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19-1488; Rev 0; 7/99
Chemistry-Independent, Level 2 Smart Battery Charger
General Description
The MAX1667 provides the power control necessary to charge batteries of any chemistry. All charging functions are controlled through the Intel System Management Bus (SMBusTM) interface. The SMBus 2-wire serial interface sets the charge voltage and current and provides thermal status information. The MAX1667 functions as a Level 2 charger, compliant with the Duracell/Intel Smart Battery Charger Specification. In addition to the feature set required for a Level 2 charger, the MAX1667 generates interrupts to signal the host when power is applied to the charger or when a battery is installed or removed. Additional status bits allow the host to check whether the charger has enough input voltage, and whether the voltage on or current into the battery is being regulated. This allows the host to determine when lithium-ion (Li+) batteries have completed the charge without interrogating the battery. The MAX1667 is available in a 20-pin SSOP with a 2mm profile height.
____________________________Features
o Charges Any Battery Chemistry: Li+, NiCd, NiMH, Lead Acid, etc. o SMBus 2-Wire Serial Interface o Compliant with Duracell/Intel Smart Battery Charger Specification Rev. 1.0 o 4A, 3A, or 1A (max) Battery Charge Current o 5-Bit Control of Charge Current o Up to 18.4V Battery Voltage o 11-Bit Control of Voltage o 1% Voltage Accuracy o Up to +28V Input Voltage o Battery Thermistor Fail-Safe Protection o Greater than 95% Efficiency o Synchronous Rectifier
MAX1667
________________________Applications
Notebook Computers Personal Digital Assistants Charger Base Stations Phones
PART MAX1667EAP
Ordering Information
TEMP. RANGE -40C to +85C PIN-PACKAGE 20 SSOP
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
CHARGE SOURCE
DCIN
IOUT VL
REF
BST DHI LX VDD DLO PGND INT CS RSENSE BATT+ SCL SMART SDA BATTERY TEMP BATTHOST CONTROLLER SCL SDA INT GND
AGND SEL DACV
CCV
MAX1667
BATT SCL SDA THM
CCI
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products 1
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
ABSOLUTE MAXIMUM RATINGS
DCIN to AGND .......................................................-0.3V to +30V BST to AGND..........................................................-0.3V to +36V BST, DHI to LX..........................................................-0.3V to +6V LX, IOUT to AGND..................................................-0.3V to +30V THM, CCI, CCV, DACV, REF, DLO to AGND .............................................-0.3V to (VL + 0.3V) VL, SEL, INT, SDA, SCL to AGND ............................-0.3V to +6V BATT, CS+ to AGND ..............................................-0.3V to +20V PGND to AGND .....................................................-0.3V to +0.3V SDA, INT Current ................................................................50mA VL Current ...........................................................................50mA Continuous Power Dissipation (TA = +70C) SSOP (derate 8mW/C above +70C) ..........................640mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDCIN = 18V, internal reference, 1F capacitor at REF, 1F capacitor at VL, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) PARAMETER SUPPLY AND REFERENCE DCIN Input Voltage Range DCIN Quiescent Current VL Output Voltage VL Load Regulation VL AC_PRESENT Trip Point REF Output Voltage SWITCHING REGULATOR Oscillator Frequency DHI Maximum Duty Cycle DHI On-Resistance DLO On-Resistance BATT Input Current (Note 1) CS Input Current (Note 1) BATT, CS Input Voltage Range CS to BATT Single-Count Current-Sense Voltage CS to BATT Full-Scale Current-Sense Voltage ChargingCurrent() = 0x0080 (128mA) SEL = VL (4A), ChargingCurrent() = 0x0F80 (3968mA) ChargingVoltage() = 0x3130 (12,592mV) and 0x41A0 (16,800mV) Voltage Accuracy ChargingVoltage() = 0x1060 (4192mV) and 0x20D0 (8400mV) TA = +25C TA = TMIN to TMAX -1.0 -3.0 1.0 3.0 TA = +25C TA = TMIN to TMAX 145 -0.8 -1.0 Not in dropout In dropout High or low High or low VL < 3.2V, VBATT = 12V VL > 5.15V, VBATT = 12V VL < 3.2V, VCS = 12V VL > 5.15V, VCS = 12V 0 5 160 175 0.8 1.0 % 200 96.5 250 97.7 4 5 1 350 1 170 7 8 5 500 5 400 19 300 kHz % A A V mV mV 0 < ISOURCE < 500A 7.5V < VDCIN < 28V, logic inputs = VL 7.5V < VDCIN < 28V, no load ILOAD = 0 to 10mA 3.20 4.055 4 4.096 5.15 7.5 4 5.4 28 6 5.65 100 5.15 4.137 V mA V mV V V CONDITIONS MIN TYP MAX UNITS
2
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Chemistry-Independent, Level 2 Smart Battery Charger
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = 18V, internal reference, 1F capacitor at REF, 1F capacitor at VL, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) PARAMETER ERROR AMPLIFIERS GMV Amplifier Transconductance GMI Amplifier Transconductance GMV Amplifier Maximum Output Current GMI Amplifier Maximum Output Current CCV Clamp Voltage with Respect to CCI CCI Clamp Voltage with Respect to CCV 1.1V < VCCI < 3.5V 1.1V < VCCV < 3.5V 25 25 1.4 0.2 80 200 80 80 200 200 mA/V mA/V A A mV mV CONDITIONS MIN TYP MAX UNITS
MAX1667
TRIP POINTS AND LINEAR CURRENT SOURCES BATT POWER_FAIL Threshold BATT POWER_FAIL Threshold Hysteresis THM THERMISTOR_OR Overrange Trip Point THM THERMISTOR_COLD Trip Point THM THERMISTOR_HOT Trip Point THM THERMISTOR_UR Underrange Trip Point THM THERMISTOR_OR, _COLD, _HOT, _UR Trip Point Hysteresis VIOUT = 0 IOUT Output Current ChargingCurrent() = 0x0001 to 0x007F (127mA) ChargingCurrent() = 0x0000 VIOUT = 17V, ChargingCurrent() = 0x0001 to 0x007F (127mA) IOUT Leakage Current CDAC Current-Setting DAC Resolution VDAC Voltage-Setting DAC Resolution LOGIC LEVELS SDA, SCL Input Voltage Low SDA, SCL Input Voltage High SDA, SCL Input Bias Current SDA Output Low Sink Current VSDA = 0.6V 2.2 -1 6 1 0.8 V V A mA VDCIN = 0, VIOUT = 20V Guaranteed monotonic Guaranteed monotonic 5 11 CURRENT- AND VOLTAGE-SETTING DACs Bits Bits 5 10 5 THM falling THM falling THM falling THM falling 89 74 22 3 BATT rising 93 95 1 91 75.5 23.5 4.5 0.5 7 9 10 93 77 25 6 97 % of VDCIN % of VDCIN % of VREF % of VREF % of VREF % of VREF % of VDCIN mA A mA A
Note 1: When DCIN is less than 4V, VL is less than 3.2V, causing the battery current to be typically 2A (CS plus BATT input current). _______________________________________________________________________________________ 3
Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
ELECTRICAL CHARACTERISTICS
(VDCIN = 18V, internal reference, 1F capacitor at REF, 1F capacitor at VL, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C. Limits over this temperature range are guaranteed by design.) PARAMETER SUPPLY AND REFERENCE DCIN Quiescent Current VL Output Voltage REF Output Voltage SWITCHING REGULATOR Oscillator Frequency DHI Maximum Duty Cycle DHI On-Resistance DLO On-Resistance BATT Input Current (Note 1) CS Input Current (Note 1) CS to BATT Full-Scale Current-Sense Voltage Not in dropout In dropout High or low High or low VL < 3.2V, VBATT = 12V VL < 3.2V, VCS = 12V VSEL = VL, ChargingCurrent() = 0x0F80 (128mA) ChargingVoltage() = 0x3130 (12,592mV), ChargingVoltage() = 0x41A0 (16,800mV) ChargingVoltage() = 0x1060 (4192mV), ChargingVoltage() = 0x20D0 (8400mV) 145 -1.0 -3.0 160 200 96.5 4 5 7 8 5 5 175 1.0 % 3.0 250 310 kHz % A A mV 7.5V < VDCIN < 28V, logic inputs = VL 7.5V < VDCIN < 28V, no load 0 < ISOURCE < 500A 5.15 4.055 4 5.4 6 5.65 4.137 mA V V CONDITIONS MIN TYP MAX UNITS
Voltage Accuracy
TRIP POINTS AND LINEAR CURRENT SOURCES THM THERMISTOR_OR Overrange Trip Point THM THERMISTOR_COLD Trip Point THM THERMISTOR_HOT Trip Point THM THERMISTOR_UR Underrange Trip Point THM THERMISTOR_OR, _COLD, _HOT, _UR Trip Point Hysteresis LOGIC LEVELS SDA, SCL Input Voltage Low SDA, SCL Input Voltage High SDA, SCL Input Bias Current SDA Output Low Sink Current VSDA = 0.6V 2.2 -1 6 1 0.5 V V A mA THM falling THM falling THM falling THM falling 88.5 73.5 21.5 2.5 1 93.5 77.5 25.5 6.5 % of VREF % of VREF % of VREF % of VREF %
4
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Chemistry-Independent, Level 2 Smart Battery Charger
TIMING CHARACTERISTICS (Figures 1 and 2)
(TA = 0C to +85C, unless otherwise noted.) PARAMETER SCL Serial-Clock High Period SCL Serial-Clock Low Period Start-Condition Setup Time Start-Condition Hold Time SDA Valid to SCL Rising-Edge Setup Time, Slave Clocking in Data SCL Falling Edge to SDA Transition SCL Falling Edge to SDA Valid, Master Clocking in Data SYMBOL tHIGH tLOW tSU:STA tHD:STA tSU:DAT tHD:DAT tDV CONDITIONS MIN 4 4.7 4.7 4 250 0 1 TYP MAX UNITS s s s s ns ns s
MAX1667
TIMING CHARACTERISTICS (Figures 1 and 2)
(TA = -40C to +85C, unless otherwise noted. Limits over this temperature range are guaranteed by design.) PARAMETER SCL Serial-Clock High Period SCL Serial-Clock Low Period Start-Condition Setup Time Start-Condition Hold Time SDA Valid to SCL Rising-Edge Setup Time, Slave Clocking in Data SCL Falling Edge to SDA Transition SCL Falling Edge to SDA Valid, Master Clocking in Data SYMBOL tHIGH tLOW tSU:STA tHD:STA tSU:DAT tHD:DAT tDV CONDITIONS MIN 4 4.7 4.7 4 250 0 1 TYP MAX UNITS s s s s ns ns s
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
START CONDITION MOST SIGNIFICANT ADDRESS BIT (A6) CLOCKED INTO SLAVE A5 CLOCKED INTO SLAVE A4 CLOCKED INTO SLAVE A3 CLOCKED INTO SLAVE
SCL
tLOW tHD:STA
tHIGH
SDA
tSU:STA
tSU:DAT
tHD:DAT
tSU:DAT
tHD:DAT
Figure 1. SMBus Serial-Interface Timing--Address
RW BIT CLOCKED INTO SLAVE
ACKNOWLEDGE BIT CLOCKED INTO MASTER
MOST SIGNIFICANT BIT OF DATA CLOCKED INTO MASTER
SCL
SDA
SLAVE PULLING SDA LOW tDV tDV
Figure 2. SMBus Serial-Interface Timing--Acknowledge
6
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
__________________________________________Typical Operating Characteristics
(Circuit of Figure 7, TA = +25C, unless otherwise noted.)
LOAD TRANSIENT (VOLTAGE REGULATION WITH CURRENT LIMIT)
CCV CCI CCI CCV VBATT 10V 5V/div ILOAD 1A 1A/div AVERAGED MEASUREMENT 500s/div VDCIN = 18V ChargingVoltage() = 12,000mV ChargingCurrent() = 1500mA 10V 5V/div AVERAGED MEASUREMENT 1ms/div VDCIN = 18V ChargingVoltage() = 12,000mV ChargingCurrent() = 1500mA CCI CCV
MAX1667TOC01
LOAD TRANSIENT (WITH CHANGE IN REGULATION LOOP)
MAX1667TOC02
CCV CCI
CCV CCI CCV CCI
50mV/div
200mV/div CCI CCV 1.4V
2V
ILOAD VBATT 1A 500mA/div
VL LINE REGULATION
NO LOAD 5.425 5.40 VL (V) VL (V) 5.400 5.35 5.30 5.375 5.25 5.350 0 5 10 15 VDCIN (V) 20 25 30 5.20 0 5
MAX1667 TOC03
VL LOAD REGULATION
VDCIN = 20V 5.45
MAX1667 TOC04
5.450
5.50
10
15
20
25
LOAD CURRENT (mA)
VL vs. TEMPERATURE
5.44 5.43 5.42 VREF (V) VL (V) 5.41 5.40 5.39 5.38 5.37 5.36 5.35 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) 4.06 0 4.07 4.09 VDCIN = 20V
MAX1667 TOC05
VREF LOAD REGULATION
MAX1667 TOC06
5.45
4.11
4.10
4.08
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 LOAD CURRENT (mA)
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7
Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
Typical Operating Characteristics (continued)
(Circuit of Figure 7, TA = +25C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT (VOLTAGE REGULATION)
MAX1667 TOC07 MAX1667 TOC08
VREF vs. TEMPERATURE
4.110 4.105 4.100 VREF (V) 4.095 4.090 4.085 VDCIN = 20V 4.080 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) 100 95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 0
EFFICIENCY vs. BATT VOLTAGE (CURRENT REGULATION)
95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 4000 0 2 4 A: VDCIN = 16V, ILOAD = 2A B: VDCIN = 20V, ILOAD = 2A C: VDCIN = 20V, ILOAD = 600mA 6 8 10 12 14 16 18 C B A
MAX1667 TOC09
A
B
100
D
E
C
A: VDCIN = 20V, VBATT = 17V B: VDCIN = 16V, VBATT = 12.75V C: VDCIN = 20V, VBATT = 12.75V D: VDCIN = 16V, VBATT = 8.5V E: VDCIN = 20V, VBATT = 8.5V 1000 2000 3000
LOAD CURRENT (mA)
BATT VOLTAGE (V)
OUTPUT V-I CHARACTERISTIC (SWITCHING REGULATOR)
DROP IN BATT OUTPUT VOLTAGE (%)
MAX1667 TOC10
OUTPUT V-I CHARACTERISTIC (LINEAR SOURCE)
7 6 IIOUT (mA) 5 4 3
MAX1667 TOC11
0.001
8
0.01
0.1
1.0 VDCIN = 20V ChargingVoltage() = 17,408mV ChargingCurrent() = 1920mA VREF = 4.096V 0 400 800 1200 1600 LOAD CURRENT (mA) 2000
10
2 1 0 0 VDCIN = 20V ChargingVoltage() = 17,408mV ChargingCurrent() = 1 to 127mA 2 4 6 8 10 12 14 16 18 20 VIOUT (V)
100
BATT VOLTAGE ERROR vs. ChargingVoltage() CODE
MAX1667 TOC12
LOAD CURRENT ERROR
VDCIN =20V VBATT = 12.75V MEASURED AT AVAILABLE ChargingCurrent() CODES
MAX1667 TOC13
1.0 0.8 BATT VOLTAGE ERROR (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 ILOAD = 600mA ILOAD = 3mA VDCIN = 20V MEASURED AT AVAILABLE ChargingVoltage() CODES
15
BATT CURRENT ERROR (%)
10
5
0
-5 2k 4k 6k 8k 10k 12k 14k 16k 18k 20k ChargingVoltage() CODE 0 500 1000 1500 2000 2500 3000 3500 4000 CODE
8
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Chemistry-Independent, Level 2 Smart Battery Charger
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 NAME IOUT DCIN VL CCV CCI SEL CS BATT REF AGND INT THM SCL SDA DACV PGND DLO DHI LX BST Linear Current-Source Output Input Voltage for Powering Charger IC Power Supply. 5.4V linear-regulator output from DCIN. Voltage-Regulation-Loop Compensation Point Current-Regulation-Loop Compensation Point Current-Range Selector. Connecting SEL to VL sets a 4A full-scale current. Leaving SEL open sets a 3A full-scale current. Connecting SEL to AGND sets a 1A full-scale current. Current-Sense Positive Input Battery Voltage Input and Current-Sense Negative Input +4.096V Reference Voltage Output or External Reference Input Analog Ground Open-Drain Interrupt Output Thermistor Sense Voltage Input Serial Clock (need external pull-up resistor) Serial Data (need external pull-up resistor) Voltage DAC Output Filtering Point Power Ground Low-Side Power MOSFET Driver Output High-Side Power MOSFET Driver Output Power Connection for the High-Side Power MOSFET Driver Power Connection for the High-Side Power MOSFET Driver FUNCTION
MAX1667
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9
Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
VCC +12V, -12V SYSTEM POWER SUPPLY DC (UNREGULATED) / VBATTERY SYSTEM POWER CONTROL AC
VBATTERY
DC (UNREGULATED)
AC-DC CONVERTER (UNREGULATED)
SYSTEM HOST (SMBus HOST)
SMART BATTERY
SAFETY SIGNAL
MAX1667
SMART BATTERY CHARGER
CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS
CHARGING VOLTAGE/CURRENT REQUESTS CRITICAL EVENTS
SMBus
Figure 3. Typical Single Smart Battery System
Smart Battery Charging System
A smart battery charging system, at a minimum, consists of a smart battery and smart battery charger compatible with the Smart Battery System specifications using Intel's system management bus (SMBus).
Smart Battery System Block Diagrams
A system may use one or more smart batteries. The block diagram of a smart battery charging system shown in Figure 3 depicts a single battery system. This is typically found in notebook computers, video cameras, cellular phones, and other portable electronic equipment. Another possibility is a system that uses two or more smart batteries. A block diagram for a system featuring multiple batteries is shown in Figure 4. The smart battery selector is used to connect batteries to either the smart battery charger or the system, or to disconnect them, as appropriate. For a standard smart battery, the following connections must be made: power (the bat10
tery's positive and negative terminals), SMBus (clock and data), and safety signal (resistance, typically temperature dependent). Additionally, the system host must be able to query any battery in the system so it can display the state of all batteries present in the system. Figure 4 shows a two-battery system where Battery 2 is being charged while Battery 1 is powering the system. This configuration may be used to "condition" Battery 1, allowing it to be fully discharged prior to recharge.
Smart Battery Charger Types
Two types of smart battery chargers are defined: Level 2 and Level 3. All smart battery chargers communicate with the smart battery using the SMBus; the two types differ in their SMBus communication mode and in whether they modify the charging algorithm of the smart battery as shown in Table 1. Level 3 smart battery chargers are supersets of Level 2 chargers and as such support all Level 2 charger commands.
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
VCC +12V, -12V AC SYSTEM POWER SUPPLY DC (UNREGULATED) / VBATTERY NOTE: SB 1 POWERING SYSTEM SB 2 CHARGING AC-DC CONVERTER (UNREGULATED)
SMART BATTERY 1
SMART BATTERY 2
SAFETY
SAFETY
SIGNAL
SIGNAL
SMBus
SMBus
VBATT
VBATT
SMBus SYSTEM HOST (SMBus HOST) SMART BATTERY SELECTOR
MAX1667
SAFETY SIGNAL VCHARGE SMART BATTERY CHARGER
CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS SMBus
Figure 4. Typical Multiple Smart Battery System
Table 1. Charger Type by SMBus Mode and Charge Algorithm Source
SMBus MODE Slave Only Slave/Master CHARGE ALGORITHM SOURCE Battery Level 2 Level 3 Modified from Battery Level 3 Level 3
Note: Level 1 smart battery chargers are defined in the version 0.95a specification. While they can correctly interpret smart battery end-of-charge messages minimizing overcharge, they do not provide truly chemistry-independent charging. They are no longer defined by the Smart Battery Charger specification and are explicitly not compliant with this and subsequent Smart Battery Charger specifications.
Level 2 Smart Battery Charger
The Level 2 or "smart-battery-controlled" smart battery charger interprets the smart battery's critical warning
messages, and operates as an SMBus slave device that responds to ChargingVoltage() and ChargingCurrent() messages sent to it by a smart battery. The charger is obliged to adjust its output characteristics in direct response to the messages it receives from the battery. In Level 2 charging, the smart battery is completely responsible for initiating communication and for providing the charging algorithm to the charger. The smart battery is in the best position to tell the smart battery charger how it needs to be charged. The charging algorithm in the battery may request a static charge condition or may choose to periodically adjust the smart battery charger's output to meet its present needs. A Level 2 smart battery charger is truly chemistry independent, and since it is defined as an SMBus slave device only, it is relatively inexpensive and easy to implement.
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11
Chemistry-Independent, Level 2 Smart Battery Charger
BATT VOLTAGE V0
V0 = VOLTAGE SET POINT I0 = CURRENT-LIMIT SET POINT
control loops can be compensated separately for optimum stability and response in each state. Whether the MAX1667 is controlling the voltage or current at any time depends on the battery's state. If the battery has been discharged, the MAX1667's output reaches the current-regulation limit before the voltage limit, causing the system to regulate current. As the battery charges, the voltage rises until the voltage limit is reached, and the charger switches to regulating voltage. The transition from current to voltage regulation is done by the charger and need not be controlled by the host. Figure 6 shows the MAX1667 block diagram.
MAX1667
Voltage Control
I0 AVERAGE CURRENT THROUGH THE RESISTOR BETWEEN CS AND BATT
Figure 5. Output V-I Characteristic
_______________Detailed Description
Output Characteristics
The MAX1667 contains both a voltage-regulation loop and a current-regulation loop. Both loops operate independently of each other. The voltage-regulation loop monitors BATT to ensure that its voltage never exceeds the voltage set point (V0). The current-regulation loop monitors current delivered to BATT to ensure that it never exceeds the current-limit set point (I0). The current-regulation loop is in control as long as BATT voltage is below V0. When BATT voltage reaches V0, the current loop no longer regulates, and the voltage-regulation loop takes over. Figure 5 shows the V-I characteristic at the BATT pin.
The internal GMV amplifier controls the MAX1667's output voltage. The voltage at the amplifier's noninverting input is set by an 11-bit DAC, which is controlled by a ChargingVoltage() command on the SMBus (see Digital Section for more information). The battery voltage is fed to the GMV amplifier through a 5:1 resistive voltage divider. The set voltage ranges between 0 and 18.416V with 16mV resolution. This allows up to four Li+ cells in series to be charged. The GMV amplifier's output is connected to the CCV pin, which compensates the voltage-regulation loop. Typically, a series-resistor/capacitor combination can be used to form a pole-zero doublet. The pole introduced rolls off the gain starting at low frequencies. The zero of the doublet provides sufficient AC gain at midfrequencies. The output capacitor then rolls off the midfrequency gain to below 1 to guarantee stability before encountering the zero introduced by the output capacitor's equivalent series resistance (ESR). The GMV amplifier's output is internally clamped to between onefourth and three-fourths of the voltage at REF.
Setting V0 and I0
Set the MAX1667's voltage and current-limit set points via the Intel SMBus 2-wire serial interface. The MAX1667's logic interprets the serial-data stream from the SMBus interface to set internal digital-to-analog converters (DACs) appropriately. The power-on-reset value for V0 and I0 is 18.4V and 7mA, respectively. See Digital Section for more information.
Current Control
An internal 7mA linear current source is used in conjunction with the PWM regulator to set the battery charge current. When the current is set to 0, the voltage regulator is on but no current is available. A current setting between 1mA and 127mA turns on the linear current source, providing a maximum of 7mA for trickle charging. For current settings above 127mA, the linear current source is disabled and the charging current is provided by the switching regulator set by the 5-bit current-control DAC. The GMI amplifier's noninverting input is driven by a 4:1 resistive voltage divider, which is driven by the 5-bit DAC. With the internal 4.096V reference, this input is approximately 1.0V at full scale, and the resolution is 31mV. The current-sense amplifier drives the inverting input to the GMI amplifier. It measures the voltage
_____________________Analog Section
The MAX1667 analog section consists of a currentmode pulse-width-modulated (PWM) controller and two transconductance error amplifiers--one for regulating current and the other for regulating voltage. The device uses DACs to set the current and voltage level, which are controlled via the SMBus interface. Since separate amplifiers are used for voltage and current control, both
12
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
REF 10k 10k 10k 10k THERMISTOR_OR IOUT THERM_SHUT THERMISTOR_COLD LOGIC BLOCK THERMISTOR_HOT SDA INT THERMISTOR_UR DCIN VL AC_PRESENT 5.4V LINEAR REGULATOR INTERNAL 4.096V REFERENCE AGND CCV CCV_LOW 3R REF CS BATT CURRENT-SENSE LEVEL SHIFT AND GAIN OF 5.5 REF FROM LOGIC BLOCK 5 5-BIT DAC CCI 3R GMI 3/8 REF = ZERO CURRENT NOTE: APPROX. REF/4 + VTHRESH TO 3/4 REF + VTHRESH NOTE: REF/4 TO 3/4 REF BST LEVEL SHIFT DRIVER DHI R AGND REF SEL SCL THERMAL SHUTDOWN DCIN 7mA
MAX1667
THM
100k AGND
30k
3k
500
R FROM LOGIC BLOCK BATT 4R AGND TO LOGIC BLOCK TO LOGIC BLOCK VOLTAGE_INREG CURRENT_INREG CLAMP MIN CLAMP TO REF (MAX) AGND R REF 11 11-BIT DAC AGND TO LOGIC BLOCK DACV POWER_FAIL DCIN/4.5 GMV CCV AGND FROM LOGIC BLOCK
SUMMING COMPARATOR BLOCK
LX
VL DRIVER FROM LOGIC BLOCK DLO
PGND
Figure 6. Functional Diagram
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13
Chemistry-Independent, Level 2 Smart Battery Charger
across the current-sense resistor (RSEN ) (which is between the CS and BATT pins), amplifies it by approximately 5.45, and level shifts it to ground. The full-scale current is approximately 0.16V/RSEN, and the resolution is 5mV/RSEN. The current-regulation loop is compensated by adding a capacitor to the CCI pin. This capacitor sets the currentfeedback loop's dominant pole. The GMI amplifier's output is clamped to between approximately one-fourth and three-fourths of the REF voltage. While the current is in regulation, the CCV voltage is clamped to within 80mV of the CCI voltage. This prevents the battery voltage from overshooting when the DAC voltage setting is updated. The converse is true when the voltage is in regulation and the current is not at the current DAC setting. Since the linear range of CCI or CCV is about 1.5V to 3.5V (about 2V), the 80mV clamp results in a relatively negligible overshoot when the loop switches from voltage to current regulation or vice versa. perturbations in the pulse width at duty ratios greater than 50%. At heavy loads, the PWM controller switches at a fixed frequency and modulates the duty cycle to control the battery voltage or current. At light loads, the DC current through the inductor is not sufficient to prevent the current from going negative through the synchronous rectifier (Figure 7, M2). The controller monitors the current through the sense resistor RSEN; when it drops to zero, the synchronous rectifier turns off to prevent negative current flow.
MAX1667
MOSFET Drivers
The MAX1667 drives external N-channel MOSFETs to regulate battery voltage or current. Since the high-side N-channel MOSFET's gate must be driven to a voltage higher than the input source voltage, a charge pump is used to generate such a voltage. The capacitor C7 (Figure 7) charges to approximately 5V through D2 when the synchronous rectifier turns on. Since one side of C7 is connected to the LX pin (the source of M1), the high-side driver (DHI) can drive the gate up to the voltage at BST (which is greater than the input voltage) when the high-side MOSFET turns on. The synchronous rectifier may not be completely replaced by a diode because the BST capacitor charges while the synchronous rectifier is turned on. Without the synchronous rectifier, the BST capacitor may not fully charge, leaving the high-side MOSFET with insufficient gate drive to turn on. Use a small MOSFET, such as a 2N7002, to guarantee that the BST capacitor is allowed to charge. In this case, most of the current at high currents is carried by the Schottky diode and not by the synchronous rectifier.
PWM Controller
The battery voltage or current is controlled by the current-mode, PWM, DC-DC converter controller. This controller drives two external N-channel MOSFETs, which switch the voltage from the input source. This switched voltage feeds an inductor, which filters the switched rectangular wave. The controller sets the pulse width of the switched voltage so that it supplies the desired voltage or current to the battery. The heart of the PWM controller is the multi-input comparator. This comparator sums three input signals to determine the pulse width of the switched signal, setting the battery voltage or current. The three signals are the current-sense amplifier's output, the GMV or GMI error amplifier's output, and a slope-compensation signal, which ensures that the controller's internal currentcontrol loop is stable. The PWM comparator compares the current-sense amplifier's output to the lower output voltage of either the GMV or the GMI amplifier (the error voltage). This current-mode feedback corrects the duty ratio of the switched voltage, regulating the peak battery current and keeping it proportional to the error voltage. Since the average battery current is nearly the same as the peak current, the controller acts as a transconductance amplifier, reducing the effect of the inductor on the output filter LC formed by the output inductor and the battery's parasitic capacitance. This makes stabilizing the circuit easy, since the output filter changes from a complex second-order RLC to a first-order RC. To preserve the inner current-control loop's stability, slope compensation is also fed into the comparator. This damps out
14
Internal Regulator and Reference
The MAX1667 uses an internal low-dropout linear regulator to create a 5.4V power supply (VL), which powers its internal circuitry. VL can supply up to 20mA, less than 10mA powers the internal circuitry, and the remaining current can power the external circuitry. The current used to drive the MOSFETs comes from this supply, which must be considered when calculating how much power can be drawn. To estimate the current required to drive the MOSFETs, multiply the total gate charge of each MOSFET by the switching frequency (typically 250kHz). To ensure VL stability, bypass the VL pin with a 1F or greater capacitor. The MAX1667 has an internal, accurate 4.096V reference voltage. This guarantees a voltage-setting accuracy of 1% max. Bypass the reference with a 1F or greater capacitor.
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
10
AGND
IOUT DCIN
1 C9 2 6 R6 3 R5 C6 D2 C11 DC SOURCE D3
C4 9 REF
SEL VL
R3
C10 R4 12 C5 (NOTE 2) D4*
THM
MAX1667
BST 5 C3 LX CCI DHI
20 18
M1
C7 19 D1 L1
7.5V-28V
DLO 4 R2 C2 CCV PGND
17
M2
16
(NOTE 1) C1
CS
7 R1
15 C8
DACV
BATT SCL SDA INT
8 13 14 D5 11
SMBCLOCK
V+
= HIGH-CURRENT TRACES (8A MAX)
SMBDATA
KINT-
NOTE 1: C6, M2, D1, AND C1 GROUNDS MUST CONNECT TO THE SAME RECTANGULAR PAD ON THE LAYOUT. NOTE 2: C5 AND C11 MUST BE PLACED WITHIN 0.5cm OF THE MAX1667, WITH TRACES NO LONGER THAN 1cm HOST & LOAD CONNECTING VL AND PGND. *OPTIONAL (SEE NEGATIVE INPUT VOLTAGE PROTECTION SECTION). SEE TABLES 2a AND 2b FOR COMPONENT SELECTION AND MANUFACTURERS.
GND
-
T
D
C
+
SMART BATTERY STANDARD CONNECTOR
Figure 7. Typical Application Circuit
______________________________________________________________________________________ 15
Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
Table 2a. Component Selection
DESIGNATION C1 Output Capacitor C2, C7, C11 C3 C4, C5, C9, C10 C6 Input Capacitor C8 1N5819 equivalent D1, D4, D5 Schottky Diodes D2, D3 L1 Inductor Motorola Central NIEC Central 33H, 1A ISAT Sumida Coiltronics Coilcraft IR M1 High-Side MOSFET M2 Low-Side MOSFET R1 Sense Resistor R2, R4 R3 R5, R6 Fairchild Motorola Motorola IRC Dale CDH74-330 UP1B-330 DS3316P-333 IRF7603 FDN359A MTSF3N03HD IRF7201 FDS4410 MMDF3N03HD 2N7002 equivalent MMBF1170LT1 40m 1%, 1W LR251201R040F WSL-2512/0.04W/1% 10k 5%, 1/16W 10k 1%, 1/16W 33 5%, 1/16W IRF7805 FDS6680 EC31 MBRS130LT3 AVX Sprague MANUFACTURER AVX Sprague 1A 3A 68F, 20V, low ESR TPSE686M020R0150 594D686X0025R2T 0.1F 47nF 1F 2 x 22F, 35V, low ESR TPSE226M035R0200 594D226X0035R2T 22nF 1N5821 equivalent MBRS340T3 CMSH3-40 NSQ03A04 Schottky diode, 50mA IDC, 30V, CMPSH-3 33H, 3A ISAT, 30V CDRH127-330 UP3B-330 33H, 4A ISAT, 30V CDRH127-270 1N5821 equivalent MBRS340T3 CMSH5-40 CMSH5-40 4A
_____________________Digital Section
SMBus Interface
The MAX1667 uses serial data to control its operation. The serial interface complies with the SMBus specification (see System Management Bus Specification, from the SBS forum at www.sbs-Forum.org or from Intel Architecture Labs: 800-253-3696). Charger functionality complies with the Duracell/Intel Smart Charger Specification for a Level 2 charger.
The MAX1667 uses the SMBus Read-Word and WriteWord protocols to communicate with the battery it is charging, as well as with any host system that monitors the battery to charger communications. The MAX1667 acts only as a slave device and never initiates communication on the bus; it receives commands and responds to queries for status information. Figures 8a and 8b show the SMBus Write-Word and Read-Word protocols. Each communication with the MAX1667 begins with the master issuing a START condition, which is a high-tolow transition on SDA while SCL is high (Figure 1).
16
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Chemistry-Independent, Level 2 Smart Battery Charger
Table 2b. Component Suppliers
MANUFACTURER AVX Central Semiconductor Coilcraft Coiltronics Dale IR IRC NIEC Siliconix Sprague Sumida Zetex PHONE 803-946-0690 516-435-1110 847-639-6400 561-241-7876 605-668-4131 310-322-3331 512-992-7900 805-867-2555 408-988-8000 603-224-1961 847-956-0666 516-543-7100 FAX 803-626-3123 516-435-1824 847-639-1469 561-241-9339 605-665-1627 310-322-3332 512-992-3377 805-867-2698 408-970-3950 603-224-1430 847-956-0702 516-864-7630
To charge a battery that has a thermistor impedance in the HOT range (i.e., THERMISTOR_HOT = 1 and THERMISTOR_UR = 0), the host must use the ChargerMode() command to clear HOT_STOP after the battery is inserted. The HOT_STOP bit returns to its default power-up condition (`1') whenever the battery is removed.
MAX1667
When the master has finished communicating with the slave, the master issues a STOP condition, which is a low-to-high transition on SDA while SCL is high. The bus is then free for another transmission. Figures 1 and 2 show timing diagrams for signals on the SMBus interface. The address byte, control byte, and data bytes are transmitted between the START and STOP conditions. Data is transmitted in 8-bit words, and after each byte either the slave or the master issues an acknowledgment (Figure 2); therefore, nine clock cycles are required to transfer each byte. The SDA state is allowed to change only while SCL is low, except for the START and STOP conditions. The MAX1667 7-bit address is preset to 0b0001001. The eighth bit indicates a Write-Word (W = 0) or a Read-Word (R = 1) command. This can also be denoted by the hexadecimal number 0x12 for a Write-Word command or a 0x13 for a Read-Word command. The following commands use the Write-Word protocol (Figure 8a): ChargerMode(), ChargingVoltage(), ChargingCurrent(), and AlarmWarning(). The ChargerStatus command uses the Read-Word protocol (Figure 8b).
ChargingVoltage() The ChargingVoltage() command uses Write-Word protocol (Figure 8a). The command code for ChargingVoltage() is 0x15 (0b00010101). The 16-bit binary number formed by D15-D0 represents the voltage set point (V0) in millivolts; however, since the MAX1667 has only 16mV of resolution in setting V0, the D0, D1, D2, and D3 bits are ignored. The maximum voltage delivered by the MAX1667 is 18.416V, corresponding to a ChargingVoltage() value of 0x47F0. This is also the floating voltage set by the power-on reset (POR). ChargingVoltage() values above 0x47F0 deliver the floating voltage and set the VOLTAGE_OR status bit. Any time the BATTERY_PRESENT status bit is clear, the ChargingVoltage() register returns to its POR state. Figure 9 shows the mapping between V0 (the voltageregulation-loop set point) and the ChargingVoltage() data. ChargingCurrent() The ChargingCurrent() command uses Write-Word protocol (Figure 8a). The command code for ChargingCurrent() is 0x14 (0b00010100). The 16-bit binary number formed by D15-D0 represents the current-limit set point (I0) in milliamps (Table 4). Connecting SEL to AGND selects a 0.896A maximum setting for I0. Leaving SEL open selects a 2.944A maximum setting for I0. Connecting SEL to VL selects a 3.968A maximum setting for I0. Two sources of current in the MAX1667 charge the battery: a linear current source begins from IOUT, and a switching regulator controls the current flowing through the current-sense resistor (R1). IOUT provides a tricklecharge current to compensate for battery self-discharge, while the switching regulator provides large currents for fast charging. IOUT sources 7mA, while the switching regulator sources from 128mA to 3968mA with a 5-bit resolution (LSB = 5.12mV / RSENSE = 128mA with a 40m sense resistor). In Table 4, DA4-DA0 denotes the bits in the current DAC code. Table 5 shows the relationship between the value programmed with the ChargingCurrent() command and IOUT source current. The CCV_LOW comparator checks to see if the output volt17
ChargerMode() The ChargerMode() command uses Write-Word protocol (Figure 8a). The command code for ChargerMode() is 0x12 (0b00010010). Table 3 describes the functions of the 16 data bits (D0-D15). Bit 0 refers to the D0 bit in the Write-Word protocol.
Whenever the BATTERY_PRESENT status bit (bit 14) of ChargerStatus() is clear, the HOT_STOP bit is set, regardless of any previous ChargerMode() command.
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
Table 3. ChargerMode() Bit Functions
BIT NAME INHIBIT_CHARGE ENABLE_POLLING POR_RESET RESET_TO_ZERO N/A BATTERY_PRESENT_MASK POWER_FAIL_MASK N/A HOT_STOP N/A BIT POSITION* 0 (LSB) 1 2 3 4 5 6 7-9 10 11-15 (MSB) POR VALUE** 0 -- -- -- -- 0 1 -- 1 -- FUNCTION 0 = Allow normal operation; clear the CHG_INHIBITED status bit. 1 = Turn the charger off; set the CHG_INHIBITED status bit. Not implemented. Write 0 into this bit. 0 = No change in any non-ChargerMode() settings. 1 = Change the voltage and current settings to 0xFFFF and 0x0007 respectively; clear the THERMISTOR_HOT and ALARM_INHIBITED bits. Not implemented. Write 0 into this bit. Not implemented. Write 1 into this bit. 0 = Interrupt on either edge of the BATTERY_PRESENT status bit. 1 = Do not interrupt because of a BATTERY_PRESENT bit change. 0 = Interrupt on either edge of the POWER_FAIL status bit. 1 = Do not interrupt because of a POWER_FAIL bit change. Not implemented. Write 1 into this bit. 0 = The THERMISTOR_HOT status bit does not turn the charger off. 1 = THERMISTOR_HOT turns the charger off. Not implemented. Write 1 into this bit.
*Bit position in the D15-D0 data. **Power-on reset value. N/A = Not applicable
age is too high by comparing CCV to REF/4. If CCV_LOW = 1 (when CCV < REF/4), IOUT shuts off. This prevents the output voltage from exceeding the voltage set point specified by the ChargingVoltage() register. VOLTAGE_NOTREG = 1 whenever the internal clamp pulls down on CCV. (The internal clamp pulls down on CCV to keep its voltage close to CCI's voltage.) With the switching regulator on, the current through R1 (Figure 7) is regulated by sensing the average voltage between CS and BATT. Figure 10 shows the relationship between the ChargingCurrent() data and the average voltage between CS and BATT. When the switching regulator is off, DHI is forced to LX and DLO is forced to ground. This prevents current from flowing through inductor L1. Table 6 shows the relationship between the ChargingCurrent() register value and the switching regulator current DAC code (DA4-DA0). To ensure that the actual output current matches the data value programmed with the ChargingCurrent() command, R1 should be as close as possible to 40m. The SEL pin setting affects the full-scale current but not the step size. ChargingCurrent() values above the full18
scale setting set the CURRENT_OR status bit. Note that whenever any current DAC bits are set, the linear-current source is turned off. The power-on reset value for the ChargingCurrent() register is 0x0007. Any time the BATTERY_PRESENT status bit is clear (battery removed), the ChargingCurrent() register returns to its power-on reset state. This ensures that upon insertion of a battery, the initial charging current is 7mA.
AlarmWarning() The AlarmWarning() command uses Write-Word protocol (Figure 8a). The command code for AlarmWarning() is 0x16 (0b00010110). The AlarmWarning() command sets the ALARM_INHIBITED status bit. The MAX1667 responds to the following alarms: OVER_CHARGED_ALARM (D15), TERMINATE_CHARGE_ALARM (D14), and OVER_TEMP_ ALARM (D12). Table 7 summarizes the AlarmWarning() command's function. The ALARM_INHIBITED status bit remains set until BATTERY_PRESENT = 0 (battery removed), a ChargerMode() command is written with the POR_RESET bit set, or a new ChargingVoltage() or ChargingCurrent() is written.
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
a) Write-Word Format
S SLAVE ADDRESS 7 bits MSB LSB Preset to 0b0001001 W 1b 0 ACK 1b COMMAND ACK BYTE 8 bits MSB LSB ChargerMode() = 0x12 ChargingCurrent() = 0x14 ChargerVoltage() = 0x15 AlarmWarning() = 0x16 1b S LOW DATA BYTE 7 bits MSB LSB D7 D0 ACK 1b HIGH DATA BYTE 8 bits MSB LSB D15 D8 ACK 1b P
b) Read-Word Format
S SLAVE ADDRESS 7 bits MSB LSB Preset to 0b0001001 W 1b 0 ACK 1b COMMAND ACK BYTE 8 bits MSB LSB ChargerStatus() = 0x13 1b S SLAVE ADDRESS 7 bits MSB LSB Preset to 0b0001001 R 1b 1 ACK 1b D7 LOW DATA BYTE 8 bits MSB LSB D0 ACK 1b HIGH DATA BYTE 8 bits MSB LSB D15 D8 NACK 1b P
Legend: S = Start Condition or Repeated Start Condition ACK = Acknowledge (logic low) W = Write Bit (logic low) MASTER TO SLAVE SLAVE TO MASTER
P = Stop Condition NACK = NOT Acknowledge (logic high) R = Read Bit (logic high)
Figure 8. SMBus a) Write-Word and b) Read-Word Protocols
ChargerStatus() The ChargerStatus() command uses Read-Word protocol (Figure 8b). The command code for ChargerStatus() is 0x13 (0b00010011). The ChargerStatus() command returns information about thermistor impedance and the MAX1667's internal state. The Read-Word protocol returns D15-D0. Table 8 describes the meaning of the individual bits. The latched bits, THERMISTOR_HOT and ALARM_INHIBITED, are cleared whenever BATTERY_PRESENT = 0 or ChargerMode() is written with POR_RESET = 1.
or cleared via the ChargerMode() command. INT stays low until the interrupt is cleared. There are two methods for clearing the interrupt: issuing a ChargerStatus() command, and using a modified Receive Byte protocol with a 0x19 (0b0011001) Alert-Response address. The MAX1667 responds to the Alert-Response address with its address (0x13) left justified as the most significant bits of the returned byte.
__________Applications Information
Negative Input Voltage Protection
In most portable equipment, the DC power to charge batteries enters through a two-conductor cylindrical power jack. It is easy for the end user to add an adapter to switch the DC power's polarity. Polarized capacitor C6 would be destroyed if a negative voltage were applied. Diode D4 in Figure 7 prevents this from happening.
19
Interrupts and the Alert-Response Address
An interrupt is triggered (INT goes low) whenever power is applied to DCIN, the BATTERY_PRESENT bit changes, or the POWER_FAIL bit changes. BATTERY_PRESENT and POWER_FAIL have interrupt masks that can be set
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
18.416V 16.368V VREF = 4.096V DCIN > 20V
12.592V
VOLTAGE SET POINT (V0)
8.400V
4.192V
0V 0b000000000000xxxx 0x000x 0b000100000110xxxx 0x106x 0b001000001101xxxx 0x20Dx 0b001100010011xxxx 0x313x 0b010010100000xxxx 0x47Fx 0b111111111111xxxx 0xFFFx
ChargingVoltage() D15-D0 DATA
Figure 9. ChargingVoltage() Data to Voltage Mapping
160 AVERAGE CS-BATT VOLTAGE IN CURRENT REGULATION (mV) 115
SEL = VL SEL = OPEN 1000
RESISTANCE (k)
100
10
35 5 A: 0x0080 0x0380 B: (128) (896) C: 0b00001 0b00111
SEL = GND
1 0x0B80 0x0F80 0xFFFF (2944) (3968) (65535) 0b10111 0b11111
0.1 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 TEMPERATURE (C)
A: ChargingCurrent( ) CODE (D15-D0) B: EQUIVALENT DECIMAL CODE C: CURRENT DAC CODE (DA4-DA0)
Figure 10. Average Voltage Between CS and BATT vs. Code
20
Figure 11. Typical Thermistor Characteristics
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Chemistry-Independent, Level 2 Smart Battery Charger
Table 4. ChargingCurrent() Bit Functions
BIT POSITION FUNCTION WEIGHT IN mA (RSENSE = 40m) D15 D14 D13 D12 D11 FS* 3968* DA4 D10 DA3 D9 DA2 512 D8 DA1 256 D7 DA0 128 D6 D5 D4 D3 IOUT** 7** D2 D1 D0
MAX1667
2048 1024
* When SEL = VL, values above 0x0F80 set the output current to 3.968A. When SEL = OPEN, values above 0x0B80 set the output current to 2.944A. When SEL = GND, values above 0x0380 set the output current to 0.896A. ** Values below 0x0080 set the output current to 7mA.
Table 5. Relationship Between IOUT Source Current and ChargingCurrent() Value
CHARGE_ INHIBITED 0 0 0 0 0 0 0 0 0 0 0 1 (Note 1) 0 0 0 0 0 0 0 0 0 0 1 x ALARM_ INHIBITED 0 0 0 0 0 0 0 0 0 1 x x ChargingVoltage() 0x0000-0x000F x 0x0010-0xFFFF 0x0010-0xFFFF 0x0010-0xFFFF 0x0010-0xFFFF 0x0010-0xFFFF 0x0010-0xFFFF x0x0010-0xFFFF x x x ChargingCurrent() x 0x0000 0x0001-0x0007 0x0001-0x0007 0x0001-0x0007 0x0008-0x007F 0x0008-0x007F 0x0008-0x007F 0x0080-0xFFFF x x x CCV_LOW x x 0 1 1 0 1 1 x x x x VOLTAGE_ NOTREG x x x 0 1 x 0 1 x x x x IOUT OUTPUT CURRENT (mA) 0 0 7 0 7 7 0 7 0 0 0 0
Note 1: THERMISTOR_HOT and HOT_STOP and NOT (THERMISTOR_UR).
If reverse-polarity protection for the DC input power is not necessary, diode D4 can be omitted. This eliminates the power lost due to the voltage drop on diode D4.
Thermistor Characterization
Figure 11 represents the expected electrical behavior of a 103ETB-type thermistor (nominally 10k at +25C 5% or better) to be used with the MAX1667. The graph is typical of the suggested thermistor's characteristics. THERMISTOR_OR bit is set only when the thermistor value is > 100k. This indicates that the thermistor is open. THERMISTOR_COLD bit is set only when the thermistor value is > 30k. The thermistor indicates a cold battery.
THERMISTOR_HOT bit is set only when the thermistor value is < 3k. THERMISTOR_UR bit is set only when the thermistor value is < 500. Multiple bits may be set depending on the values of the thermistor (e.g., a 450 thermistor will cause both the THERMISTOR_HOT and the THERMISTOR_UR bits to be set). The thermistor may be replaced by fixed-value resistors in battery packs that do not require the thermistor as a secondary fail-safe indicator. In this case, it is the responsibility of the battery pack to manipulate the resistance to obtain correct charger behavior.
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21
Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
Table 6. Relationship Between Current DAC Code and the ChargingCurrent() Value
SEL = GND CURRENT DAC CODE SEL = OPEN CURRENT DAC CODE SEL = VL CURRENT DAC CODE
CHARGE_INHIBITED
ALARM_INHIBITED
ChargingVoltage()
ChargingCurrent()
SEL = GND CURRENT_OR
SEL = OPEN CURRENT_OR
0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 1 x
0 0 0 0 0 0 0 0 0 0 0 0 1 x x
0x0000-0x000F 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF 0x000F-0xFFFF x x x
x 0x0000-0x007F 0x0080-0x00FF 0x0100-0x037F 0x0380-0x03FF 0x0400-0x047F 0x0480-0x0B7F 0x0B80-0x0BFF 0x0C00-0x0C7F 0x0C80 0x0F80-0x0FFF 0x1000-0xFFFF x x x
N/A 0 1 2-6 7 7 7 7 7 7 7 7 N/A N/A N/A
No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No
0 0 0 0 0 1 1 1 1 1 1 1 N/A N/A N/A
N/A 0 1 2-6 7 8 9-22 23 23 23 23 23 N/A N/A N/A
No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No
0 0 0 0 0 0 0 0 1 1 1 1 N/A N/A N/A
N/A 0 1 2-6 7 8 9-22 23 24 25-30 31 31 N/A N/A N/A
No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No
Note 1: THERMISTOR_HOT and HOT_STOP and NOT (THERMISTOR_UR).
Table 7. Effect of the AlarmWarning() Command
AlarmWarning() DATA BITS D15 D14 D13 D12 D11 1 x x x 1 x x x x x x 1 x x x D10 x x x D9 x x x D8 x x x D7 x x x D6 x x x D5 x x x D4 x x x D3 x x x D2 x x x D1 x x x D0 x x x RESULT Set ALARM_INHIBITED Set ALARM_INHIBITED Set ALARM_INHIBITED
22
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SEL = VL CURRENT_OR 0 0 0 0 0 0 0 0 0 0 0 1 N/A N/A N/A
SEL = GND SW REG ON?
SEL = OPEN SW REG ON?
SEL = VL SW REG ON?
(Note 1)
Chemistry-Independent, Level 2 Smart Battery Charger
Table 8. ChargerStatus() Bit Descriptions
NAME CHARGE_INHIBITED MASTER_MODE VOLTAGE_NOTREG CURRENT_NOTREG LEVEL_2 LEVEL_3 CURRENT_OR VOLTAGE_OR THERMISTOR_OR THERMISTOR_COLD BIT POSITION 0 1 2 3 4 5 6 7 8 9 LATCHED? Yes N/A No No N/A N/A No No No No DESCRIPTION 0 = Ready to charge a smart battery 1 = Charger is off; IOUT current = 0mA; DLO = PGND; DHI = LX Always returns `0' 0 = BATT voltage is limited at the voltage set point (BATT = V0). 1 = BATT voltage is less than the voltage set point (BATT < V0). 0 = Current through R1 is at its limit (IBATT = I0). 1 = Current through R1 is less than its limit (IBATT < I0). Always returns 1 Always returns 0 0 = ChargingCurrent() value is valid for MAX1667. 1 = ChargingCurrent() value exceeds what MAX1667 can actually deliver. 0 = ChargingVoltage() value is valid for MAX1667. 1 = ChargingVoltage() value exceeds what MAX1667 can actually deliver. 0 = THM voltage < 91% of REF voltage 1 = THM voltage > 91% of REF voltage 0 = THM voltage < 75% of REF voltage 1 = THM voltage > 75% of REF voltage This bit reports the state of an internal SR flip-flop (denoted THERMISTOR_HOT flip-flop). The THERMISTOR_HOT flip-flop is set whenever THM is below 23% of REF. It is cleared whenever BATTERY_PRESENT = 0 or ChargerMode() is written with POR_RESET = 1. 0 = THM voltage > 5% of REF voltage 1 = THM voltage < 5% of REF voltage This bit reports the state of an internal SR flip-flop (denoted ALARM_INHIBITED flip-flop). The ALARM_INHIBITED flip-flop is set whenever the AlarmWarning() command is written with D15, D14, or D12 set. The ALARM_INHIBITED flip-flop is cleared whenever BATTERY_PRESENT = 0, or ChargerMode() is written with POR_RESET = 1, or ChargingVoltage() or ChargingCurrent() is written. 0 = BATT voltage < 89% of DCIN voltage 1 = BATT voltage > 89% of DCIN voltage 0 = No battery is present (THERMISTOR_OR = 1). 1 = A battery is present (THERMISTOR_OR = 0). 0 = VL voltage < 4V 1 = VL voltage > 4V
MAX1667
THERMISTOR_HOT
10
Yes
THERMISTOR_UR
11
No
ALARM_INHIBITED
12
Yes
POWER_FAIL BATTERY_PRESENT AC_PRESENT
13 14 15
No No No
*Bit position in the D15-D0 data N/A = Not applicable
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23
Chemistry-Independent, Level 2 Smart Battery Charger
HIGH-CURRENT PATH
SENSE RESISTOR
MAX1667
Figure 12. Kelvin Connections for the Current-Sense Resistors
PC Board Layout Considerations
Good PC board layout is required to achieve specified noise, efficiency, and stable performance. The PC board layout artist must be given explicit instructions, preferably a pencil sketch showing the placement of power-switching components and high-current routing. Refer to the PC board layout in the MAX1667 evaluation kit manual for examples. A ground plane is essential for optimum performance. In most applications, the circuit will be located on a multilayer board, and full use of the four or more copper layers is recommended. Use the top layer for high-current connections, the bottom layer for quiet connections (REF, CCV, CCI, DACV, GND), and the inner layers for an uninterrupted ground plane. Use the following step-by-step guide: 1) Place the high-power components (C1, C6, M1, M2, D1, L1, and R1) first, with their grounds adjacent: * Minimize current-sense resistor trace lengths and ensure accurate current sensing with Kelvin connections (Figure 12). * Minimize ground trace lengths in the high-current paths. * Minimize other trace lengths in the high-current paths: -- Use > 5mm-wide traces. -- Connect CIN to high-side MOSFET drain: 10mm max length. -- Connect rectifier diode cathode to low side. -- MOSFET: 5mm max length. -- LX node (MOSFETs, rectifier cathode, inductor): 15mm max length.
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Ideally, surface-mount power components are butted up to one another with their ground terminals almost touching. These high-current grounds are then connected to each other with a wide, filled zone of top-layer copper so they do not go through vias. The resulting top-layer subground plane is connected to the normal inner-layer ground plane at the output ground terminals, which ensures that the IC's analog ground is sensing at the supply's output terminals without interference from IR drops and ground noise. Other high-current paths should also be minimized, but focusing primarily on short ground and current-sense connections eliminates about 90% of all PC board layout problems. 2) Place the IC and signal components. Keep the main switching nodes (LX nodes) away from sensitive analog components (current-sense traces and REF capacitor). Place the IC and analog components on the opposite side of the board from the powerswitching node. Important: The IC must be no further than 10mm from the current-sense resistors. Keep the gate-drive traces (DH, DL, and BST) shorter than 20mm and route them away from CSH, CSL, and REF. Place ceramic bypass capacitors close to the IC. The bulk capacitors can be placed further away. 3) Use a single-point star ground where the input ground trace, power ground (subground plane), and normal ground plane meet at the supply's output ground terminal. Connect both IC ground pins and all IC bypass capacitors to the normal ground plane.
MAX1667
Upgrading from MAX1647 to MAX1667
The MAX1667 is a pin- and software-compatible upgrade to the MAX1647, with the following functional differences: 1) The PWM duty cycle has been extended to 97%. 2) The internal reference has been changed to +4.096V with 1% accuracy over line, load, and temperature. 3) The internal voltage DAC has been changed to allow a program voltage of 18,416mV. Up to four Li+ cells can be charged. 4) The linear current source (IOUT) has been reduced to 7mA and turns off when the switching regulator is on. 5) An internal diode has been added to the IOUT pin to prevent reverse current from BATT when the DC source is removed. 6) The internal current DAC was changed from 6-bit to 5-bit resolution.
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Chemistry-Independent, Level 2 Smart Battery Charger
7) The SEL pin digitally limits the output current to 4A, 3A, or 1A without a change in sense resistor value between the three modes. 8) The single count current-sense voltage has been changed to 5mV. R1 required is now 40m. 9) After the AlarmWarning() message, the charger is not locked off. Subsequent ChargingVoltage() or ChargingCurrent() commands allow the MAX1667 to resume the charge. 10) The Alert-Response address is 0x13 (0b00010011). When upgrading a MAX1647 design, follow these recommended or required changes (part numbers refer to Figure 3 of the MAX1647 data sheet): 1) Change R1 to 40m (required). 2) Remove diodes D5 and D6, transistor Q1, and resistor R6. Connect IOUT directly to BATT (recommended). 3) Remove the external +4.096V reference (recommended). 4) Remove D6 (recommended). When doing this, also place a small-signal diode in series with R7 and connect it directly to the DC source (see D3 and R5 on Figure 3 of the MAX1647 data sheet).
Pin Configuration
TOP VIEW
IOUT 1 20 BST 19 LX 18 DHI 17 DLO DCIN 2 VL 3 CCV 4 CCI 5
MAX1667
MAX1667
16 PGND 15 DACV 14 SDA 13 SCL 12 THM 11 INT
SEL 6 CS BATT REF 7 8 9
AGND 10
SSOP
Chip Information
TRANSISTOR COUNT: 6378 SUBSTRATE CONNECTED TO AGND
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
________________________________________________________Package Information
SSOP.EPS
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
NOTES
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Chemistry-Independent, Level 2 Smart Battery Charger MAX1667
NOTES
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
28 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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