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Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer
POWER MANAGEMENT Description
The SC804A is a fully integrated full-feature, single cell constant-current/constant-voltage (CC/CV) 4.4V LithiumIon battery charger. With an integrated timer and complete charge control algorithm, the SC804A is ideal for stand-alone charger applications. The SC804A contains programmable pre-charge, fast-charge and termination current settings. The SC804A can be programmed to terminate charging based on the output current or the time-out of the programmable timer. The fast charge current is typically set with an external resistor, but it can also be adjusted by applying an analog voltage to the AFC pin. This feature allows use of a microcontroller to set charging current via a DAC output. The SC804A's 14V input voltage range eliminates the need for additional protection circuitry required by other 5V chargers to protect against faulty adapters. The SC804A also incorporates an under-voltage lockout falling threshold of 3V so that charging will continue if the input supply goes into a current-limited mode. Reference ground and battery sense inputs are provided to eliminate voltage drops during charging due to high charging currents. The output voltage to the battery is controlled to within 1% of the programmed voltage. The SC804A can also function Application purpose current source or as a Typical as a general Circuit current source for charging nickel-cadmium (NiCd) and nickel-metal-hydride (NiMH) batteries.
SC804A
PRELIMINARY Features
Fully integrated charger with FET pass transistor, reverse-blocking diode, sense resistor, timer, and thermal protection Battery voltage controlled to 1% accuracy Programmable precharge, fastcharge & termination current over wide range, with analog current control reference input for design flexibility Up to 1.5A continuous charge current Input voltage range from 3V to 14V Soft-start reduces start-of-charge adapter load transients NTC thermistor sense input and adjustable cold temperature threshold Adjustable 2 - 6 hour programmable charge timer 0.1A battery drain current in shutdown and monitor modes Small 4mm x 4mm 16 lead MLPQ package Over-current protection in all modes Over-voltage protection Remote Kelvin sensing at the battery terminals Status indicators for charger-present, charger-active, over-voltage fault, and error notification
Applications
Cellular phones PDAs Handheld meters Charging stations Handheld computers Digital cameras Programmable current source
Typical Application Circuit
Charger VIN OV_FLT 14 R3 VCC CPB 13 OVPB CHRGB 3 IPRGM RTIM 7 CTO NTC 4 BSEN ITERM 8 VOUT FLTB 6 VOUT GND 5 AFC RGND SC804A DAC ISET
11 10 12 2 1 16 15 9 Red Green
C1 2.2 F
RT NTC R1 R2
R5 Battery C2 2.2F R4
R6
ERROR
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SC804A
POWER MANAGEMENT Absolute Maximum Ratings
Parameter VCC, CTO, NTC to GND VOUT, BSEN, RTIM, AFC, IPRGM, CPB, CHRGB, OVPB, ITERM, FLTB, to GND RGND to GND VOUT Output Current Power Dissipation MLP (Derate 20mW/C above 85C) Thermal Impedance, Junction to Ambient(1) Junction Temperature Operating Ambient Temperature Range IR Reflow Temperature Storage Temperature Range VOUT short to GND ESD Protection Level(2) VESD IVOUT Pd JA TJ TA TLEAD TSTG Symbol Maximum -0.3 to 14.0 -0.3 to +6.0 -0.3 to 0.3 1.5 2 48 150 -40 to +85 260 -65 to 150 Continuous 2 kV
PRELIMINARY DRAFT
Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied.
Units V V V A W C/W C C C C
Notes: 1) Calculated from package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. 2) Tested according to JEDEC standard JESD22-A11 4-B.
Electrical Characteristics
Unless otherwise noted: VCC = 4.75V - 5.25V. Typical values are at TA = 25C Min and Max are for -40C < TA < +85C unless noted.
Parameter Operating Voltage VCC UVLO Rising Threshold VCC UVLO Falling Threshold VCC OVP Rising Threshold VCC OVP Falling Threshold VCC OVP Hysteresis
Symbol VCCOP VTUVLOR VTUVLOF VTOVPR VTOVPF VTOVPH ICCDIS
Conditions
Min 4.28
Typ 5.0 4.08 3.06 6.94 6.63 350 1.9
Max 6.22(1) 4.28 3.26 7.40 7.00 600
Units V V V V V mV
Charging begins when threshold is exceeded Charging continues until threshold is reached
3.88 2.86 6.63 6.22 200
Operating Current ICCCHG
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Shutdown Mode - CHRGB, CPB, OVPB, FLTB off NTC = 0V Charging Mode - CHRGB, CPB, OVPB, FLTB off NTC = 2.5V
2
mA 2.0
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SC804A
POWER MANAGEMENT Electrical Characteristics (Cont.)
Parameter Battery Leakage Current (VOUT and BSEN) Regulated Constant Voltage RGND Output Accuracy VOUT = VOUTNOM + RGND RGND Current Battery Pre-Charge Current Battery Termination Current Battery Fast-Charge Current AFC DAC Fast-Charge Current AFC Enable/Disable Threshold ITERM Regulated Voltage IPROG Regulated Voltage VBAT Precharge Threshold VBAT Recharge Threshold Over-Temperature Shutdown Symbol ILEAKBAT VCV VRGND IRGND IPREQ ITERM IFAST IDACADJ VTAFC VITERM VIPRGM VTPreQ VTReQ TOT 0C TJ 125C VCV - VBSEN, 0C TA 85C Hysteresis = 10C Conditions VCC = 0V, VOUT = BSEN = 4.5V 0C TJ 125C RGND - GND = 30mV RGND = 0V RITERM = 499, 0C TJ 125C RITERM = 499, 0C TJ 125C RPRGM = 1.87k, VOUT = 3.8V 0C TJ 125C RPRGM = 1.87k, V(AFC) = 0.75V 0C TJ 125C VCC - VAFC > VTAFC disables Analog Fast Charge 1.45 1.45 2.9 60 270 270 753 364 4.314 22 Min Typ 0.1 4.357 30 35 300 300 815 405 1 1.557 1.557 3.01 100 150 1.66 1.66 3.11 140 330 330 878 447
PRELIMINARY DRAFT
Max 2 4.40 38 Units A V mV A mA mA mA mA V V V V mV C
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SC804A
POWER MANAGEMENT Electrical Characteristics (Cont.)
Parameter Symbol VTNTCDIS Conditions SC804A Disabled NTC Hot VTH Applies to falling threshold 4.3V VCC 6.5V at VCC = 5V NTC Cold VTH, VCTO = 0V Applies to rising threshold 4.3V VCC 6.5V at VCC = 5V NTC Hot & Cold VTNTCx hysteresis (VTNTCx Rising - VTNTCx Falling) Applies to internal NTC thresholds CTO Voltage (Adjustable NTC Cold Rising Threshold) Setting Range(2), -40C TA 25C (NTC Cold Rising Threshold is VTNTCC when CTO tied to GND) Threshold Error(3), -40C TA 25C VTCTOHYS Internal hysteresis on CTO (VCTO Rising - VCTO Falling) Applies to externally set NTC cold threshold 3.5V VOUT VCC - 150mV 0C TJ 125C 3.5V VOUT VCC - 150mV 3.5V VOUT VCC - 150mV RRTIM = 37.4k VRTIM VTTIMER disables internal timer VCC-VRTIM > VTINTTS selects internal timer 150 1.450 0.65 1.557 0.85 1.1 1.660 3.189 Min 0.3 29 1.45 73.4 3.67 Typ 0.6 30 1.50 74.4 3.72
PRELIMINARY DRAFT
Max 0.8 31 1.55 75.4 3.77 Units V % of VCC V % of VCC V
VTNTCH
VTNTCC
NTC Thresholds
VTNTCHYS
50
mV
50
90
VCTO
% of VCC
-70
70
mV
50
mV
Adjust Mode BSEN Voltage Adjust Mode Enable Voltage, VOUT-BSEN Adjust Mode Disable Voltage, VOUT-BSEN External RTIM Regulation Voltage Timer Disable Threshold Internal Timer Select
VBSEN-ADJ VADJEN VADJDIS VRTIM VTTIMER VTINTTS
3.217
3.253 400
V mV mV V V V
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SC804A
POWER MANAGEMENT Electrical Characteristics (Cont.)
Parameter Pre-Charge Fault Time-out Complete Charge Time-out CHRGB On CHRGB Off CPB On CPB Off OVPB On OVPB Off FLTB On FLTB Off Symbol TPreQF TQCOMP VCHRGB ICHRGB VCPB ICPB VOVPB IOVPB VFLTB IFLTB Conditions RRTIM = 37.4k RTIM pulled to VCC RRTIM = 37.4k RTIM pulled to VCC Load = 5mA Leakage Current, V = 5V Load = 5mA Leakage Current, V = 5V Load = 5mA Leakage Current, V = 5V Load = 5mA Leakage Current, V = 5V 0.5 0.5 0.5 Min -20% -35% -20% -35% Typ 51 44 3.37 2.89 0.5
PRELIMINARY DRAFT
Max +20% +35% +20% +35% 1 1 1 1 1 1 1 1 Units min hr V A V A V A V A
Notes: 1) VCC_OP Max is the "Maximum Vsupply" as defined in EIA/JEDEC Standard No. 78, paragraph 2.11. 2) The absolute voltage on CTO must not exceed 6.0V to ensure normal operation. 3) The threshold error is tested at VCTO min and max only.
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SC804A
POWER MANAGEMENT Pin Configuration
OVPB VOUT VOUT VCC
PRELIMINARY Ordering Information DRAFT
DEVICE SC804AMLTRT(1) SC804EVB PACKAGE MLPQ -16(2) Evaluation Board
(2)
16
BSEN
15
14
13 12 11 10
RTIM
1 2 3 4 5
RGND
TOP VIEW
CTO
CPB CHRGB
IPRGM ITERM
T 6
GND
9 7
NTC
AFC
8
FLTB
Notes: 1) Available in tape and reel packaging only. A reel contains 3000 devices. 2) Available in lead-free packaging only. This product is fully WEEE and RoHS compliant.
MLPQ16: 4X4 16 LEAD
Pin Descriptions
Pin # 1 2 3 4 5 6 Pin Name BSEN CTO IPRGM ITERM RGND GND Pin Function Battery voltage sense. Connect to battery positive terminal for Kelvin voltage sensing, VOUT otherwise. Do not leave open. Cold Temperature Offset. Adjustable NTC input high voltage (cold temperature) threshold. When the pin is connected to GND the NTC high voltage threshold defaults to VTNTCCxVVCC. Charger current program pin for fast-charge mode. Requires a resistor to GND to program fast-charge current. Charger termination current program pin. Requires a resistor to GND to program pre-charge and termination current. Reference ground. Connect to battery's negative terminal for Kelvin voltage sensing, GND otherwise. Do not leave open. Ground. Input for battery NTC thermistor network. Voltage between VTNTCHxVVCC, normally the hot threshold, and the CTO voltage (VTNTCCxVVCC if CTO is tied to GND), normally the cold threshold, enables charging. Voltages outside this range suspend charging and drive FLTB pin active (low). Voltage below VTNTCDIS (nominally 0.6V) disables the SC804A and resets the charge timer (with FLTB pin inactive). Open drain fault indicator. Active low when a fault condition occurs. Analog Fast Charge input. Connect to a DAC for analog control of fast charge current level, connect to VCC to disable this feature. Do not leave open. Open drain charge status indicator. Active low when the charger is on and the output current exceeds the termination current setting, high impedance when IVOUT < ITERM. Open drain charger-present indicator. Active low when VCC exceeds UVLO. Programmable timer input pin. Connect to VCC to select the default time-out of 3 hrs., connect to GND to disable timer, or connect an external resistor to GND to program the time-out period. Open drain over-voltage indicator. Active low when an input over-voltage fault occurs. Input supply pin. Connect to adapter power. Charger output. Connect to battery. Charger output. Connect to battery. Thermal-conduction pad on bottom of the package. Solder directly to the ground plane with multiple thermal vias to all other ground planes.
7
NTC
8 9 10 11 12 13 14 15 16 T
FLTB AFC CHRGB CPB RTIM OVPB VCC VOUT VOUT THERMAL PAD
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SC804A
POWER MANAGEMENT Block Diagram PRELIMINARY DRAFT
14 VCC BSEN 1 VCV (VBSEN-ADJ in Adj. Mode) AFC 9 Reference Voltages Fast-Charge Ref Pre - Charge Ref RGND 5
VT NTCC VT NTCH
CTO
2
Cold Threshold Offset Control
Pre-Charge On Fast-Charge On Over-Temp Under-Voltage Over-Voltage
15 VITERM 16
VOUT VOUT
GND
6
NTC
7
NTC Interface
Timer
4 3 VIPRGM
ITERM IPRGM
RTIM
12
CHRGB 10
8
FLTB
CPB
11
13
OVPB
Figure 1 - SC804A Functional Block Diagram
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SC804A
POWER MANAGEMENT Applications Information
General Operation
The SC804A can be configured independently with respect to fast-charge and termination current, output voltage, and timing, depending on the application. A typical charging cycle is described below. Details on alternative applications and output programmability are covered in the individual sections. The charging cycle begins when the power adapter is connected to the device. The SC804A performs glitch filtering on the VCC input and initiates a charge cycle when VVCC is greater than the under-voltage lockout (UVLO) rising threshold voltage. If the battery voltage is less than the pre-charge threshold level, the SC804A will output the pre-charge current. Once the pre-charge threshold voltage is exceeded, the SC804A enters fast-charge constant current (CC) mode. When the battery voltage reaches its final value, the charger enters the constant voltage (CV) mode. In this mode the output current decreases as the battery continues to charge until the termination current level is reached. The CHRGB output turns off when IOUT drops below the termination current. If the charge timer is active, the SC804A continues to hold the battery in CV charge mode until the timer expires. When the timer expires the charger enters the monitor mode where the output remains off until the voltage at VOUT drops by VTReQ. At this point a new charge cycle is initiated.
PRELIMINARY
Fast-Charge Mode (CC)
DRAFT
The fast-charge CC (Constant Current) mode is active when the battery voltage is above VTPreQ and less than VCV. The fast-charge current can be set to a maximum of 1.5A and is selected by the program resistor on the IPRGM pin. The voltage on this pin will represent the current through the battery, enabling a microprocessor via an analog-to-digital converter (ADC) to monitor battery current by sensing the voltage on the IPRGM pin. The equation to set the fastcharge current is given by: VIPRGM_Typ RIPRGM
FCI =
x 1000
The superior fast-charge current accuracy of the SC804A is obtained by use of a patented* polarity-switched (i.e., chopped) current sense amplifier to nullify current measurement offset errors. Compliance with the absolute maximum output current IVOUTMAX, allowing for current regulation tolerance, requires that RIPRGM be no smaller than 1.05k nominal. RIPRGM can be as large as 12.1k, for a nominal FCI as small as 130 mA, but must exceed PCI by at least 80mA. Note that for a given program resistor the current into the battery in CV mode can be determined by replacing VIPRGM_Typ with the actual voltage on the IPRGM pin in the above equation. The CC current can also be modified by applying an analog voltage to the AFC pin as described below.
Pre-Charge Mode
Pre-charge mode is automatically enabled whenever the battery voltage is below the pre-charge threshold voltage, VTPreQ. It is used to limit the power dissipation and precondition the battery for fast charging. The pre-charge current value is determined by the resistor on the ITERM pin. The pre-charge current is programmable from 50mA to 350mA. The equation to select the pre-charge current is given by: VITERM_Typ PCI = x 100 RITERM where VITERM_Typ designates the typical value of VITERM. When the timer is enabled there is also a maximum allowed precharge duration. If the pre-charge time exceeds 25% of the total charge cycle the charger will turn off due to a pre-charge fault. This fault is cleared when VCC is toggled or the output voltage rises above VTPreQ.
Analog Fast Charge (AFC Pin)
Many applications require more than one current setting for fast-charge. This behavior is obtained in the SC804A using the AFC function. When the AFC pin is connected to VCC the device behaves as described in the previous section. When the AFC pin is driven by an analog voltage between 0V and (VVCC-1.0)V, the SC804A automatically uses this pin voltage to set the maximum fast-charge current according to the following equation: FCI = VAFC RIPRGM x 1000
This adjustment to the fast charge current is obtained by replacing the fixed VIPRGM reference voltage with the
*US Patent 6,836,095.
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SC804A
POWER MANAGEMENT Applications Information (Cont.)
AFC voltage. (Note that AFC voltages above VIPRGM will produce IVOUT exceeding that programmed as per the FastCharge Mode (CC) section.) For any applied AFC voltage, FCI must not drop below 130mA, and FCI must always remain at least 80mA greater than PCI.
PRELIMINARY
in the event of a faulty battery and to maximize DRAFT charging capacity. The RTIM pin is connected to VCC to select the internal timer, and to GND to disable the timer. Connecting a resistor between RTIM and GND will program the total charge time according to the following equation: Charge time =
Termination Current
Once the battery voltage reaches VCV the SC804A will transition from constant current mode to constant voltage mode. The current through the battery will decrease while the voltage remains constant as the battery becomes fully charged. When the current falls below the programmed termination current set by the termination resistor connected to the ITERM pin, the SC804A will disable CHRGB. If the timer is enabled the output will continue to float-charge in CV mode until the timer expires. If the timer is disabled, the output will turn off as soon as the termination current level is reached. The equation to set the termination current is given by: ITERM = VITERM_Typ RITERM x 100
(--------)
RRTIM 3.08
1 x ------ 3600
With charge time expressed in hours. The timer is programmable over the range of 2 to 6 hours. The internal timer selection results in a charge time of 3 hours. The SC804A will automatically turn off the output when the charge timer times out.
NTC Interface
The NTC pin provides an interface to a battery pack Negative Temperature Coefficient (NTC) thermistor. The typical NTC network has a fixed resistor from VCC to the NTC pin, and the battery pack NTC thermistor connected from the NTC pin to ground. In this configuration, an increasing battery temperature produces a decreasing NTC pin voltage, and a decreasing battery temperature produces an increasing NTC pin voltage. This configuration is shown in the typical application schematic on page 1 of this datasheet. When the NTC voltage from the divider is greater than the high (cold) threshold or less than the low (hot) threshold, the SC804A suspends the charge cycle by turning off the output, halting (but not resetting) the charge timer, and indicating a fault on the FLTB pin. Hysteresis is included for both high and low NTC thresholds to avoid chatter at the NTC trip points. When the NTC pin voltage returns to the valid range, the SC804A automatically resumes the charge cycle. The charge timer will time-out when the SC804A output ontime exceeds the timer setting regardless of how long it has been disabled due to the NTC temperature. An input voltage between VTNTCHxVVCC and the CTO input voltage VCTO (VTNTCCxVVCC if CTO is tied to GND) enables charging. An input voltage outside this range suspends charging and drives FLTB pin active (low). The internal NTC thresholds of VTNTCH and VTNTCC were designed to work with standard thermistors available from numerous vendors. NTC pin voltage below VTNTCDIS (nominally 0.6V) disables
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ITERM can be programmed to be as high as 300mA or as low as 50mA, though accuracy is not guaranteed below 100mA. ITERM must be programmed to be less than FCI for correct operation of the charge cycle.
Monitor Mode
When a charge cycle is complete, the SC804A output turns off and the device enters monitor mode. If the voltage of the battery falls below the recharge threshold (VCV - VReQ), the charger will clear the charge timer and re-initiate a charge cycle. The maximum current drain of the battery during monitor mode will be no more than 1A over temperature. The status of the charger output as a function of the timer and IOUT is tabulated below.
Timer T < Timeout T > Timeout Disabled Iout N/A N/A < Itermination Output State On Off Off
Charge Timer
The timer on the SC804A has two functions: to protect
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SC804A
POWER MANAGEMENT Applications Information (Cont.)
the SC804A and resets the charge timer (with the FLTB pin inactive). The NTC pin can be pulled down to ground by an external n-channel FET transistor or processor GPIO to disable or reset the SC804A. Note that the response of the SC804A to NTC pin voltage above the high threshold and below the low threshold is the same. Thus it is possible to configure the NTC network with the battery pack thermistor between NTC and VCC, and a fixed resistor between NTC and ground. This configuration may be useful if it is desired to reset the charge timer (and the CHRGB output) when the battery pack is removed (so the fixed resistor pulls the NTC pin to ground) while VCC is present.
PRELIMINARY DRAFT or R3 = 2.333xRHOT = 13.624k exactly. The closest 1% standard nominal value is R3 = 13.7k.
Step 2: Verify acceptable thermistor self heating. In general, lower values of RT provide more noise immunity for the NTC voltage, but at the expense of bias current from the input adapter and power dissipation in the NTC network. The dissipation constant is the power rating of the thermistor resulting in a 1oC self heating error. The greatest self-heating occurs at low thermistor resistance (at high temperature). Since temperature sensing accuracy matters only at the charging temperature range thresholds, self heating is assessed only at the worst case high temperature threshold of +40oC. For VVCC = 5V, the 40oC NTC network current INTC_HOT = VVCC /(R3 + RHOT) = 0.246mA. Power dissipation in the thermistor at this temperature, PHOT = RHOT x (INTC_HOT)2 = 0.38mW, for self heating of approximately 0.13oC. The actual high temperature threshold will thus be lower by 0.13oC. This self-heating error is usually acceptable. If it is not, then a thermistor with a greater RHOT must be chosen. Step 3: Determine the desired high (cold) threshold. Compute the NTC network resistor divider voltage, as a function of VVCC, at the cold temperature threshold. NTCCOLD = VCC x RCOLD R3 + RCOLD = 0.6591 x VCC
Cold Temperature Offset (CTO)
The voltage applied to the CTO pin sets the NTC high voltage (normally the cold temperature threshold) for the NTC input. The default NTC high threshold (VTNTCCxVVCC) can be selected by connecting the CTO pin to ground. If it is desired to change this threshold, the voltage on the CTO pin can be set between 0.5xVVCC and 0.9xVVCC. This feature is especially useful if a single PCB design is needed to satisfy similar applications with different requirements. The temperature range for normal charging can be adjusted by adjusting resistor values on a divider network without changing the NTC thermistor, which is often enclosed in the battery pack. An example of a typical application is shown in Figure 2.
NTC/CTO Design Example
The following example assumes the NTC network configuration of Figure 2, with a fixed resistor R3 connected between NTC and VCC, and a battery NTC thermistor RT connected between NTC and ground. The battery temperature range over which charging is permitted is 0oC through 40oC. The datasheet for the selected NTC thermistor indicates that RT = 5.839k at 40oC, at RT = 26.49k at 0oC, with a dissipation constant DC = 3mW. Designate RHOT = 5.839k and RCOLD = 26.49k. Step 1: Select R3. For the normal (NTC thermistor to ground) configuration, solve the NTC network voltage divider for R3 to place the NTC voltage at 0.3xVCC when RT = RHOT. VCC x RHOT 0.3 x VCC = R3 + RHOT
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Step 4: Configure CTO. If NTCCOLD is sufficiently close to the default cold threshold (VTNTCCxVVCC), then simply connect CTO to ground, disabling the CTO function, to complete the design. But in this example it is not, so the voltage on CTO must be set to 0.6591xVVCC. The simple resistive voltage divider network of Figure 2 can be used to obtain the desired CTO voltage. VCTO = NTCCOLD = 0.6591 x VCC = or RCT1 RCT2 1 0.6591 = 0.5172 0.6591 VCC x RCT2 RCT1 + RCT2
=
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SC804A
POWER MANAGEMENT Applications Information (Cont.)
The choice of RCT1 and RCT2 is somewhat arbitrary. The simplest approach is to pick one and compute the other. A good choice here is RCT1 = 115k, and RCT2 = 221k, as these standard 1% tolerance values produce the closest match to the desired voltage divider ratio. With these resistor nominal values, VCTO = VCC x RCT2 = 0.6577 x VCC RCT1 + RCT2
PRELIMINARY
internal voltage references as VOUT pulls VCC DRAFT down to near, or below, VCV, creating a reduced output regulation voltage approximately 200mV below VCC. Thus VCC cannot be pulled down below VOUT + 200mV. The dropout voltage will be larger than 200mV whenever the minimum path resistance multiplied by the output current exceeds 200mV, but it cannot be smaller than 200mV. This greatest-of-two-limit dropout voltage behavior is evident in the dropout voltage typical performance plot. When operating in Adjust Mode (next section), the regulated minimum dropout voltage depends on the programmed VOUT regulation voltage, and dropout also varies with the actual output voltage during CC charging. See Figure 4 for an illustration of dropout voltage data.
which is, nominally, only 0.2% below the target value of 0.6591xVVCC. The CTO network will present a load of only 15A to a 5V charging adapter. The nominal impedance presented to the CTO pin is RCT1 || RCT2 = 75.6k. Any impedance on the order of 100k (or less) is acceptable.
Remote Kelvin Sensing at the Battery
The BSEN pin provides the positive Kelvin sensing voltage feedback to the CV amplifier and should be connected as close to the battery + terminal as possible. Likewise, the RGND pin should be connected directly to the negative terminal of the battery. This allows the designer great flexibility in PCB layout and achieves greater accuracy by sensing the battery voltage directly at the battery terminals. When laying out the PCB, the designer should route the BSEN and RGND trace directly to the battery connection terminals, rather than just to the VOUT and GND pins on the device.
Adjust Mode
The SC804A can be configured for an output voltage other than VCV using Adjust (ADJ) Mode. In Adjust Mode the output voltage is determined by an external resistor divider from VOUT to BSEN. When BSEN is connected in this fashion, VVOUT (during Constant Voltage (CV) charging) will be controlled such that the voltage at the BSEN pin (VBSEN) is the reference voltage VBSEN-ADJ. The output voltage can be set to any voltage desired by an appropriate choice of divider network resistors, within the following limits. When the SC804A is programmed for adjust mode, VVOUT is required to be 150mV less than VVCC, and VVOUT is required to be 400mV greater than VBSEN. VVOUT within 150mV of VBSEN guarantees normal mode operation. This implies that, for BSEN used as a Kelvin sense of battery voltage, the product of the fast charge current and the charge path resistance from VOUT to the Kelvin sense point should not exceed 150mV to ensure normal mode operation. The SC804A Adjust Mode schematic is shown in Figures 3a and 3b. Referring to these schematics, the equation for setting the output voltage is: R11 VOUT = VBSEN-ADJ_TYP x 1 + R12
Dropout Voltage
Dropout voltage is the smallest achievable difference voltage between VCC and VOUT under a particular operating condition. Dropout voltage is encountered during CC charging whenever the current limit of the charging adapter is less than the SC804A FCI programmed current. In this case, the adapter voltage (the SC804A input voltage) will be pulled down to the battery voltage (the SC804A output voltage) plus the dropout voltage. Dropout voltage is the larger of two values: (1) the I-R component, which is the output current multiplied by the minimum VCC-to-VOUT path resistance (which is highly temperature dependent), and (2) a regulated minimum difference voltage, which is output voltage dependent but is independent of the output current. The regulated minimum dropout voltage results from the collapse of
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(
)
The capacitor C3 across R8 in the feedback network introduces zero-pole frequency compensation for stability. Place the zero according to the following equation to ensure stability: 1 R11 x C3 = 2 x 100kHz
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SC804A
POWER MANAGEMENT Applications Information (Cont.)
Charger VIN OV_FLT 14 VCC CPB 13 OVP CHRGB 3 IPRGM RTIM 7 NTC CTO 4 ITERM BSEN 8 FLTB VOUT 6 GND VOUT 5 RGND AFC SC804A 11 10 12 2 1 16 15 9 C2 2.2F Red RCT1 RCT2 R5 R6 Green
PRELIMINARY DRAFT
C1 2.2 F
R3
RT NTC R1 R2
R4
ERROR
Figure 2 - Application Circuit with AFC Disabled, and with NTC and CTO Resistor Networks
Charger VIN OV_FLT 14 VCC CPB 13 OVP CHRGB 3 IPRGM RTIM 7 NTC CTO 4 ITERM BSEN 8 FLTB VOUT 6 GND VOUT 5 RGND AFC SC804A 11 10 12 2 1 16 15 9
C1 2.2 F
R3
Red
Green
RT NTC R1 R2
R11 R5 C3 C2 2.2F R4 R12 R6
ERROR
Figure 3a - Application Circuit for Adjust Mode
Charger VIN OV_FLT 14 CPB VCC 13 CHRGB OVP 3 RTIM IPRGM 7 CTO NTC 4 BSEN ITERM 8 VOUT FLTB 6 VOUT GND 5 AFC RGND SC804A 11 10 12 2 1 16 15 9 R11 R4 C3 C2 2.2F R12 R5 R6
C1 2.2 F
R3
Red
Green
RT NTC R1 R2
ERROR
Figure 3b - Application Circuit for Adjust Mode, with Adapter-only Voltage Sensing
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SC804A
POWER MANAGEMENT Applications Information (Cont.) PRELIMINARY
Overcurrent and Max Temperature Protection
0.8
DRAFT
0.6
0.4
0.2
3.2
3.4
3.6
3.8 4 Output voltage, V
4.2
4.4
4.6
Figure 4 - Adjust Mode Minimum Dropout Voltage
The actual dropout voltage is the greater of the Minimum Dropout Voltage at various programmed VCV and instantaneous VOUT voltages (shown here, with several programmed VCV voltages indicated in the figure by `o'), and the IR drop due to the product of IOUT and RDS-ON (not shown here). Adjust mode operation is ensured for any IOUT current at programmed VCV voltages up to approximately 4.41V.
Overcurrent protection is inherent in all modes of operation. When the device is in charge mode the output is currentlimited to either the pre-charge current limit value or the fast charge current limit value depending on the voltage at the output. Max die temperature protection is also included. This feature allows the SC804A to operate with maximum power dissipation by disabling the output current when the die temperature reaches the maximum operating temperature. The result is that the SC804A will operate as a pulse charger in extreme power dissipation applications, delivering the maximum allowable output current while regulating the internal die temperature to a safe level. Indicator Flags There are four indicator outputs/LED drivers ont he SC804A; CPB (Charger Present), CHRGB (Charge Active), OVPB (Over Voltage Fault), and FLTB (Fault). These outputs are all active-low; open drain NMOS drivers capable of sinking up to 10mA. The following table defines each indicator's output state.
FLAG CPB CHRGB OVPB ON UVLO < VCC < OVP IOUT > ITERM VCC > OVP VCC > OVP VCC UVLO NTC Temp Fault Pre-Charge Time-out (OT (Tj > 150C) OFF Input out of range IOUT < ITERM VCC < OVP
NOTE: When using Adjust Mode to program a CV regulation voltage greater than VCV, care must be taken when CC charging with a charging adapter operating in current limit. Adapter current-limited operation occurs when the adapter current limit is less than the programmed SC804A fast charge current, such that the adapter voltage is pulled down to VVOUT plus the SC804A dropout voltage. A low adapter current limit multiplied by the low minimum path resistance of the main pass transistor and current sense resistor (as low as 290m total at extremely low temperature) can result in a voltage drop from VCC to VOUT of less than 150mV if the Adjust Mode CV regulation voltage is programmed above VCV + 50mV. If VVCC - VVOUT < 150mV, Adjust Mode may not operate correctly. Adjust Mode will operate correctly whenever the programmed VOUT CV voltage is less than VCV + 50mV, regardless of the adapter current limit, because the regulated minimum dropout voltage is always greater than 150mV in this case. It will also operate correctly with an adapter current limit greater than 550 mA, regardless of the programmed output voltage, because the I-R dropout voltage will exceed 150mV at even the lowest specified operating temperature. Normal mode (that is, not Adjust Mode) has a regulated minimum dropout voltage of approximately 200mV, which is constant for any VVOUT, and so operates correctly for any adapter current limit.
(c) 2005 Semtech Corp.
Minimum dropout voltage, V
FLTB
Normal Operation or NTC Disable
The CPB output can be used as a VCC-present indicator. Regardless of teh state of NTC, the CPB output reflects the VCC voltage. When VCC is between the UVLO and OVP thresholds the CPB output is low. If VCC is outside these limits, this output is high impedance. The CHRGB output indicates the charging status. When the output current is greater than ITERM, CHRGB is low. CHRGB is high impedance when IOUT is less than ITERM. The CHRGB output is latched during the charge cycle when the output current is less than ITERM. This latch is reset when the battery enters a recharge cycle, or if NTC or VCC are toggled.
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SC804A
POWER MANAGEMENT Charge Mode Timing Diagram
The OVPB signal is an active-low output that signals when the input voltage exceeds the OVP threshold. When the voltage on VCC is less than the OVP threshold voltage this output is high impedance. The FLTB output is activated when the device experiences a fault condition. This output can be used to notify the system controller of a fault condition when connected to an interrupt input, or it can be used like CPB and CHRGB to drive an indicator LED. There are five fault modes signaled by FLTB: input over-voltage, input under-voltage, NTC temperature out of range, max die temperature (OT),
PRELIMINARY DRAFT and pre-charge timeout. When any of these conditions occurs the FLTB output goes low; otherwise it remains high impedance.
Capacitor Selection Low cost, low ESR ceramic capacitors such as the X5R and X7R dielectric material types are recommended for use with the SC804A. The output capacitance range is 1F to 4.7F. The input capacitor is typically between 0.1F to 2.2F, but larger values will not degrade performance
VCC
UVLO
VOUT
VTPreQ Fast Charge Soft Start Pre-Charge CC Mode CV Mode Termination Current
Re-Charge Threshold
IOUT
CPB
CHRGB
On
Off
On
Off
On
TIMER
On
Off
On
Hold
On
FLTB
Off
On
Off
NTC
Fault
Figure 5 - Charge Mode Timing
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT State Diagram
Over-Voltage, Under-Voltage or Over-Temperature will force the SC804A into Shutdown Mode from any state.
OVP > VCC > UVLO Shutdown Mode : VOUT & IOUT off, CHRGB High Z, CPB Low.
PRELIMINARY DRAFT
En = Hi Yes Soft Start Vout CHRGB Low Timer Enabled? Yes Start Timer Start Pre Charge CC = Constant Current CV = Constant Voltage
Soft Start CC Mode
Yes
VOUT > VTPreQ
IOUT = IFAST
IOUT = IPREQ
Time >TMAX/4 Yes
VOUT = VCV Yes Start CV Mode
Pre- Charge Timeout Fault FLTB goes low . Cleared by VBAT > VTPreQ or Re- cycle VCC
IOUT low temp> NTC Temp> high temp
NTC out of Range Fault FLTB goes active low Timer is frozen Charge resumes when NTC Temperature is valid Time > TMAX Float Charge Mode VOUT = VCV
Monitor Mode VOUT off Yes VOUT < VCV - VReQ
Yes
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT Typical Charge Cycle PRELIMINARY DRAFT
Typical Charge Cycle Evaluation Board configured for internal timer, 1.5V on IPRGM = 843mA, 1.5V on ITERM = 300mA, VCC = 5.0V, Li-Ion battery capacity = 850mAh. A 237 load resistor (18mA at a battery voltage of 4.36V) was applied to the battery following completion of precharge, to slowly discharge the battery following charge timer timeout to illustrate a recharge cycle. The alphabetic markers indicate the following: (a) precharge; (b) fast charge, or Constant Current (CC) charging; (c) Constant Voltage (CV) charging; (d) termination; (e) CV ("float") charging until charge timer timeout; (f) charge timer timeout; (g) discharge of the battery due to 18mA load; (h) recharge cycle initiated when battery voltage drops below the recharge threshold.
5 4.36 4 3.5 3 2.5 2 1.5 1 0.5 0 0 30 60 90 120 150 180 210 240 270 300 330 360
b
c
e
f
g
VBATTERY, VCHRGB, (V)
a d h
Time (minutes)
900 800 700
b
IVOUT mA
600 500 400 300 200 100 0 0
a
c
h
f
30 60 90 120 150 180 210 240 270 300 330 360
Time (minutes)
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT Typical Characteristics
4.356 4.354 4.352 4.350
PRELIMINARY DRAFT VOUT VCV Load Regulation vs. Line, T = +25C
VCC = 5.0V 4.354 VCC = 5.5V 4.352 4.350
VOUT VCV Line Regulation vs. Load, T = +25C
Iout = 500mA
4.356
VOUT (V)
Iout = 750mA 4.348 4.346 4.344 4.342 4.340 4.338 5.00 Iout = 1500mA Iout = 1000mA
VOUT (V)
4.348 VCC = 6.0V 4.346 4.344 VCC = 6.5V 4.342 4.340 4.338 500
5.20
5.40
5.60
5.80
6.00
6.20
6.40
750
1000
1250
1500
VIN (V)
IOUT (mA)
4.360
VOUT VCV Regulation vs. Temperature, VCC = 5.0V, IOUT = 800mA
840
IOUT Line Regulation vs. Temperature, RPRGM = 1.87k
T = +85C
4.358
836
4.356
832
T = +25C
IOUT, mA
VOUT,V
4.354
828
4.352
824 T = -40C
4.350
820
4.348 -50 -25 0 25 50 75 100
816 5.00
5.25
5.50
5.75
6.00
6.25
6.50
Ambient Temperature, C
VCC, V
IOUT vs. IPRGM Resistance, T = +25C
1800 400.0 350.0 300.0 250.0 200.0 150.0 100.0 600 50.0 0.0 0
Precharge and Termination Current vs. ITERM Resistance
1600
1400
IOUT, mA
1200
1000
800
400 0.3 0.5 0.7 0.9 1.1
IOUT, mA
1/Riprgm, 1/k
0.5
1
1.5
2
2.5
1/RIPRGM, 1/k
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT Typical Characteristics (Cont.)
Dropout Voltage vs. IOUT
0.900 0.800 TJ = +125C 0.700 0.620 TJ = +125C 0.570
PRELIMINARY
Rds-on vs. IOUT
DRAFT
0.520 TJ = +85C
TJ = +85C
Dropout (V)
Rds-on ()
0.600 0.500 0.400 0.300
0.470
0.420
TJ = +25C
0.370 TJ = +25C TJ = -40C
0.200 TJ = - 40C 0.100 400 600 800 1000 1200 1400 1600
0.320
0.270 400
600
800
1000
1200
1400
1600
IOUT (mA)
IOUT (mA)
1200
AFC Operation, RPRGM = 1.87k
AFC Pin Tied to VCC
1000
800
Iout (mA)
600
Actual AFC Response
400
200
Ideal AFC Response
0 0 0.5 1 1.5 2
VAFC, V
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT Evaluation Board Schematic
CHARGER+ 1 CHARGER1 RTIM 1
PRELIMINARY DRAFT
C1 1 R9 1 2 2 JP6 1 JP1 1 1 16 15 R11 0 2 14 13 1 C2 2.2u 3 CTO JP5 1 2 1 1 C3 1 2 3 4 1 R12 1 1 R6 1.87k 2 2 R5 499 2 BSEN CTO IPRGM ITERM RGND FLTB GND NTC 1 2 1 390 R15 2 2 12 11 10 9 1 JP3 CHRGB AFC 1 2 JP7 1 1 2 37.4k JP2 CPB 2 1 390 1 390 1 100k R2 2 R3 2 R13 2 2 2 RTIM 1 2 R1 2 2 R10 1 1 D1 2 2.2u
1
1
VOUT
D2
D3
1 D4
VCC
GND
1
2
2
U1 SC804A
IPRGM
ITERM
1
5
6
7
8
OVPB
VOUT
VOUT
JP4 1 R14 RGND 1 2 0 R8 GND 1 1 R16 1 3 2 1 1 NTC 2 1 10k R7 2 1 2 1
R4 2 390
GND
POT_3296W-105
Evaluation Board Gerber Plot,Top/Bottom Views
(c) 2005 Semtech Corp.
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SC804A
POWER MANAGEMENT Outline Drawing - MLPQ-16 PRELIMINARY DRAFT
DIM
A D B
A A1 A2 b D D1 E E1 e L N aaa bbb
DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX
.031 .040 .000 .002 (.008) .010 .012 .014 .153 .157 .161 .079 .085 .089 .153 .157 .161 .079 .085 .089 .026 BSC .012 .016 .020 16 .003 .004 0.80 1.00 0.00 0.05 (0.20) 0.25 0.30 0.35 3.90 4.00 4.10 2.00 2.15 2.25 3.90 4.00 4.10 2.00 2.15 2.25 0.65 BSC 0.30 0.40 0.50 16 0.08 0.10
PIN 1 INDICATOR (LASER MARK)
E
A2 A aaa C A1 D1 e/2 LxN
E/2
C
SEATING PLANE
E1
2 1 N e D/2 bxN bbb CAB
NOTES: 1. 2. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
Marking Information
804A yyww xxxxx xxxx
yyww = Date Code (Example: 0552) xxxxx xxxx = Semtech Lot Number (Example: E9010 01-1)
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SC804A
POWER MANAGEMENT Land Pattern - MLPQ-16 PRELIMINARY DRAFT
K
DIM
2x (C) H 2x G 2x Z C G H K P X Y Z
DIMENSIONS INCHES MILLIMETERS
(.156) .122 .091 .091 .026 .016 .033 .189 (3.95) 3.10 2.30 2.30 0.65 0.40 0.85 4.80
Y X P
NOTES: 1.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 FAX (805)498-3804
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