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DS2715
NiMH Battery Pack Charge Controller
www.maxim-ic.com
DESCRIPTION
The DS2715 is well suited for cost-sensitive charger applications where the battery is either internal or in a unique battery pack. It has been optimized for safe reliable charging of 1 to10 NiMH cells in series. The DS2715 has an internal gain block that can be selected as either a comparator or transconductance amplifier for charge current regulation. The DS2715 is configurable as a switched DC charger, a linear current regulator, or a switchmode current source. The DS2715 pre-conditions severely depleted cells are pre-conditioned before entering full charge mode. The DS2715 terminates full charge using the dT/dt technique. It requires an external thermistor for dT/dt detection. Over-temperature, under-temperature, and over-voltage detection prevents charging under unsafe environmental conditions. A user selectable charge timer allows charge rates from 0.15C to 2C. Fast-charge, top-off and charge done modes are included for highly reliable, safe charging of NiMH cells. Discharge mode allows the DS2715 to enter a low power sleep state while the cell pack is being discharged.
PIN CONFIGURATION
CBIAS CC1 VCH CC2 VSS LED1 LED1 VSS LED2 LED2 VSS CSOUT CTG VN1 CTG VN0
1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9
VBATT VP2 THM VP1 RT THM2 VDD THM1 SNSVDD SNS+ TMR DIV CTST MODE DMSEL
16 SO
See Table 1 for Ordering Information.
Table 1. ORDERING INFORMATION
PART DS2715Z+ DS2715Z+T&R MARKING DS2715+ DS2715+ PIN-PACKAGE 16 SO 16 SO Tape-and-Reel
FEATURES

Charges 1 to 10 NiMH Cells Fast Charges up to a 2C Rate Pre-Charge and Top-Off Charge Modes Help Cell Conditioning Load Detection Allows the DS2715 to Enter Low Power Sleep Mode (Less than 10A) while the Cell Pack is Discharged dT/dt Charge Termination Eliminates Cell Charge Stress Monitors Voltage, Temperature, and Time for Safety and Secondary Termination Regulates Current through Either Linear Control or Switch-Mode Control LED Outputs Display Charge State Small 16-Pin SO Package
+ Denotes lead-free package.
OPERATIONAL DIAGRAM
CHARGE SOURCE/LOAD
Vch Vdd Vbatt
Divide by n
DS2715
THM
+
GROUND
Sense
n Cells
APPLICATIONS
Portable DVD Players Portable Television Sets Handheld Gaming Test Equipment Handheld POS Terminals
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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042605
DS2715: NiMH Cell Pack Charge Controller
ABSOLUTE MAXIMUM RATINGS*
Voltage on VDD and VCH Pins with Respect to VSS Voltage on LED1 and LED2 Pins Voltage on SNSVoltage on CBIAS Voltage on all Other Pins Continuous Sink Current VCH, LED1, and LED2 Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +18V -0.3V to +18V -0.3V to +0.3V -0.3V to 6V -0.3V to VCbias 28mA -20C to +85C -55C to +125C See IPC/JEDECJ-STD-020
*This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER Supply Voltage LED1, LED2 Voltage Mode Voltage VCH Voltage CBIAS Capacitor Range RT Resistor Range SYMBOL VDD VLED VMODE VVCH CCbias RRt CONDITIONS (Note 1) (Note 1) (Note 1) (Note 1) (4.5V VDD 16.5V; TA = 0C to +70C.) MIN TYP MAX UNITS 4.5 0.0 0.0 0.0 .02 20 16.5 16.5 VCbias 16.5 .15 240 V V V V F K
DC ELECTRICAL CHARACTERISTICS
PARAMETER Operating Current (Note 2) Idle Current Discharge Current UVLO Threshold UVLO Hysteresis VCH Sink Current LED1, LED2 Sink Current Leakage Current, VCH, LED1, LED2 THM Pin Leakage Current VBATT Pin Leakage Current CBIAS Voltage DIV Pin Load Current Current Sense Amplifier Gain Current Sense Comparator Gain SYMBOL IDDA IDDS IDDD VUVLO VUVLO-HYS IOL-Vch IOL-LED ILKG ILKG-THM ILKG-Vbatt VCbias IDiv GERR GCOMP 100A < I Vch < 20mA (Note 7) 5 10 6.25 0 < ICbias < 0.4ma (4.5V VDD 16.5V, TA = 0C to +70C, unless otherwise noted.) CONDITIONS MIN TYP MAX UNITS Linear Mode, VDD = 16.5V Comparator Mode, VDD = 16.5V VDD < VUVLO Discharge latch set (Note 2) VDD Rising (Note 3) VDD Falling VOL = 1.5V VOL = 1.0V Pin inactive or Device Idle 20 20 -1 -1 -50 3.9 4.0 +1 +1 +50 4.3 500 7.5 3.8 3.9 35 1.3 150 1.6 250 10 200 4.0 mA A A A V mV mA mA A A nA V uA
-1
-1
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DS2715: NiMH Cell Pack Charge Controller
AC ELECTRICAL CHARACTERISTICS
PARAMETER UVLO Debounce Time Current Sense Comparator Propagation Delay Discharge Detect Propagation Delay Return To Normal Function (Op-Amp or Comparator Mode) RT Timing Accuracy Internal Clock Accuracy SYMBOL tUVLO tCOMP tDD tRNF tRt tBASE (Note 7) From detection of current reversal Time from reset of discharge latch (Note 4) -10 -10 (4.5V VDD 16.5V, TA = 0C to +70C, unless otherwise noted.) CONDITIONS MIN TYP MAX UNITS 10 250 1 1 +10 +10 s ns s s % %
ELECTRICAL CHARACTERISTICS: CHARGING
PARAMETER Fast Charge Comparator Threshold Fast Charge Comparator Hysteresis Top-off and Pre-Charge Comparator Threshold Top-off and Pre-Charge Comparator Hysteresis Discharge Latch Reset Threshold Discharge Latch Set Threshold Low Battery Detect Threshold Cell Detect Threshold No Cell Detect Threshold Presence Detect Threshold Hysteresis Minimum Charge Temp Maximum Charge Temp Over Temp dT/dt Detect dT/dt Blanking Time Fast Charge Timer Range Top-Off to Fast Charge Duration Ratio SYMBOL VFC VHYS-FC VTO VHYS-TO VDCHG-RST VDCHG-SET VLB VDET VOPEN VHYS-PD VTHM-MIN VTHM-MAX VTHM-STOP TTERM tBLANK tFC (Note 5, 6) (Note 5, 6) (Note 5, 6) Reverse current through sense resistor From presence detect into pre-charge (4.5V VDD 16.5V, TA = 0C to +70C, unless otherwise noted.) CONDITIONS MIN TYP MAX UNITS Fast charge Fast charge Top-off and pre-charge Top-off and pre-charge -127 -31 -38 -10 -15 5 0.95 1.50 1.60 90 2.88 1.28 1.12 0.425 3.85 0.5 1:2 -121 -28 -33 -8 -10 10 1.0 1.55 1.65 100 2.92 0 1.32 45 1.16 50 0.5 4.3 -115 -25 -28 -6 -5 15 1.05 1.60 1.70 110 2.96 1.36 1.20 0.575 4.75 6 mV mV mV mV mV mV V V V mV V C V C V C C/min Min Hours
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DS2715: NiMH Cell Pack Charge Controller
Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Voltages relative to VSS. Does not include current through VCH, RT, and DIV pins. Below this voltage no I/O pins are active. Does not include tolerance of RT resistor. VBIAS and resistor tolerances must be added to determine actual threshold. Specified temperature thresholds are only valid if recommended thermistor types are used. Specification is guaranteed by design.
DETAILED PIN DESCRIPTION
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 NAME CBIAS VCH VSS LED1 LED2 VSS CTG CTG MODE DIV SNS+ SNSVDD RT THM VBATT DESCRIPTION Bypass for Internal Voltage Regulator Cell Stack Charge Control Output Ground Reference and Chip Supply Return Charging Indicator Output Done Indicator Output Ground Reference and Chip Supply Return Connect to Ground Connect to Ground Mode Select. Connect to VSS for linear mode of operation or CBIAS for comparator mode of operation. Thermistor Divider. Stable output to form a resistor divider for measuring temperature on THM. Positive Current Sense. Connect to the pack side of the sense resistor. Negative Current Sense. Connect to the cell stack side of the sense resistor. Chip Supply Input: +4.0V to +5.5V range. Failsafe Timeout. Timeout is selected by an external resistor from RT to VSS. Thermistor Input. Connect to a thermistor located in the cell pack and a divider resistor from the Div pin. Battery Voltage Sense Input. Connect to a divider from the positive terminal of the cell stack to measure the voltage of a single cell.
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DS2715: NiMH Cell Pack Charge Controller
Figure 1. BLOCK DIAGRAM
DS2715
Cbias VDD HV
VUVLO Regulator
Pwr
R E F
Ref
M U X
Vbatt
Th
UVLO
THM
Div
Disable during discharge
State Machine Pre-Charge Low Cells
Oscillator
A D C
LED1 LED2
HV HV
Pwr
Fast Charge Exit on Full Or Timeout
Mode
Disch. Detect @-0.01V
+ -
Ref SNS+
25% Top-Off Charge (Set by Timer)
Rt start-up test
Ref
Vsns Ref
AMP or Comp
R
Rt Rt
Charge Timer
Done, Waiting for event to start charging
121mV, 33mV, 10mV
+
+
SNS+ SNSVch
RS Latch
VSS
Latch is set until Vsns negative WRT Vss
VSS
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DS2715: NiMH Cell Pack Charge Controller
Figure 2. STATE DIAGRAM
DS2715 State Diagram
VDD < VUVLO-VUVLO-HYS (asynchronously from anywhere)
Discharge Latch Set
Reset
Latch Reset t < PCTimeout AND
Standby power Check Rt, set mode Vch = Hi-Z LEDx = Hi-Z
VDD > VUVLO
Presence TEST
Vch = Hi-Z LED Hi-Z= No Battery
Vbatt>1.65
4 Sec Delay
PreCHG
Vref = 0.033V LED1 = Charging 30 min PCtimeout
Discharge Mode Pwr=Low
LEDs = OFF Vch = LOW
Vbatt < 1V
La tc h
Di sc ha rg e
Discharge Latch Still Set?
t > PCTimeout OR T > 50 Vbatt>1V AND T < PCTimeout AND T < 50C
FAULT
Vch = Hi-Z LED2 = Fault Flash until Vbatt>1.65
t < Fast Timeout
Fast CHARGE
Vref = 0.121V LED1 = Charging
Overtemp, Overvoltage Detect
Vbatt > 1.65
Discharge latch set
dT/dt OR t > Fast Timeout
T > 50 Vbatt > 1.65 or Vbatt < 1.0 T > 50 OR t > Topoff Timeout
t < Topoff Timeout
Topoff CHARGE
Vref= 0033V LED1 = Charging
DONE
Vch = Hi-Z LED2 = DONE
Discharge latch set Vbatt > 1.65
Discharge latch set
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D i sc
se t
ha
rg e
la t
ch
Vbatt < 1.55V AND 0C < T < 45C
Vbatt > 1.65V OR T < 0C OR T > 45C
se t
DS2715: NiMH Cell Pack Charge Controller
DETAILED DESCRIPTION
Charge Cycle Overview
The DS2715 regulates the charge of up to 10 NiMH cells in a series configuration. With the mode select pin the DS2715 can be configured to regulate either as an error amplifier in linear mode or as a comparator in switched mode. A charge cycle begins in one of two ways: with the application of power to the DS2715 with cell pack already inserted or with the detection of cell insertion after power-up. The charge cycle begins with pre-charge qualification to prevent fast charging of deeply depleted cells or charging under extreme temperature conditions. Pre-charging is performed at a reduced rate until each cell reaches 1V. The algorithm proceeds to a fast-charge phase. Fast charging continues as long as the cell pack temperature is less than 50C based on the THM voltage, the cell voltage as measured by the VBATT pin remains below 1.65V indicating the cell pack is still present. Fast charging terminates by measuring the cell pack's thermal rate of change dT/dt. When the cell pack's thermal rate of change exceeds 0.5C per minute the DS2715 enters top-off. The DS2715 has an internal charge timer as secondary overcharge protection if the charge is not terminated by the dT/dt method. The charge termination timer duration is user selectable from 30 minutes up to 6 hours by an external resistor on the RT pin. The DS2715 remains in top-off for one-half of the period of the fast charge timer duration as selected by the external resistor on RT. After the top-off charge timer expires, the done phase continues indefinitely until the cell pack is removed from the charger or a load is attached. When a load attached to the cell pack, the DS2715 switches to discharge mode. All charge functions are disabled and the regulation FET is driven on to allow the cell pack to discharge. Two LED indicators display the charge status to the user.
Undervoltage Lockout (Reset)
The UVLO circuit serves as a power-up and brownout detector by monitoring VDD to prevent charging until VDD rises above VUVLO, or when VDD drops below VUVLO - VUVLO-HYS. If UVLO is active, charging is prevented, the state machine is forced to the RESET state, and all charge timers are reset. A 10ms deglitch circuit provides noise immunity. Once VDD reaches an acceptable operating voltage the DS2715 enters the PRESENCE state.
Presence
The DS2715 enters the PRESENCE state whenever VDD > VUVLO and VBATT > VOPEN indicating that the charge source is present, but no cell is available to charge. The DS2715 will remain in the presence state until a cell is inserted into the circuit causing the voltage on VBATT to fall below 1.55V (VDET) and the cell temperature is inside a valid charging range between 0C and 45C (TTHM-MIN and TTHM-MAX). If both these conditions are met the DS2715 will enter pre-charge. If cells are inserted, but the temperature is outside the valid charging range the DS2715 will remain in the PRESENCE state until the cell temperature falls within the valid charging range.
Pre-Charge
The DS2715 enters the PRE-CHARGE state when a valid cell voltage is applied to VBATT and the cell temperature as measured by the DS2715 is within the valid charging range. Pre-charge has a 4 second filter to suppress noise on VBATT caused by cell insertion. The DS2715 pre-charges the cell by regulating the voltage drop across the sense resistor to -33mV (VTO) in linear mode or -29mV (VTO - 0.5 x VHYS-TO) in comparator mode. Pre-charge will last until the cell voltage measured by VBATT exceeds 1.0V (VBATT > VLB) at which time the DS2715 will enter FAST CHARGE state. If the cell voltage does not exceed VLB within 30 minutes or if the cell temperature exceeds 50C at any time during pre-charge, the DS2715 enters the FAULT state. If at any time during pre-charge the voltage on VBATT exceeds 1.65V (VOPEN), the DS2715 determines that the cell pack has been removed and returns to the PRESENCE state.
Fast Charge
In fast charge mode, the DS2715 regulates the voltage across the sense resistor to -121mV (VFC) in linear mode or -107mV (VFC - 0.5 x VHYS-FC) in comparator mode. LED1 indicates the cell pack is being charged. During fast charge the DS2715 constantly measures the rate of change of the cell temperature (dT/dt). When the cell pack's dT/dt exceeds 0.5C per minute (TTERM) the DS2715 enters the TOP-OFF state. The DS2715 ignores changes in the cell temperature caused by charge initiation for the first 4.3 minutes (tBLANK). As secondary overcharge protection, the DS2715 will terminate fast charge and enter top-off based on a time delay set by the external resistor on the RT pin. This resistor value can set the secondary charge termination delay to anywhere from 30 minutes up to 6 hours. If the cell temperature exceeds 50C at any time during fast charge, the DS2715 enters the 7 of 12
DS2715: NiMH Cell Pack Charge Controller DONE state. If at any time during fast charge the voltage on VBATT exceeds 1.65V (VOPEN), the DS2715 determines that the cell pack has been removed and returns to the PRESENCE state.
Top-Off
In top-off mode, the DS2715 regulates the voltage across the sense resistor to -33mV (VTO) in linear mode or 29mV (VTO - 0.5 x VHYS-TO) in comparator mode. LED1 indicates the cell pack is being charged. The charge timer is reset and restarted with a time-out period of one half the fast-charge duration. When the charge timer expires or if the measured temperature exceeds 50C, the charger enters the DONE state.
DONE/Maintenance
The DS2715 enters the DONE state whenever the charge completes normally or if the measured cell temperature exceeds 50C during the charge. While in the done state VCH is driven to high impedance to prevent further charging of the cell pack and LED is driven on to indicate charge completion. A maintenance charge can be applied to the cells by providing a resistive path from the cell pack to the charge source bypassing the regulator. See the example circuit in Figure 3. The DS2715 remains in DONE until a cell voltage greater than 1.65V (VOPEN) is detected on VBATT indicating the cell pack has been removed. The DS2715 then enters the PRESENCE state and waits for the next cell insertion.
FAULT
The DS2715 enters FAULT if pre-charge is unable to charge the cell above 1.0V (VLB) before the 30 minute precharge timeout of if the cell temperature exceeds 50C during pre-charge. In the fault state VCH is driven to high impedance and LED2 blinks to indicate the fault condition. The DS2715 remains in FAULT until a cell voltage greater than 1.65V (VOPEN) is detected on VBATT indicating the cell pack has been removed. The DS2715 then enters the PRESENCE state and waits for the next cell insertion.
Discharge Mode
When the DS2715 detects a discharge current voltage drop of VDCHG-SET or greater across the sense resistor, charging is terminated and the DS2715 enters the DISCHARGE state. While in this mode, voltage sensing, thermal sensing, and LED outputs are disabled. The VCH pin is driven low to allow the pack to be discharged. Current drain of the DS2715 drops to IDDD. The DS2715 remains in discharge mode until a charge current of at least VDCHG-RST is detected. When this occurs the DS2715 enters the presence detect state to begin a new charge cycle.
Application Circuit
Figure 3 shows a typical application circuit for charging a 3-cell stack. The mode pin is tied to VSS for linear operation. A 75m sense resistor (R10) sets the charge current at 1.6A. The DS2715 regulates the current through Q1. 68k on RT (R6) sets the fast charge timeout to 102 minutes. R5 and R8 form a 1:3 voltage divider to allow VBATT to measure the voltage of a single cell. The charge source is isolated with diode CR1 to prevent discharge through the source connection. R1 and CR2 form a maintenance charge path to supply the cell pack with ~40mA constant current after the charge completes. Lastly VR1 and R4 create a current leakage path to bias the regulator circuit and prevent an in-rush current spike when the cell stack is connected to the powered circuit.
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DS2715: NiMH Cell Pack Charge Controller
Figure 3. TYPICAL APPLICATION CIRCUIT FOR A 3-CELL STACK
LOAD
CR2 CR1 LED2 LED1 C1 10 uF R2 470 R3 1K R12 1K 100 R1
+9VDC
Q1 IRF9Z24 U1 DS2715
VR1
5.6V R4 100 R5 200K C2 47 uF
LED1 Vch LED2 Vbatt
C3 10 uF
Vdd Rt
R6 68K
Div
R7 10K
Mode SNS+ Cbias
VSS THM VSS CTG SNS-
R8 100K
R9 47
C4 0.1 uF
R11 47
THM1 10K
R10 0.075
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DS2715: NiMH Cell Pack Charge Controller
CURRENT REGULATION
Three basic modes of charging operation are supported by the DS2715: Offline switching through an optocoupler, linear regulation, and DC input switched mode. The DC Switched method requires a currrent-limited power source. Mode of operation is selected through the Mode pin. Connecting the Mode pin to VSS configures the analog block as a transconductance amplifier for linear mode of operation. Connecting the Mode pin to the Cbias pin configures the DS2715 as a comparator for switched mode of operation.
Current-Sense Amplifier Mode
An error amplifier block provides several options to regulate the charge current. The 20mA open-drain output can drive a PMOS or PNP pass element for linear regulation, or the output can drive an optocoupler for isolated feedback to a primary-side PWM controller. The SNS- pin is a remote-sense return and should be connected to the grounded side of the sense resistor using a separate, insulated conductor. During fast charge, an error signal between the current-sense signal (across the sense resistor) and the internal reference is produced so the voltage across the sense resistor is maintained at VFC in a closed-loop circuit. During top-off the voltage across the sense resistor is maintained at VTO.
Current-Sense Comparator Mode
The comparator in the DS2715 switches between ON and OFF and is capable of driving a PNP bipolar or a PMOS transistor, enabling the use of a switched-mode power stage. Hysteresis on the comparator input provides noise rejection. In a closed-loop regulation circuit, the comparator regulates voltage across the sense resistor to a DC average of: VRSNS = VFC - 0.5 x VHYS-FC = -0.107V during fast charge VRSNS = VTO - 0.5 x VHYS-TO = -0.029V during top-off
Charge Rate Selection
The charge rate is determined by an external sense resistor connected between the SNS+ and SNS- pins. The DS2715 will regulate the charge current to maintain a voltage drop of VFC (VFC - 0.5 x VHYS-FC in comparator mode) across the sense resistor during fast charge. The sense resistor can therefore be selected by: Linear Mode: Comparator Mode: R = VFC / Desired Fast Charge Current R = (VFC - 0.5 x VHYS-FC) / Desired Fast Charge Current
Charge Time and Top-Off Time Selection
Pre-charge has a fixed 30 minute limit generated by an internal oscillator. Charge time and top-off time are controlled by an external resistor from the RT pin to VSS. Resistors can be selected to support fast-charge time-out periods of 0.5 to 6 hours and top-off charge time-out periods of 0.25 to 3 hours. If the timer expires in fast-charge, the timer count is reset and charging proceeds to the top-off charge phase. The top-off time-out period is half of the fast charge time-out period. If the timer expires in top-off, the DS2715 enters the DONE state. The programmed charge time approximately follows the equation: t = 1.5 x R / 1000 (time in minutes)
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DS2715: NiMH Cell Pack Charge Controller
TEMPERATURE SENSE
Accurate temperature sensing is needed to determine end of charge by dT/dt and to detect over temperature fault conditions. Connecting an external 10kW NTC thermistor between THM and VSS, and a 10kW bias resistor between Div and THM allows the DS2715 to sense temperature. To sense the temperature of the cell pack, locate the thermistor close to the body of a cell, preferably in the middle of the cell pack. Several recommended 10kW thermistors are shown in Table 2.
Min, Max Temperature Compare
The voltage thresholds of the THM input (VTHM-MIN, VTHM-MAX) are set to allow charging to start if 0C < TCELL < 45C when using the recommended 10kW bias and 10kW thermistor. If pre-charging is in progress, and the voltage on THM reaches VTHM-STOP, pre-charging stops and a fault condition is generated. If the voltage on THM reaches VTHMSTOP during fast charge or top-off, charging stops and the DS2715 enters the DONE state. Fast charging will complete normally and top-off will begin if the voltage change on THM exceeds TTERM C per minute (dT/dt charge termination).
Table 2. THM1, THM2 THRESHOLDS
THM THRESHOLD MIN MAX STOP RATIO OF VCBIAS 0.73 0.33 0.29 THERMISTOR RESISTANCE (W) 27.04k 4.925k 4.085k TEMPERATURE (C) Semitec 103AT-2 0C 45C 50C Fenwal 197-103LAG-A01 173-103LAF-301 4C 42C 47C
Used with a 10k resistor the Semitec 103AT-2 provides about 0.9% full scale per degree sensitivity. This linearity is shown in the curve in Figure 4. The left axis is the ratio of the sensed voltage to the divider's input voltage (VCbias).
Figure 4. RATIO OF THM PIN TO CBIAS PIN OVER TEMPERATURE
Divider Output
0.75 0.70 0.65
Voltage Ratio
0.60 0.55 0.50 0.45 0.40 0.35 0.30 0 10 20 30 40 50 Degrees Centigrade
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DS2715: NiMH Cell Pack Charge Controller
LED1 and LED2 Outputs
Open-drain outputs LED1 and LED2 pull low to indicate charge status. When inactive, the outputs are high impedance. LED1 displays the state of charge and LED2 displays the charge results. The LED1 pin drives low in a 1Hz, 50% duty cycle "blink" pattern to indicate cells are charging. LED2 drives low with 100% duty cycle to signal a successful charge completion or blinks at 4Hz, 50% duty cycle to signal a charging fault has occurred. Both LED pins remain in a high-impedance state when no cells are present or the discharge latch is set. LED pins can be tied together if only one LED display is desired. Table 3 summarizes the LED operation for each charge condition.
Table 3. LED DISPLAY PATTERNS BASED ON CHARGE STATE
CHARGE STATE NO BATTERY LED1 LED2 LED1 + LED2 High-Z High-Z High-Z CHARGING Blinks at 1HZ, 50% duty cycle High-Z Blinks at 1HZ, 50% duty cycle DONE High-Z Low Low FAULT High-Z Blinks at 4Hz, 50% duty cycle Blinks at 4Hz, 50% duty cycle DISCHARGE MODE High-Z High-Z High-Z
High-Z = High Impedance
Package Information
For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.
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