FULLY_CHARGED
DISCHARGING
INITIALIZED
Reserved
Write LTCO() 7'b0001_001 8'h3C
Permitted Values 1/0 1/0 1/0 1/0 Register Reserved Permitted Values Return Values 7'b0001_100 N/A Status Not Supported Return Values
NO_LOWI
Ignored
LTC4100's Version Identification
Write Read Alert Response Address Read Byte
Ignored 0 0 0
1/0 1/0 0 0 1 0 0
Ignored 0 0 0 0 0 1 0
Undefined
LTC4100's Address
0
0
0
1
0
ERROR
0
1
X
INHIBIT_CHARGE
RESET_TO_ZERO
POR_RESET
10
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Access D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 DO CHARGER_SPEC Read Return Values 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0
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LTC4100
OPERATIO
The ENABLE_POLLING bit is not supported by the LTC4100. Values written to this bit are ignored. The POR_RESET bit sets the LTC4100 to its power-on default condition. The RESET_TO_ZERO bit sets the ChargingCurrent()and ChargingVoltage() values to zero. This function ALWAYS clears the ChargingVoltage() and ChargingCurrent() values to zero even if the INHIBIT_CHARGE bit is set. ChargerStatus() ('h13) Description: The SMBus Host uses this command to read the LTC4100's status bits. Purpose: Allows the SMBus Host to determine the status and level of the LTC4100. * SMBus Protocol: Read Word. Output: The CHARGE_INHIBITED bit reflects the status of the LTC4100 set by the INHIBIT_CHARGE bit in the ChargerMode() function. The POLLING_ENABLED, VOLTAGE_NOTREG, and CURRENT_NOTREG are not supported by the LTC4100. The LTC4100 always reports itself as a Level 2 Smart Battery Charger. CURRENT_OR bit is set only when ChargingCurrent() is set to a value outside the current regulation range of the LTC4100. This bit may be used in conjunction with the INHIBIT_CHARGE bit of the ChargerMode() and ChargingCurrent() to determine the current capability of the LTC4100. When ChargingCurrent() is set to the programmatic maximum current + 1, the CURRENT_OR bit will be set. VOLTAGE_OR bit is set only when ChargingVoltage() is set to a value outside the voltage regulation range of the LTC4100. This bit may be used in conjunction with the INHIBIT_CHARGE bit of the ChargerMode() and ChargingVoltage() to determine the voltage capability of the LTC4100. When ChargingVoltage() is set to the programmatic maximum voltage, the VOLTAGE_OR bit will be set. The RES_OR bit is set only when the SafetySignal resistance value is greater than 95k. This indicates that the SafetySignal is to be considered as an open circuit.
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The RES_COLD bit is set only when the SafetySignal resistance value is greater than 28.5k. The SafetySignal indicates a cold battery. The RES_COLD bit will be set whenever the RES_OR bit is set. The RES_HOT bit is set only when the SafetySignal resistance is less than 3150, which indicates a hot battery. The RES_HOT bit will be set whenever the RES_UR bit is set. The RES_UR bit is set only when the SafetySignal resistance value is less than 575. ALARM_INHIBITED bit is set if a valid AlarmWarning() message has been received and charging is inhibited as a result. This bit is cleared if both ChargingVoltage() and ChargingCurrent() are re-written to the LTC4100, power is removed (DCDIV < VACP), or if a battery is removed. The setting of the ALARM_INHIBITED will activate the LTC4100 SMBALERT pull-down. POWER_FAIL bit is set if the LTC4100 does not have sufficient DCIN voltage to charge the battery or if an external device is pulling the CHGEN input signal low. Charging is disabled whenever this bit is set. The setting of this bit does not clear the values in the ChargingVoltage() and ChargingCurrent() function values, nor does it necessarily affect the charging modes of the LTC4100. BATTERY_PRESENT is set if a battery is present otherwise it is cleared. The LTC4100 uses the SafetySignal in order to determine battery presence. If the LTC4100 detects a RES_OR condition, the BATTERY_PRESENT bit is cleared immediately. The LTC4100 will not set the BATTERY_PRESENT bit until it successfully samples the SafetySignal twice and does not detect a RES_OR condition on either sampling. If AC is not present (e.g. DCDIV < VACP), this bit may not be set for up to one-half second after the battery is connected to the SafetySignal. The ChargingCurrent() and ChargingVoltage() function values are immediately cleared whenever this bit is cleared. Charging will never be allowed if this bit is cleared. A change in BATTERY_PRESENT will activate the LTC4100 SMBALERT pull-down. AC_PRESENT is set if the voltage on DCDIV is greater than VACP. This does not necessarily indicate that the voltage on DCIN is sufficient to charge the battery. A change in
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LTC4100
OPERATIO
AC_PRESENT will activate the LTC4100 SMBALERT pulldown. ChargingCurrent() ('h14) Description: The Battery, System Host or other master device sends the desired charging current (mA) to the LTC4100 . Purpose: The LTC4100 uses RILIM, the granularity of the IDAC, and the value of the ChargingCurrent() function to determine its charging current supplied to the battery. The charging current will never exceed the maximum current permitted by RILIM. The ChargingCurrent() value will be truncated to the granularity of the IDAC. The charging current will also be reduced if the battery voltage exceeds the programmed charging voltage. * SMBus Protocol: Write Word. Input: The CHARGING_CURRENT is an unsigned 16 bit integer specifying the requested charging current in mA. The following table defines the maximum permissible value of CHARGING_CURRENT that will not set the CURRENT_OR in the ChargerStatus() function for a given value of the RILIM:
RILIM Short to GND 10k 1% 33k 1% ChargingCurrent() Current 0x0000 through 0x03FF 0mA through 1023mA 0x0000 through 0x07FF 0mA through 2047mA 0x0000 through 0x0BFF 0mA through 3071mA
Open (or short to VDD) 0x0000 through 0x0FFF 0mA through 4095mA
ChargingVoltage() ('h15) Description: The Battery, SMBus Host or other master device sends the desired charging voltage (mV) to the LTC4100. Purpose: The LTC4100 uses RVLIM, the granularity of the VDAC, and the value of the ChargingVoltage() function to determine its charging voltage supplied to the battery. The charging voltage will never be forced beyond the voltage permitted by RVLIM. The ChargingVoltage() value will be truncated to the granularity of the VDAC. The charging voltage will also be reduced if the battery current exceeds the programmed charging current. * SMBus Protocol: Write Word.
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Input: The CHARGING_VOLTAGE is an unsigned 16-bit integer specifying the requested charging voltage in mV. The LTC4100 considers any value from 0x0001 through 0x049F the same as writing 0x0000. The following table defines the maximum permissible value of CHARGING_VOLTAGE that will not set the VOLTAGE_OR in the ChargerStatus() function for a given value of RVLIM:
RVLIM Short to GND 10k 1% 33k 1% 100k 1% Open (or short to VDD) Maximum ChargingVoltage() 0x225F (8796mV) 0x332F (13100mV) 0x43FF (17404mV) 0x54CF (21708mV) 0x6D5F (27999mV)
AlarmWarning() ('h16) Description: The Smart Battery, acting as a bus master device, sends the AlarmWarning() message to the LTC4100 to notify it that one or more alarm conditions exist. Alarm indications are encoded as bit fields in the Battery's Status register, which is then sent to the LTC4100 by this function. Purpose: The LTC4100 will use the information sent by this function to properly charge the battery. The LTC4100 will only respond to certain alarm bits. Writing to this function does not necessarily cause an alarm condition that inhibits battery charging. * SMBus Protocol: Write Word. Input: Only the OVER_CHARGED_ALARM, TERMINATE _CHARGE_ALARM,reserved (0x2000), and OVER _TEMP_ALARM bits are supported by the LTC4100. Writing a one to any of these specified bits will inhibit the charging by the LTC4100 and will set the ALARM_INHIBITED bit in the ChargerStatus() function. The TERMINATE_DISCHARGE_ALARM, REMAINING_ CAPACITY_ALARM, REMAINING_TIME_ALARM, and the ERROR bits are ignored by the LTC4100. LTC0() ('h3C) Description: The SMBus Host uses this command to determine the version number of the LTC4100 and set extended operation modes not defined by the Smart Battery Charger Specification.
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LTC4100
OPERATIO
Purpose: This function allows the SMBus Host to determine if the battery charger is an LTC4100. Identifying the manufacturer and version of the Smart Battery Charger permits software to perform tasks specific to a given charger. The LTC4100 also provides a means of disabling the LOWI current mode of the IDAC. * SMBus Protocol: Write Word. Input: The NO_LOWI is the only bit recognized by this function. The default value of NO_LOWI is zero. The LTC4100 LOWI current mode provides a more accurate average charge current when the charge current is less than 1/16 of the full-scale IDAC value. When the NO_LOWI is set, a less accurate IDAC algorithm is used to generate the charging current, but because the charger is not pulsed on and off, it may be preferred. * SMBus Protocol: Read Word. Output: The NO_LOWI indicates the IDAC mode of operation. If clear, then the LOWI current mode will be used when the charging current is less than 1/16 of the fullscale IDAC value. The LTC Version Identification will always be 0x202 for the LTC4100. Alert Response Address (ARA) Description: The SMBus system host uses the Alert Response Address to quickly identify the generator of an SMBALERT# event. Purpose: The LTC4100 will respond to an ARA if the SMBALERT signal is actively pulling down the SMBALERT# bus. The LTC4100 will follow the prioritization reporting as defined in the System Management Bus Specification, Version 1.1, from the SBS Implementers Forum. * SMBus Protocol: A 7-bit Addressable Device Responds to an ARA. Output: The Device Address will be sent to the SMBus system host. The LTC4100 Device address is 0x12 (or 0x09 if just looking at the 7-bit address field). The following events will cause the LTC4100 to pull-down the SMBALERT# bus through the SMBALERT pin: * Change of AC_PRESENT in the ChargerStatus() function.
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* Change of BATTERY_PRESENT in the ChargerStatus() function. * Setting ALARM_INHIBITED in the ChargerStatus() function. * Internal power-on reset condition. SMBus Accelerator Pull-Ups Both SCL and SDA have SMBus accelerator circuits which reduce the rise time on systems with significant capacitance on the two SMBus signals. The dynamic pull-up circuitry detects a rising edge on SDA or SCL and applies 1mA to 10mA pull-up to VDD when VIN > 0.8V until VIN < VDD - 0.8V (external pull-up resistors are still required to supply DC current). This action allows the bus to meet SMBus rise time requirements with as much as 250pF on each SMBus signal. The improved rise time will benefit all of the devices which use the SMBus, especially those devices that use the I2C logic levels. Note that the dynamic pull-up circuits only pull to VDD, so some SMBus devices that are not compliant to the SMBus specifications may still have rise time compliance problems if the SMBus pullup resistors are terminated with voltages higher than VDD. The Control Block The LTC4100 charger operations are handled by the control block. This block is capable of charging the selected battery autonomously or under SMBus Host control. The control block can request communications with the system management host (SMBus Host) by asserting SMBALERT = 0; this will cause the SMBus Host, if present, to poll the LTC4100. The control block receives SMBus slave commands from the SMBus interface block. The control block allows the LTC4100 to meet the following Smart Battery-controlled (Level 2) charger requirements: 1. Implements the Smart Battery's critical warning messages over the SMBus. 2. Operates as an SMBus slave device that responds to ChargingVoltage() and ChargingCurrent() commands and adjusts the charger output parameters accordingly.
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LTC4100
OPERATIO
3. The host may control charging by disabling the Smart Battery's ability to transmit ChargingCurrent() and ChargingVoltage() request functions and broadcasting the charging commands to the LTC4100 over the SMBus. 4. The LTC4100 will still respond to Smart Battery critical warning messages without host intervention. Wake-up Charging Mode The following conditions must be met in order to allow wake-up charging of the battery: 1. The SafetySignal must be RES_COLD, RES_IDEAL, or RES_UR. 2. AC must be present. This is qualified by DCDIV > VACP. Wake-up charging initiates when a newly inserted battery does not send ChargingCurrent() and ChargingVoltage() functions to the LTC4100. The following conditions will terminate the Wake-up Charging Mode. 1. A TTIMEOUT period is reached when the SafetySignal is RES_COLD or RES_UR. 2. The SafetySignal is registering RES_OR. 3. The successful writing of the ChargingCurrent() AND ChargingVoltage() function. The LTC4100 will proceed to the controlled charging mode after these two functions are written. 4. The SafetySignal is registering RES_HOT. 5. The AC power is no longer present. (DCDIV < VACP) 6. The ALARM_INHIBITED becomes set in the ChargerStatus() function. 7. The INHIBIT_CHARGE is set in the ChargerMode() function. 8. The CHGEN pin is pulled low by an external device. The LTC4100 will resume wake-up charging, if the CHGEN pin is released by the external device. Toggling the CHGEN pin will not reset the TTIMEOUT timer.
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9. There is insufficient DCIN voltage to charge the battery. The LTC4100 will resume wake-up charging when there is sufficient DCIN voltage to charge the battery. This condition will not reset the TTIMEOUT timer. Controlled Charging Algorithm Overview The following conditions must be met in order to allow controlled charging to start on the LTC4100: 1. The ChargingVoltage() AND ChargingCurrent() function must be written to non-zero values. 2. The SafetySignal must be RES_COLD, RES_IDEAL, or RES_UR. 3. AC must be present. This is qualified by DCDIV > VACP. The following conditions will stop the Controlled Charging Algorithm and will cause the Battery Charger Controller to stop charging: 1. The ChargingCurrent() AND ChargingVoltage() functions have not been written for TTIMEOUT. 2. The SafetySignal is registering RES_OR. 3. The SafetySignal is registering RES_HOT. 4. The AC power is no longer present. (DCDIV < VACP) 5. ALARM_INHIBITED is set in the ChargerStatus() function. 6. INHIBIT_CHARGE is set in the ChargerMode() function. Clearing INHIBIT_CHARGE will cause the LTC4100 to resume charging using the previous ChargingVoltage() AND ChargingCurrent() function values. 7. RESET_TO_ZERO is set in the ChargerMode() function. 8. CHGEN pin is pulled low by an external device. The LTC4100 will resume charging using the previous ChargingVoltage() AND ChargingCurrent() function values, if the CHGEN pin is released by the external device. 9. Insufficient DCIN voltage to charge the battery. The LTC4100 will resume charging using the previous ChargingVoltage() AND ChargingCurrent() function val4100i
LTC4100
OPERATIO
ues, when there is sufficient DCIN voltage to charge the battery. 10. Writing a zero value to ChargingVoltage() function. 11. Writing a zero value to ChargingCurrent() function. The SafetySignal Decoder Block This block measures the resistance of the SafetySignal and features high noise immunity at critical trip points. The low power standby mode supports only battery presence SMB charger reporting requirements when AC is not present. The SafetySignal decoder is shown in Figure 4. The value of RTHA is 1.13k and RTHB is 54.9k. SafetySignal sensing is accomplished by a state machine that reconfigures the switches of Figure 4 using THA_SELB and THB_SELB, a selectable reference generator, and two comparators. This circuit has two modes of operation based upon whether AC is present. When AC is present, the LTC4100 samples the value of the SafetySignal and updates the ChargerStatus register approximately every 32ms. The state machine successively samples the SafetySignal value starting with the RES_OR RES_COLD threshold, then RES_C0LD RES_IDEAL threshold, RES_IDEAL RES_HOT threshold, and finally the RES_HOT RES_UR threshold. Once the SafetySignal
VDD RTHA 1.13k THA THA_SELB
MUX
25k VLIM
RES_COLD LATCH RES_H0T RES_UR
12.5k
4100 F04
Figure 4. SafetySignal Decoder Block
Figure 5. Simplified VLIM Circuit Concept (ILIM is Similar)
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+
-
CSS
THB RSafetySignal
RVLIM
25k
+
RES_OR
-
RTHB 54.9k
THB_SELB
25k
+
SafetySignal CONTROL
-
VDD
LO_REF
-
REF
33k
+
+
HI_REF
-
+
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range is determined, the lower value thresholds are not sampled. The SafetySignal decoder block uses the previously determined SafetySignal value to provide the appropriate adjustment in threshold to add hysteresis. The RTHB resistor value is used to measure the RES_OR RES_COLD and RES_COLD RES_IDEAL thresholds by connecting the THB pin to VDD and measuring the voltage resultant on the THA pin. The RTHA resistor value is used to measure the RES_IDEAL RES_HOT and RES_HOT RES_UR thresholds by connecting the THA pin to VDD and measuring the voltage resultant on the THB pin. The SafetySignal decoder block uses a voltage divider network between VDD and GND to determine SafetySignal range thresholds. Since the THA and THB inputs are sequentially connected to VDD, this provides VDD noise immunity during SafetySignal measurement. When AC power is not available the SafetySignal block supports the following low power operating features: 1. The SafetySignal is sampled every 250ms or less, instead of 32ms. 2. A full SafetySignal status is sampled every 30s or less, instead of every 32ms The SafetySignal impedance is interpreted according to Table 4.
VDD AC_PRESENT
TH_HI
12.5k
TH_LO
4 VLIM [3:0] ENCODER
4100 F05
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LTC4100
OPERATIO
SafetySignal RESISTANCE 0 to 500
Table 4. SafetySignal State Ranges
CHARGE STATUS BITS RES_UR, RES_HOT BATTERY_PRESENT RES_HOT BATTERY_PRESENT BATTERY_PRESENT RES_COLD BATTERY_PRESENT RES_OR RES_COLD DESCRIPTION Underrange
500 to 3k 3k to 30k 30k to 100k Above 100k
Note: The underrange detection scheme is a very important feature of the LTC4100. The RTHA/RSafetySignal divider trip point of 0.333 * VDD (1V) is well above the 0.047 * VDD (140mV) threshold of a system using a 10k pull-up. A system using a 10k pull-up would not be able to resolve the important underrange to hot transition point with a modest 100mV of ground offset between battery and SafetySignal detection circuitry. Such offsets are anticipated when charging at normal current levels.
The required values for RTHA and RTHB are shown in Table 5.
Table 5. SafetySignal External Resistor Values
EXTERNAL RESISTOR RTHA RTHB VALUE () 1130 1% 54.9k 1%
CSS represents the capacitance between the SafetySignal and GND. CSS may be added to provide additional noise immunity from transients in the application. CSS can not exceed 1nF if the LTC4100 is to properly sense the value of RSafetySignal. The ILIM Decoder Block The value of an external resistor connected from this pin to GND determines one of four current limits that are used for maximum charging current value. These limits provide a measure of safety with a hardware restriction on charging current which cannot be overridden by software.
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Table 6. ILIM Trip Points and Ranges
EXTERNAL RESISTOR (RILIM) Short to GND 10k 1% Hot 33k 1% Ideal Cold Overrange Open (>250k, or Short to VDD) CONTROLLED CHARGING CURRENT RANGE GRANULARITY 0 < I < 1023mA 0 < I < 2046mA 0 < I < 3068mA 0 < I < 4092mA 1mA 2mA 4mA 4mA ILIM VOLTAGE VILIM < 0.09VDD 0.17VVDD < VILIM < 0.34VVDD 0.42VVDD < VILIM < 0.59V 0.66VVDD < VILIM
The VLIM Decoder Block The value of an external resistor connected from this pin to GND determines one of five voltage limits that are applied to the charger output value. These limits provide a measure of safety with a hardware restriction on charging voltage which cannot be overridden by software.
Table 7. VLIM Trip Points and Ranges (See Figure 5)
EXTERNAL RESISTOR (RVLIM) Short to GND 10k 1% 33k 1% 100k 1% Open or Tied to VDD CONTROLLED CHARGING VOLTAGE (VOUT) RANGE GRANULARITY 2900mV < VOUT < 8800mV 2900mV < VOUT < 13.104mV 2900mV < VOUT < 17.408mV 2900mV < VOUT < 21.712mV 2900mV < VOUT < 28000mV 16mV 16mV 16mV 16mV 16mV
VLIM VOLTAGE VVLIM < 0.09VVCCP 0.17VVDD < VVLIM < 0.34VVDD 0.42VVCCP < VVLIM < 0.59VVDD 0.66VVDD < VVLIM < 0.84VVDD 0.91VVDD < VVLIM
The Voltage DAC Block Note that the charger output voltage is offset by VREF. Therefore, the value of VREF is subtracted from the SMBus ChargingVoltage() value in order for the output voltage to be programmed properly (without offset). If the ChargingVoltage() value is below the nominal reference voltage of the charger, nominally 1.184V, the charger output voltage is programmed to zero. In addition, if the ChargingVoltage() value is above the limit set by the VLIM pin, then the charger output voltage is set to the value determined by the VLIM resistor and the VOLTAGE_OR bit is set. These limits are demonstrated in Figure 6.
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LTC4100
OPERATIO
25 20 CHARGER VOUT (V)
RVLIM = 33k
15
RSET
10
- MODULATOR
5
Figure 7. Current DAC Operation
0 0 5 20 15 10 25 30 PROGRAMMED VALUE (V) 35
4100 F06
ILIMIT/8 0 ~40ms
4100 F08
NOTE: THE LTC4100 CAN BE PROGRAMMED WITH ChargingVoltage() FUNCTION VALUES BETWEEN 1.184V AND 2.9V, HOWEVER, THE BATTERY CHARGER CONTROLLER OUTPUT VOLTAGE MAY BE ZERO WITH PROGRAMMED VALUES BELOW 2.9V.
Figure 6. Transfer Function of Charger
Figure 8. Charging Current Waveform in Low Current Mode
The Current DAC Block The current DAC is a delta-sigma modulator which controls the effective value of an external resistor, RSET, used to set the current limit of the charger. Figure 7 is a simplified diagram of the DAC operation. The delta-sigma modulator and switch convert the ChargingCurrent() value, received via the SMBus, to a variable resistance equal to: 1.25RSET/ChargingCurrent()/ILIM[x]) Therefore, programmed current is equal to: (102.3mV/RSENSE) (ChargingCurrent()/ILIM[x]), for ChargingCurrent() < ILIM[x]. When a value less than 1/16th of the maximum current allowed by ILIM is applied to the current DAC input, the current DAC enters a different mode of operation called LOWI. The current DAC output is pulse width modulated with a high frequency clock having a duty cycle value of 1/8. Therefore, the maximum output current provided by the charger is IMAX/8. The delta-sigma output gates this low duty cycle signal on and off. The delta-sigma shift registers are then clocked at a slower rate, about 45ms/bit, so that the charger has time to settle to the IMAX/8 value. The resulting average charging current is equal to that requested by the ChargingCurrent() value. Note: The LOWI mode can be disabled by setting the NO_LOWI bit in the LTC0() function.
When wake-up is asserted to the current DAC block, the delta-sigma is then fixed at a value equal to 80mA, independent of the ILIM setting. Input FET The input FET circuit performs two functions. It enables the charger if the input voltage is higher than the CLP pin, and provides an indication of this condition at both the CHGEN pin and the PWR_FAIL bit in the ChargerStatus() register. It also controls the gate of the input FET to keep a low forward voltage drop when charging and prevents reverse current flow through the input FET. If the input voltage is less than VCLP, it must go at least 130mV higher than VCLP to activate the charger. The CHGEN pin is forced low unless this condition is met. The gate of the input FET is driven to a voltage sufficient to keep a low forward voltage drop from drain to source. If the voltage between DCIN and CLP drops to less than 25mV, the input FET is turned off slowly. If the voltage between DCIN and CLP is ever less than -25mV, then the input FET is turned off quickly to prevent significant reverse current from flowing in the input FET. In this condition the CHGEN pin is driven low and the charger is disabled.
+
VREF
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IPROG (FROM CA1 AMP) IDC ITH CHARGING_CURRENT VALUE
4100 F07
AVERAGE CHARGER CURRENT
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LTC4100
OPERATIO
The AC Present Block (AC_PRESENT) The DCDIV pin is used to determine AC presence. If the DCDIV voltage is above the DCDIV comparator threshold (VACP), then the ACP output pin will be switched to VDD and the AC_PRESENT bit in the ChargerStatus() function will
APPLICATIO S I FOR ATIO
Adapter Limiting
An important feature of the LTC4100 is the ability to automatically adjust charging current to a level which avoids overloading the wall adapter. This allows the product to operate at the same time that batteries are being charged without complex load management algorithms. Additionally, batteries will automatically be charged at the maximum possible rate of which the adapter is capable. This feature is created by sensing total adapter output current and adjusting charging current downward if a preset adapter current limit is exceeded. True analog control is used, with closed loop feedback ensuring that adapter load current remains within limits. Amplifier CL1 in Figure 9 senses the voltage across RCL, connected between the CLP and CLN pins. When this voltage exceeds 100mV, the amplifier will override programmed charging current to limit adapter current to 100mV/RCL. A lowpass filter formed by 4.99k and 0.1F is required to eliminate switching noise. If the current limit is not used, CLP should be connected to CLN.
LTC4100 CLP VIN 0.1F CLN 100mV INFET RCL*
-
CL1
*RCL =
100mV ADAPTER CURRENT LIMIT
Figure 9. Adapter Current Limiting
Setting Input Current Limit To set the input current limit, you need to know the minimum wall adapter current rating. Subtract 7% for the
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4100 F09
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be set. If the DCDIV voltage is below the DCDIV comparator threshold minus the DCDIV comparator hysteresis, then the ACP output pin is switched to GND and the AC_PRESENT bit in the ChargerStatus() function is cleared. The ACP output pin is designed to drive 2mA continuously. input current limit tolerance and use that current to determine the resistor value. RCL = 100mV/ILIM ILIM = Adapter Min Current - (Adapter Min Current * 7%)
Table 8. Common RCL Resistor Values
ADAPTER RATING (A) 1.5 1.8 2 2.3 2.5 2.7 3 RCL VALUE* () 1% 0.06 0.05 0.045 0.039 0.036 0.033 0.03 RCL POWER DISSIPATION (W) 0.135 0.162 0.18 0.206 0.225 0.241 0.27 RCL POWER RATING (W) 0.25 0.25 0.25 0.25 0.5 0.5 0.5 * Values shown above are rounded to nearest standard value.
As is often the case, the wall adapter will usually have at least a +10% current limit margin and many times one can simply set the adapter current limit value to the actual adapter rating (see Table 8). Charge Termination Issues Batteries with constant current charging and voltagebased charger termination might experience problems with reductions of charger current caused by adapter limiting. It is recommended that input limiting feature be defeated in such cases. Consult the battery manufacturer for information on how your battery terminates charging. Setting Output Current Limit (Refer to Figure 1) The LTC4100 current DAC and the PWM analog circuitry must coordinate the setting of the charger current. Failure to do so will result in incorrect charge currents.
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LTC4100
APPLICATIO S I FOR ATIO
Table 9. Recommended Resistor Values
IMAX (A) 1.023 2.046 3.068 4.092 RSENSE () 1% 0.100 0.05 0.025 0.025 RSENSE (W) 0.25 0.25 0.5 0.5 RILIM () 1% 0 10k 33k Open
Warning DO NOT CHANGE THE VALUE OF RILIM DURING OPERATION. The value must remain fixed and track the RSENSE value at all times. Changing the current setting can result in currents that greatly exceed the requested value and potentially damage the battery or overload the wall adapter if no input current limiting is provided. Inductor Selection Higher operating frequencies allow the use of smaller inductor and capacitor values. A higher frequency generally results in lower efficiency because of MOSFET gate charge losses. In addition, the effect of inductor value on ripple current and low current operation must also be considered. The inductor ripple current IL decreases with higher frequency and increases with higher VIN.
IL =
( )( )
V VOUT 1 - OUT VIN fL 1
Accepting larger values of IL allows the use of low inductances, but results in higher output voltage ripple and greater core losses. A reasonable starting point for setting ripple current is IL = 0.4(IMAX). Remember the maximum IL occurs at the maximum input voltage. The inductor value also has an effect on low current operation. The transition to low current operation begins when the inductor current reaches zero while the bottom MOSFET is on. Lower inductor values (higher IL) will cause this to occur at higher load currents, which can cause a dip in efficiency in the upper range of low current operation. In practice 10H is the lowest value recommended for use.
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Table 10 Recommended Inductor Values
Maxaimum Average Current (A) 1 1 2 2 3 3 4 4 Input Voltage (V) 20 >20 20 >20 20 >20 20 >20 Minimum Inductor Value (H) 40 20% 56 20% 20 20% 30 20% 15 20% 20 20% 10 20% 15 20%
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Calculating IC Power Dissipation The power dissipation of the LTC4100 is dependent upon the gate charge of the top and bottom MOSFETs (Q2 & Q3 respectively) The gate charge (QG) is determined from the manufacturer's data sheet and is dependent upon both the gate voltage swing and the drain voltage swing of the MOSFET. Use 6V for the gate voltage swing and VDCIN for the drain voltage swing. PD = VDCIN * (fOSC (QGQ2 + QGQ3) + IDCIN) Example: VDCIN = 19V, fOSC = 345kHz, QGQ2 = 25nC, QGQ3 = 15nC, IDCIN = 3mA. PD = 320mW Soft Start and Undervoltage Lockout The LTC4100 is soft started by the 0.12F capacitor on the ITH pin. On start-up, ITH pin voltage will rise quickly to 0.5V, then ramp up at a rate set by the internal 30A pull-up current and the external capacitor. Battery charging current starts ramping up when ITH voltage reaches 0.8V and full current is achieved with ITH at 2V. With a 0.12F capacitor, time to reach full charge current is about 2ms and it is assumed that input voltage to the charger will reach full value in less than 2ms. The capacitor can be increased up to 1F if longer input start-up times are needed.
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LTC4100
APPLICATIO S I FOR ATIO
In any switching regulator, conventional timer-based soft starting can be defeated if the input voltage rises much slower than the time out period. This happens because the switching regulators in the battery charger and the computer power supply are typically supplying a fixed amount of power to the load. If input voltage comes up slowly compared to the soft start time, the regulators will try to deliver full power to the load when the input voltage is still well below its final value. If the adapter is current limited, it cannot deliver full power at reduced output voltages and the possibility exists for a quasi "latch" state where the adapter output stays in a current limited state at reduced output voltage. For instance, if maximum charger plus computer load power is 30W, a 15V adapter might be current limited at 2.5A. If adapter voltage is less than (30W/2.5A = 12V) when full power is drawn, the adapter voltage will be pulled down by the constant 30W load until it reaches a lower stable state where the switching regulators can no longer supply full load. This situation can be prevented by utilizing the DCDIV resistor divider, set higher than the minimum adapter voltage where full power can be achieved. Input and Output Capacitors In the 4A Lithium Battery Charger (Typical Application on back page), the input capacitor (C2) is assumed to absorb all input switching ripple current in the converter, so it must have adequate ripple current rating. Worst-case RMS ripple current will be equal to one half of output charging current. Actual capacitance value is not critical. Solid tantalum low ESR capacitors have high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capacitors are used for input or output bypass. High input surge currents can be created when the adapter is hot-plugged to the charger or when a battery is connected to the charger. Solid
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tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. Only Kemet T495 series of "Surge Robust" low ESR tantalums are rated for high surge conditions such as battery to ground. The relatively high ESR of an aluminum electrolytic for C1, located at the AC adapter input terminal, is helpful in reducing ringing during the hot-plug event. Refer to AN88 for more information. The highest possible voltage rating on the capacitor will minimize problems. Consult with the manufacturer before use. Alternatives include new high capacity ceramic (at least 20F) from Tokin, United Chemi-Con/Marcon, et al. Other alternative capacitors include OSCON capacitors from Sanyo. The output capacitor (C3) is also assumed to absorb output switching current ripple. The general formula for capacitor current is: V 0.29(VBAT ) 1 - BAT VDCIN = (L1)(f) IRMS For example, VDCIN = 19V, VBAT = 12.6V, L1 = 10H, and f = 300kHz, IRMS = 0.41A. EMI considerations usually make it desirable to minimize ripple current in the battery leads, and beads or inductors may be added to increase battery impedance at the300kHz switching frequency. Switching ripple current splits between the battery and the output capacitor depending on the ESR of the output capacitor and the battery impedance. If the ESR of C3 is 0.2 and the battery impedance is raised to 4 with a bead or inductor, only 5% of the current ripple will flow in the battery.
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LTC4100
APPLICATIO S I FOR ATIO
Protecting SMBus Inputs The SMBus inputs, SCL and SDA, are exposed to uncontrolled transient signals whenever a battery is connected to the system. If the battery contains a static charge, the SMBus inputs are subjected to transients which can cause damage after repeated exposure. Also, if the battery's positive terminal makes contact to the connector before the negative terminal, the SMBus inputs can be forced below ground with the full battery potential, causing a potential for latch-up in any of the devices connected to the SMBus inputs. Therefore it is good design practice to protect the SMBus inputs as shown in Figure 10.
VDD
HIGH FREQUENCY CIRCULATING PATH
CONNECTOR TO BATTERY
TO SYSTEM
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Figure 10. Recommended SMBus Transient Protection
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PCB Layout Considerations For maximum efficiency, the switch node rise and fall times should be minimized. To prevent magnetic and electrical field radiation and high frequency resonant problems, proper layout of the components connected to the IC is essential. (See Figure 11.) Here is a PCB layout priority list for proper layout. Layout the PCB using this specific order.
SWITCH NODE L1 VBAT VIN C2 D1 C4 BAT
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Figure 11. High Speed Switching Path
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LTC4100
APPLICATIO S I FOR ATIO
1. Input capacitors need to be placed as close as possible to switching FET's supply and ground connections. Shortest copper trace connections possible. These parts must be on the same layer of copper. Vias must not be used to make this connection. 2. The control IC needs to be close to the switching FET's gate terminals. Keep the gate drive signals short for a clean FET drive. This includes IC supply pins that connect to the switching FET source pins. The IC can be placed on the opposite side of the PCB relative to above. 3. Place inductor input as close as possible to switching FET's output connection. Minimize the surface area of this trace. Make the trace width the minimum amount needed to support current--no copper fills or pours. Avoid running the connection using multiple layers in parallel. Minimize capacitance from this node to any other trace or plane. 4. Place the output current sense resistor right next to the inductor output but oriented such that the IC's current sense feedback traces going to resistor are not long. The feedback traces need to be routed together as a single pair on the same layer at any given time with
Figure 12. Kelvin Sensing of Charging Current
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smallest trace spacing possible. Locate any filter component on these traces next to the IC and not at the sense resistor location. 5. Place output capacitors next to the sense resistor output and ground. 6. Output capacitor ground connections need to feed into same copper that connects to the input capacitor ground before tying back into system ground. Interfacing with a Selector The LTC4100 is designed to be used with a true analog multiplexer for the SafetySignal sensing path. Some selector ICs from various manufacturers may not implement this. Consult LTC applications department for more information. Electronic Loads The LTC4100 is designed to work with a real battery. Electronic loads will create instability within the LTC4100 preventing accurate programming currents and voltages. Consult LTC applications department for more information.
DIRECTION OF CHARGING CURRENT RSENSE
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TO CSP AND BAT
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LTC4100
PACKAGE DESCRIPTIO
7.8 - 8.2
0.42 0.03 RECOMMENDED SOLDER PAD LAYOUT
5.00 - 5.60** (.197 - .221)
0.09 - 0.25 (.0035 - .010)
0.55 - 0.95 (.022 - .037)
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
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G Package 24-Lead Plastic SSOP (5.3mm)
(Reference LTC DWG # 05-08-1640)
1.25 0.12 7.90 - 8.50* (.311 - .335) 24 23 22 21 20 19 18 17 16 15 14 13 5.3 - 5.7 7.40 - 8.20 (.291 - .323) 0.65 BSC 1 2 3 4 5 6 7 8 9 10 11 12 2.0 (.079) 0 - 8 0.65 (.0256) BSC 0.22 - 0.38 (.009 - .015) 0.05 (.002)
G24 SSOP 0802
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LTC4100
TYPICAL APPLICATIO
LTC4100 Li-Ion Battery Charger ILIM = 4A/VLIM = 17.4V, Adapter Rating = 2.7A
RCL 0.033 0.5W 1% C9 0.1F 10V R10 13.7k 1% 4 5 11 R11 1.21k 1% R5 6.04k 1% DCIN DCDIV BGATE 19 ITH PGND LTC4100 CSP 21 RSNS 0.025 0.5W, 1% C4 0.01F 25V VSET 18 C5 0.1F 10V 16 15 RTHB 54.9k 1% D1: MBRM140T3 D2-D5: SMALL SIGNAL SCHOTTKY Q1: 1/2 Si4825 Q2: Si4431ADY Q3: Si3456DY SMART BATTERY 3 2 L1 10H 4A Q3 D1 24 R1 4.9k 23 CLN TGATE 1 Q2 C2, C3 10F x 2 25V
15V TO 20V DCIN FROM WALL ADAPTER
C1 0.1F
IDC C8, 0.082F 12 10V, X7R GND 0.1F 17 10V VDD R6, RVLIM 33k 14 VLIM 13 10 3V TO 5.5V 10k SDA D3 D4 SCL D5 9 8 10k D2 6 7 ILIM ACP CHGEN SMBALERT SDA SCL
RELATED PARTS
PART NUMBER LTC1760 LTC1960 LTC1980 LTC4006 DESCRIPTION Smart Battery System Manager Dual Battery Charger/Selector with SPI Interface COMMENTS Autonomous Power Management and Battery Charging for Two Smart Batteries, SMBus Rev 1.1 Compliant. Simultaneous Charge or Discharge of 2 Batteries; DAC Programmable Current and Voltage; Input Current Limiting Maximizes Charge Current
Combination Battery Charger and DC/DC Converter Input Supply Maybe Above or Below Battery Voltage, Up to 8.4V Float Voltage, 24-Pin SSOP Package Small, High Efficiency, Fixed Voltage, Lithium-ion Battery Charger High Efficiency, Programmable Voltage Battery Charger with Termination. High Efficiency, Programmable Voltage/Current Battery Charger Low Loss PowerPath Controller Constant Current/ Constant Voltage Switching Regulator with Termination Timer; AC Adapter Current Limit and SafetySignal Sensor in a Small 16pin Package Complete Charger for 3- or 4-Cell Li-Ion batteries, AC Adapter Current Limit, SafetySignal Sensor and Indicator Outputs. Constant Current/Constant Voltage Switching Regulator; Resistor Voltage/ Current Programming, AC Adapter Current Limit and SafetySignal Sensor Very Low Loss Replacement for Power Supply OR'ing Diodes using Minimal External Components
4100i LT/TP 0703 1K * PRINTED IN USA
LTC4007 LTC4008 LTC4412
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
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Q1 INFET CLP C6, 0.12F 10V, X7R C7, 0.0015F 10V, X7R 20 BAT 22 C4,C5 10F x 2 25V R4 100 10k RTHA 1.13k 1% SafetySignal THA THB
4100 TA02
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2002

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