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Lithium-Ion/Polymer Battery Charger General Description
The AAT3687 BatteryManager is a member of AnalogicTech's Total Power Management ICTM (TPMICTM) product family. This device is a highly integrated single-cell lithium-ion/polymer battery charger IC designed to operate with AC adapter inputs. It requires a minimum number of external components. The AAT3687 precisely regulates battery charge voltage and current for 4.2V lithiumion/polymer battery cells. Adapter charge current rates can be programmed up to 1.5A. An active thermal management system regulates the fast charge constant current for all ambient temperature and input vs. output voltage conditions. Battery temperature and charge state are fully monitored for fault conditions. In the event of an over-voltage or over-temperature failure, the device will automatically shut down, thus protecting the charging device, control system, and the battery under charge. Status monitor output pins are provided to indicate the battery charge status by directly driving two external LEDs. A serial interface output is available to report 12 various charging status states to a microcontroller. The AAT3687 is available in a Pb-free, thermallyenhanced, space-saving 12-pin TDFN 3x3mm package and is rated over the -40C to +85C temperature range.
AAT3687
Features
* * * *
BatteryManagerTM
* * * * * * * * *
Input Voltage Range: 4.0V to 5.5V Up to 1.5A Charging Current Adapter Present Indicator (ADPP#) High Level of Integration with Internal: -- Charging Device -- Reverse Blocking Diode -- Current Sensing Active Thermal Loop Charge Reduction Automatic Recharge Sequencing Battery Temperature Monitoring Full Battery Charge Auto Turn-Off / Sleep Mode Over-Voltage, Over-Temperature, and Emergency Thermal Protection Power On Reset and Soft Start Serial Interface Status Report 12-Pin 3x3mm TDFN Package -40C to +85C Temperature Range
Applications
* * * * * * Cellular Telephones Digital Still Cameras Hand Held PCs MP3 Players Personal Data Assistants (PDAs) Other Lithium-Ion/Polymer Battery-Powered Devices
Typical Application
Adapter Present Enable Serial Interface
BATT+
ADPP# EN DATA TS BAT COUT 10F
+
BATT-
AAT3687
CT Adapter CIN 10F RSET RB1 LED1 RB2 ADP ADPSET STAT1 GND STAT2 CT 0.1F
TEMP
Battery Pack
LED2
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Lithium-Ion/Polymer Battery Charger Pin Descriptions
Pin #
1 2 3 4
AAT3687
Name
BAT ADP GND EN
Type
Out In Ground In
Function
Battery charging and sensing. Adapter input. Ground connection. AAT3687: Enable pin. Logic high enables the IC. AAT3687-2: Enable pin. Logic high enables the IC. EN tied to internal 4M pull-up resistor to ADP. Adapter present indicator. This pin is open drain until ADP pin reaches threshold. Connect to 10k NTC thermistor. Status report to microcontroller via serial interface: open drain. Battery charge status indicator pin to drive an LED: active low, open drain. Battery charge status indicator pin to drive an LED: active low, open drain. Timing capacitor to adjust internal watchdog timer. Set maximum charge time for adapter powered trickle, CC, and CV charge modes. If timing function is not needed, terminate this pin to ground. No connection. Use resistor at this pin to set adapter charging current. Exposed paddle (bottom); connect to GND directly beneath package.
5 6 7 8 9 10
ADPP# TS DATA STAT2 STAT1 CT
Out In/Out Out Out Out In/Out
11 12 EP
N/C ADPSET In/Out
Pin Configuration
TDFN33-12 (Top View)
BAT ADP GND EN ADPP# TS
1 2 3 4 5 6
12 11 10 9 8 7
ADPSET N/C CT STAT1 STAT2 DATA
2
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Lithium-Ion/Polymer Battery Charger AAT3687 Feature Options
Product
AAT3687 AAT3687-2
AAT3687
Trickle Charge
Yes No
Internal Pull-Up Resistor on EN Pin
No Yes
Can Leave TS Pin Open
No Yes
Absolute Maximum Ratings1
Symbol
VP VP VN TJ TLEAD
Description
ADP Input Voltage, <30ms, Duty Cycle <10% ADP Input Voltage, Continuous BAT, TS, ADPSET, ADPP#, DATA, CT, EN, STAT1, STAT2 Operating Junction Temperature Range Maximum Soldering Temperature (at leads)
Value
-0.3 to 7.0 -0.3 to 6.0 -0.3 to VP + 0.3 -40 to 150 300
Units
V V V C C
Thermal Information
Symbol
JA PD
Description
Maximum Thermal Resistance Maximum Power Dissipation
2
Value
50 2.0
Units
C/W W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on an FR4 board. 3687.2006.06.1.5
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Lithium-Ion/Polymer Battery Charger Electrical Characteristics1
VADP = 5V, TA = -25C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol
Operation ADP VADPP VUVLO IOP ISLEEP ILeakage
AAT3687
Description
Adapter Voltage Range Adapter Present Indicator Threshold Voltage Under-Voltage Lockout (UVLO) UVLO Hysteresis Operating Current Sleep Mode Current
Conditions
Min
4.0 4.25
Typ
Max Units
5.5 V V V mV mA A A 4.242 3.15 V % V V mA % V
4.5 3.0 150 0.75 0.3 1 1.0
4.7
Rising Edge Charge Current = 100mA AAT3687: VBAT = 4.25V AAT3687-2: VBAT = 4.25V VBAT = 4V, ADP Pin Open 4.158 AAT3687 Only 2.8
1.5 1.0 3
Reverse Leakage Current from BAT Pin Voltage Regulation VBAT_EOC1 End of Charge Voltage Accuracy VCH/VCH Output Charge Voltage Tolerance VMIN Preconditioning Voltage Threshold VRCH Battery Recharge Voltage Threshold Current Regulation ICH Charge Current ICH/ICH Charge Current Regulation Tolerance VADPSET ADPSET Pin Voltage KIA Current Set Factor: ICH/IADPSET Charging Devices Adapter Charging Transistor RDS(ON) On Resistance
4.20 0.5 3.0 VBAT_EOC - 0.1
100 CC Mode 10 2.0 4000 0.2 0.25
1500
VIN = 5.5V
0.35
1. The AAT3687 output charge voltage is specified over the 0 to 70C ambient temperature range; operation over the -25C to +85C temperature range is guaranteed by design.
4
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Lithium-Ion/Polymer Battery Charger Electrical Characteristics1
VADP = 5V, TA = -25C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol Description Conditions Min
1.6 AAT3687-2 Only; VEN = 5V ADPP# Pin Sinks 500A CCT = 100nF, VADP = 5.5V AAT3687 Only; CCT = 100nF, VADP = 5.5V CCT = 100nF, VADP = 5.5V STAT Pin Sinks 4mA 3.0 25 3.0 0.4 8.0 4.4 10 7.5 70 310 2.2 3 8 1.6 0.4 200 50 20 90 110 85 145 80 330 15 2.3 10 90 350 2.4 0.4 10 0.4
AAT3687
Typ
Max
Units
V V A V Hours Minutes Hours V mA V % % A mV V mV mA mA V V ns s kHz C C C C
Logic Control / Protection VEN(H) Input High Threshold VEN(L) Input Low Threshold IEN(H) EN Input Current VADPP# Output Low Voltage Preconditioning and Constant TC Current Mode Time Out TP TV VSTAT ISTAT VOVP ITK/ICHG Preconditioning Time Out
ITS TS1 TS2 IDATA IADPP# VDATA(H) VDATA(L) SQPULSE tPERIOD fDATA TREG TLOOP_IN TLOOP_OUT TOVSD
Constant Voltage Mode Time Out Output Low Voltage STAT Pin Current Sink Capability Over-Voltage Protection Threshold Pre-Charge Current AAT3687 Only Charge Termination Threshold Current ITERM/ICHG Current Source from TS Pin Threshold TS Hot Temperature Fault Hysteresis Threshold TS Cold Temperature Fault Hysteresis DATA Pin Sink Current DATA Pin is Active Low State ADPP# Current Sink ADPP# Pin is Active Low State Input High Threshold Input Low Threshold Status Request Pulse Width Status Request System Clock Period Data Output Frequency Thermal Loop Regulation Thermal Loop Entering Threshold Thermal Loop Exiting Threshold Over-Temperature Shutdown Threshold
1. The AAT3687 output charge voltage is specified over the 0 to 70C ambient temperature range; operation over the -25C to +85C temperature range is guaranteed by design. 3687.2006.06.1.5
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Lithium-Ion/Polymer Battery Charger Typical Characteristics
IFASTCHARGE vs. RSET
10000
4.242
AAT3687
Battery Voltage vs. Supply Voltage
IFASTCHARGE (mA)
4.221
1000
VBAT (V)
100 10 1 10 100
4.200
4.179
4.158 4.5 4.75 5.0 5.25 5.5
RSET (k)
Supply Voltage (V)
End of Charge Voltage Regulation vs. Temperature
4.242
Preconditioning Threshold Voltage vs. Temperature
3.05 3.04
4.221
3.03 3.02
VBAT (V)
VMIN (V)
3.01 3.00 2.99 2.98 2.97 2.96
4.200
4.179
4.158 -50
2.95
-25 0 25 50 75 100
-50
-25
0
25
50
75
100
Temperature (C)
Temperature (C)
Preconditioning ICH vs. Temperature
(ADPSET = 8.06k)
120 1100 1080
Fast Charge Current vs. Temperature
(ADPSET = 8.06k)
ICH ADP (mA)
ICH ADP (mA)
-25 0 25 50 75 100
110
1060 1040 1020 1000 980 960 940 920
100
90
80 -50
900 -50 -25 0 25 50 75 100
Temperature (C)
Temperature (C)
6
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Lithium-Ion/Polymer Battery Charger Typical Characteristics
Charging Current vs. Battery Voltage
(ADPSET = 8.06k; VIN = 5.0V)
1.2 1.0 0.8
AAT3687
Fast Charge Current vs. Supply Voltage
(ADPSET = 8.06k)
1200
VBAT = 3.3V
1000 800 600 400 200 0 4.0
0.6 0.4 0.2 0.0 2.5 2.9 3.3 3.7 4.1 4.5
ICH (mA)
VBAT = 3.9V VBAT = 3.5V
ICH (A)
4.5
5.0
5.5
6.0
Battery Voltage (V)
Supply Voltage (V)
VIH vs. Supply Voltage EN Pin (Rising)
1.4 1.3 1.2 1.1 1.4 1.3 1.2 1.1
VIL vs. Supply Voltage EN Pin (Falling)
VIH (V)
0.9 0.8 0.7 0.6 0.5 0.4 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0
VIH (V)
1.0
-40C
+25C
1.0 0.9 0.8 0.7
-40C
+25C
+85C
0.6 0.5 0.4 4.2 4.4 4.6 4.8
+85C
5.0 5.2 5.4 5.6 5.8 6.0
Supply Voltage (V)
Supply Voltage (V)
Adapter Mode Supply Current vs. ADPSET Resistor
0.80 10
Counter Timeout vs. Temperature
(CT = 0.1F)
Counter Timeout (%)
1000
0.70 0.60
8 6 4 2 0 -2 -4 -6 -8
IQ (mA)
0.50 0.40 0.30 0.20 0.10 0.00 1 10
Constant Current
Pre-Conditioning
100
-10 -50
-25
0
25
50
75
100
ADPSET Resistor (k)
Temperature (C)
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Lithium-Ion/Polymer Battery Charger Typical Characteristics
CT Pin Capacitance vs. Counter Timeout
2.0 1.8
AAT3687
Temperature Sense Output Current vs. Temperature
88
Capacitance (F)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 2 4 6 8 10
TS Pin Current (A)
86 84 82 80 78 76 74 72 -50 -25 0 25 50 75 100
Precondition Timeout
Precondition + Constant Current Timeout or Constant Voltage Timeout
Time (hours)
Temperature (C)
8
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Lithium-Ion/Polymer Battery Charger Functional Block Diagram
Constant Current Charge Control CV/ Precharge1
AAT3687
UVLO
4.2V
BAT
ADPSET ADP ADPP#
Voltage Sense
Current Compare
OverTemperature Protection
Reverse Blocking
80A
STAT1 STAT2 DATA EN
Charge Status
TS
Window Comparator
Serial Data
IC enable
Watchdog Timer
CT
GND
Functional Description
The AAT3687 is a highly integrated single-cell lithiumion/polymer battery charger IC designed to operate with standard AC adapter input sources, while requiring a minimum number of external components. The AAT3687 precisely regulates battery charge voltage and current for 4.2V lithium-ion/polymer battery cells. The adapter charge input constant current level can be programmed up to 1.5A for rapid charging applications. The AAT3687 is rated for operation from 40C to +85C. In the event of operating ambient temperatures exceeding the power dissipation abilities of the device package for a given constant current charge level, the charge control will enter into thermal regulation. When the system thermal regulation becomes active, the programmed constant current charge amplitude will be automatically reduced to a safe level for the current operating condition. Should the ambient operating temperature drop below the thermal loop threshold, the system will automatically resume charging at the full programmed constant cur-
rent level. This intelligent thermal management system permits the AAT3687 to operate and safely charge a battery cell over a wide range of ambient conditions while maximizing the greatest possible charge current for the given set of conditions. Status monitor output pins are provided to indicate the battery charge state by directly driving two external LEDs. A serial interface output is also available to report any one of 12 distinct charge states to the system microcontroller. Battery temperature and charge state are fully monitored for fault conditions. In the event of an over-voltage or over-temperature failure, the device will automatically shut down, thus protecting the charging device, control system, and the battery under charge. In addition to internal charge controller thermal protection, the AAT3687 also provides a temperature sense feedback function (TS pin) from the battery to shut down the device in the event the battery exceeds its own thermal limit during charging. All fault events are reported to the user either by the simple status LEDs or via the DATA pin function.
1. Precharge applies to AAT3687 only. 3687.2006.06.1.5
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Lithium-Ion/Polymer Battery Charger
Preconditioning Trickle Charge Phase Constant Current Charge Phase I = Max CC Constant Voltage Charge Phase
AAT3687
Charge Complete Voltage Regulated Current
Constant Current Mode Voltage Threshold
Trickle Charge and Termination Threshold
I = CC / 10
Figure 1: Current vs. Voltage Profile During Charging Phases.
Charging Operation
The AAT3687 has four basic modes for the battery charge cycle: pre-conditioning / trickle charge; constant current / fast charge; constant voltage; and end of charge (see Figure 1.) (AAT3687-2 does not have trickle charge.) Battery Preconditioning Before the start of charging, the AAT3687 checks several conditions in order to assure a safe charging environment. The input supply must be above the minimum operating voltage, or under-voltage lockout threshold (VUVLO), for the charging sequence to begin. Also, the cell temperature, as reported by a thermistor connected to the TS pin from the battery, must be within the proper window for safe charging. When these conditions have been met and a battery is connected to the BAT pin, the AAT3687 checks the state of the battery. If the cell voltage is below the preconditioning voltage threshold (VMIN), the charge control begins preconditioning the cell. The battery preconditioning trickle charge current is equal to the fast charge constant current divided by 10. For example, if the programmed fast charge current is 1.5A, then the preconditioning mode (trickle charge) current will be 150mA. Cell preconditioning is a safety precaution for deeply discharged battery cells and also aids in limiting power dissipation in the pass transistor when the voltage across the device is at the greatest potential. Fast Charge / Constant Current Charging Battery cell preconditioning continues until the voltage on the BAT pin exceeds the preconditioning voltage threshold (VMIN). At this point, the AAT3687 begins the constant current fast charging phase. 10
The fast charge constant current (ICC) amplitude is programmed by the user via the RSET, resistor. The AAT3687 remains in the constant current charge mode until the battery reaches the voltage regulation point, VBAT. Constant Voltage Charging The system transitions to a constant voltage charging mode when the battery voltage reaches the output charge regulation threshold (VBAT) during the constant current fast charge phase. The regulation voltage level is factory programmed to 4.2V (1%). Charge current in the constant voltage mode drops as the battery cell under charge reaches its maximum capacity. End of Charge Cycle Termination and Recharge Sequence When the charge current drops to 7.5% of the programmed fast charge current level in the constant voltage mode, the device terminates charging and goes into a sleep state. The charger will remain in a sleep state until the battery voltage decreases to a level below the battery recharge voltage threshold (VRCH). When the input supply is disconnected, the charger will automatically transition into a power-saving sleep mode. Only consuming an ultra-low 0.3A in sleep mode (1A for AAT3687-2), the AAT3687 minimizes battery drain when it is not charging. This feature is particularly useful in applications where the input supply level may fall below the battery charge or under-voltage lockout level. In such cases where the AAT3687 input voltage drops, the device will enter sleep mode and automatically resume charging once the input supply has recovered from the fault condition.
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System Operation Flow Chart
AAT3687
Output ADPP
Yes
ADP Voltage ADP > VADPP No
Yes
UVLO VP > VUVLO No
Yes
Switch No Sleep Mode Thermal Loop
Power On Reset
ADP Loop
Enable
No Timing Fault Conditions Monitor OV, OT Yes Device Temperature Monitor TJ > 110C Yes Thermal Loop Current Reduction
No Shut Down Yes Battery Temperature Monitor VTS1 < TS < VTS2 No
Expire
No
Recharge Test VRCH > VBAT
Battery Temperature Charge Safety Timer Set
Yes (AAT3687-2)
Yes (AAT3687) Yes Low Current Conditioning
Preconditioning Test VMIN > VBAT
No Yes Current Charging Mode
Current Phase Test VCH > VBAT
No Yes Voltage Charging Mode
Voltage Phase Test IBAT > IMIN No Charge Completed
Application Information
Adapter Power Input
Constant current charge levels up to 1.5A may be programmed by the user when powered from a sufficient input power source. The AAT3687 will operate from the adapter input over a 4.0V to 5.5V range.
The constant current fast charge current for the adapter input is set by the RSET resistor connected between the ADPSET and ground. Refer to Table 1 for recommended RSET values for a desired constant current charge level. The presence of voltage on the adapter input is indicated by the ADPP# pin function. This indicator pin uses an internal open drain device that will pull the ADPP# pin low when
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Lithium-Ion/Polymer Battery Charger
voltage is detected on the ADP pin. The precise charging function of the AAT3687 may be read from the DATA pin and/or status LEDs. Please refer to the Battery Charge Status Indication discussion for further details on data reporting. Thermal Loop Control Due to the integrated nature of the linear charging control pass device for the adapter input, a special thermal loop control system has been employed to maximize charging current under all operating conditions. The thermal management system measures the internal circuit die temperature and reduces the fast charge current when the device exceeds a preset internal temperature control threshold. Once the thermal loop control becomes active, the fast charge current is initially reduced by a factor of 0.44. The initial thermal loop current can be estimated by the following equation: Eq. 1:
AAT3687
Enable / Disable
The AAT3687 provides an enable function to control the charger IC on and off. The enable (EN) pin is active high. When pulled to a logic low level, the AAT3687 will be shut down and forced into the sleep state. Charging will be halted regardless of the battery voltage or charging state. When the device is reenabled, the charge control circuit will automatically reset and resume charging functions with the appropriate charging mode based on the battery charge state and measured cell voltage on the BAT pin.
Programming Charge Current
The fast charge constant current charge level is user programmed with a set resistor placed between the ADPSET pin and ground. The accuracy of the fast charge, as well as the preconditioning trickle charge current, is dominated by the tolerance of the set resistor used. For this reason, a 1% tolerance metal film resistor is recommended for the set resistor function. Fast charge constant current levels from 50mA to 1.5A can be set by selecting the appropriate resistor value from Table 1.
ITLOOP = ICC * 0.44
The thermal loop control re-evaluates the circuit die temperature in 330ms intervals and adjusts the fast charge current back up in small steps to the full fast charge current level or until an equilibrium current is discovered and maximized for the given ambient temperature condition. The thermal loop controls the system charge level; therefore, the AAT3687 will always provide the highest level of constant current in the fast charge mode possible for any given ambient temperature condition. Adapter Input Charge Inhibit and Resume The AAT3687 has a UVLO and power on reset feature so that the charger will suspend charging and shut down if the input supply to the adapter pin drops below the UVLO threshold. When power is re-applied to the adapter pin or the UVLO conditions recovers, the system charge control will assess the state of charge on the battery cell and will automatically resume charging in the appropriate mode for the condition of the battery.
ICC
50 75 100 200 300 400 500 600 700
ADP RSET (k)
N/A N/A 84.5 43.2 28.0 21.0 16.9 13.3 11.5
ICC
800 900 1000 1100 1200 1300 1400 1500
ADP RSET (k)
10.2 9.09 8.06 7.32 6.65 6.04 5.62 5.36
Table 1: Recommended RSET Values.
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Lithium-Ion/Polymer Battery Charger
10000
AAT3687
IFASTCHARGE (mA)
pin to ground. The CT pin should not be left floating or un-terminated, as this will cause errors in the internal timing control circuit. The constant current provided to charge the timing capacitor is very small, and this pin is susceptible to noise and changes in capacitance value. Therefore, the timing capacitor should be physically located on the printed circuit board layout as close as possible to the CT pin. Since the accuracy of the internal timer is dominated by the capacitance value, a 10% tolerance or better ceramic capacitor is recommended. Ceramic capacitor materials, such as X7R and X5R types, are a good choice for this application. Over-Voltage Protection An over-voltage event is defined as a condition where the voltage on the BAT pin exceeds the maximum battery charge voltage and is set by the over-voltage protection threshold (VOVP). If an over-voltage condition occurs, the AAT3687 charge control will shut down the device until the voltage on the BAT pin drops below VOVP. The AAT3687 will resume normal charging operation after the over-voltage condition is removed. During an overvoltage event, the STAT LEDs will report a system fault, and the actual fault condition can be read via the DATA pin signal. Over-Temperature Shutdown The AAT3687 has a thermal protection control circuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold. Battery Temperature Fault Monitoring In the event of a battery over-temperature condition, the charge control will turn off the internal pass device and report a battery temperature fault on the DATA pin function. The STAT LEDs will also display a system fault. After the system recovers from a temperature fault, the device will resume charging operation. The AAT3687 checks battery temperature before starting the charge cycle, as well as during all stages of charging. This is accomplished by monitoring the voltage at the TS pin. This system is intended for use with negative temperature coefficient thermistors (NTC) which are typically integrated into the battery package. Most of the commonly used NTC thermistors in battery packs are 13
1000
100
10 1 10 100
RSET (k)
Figure 2: IFASTCHARGE vs. RSET.
Protection Circuitry
Programmable Watchdog Timer The AAT3687 contains a watchdog timing circuit to shut down charging functions in the event of a defective battery cell not accepting a charge over a preset period of time. Typically, a 0.1F ceramic capacitor is connected between the CT pin and ground. When a 0.1F ceramic capacitor is used, the device will time out a shutdown condition if the trickle charge mode exceeds 25 minutes (AAT3687 only) and a combined trickle charge plus fast charge mode of 3 hours. When the device transitions to the constant voltage mode, the timing counter is reset and will time out after an additional 3 hours if the charge current does not drop to the charge termination level. Mode
Trickle Charge (TC) Time Out Trickle Charge (TC) + Fast Charge (CC) Time Out Constant Voltage (VC) Mode Time Out
Time
25 minutes (AAT3687 only) 3 hours 3 hours
Table 2: Summary for a 0.1F Ceramic Capacitor Used for the Timing Capacitor. The CT pin is driven by a constant current source and will provide a linear response to increases in the timing capacitor value. Thus, if the timing capacitor were to be doubled from the nominal 0.1F value, the time-out periods would be doubled. If the programmable watchdog timer function is not needed, it can be disabled by terminating the CT
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Lithium-Ion/Polymer Battery Charger
approximately 10k at room temperature (25C). The TS pin has been specifically designed to source 80A of current to the thermistor. The voltage on the TS pin resulting from the resistive load should stay within a window of 335mV to 2.32V. If the battery becomes too hot during charging due to an internal fault or excessive fast charge current, the thermistor will heat up and reduce in value, pulling the TS pin voltage lower than the TS1 threshold, and the AAT3687 will signal the fault condition. If the use of the TS pin function is not required by the system, it should be terminated to ground using a 10k resistor. Alternatively, on the AAT3687-2, the TS pin may be left open. simply wants to have a single lamp to show "charging" or "not charging." This can be accomplished by using the STAT1 pin and a single LED. Using two LEDs and both STAT pins simply gives the user more information to the charging states. Refer to Table 3 for LED display definitions. The LED anodes should be connected to VADP. The LEDs should be biased with as little current as necessary to create reasonable illumination; therefore, a ballast resistor should be placed between the LED cathodes and the STAT1/2 pins. LED current consumption will add to the overall thermal power budget for the device package, hence it is good to keep the LED drive current to a minimum. 2mA should be sufficient to drive most low-cost green or red LEDs. It is not recommended to exceed 8mA for driving an individual status LED. The required ballast resistor values can be estimated using the following formulas:
AAT3687
Battery Charge Status Indication
The AAT3687 indicates the status of the battery under charge with two different systems. First, the device has two status LED driver outputs. These two LEDs can indicate simple functions such as no battery charge activity, battery charging, charge complete, and charge fault. The AAT3687 also provides a bi-directional data reporting function so that a system microcontroller can interrogate the DATA pin and read any one of 12 system states. Status Indicator Display Simple system charging status states can be displayed using one or two LEDs in conjunction with the STAT1 and STAT2 pins on the AAT3687. These two pins are simple open drain switches used to connect the LED cathodes to ground. It is not necessary to use both display LEDs if a user
Eq. 2: RB(STAT1/2) = Example: Eq. 3: RB(STAT1) =
(VADP - VF(LED)) ILED(STAT1/2)
(5.5V - 2.0V) = 1.75k 2mA
Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA
Event Description
Charge Disabled or Low Supply Charge Enabled Without Battery Battery Charging Charge Completed Fault
STAT1
Off Flash1 On Off On
STAT2
Off Flash1 Off On On
Table 3: LED Status Indicator.
1. Flashing rate depends on output capacitance.
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Digital Charge Status Reporting
The AAT3687 has a comprehensive digital data reporting system by use of the DATA pin feature. This function can provide detailed information regarding the status of the charging system. The DATA pin is a bi-directional port which will read back a series of data pulses when the system microcontroller asserts a request pulse. This single strobe request protocol will invoke one of 12 possible return pulse counts that the system microcontroller can look up based on the serial report data listed in Table 4. The DATA pin function logic is active low and should normally be pulled high to VADP. This data line can also be pulled high to the same level as the high state for the logic I/O port on the system microcontroller. In order for the DATA pin control circuit to generate clean, sharp edges for the data output, and to maintain the integrity of the data timing for the system, the pull-up resistor on the data line should be low enough in value so that the DATA signal returns to the high state without delay. If the pull-up resistor is too high, the strobe pulse from the system microcontroller could exceed the maximum pulse time and the DATA output control could issue false status reports. A 1.5k resistor is recommended when pulling the DATA pin high to 5.0V on the VADP input. If the data line is pulled high to a voltage level less than 5.0V, the pull-up resistor can be calculated based on a recommended minimum pull-up current of 3mA. Use the following formula:
AAT3687
Eq. 4: RPULL-UP
VPULL-UP 3mA
1.8V to 5.0V
IN
AAT3687 Status Control
OUT
RPULL_UP DATA Pin
GPIO
IN
OUT
P GPIO Port
Figure 3: Data Pin Application Circuit.
Data Timing
The system microcontroller should assert an active low data request pulse for minimum duration of 200ns; this is specified by TLO(DATA). Upon sensing the rising edge of the end of the data request pulse,
the AAT3687 status data control will reply the data word back to the system microcontroller after a delay specified by the data report time specification TDATA(RPT). The period of the following group of data pulses will be specified by TDATA.
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Lithium-Ion/Polymer Battery Charger
Timing Diagram
SQPULSE System Reset System Start PDATA
AAT3687
SQ
CK
TSYNC TLAT TOFF
Data
TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA TOFF > 2 PDATA
N=1
N=2
N=3
N
1 2 3 4 5 6 7 8 9 10 11 12 23
DATA Report Status
Chip Over-Temperature Shutdown. Battery Temperature Fault. Over-Voltage Turn Off. Not Used. ADP Watchdog Time-Out in Battery Condition Mode. ADP Battery Condition Mode. ADP Watchdog Time-Out in Constant Current Mode. ADP Thermal Loop Regulation in Constant Current Mode. ADP Constant Current Mode. ADP Watchdog Time-Out in Constant Voltage Mode. ADP Constant Voltage Mode. ADP End of Charging. Data Report Error. Table 4: Serial Data Report Table.
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Lithium-Ion/Polymer Battery Charger
Thermal Considerations
The AAT3687 is offered in a 3x3mm TDFN package which can provide up to 2.0W of power dissipation when it is properly bonded to a printed circuit board and has a maximum thermal resistance of 50C/W. Many considerations should be taken into account when designing the printed circuit board layout, as well as the placement of the charger IC package in proximity to other heat generating devices in a given application design. The ambient temperature around the charger IC will also have an effect on the thermal limits of a battery charging application. The maximum limits that can be expected for a given ambient condition can be estimated by the following discussion. First, the maximum power dissipation for a given situation should be calculated: Eq. 5: PD = [(VIN - VBAT) * ICC + (VIN * IOP)] Where: TA = Ambient Temperature in C TJ = Maximum Device Junction Temperature Below the Thermal Loop Threshold PD = Total Power Dissipation by the Device JA = Package Thermal Resistance in C/W Example: For an application where the fast charge current for the adapter mode is set to 1A, VADP = 5.0V and the battery voltage at 3.6V, what is the maximum ambient temperature at which the thermal loop will become active? Given: VADP = 5.0V VBAT = 3.6V ICC IOP Where: PD = Total Power Dissipation by the Device VIN = Input Voltage Amplitude, VADP VBAT = Battery Voltage as Seen at the BAT Pin ICC IOP = Maximum Constant Fast Charge Current Programmed for the Application = Quiescent Current Consumed by the Charger IC for Normal Operation TJ = 1A = 0.75mA = 110C
AAT3687
JA = 50C/W Using Equation 5, calculate the device power dissipation for the stated condition: Eq. 7: PD = (5.0V - 3.6V)(1A) + (5.0V * 0.75mA)
= 1.40375W
The maximum ambient temperature before the AAT3687 thermal loop becomes active can now be calculated using Equation 6: Eq. 8: TA = 110C - (50C/W * 1.40375W)
Next, the maximum operating ambient temperature for a given application can be estimated based on the thermal resistance of the 3x3mm TDFN package when sufficiently mounted to a PCB layout and the internal thermal loop temperature threshold. Eq. 6: TA = TJ - (JA * PD)
= 39.8125C
Therefore, under the stated conditions for this worst case power dissipation example, the AAT3687 will enter the thermal loop and lower the fast charge constant current when the ambient operating temperature rises above 39.8C.
3687.2006.06.1.5
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Lithium-Ion/Polymer Battery Charger
Capacitor Selection
Input Capacitor In general, it is good design practice to place a decoupling capacitor between the ADP pin and ground. An input capacitor in the range of 1F to 22F is recommended. If the source supply is unregulated, it may be necessary to increase the capacitance to keep the input voltage above the under-voltage lockout threshold during device enable and when battery charging is initiated. If the AAT3687 adapter input is to be used in a system with an external power supply source, such as a typical AC-to-DC wall adapter, then a CIN capacitor in the range of 10F should be used. A larger input capacitor in this application will minimize switching or power transient effects when the power supply is "hot plugged" in. Output Capacitor The AAT3687 only requires a 1F ceramic capacitor on the BAT pin to maintain circuit stability. This value should be increased to 10F or more if the battery connection is made any distance from the charger output. If the AAT3687 is to be used in applications where the battery can be removed from the charger, such as with desktop charging cradles, an output capacitor greater than 10F may be required to prevent the device from cycling on and off when no battery is present.
AAT3687
Printed Circuit Board Layout Considerations
For the best results, it is recommended to physically place the battery pack as close as possible to the AAT3687 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. For maximum power dissipation of the AAT3687 3x3mm TDFN package, the metal substrate should be solder bonded to the board. It is also recommended to maximize the substrate contact to the PCB ground plane layer to further increase local heat dissipation. Refer to the AAT3687 evaluation board for a good layout example (see Figures 4 and 5).
AAT3687 Evaluation Board Layout
Figure 4: AAT3687 Evaluation Board Component Side Layout.
Figure 5: AAT3687 Evaluation Board Solder Side Layout.
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3687.2006.06.1.5
Lithium-Ion/Polymer Battery Charger
AAT3687 Evaluation Board Schematic Diagram
ADP GND
1 2
AAT3687
C1 10F
J1 ON/OFF
123
RED GRN RED LED D3 LED D2 LED D1
R3 4.99k R1 Open U1
2 1 4
R4 4.99k
R5 4.99k
R7 1k
(TDFN33-12)
ADP BAT EN
ADPP# STAT2 STAT1 DATA
5 8 9 7
BAT TS GND
1 3 2
DATA
AAT3687
C2 10F R2 10k
ADPSET
6
12
TS GND
3
CT
10
R6 8.06k C3 0.1F
SW1
CT
3687.2006.06.1.5
19
Lithium-Ion/Polymer Battery Charger
AAT3687 Evaluation Board Bill of Materials (BOM)
Quantity Description
1 1 1 2 1 2 1 1 1 3 1 1 1 1 Test Pin Connecting Terminal Block, 2.54mm, 2 Position Connecting Terminal Block, 2.54mm, 3 Position Capacitor, Ceramic, 10F 6.3V 10% X5R 0805 Capacitor, Ceramic, 1F 10% 25V X5R 0603 Typical Red LED, Ultra-Bright Typical Green LED
AAT3687
Desig.
DATA ADP, GND BAT, GND, TS C1, C2 C3 D1, D3 D2
Footprint
PAD TBLOK2 TBLOK3 0805 0603 1206LED
Manufacturer
Mill-Max Phoenix Contact Phoenix Contact Murata Murata
Part Number
6821-0-0001-00-00-08-0 277-1274-ND 277-1273-ND 490-1717-1-ND 478-1244-2-ND CMD15-21SRC/TR8 CMD15-21VGC/TR8 6821-0-0001-00-00-08-0 P10KCFCT-ND P4.99KHTR-ND P8.06KHCT-ND P1.0KCGCT-ND CKN9012-ND AAT3687IWP-4.2
Header, 3-Pin J1 Resistor, 10k, 1/16W R2 5% 0603 SMD Resistor, 4.99k, 1/16W R3, R4, R5 1% 0603 SMD Resistor, 8.06k, 1/16W R6 1% 0603 SMD Resistor, 1k, 1/16W R7 5% 0603 SMD Switch Tact 6mm SPST SW1 H = 5.0mm AAT3687 Lithium-Ion/Polymer U1 Battery Charge Controller
Chicago Miniature Lamp 1206LED Chicago Miniature Lamp HEADER2MM-3 Sullins 0603 Panasonic/ECG 0603 0603 0603 Switch TDFN33-12 Panasonic/ECG Panasonic/ECG Panasonic/ECG ITT Industries/ C&K Div AnalogicTech
20
3687.2006.06.1.5
Lithium-Ion/Polymer Battery Charger Ordering Information
Trickle Charge
Yes No
AAT3687
Package
TDFN33-12 TDFN33-12
Marking1
PIXYY RTXYY
Part Number (Tape and Reel)2
AAT3687IWP-4.2-T1 AAT3687IWP-4.2-2-T1
All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
Index Area (D/2 x E/2) Detail "B"
3.00 0.05
2.40 0.05
0.3 0.10 0.16 0.375 0.125 0.075 0.075 0.1 REF
Top View
Bottom View
Pin 1 Indicator (optional)
7.5 7.5
+ 0.05 0.8 -0.20
0.229 0.051
0.05 0.05
Option A: C0.30 (4x) max Chamfered corner
Option B: R0.30 (4x) max Round corner
Detail "B"
Side View
Detail "A"
All dimensions in millimeters.
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3687.2006.06.1.5
0.23 0.05
0.45 0.05
Detail "A"
3.00 0.05
1.70 0.05
21
Lithium-Ion/Polymer Battery Charger
AAT3687
(c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 22
3687.2006.06.1.5

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