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USB Port Lithium-Ion/Polymer Battery Charger General Description
The AAT3688 BatteryManagerTM is a highly integrated single cell lithium-ion/polymer battery charger IC designed to operate with USB port inputs. It requires the minimum number of external components. The AAT3688 precisely regulates battery charge voltage and current for 4.2V lithium-ion/polymer battery cells. Depending on the USB port type, the AAT3688 charge current can be programmed for two separate levels up to 500mA. An optional Charge Reduction Loop is built in to allow users to charge the battery with available current from a USB port, while keeping the port voltage regulated. 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 any one of 14 various status states to a microcontroller. The AAT3688 is available in a Pb-free, thermallyenhanced, space-saving 12-pin 3x3mm TDFN package and is rated over the -40C to +85C temperature range.
AAT3688
Features
* * *
BatteryManagerTM
* * * * * * * * *
USB Charger -- Programmable up to 500mA Max 4.0V to 5.5V Input Voltage Range High Level of Integration With Internal: -- Charging Device -- Reverse Blocking Diode -- Current Sensing Automatic Recharge Sequencing Charge Reduction Loop for USB Charging Battery Temperature Monitoring Full Battery Charge Auto Turn-Off Over-Voltage Protection Emergency Thermal Protection Power On Reset and Soft Start Serial Interface Status Reporting 12-Pin 3x3mm TDFN Package
Applications
* * * * * * * BluetoothTM Headsets Cellular Telephones Digital Still Cameras Hand-Held PCs MP3 Players Personal Data Assistants (PDAs) Other Lithium-Ion/Polymer Battery-Powered Devices
Typical Application
Enable USB Input USB Hi/Lo Select
USB USBSEL USBH RSETH RSETL USBL BAT TS C2 10F EN CHR
BATT+
AAT3688
GND
BATT-
DATA STAT1 STAT2
TEMP
Battery Pack
Serial Data
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USB Port Lithium-Ion/Polymer Battery Charger Pin Descriptions
Pin #
1 2 3 4
AAT3688
Name
USB BAT GND CHR
Type
In In/Out Ground In/Out
Function
USB power supply input. Battery charging and sensing. Ground connection. Resistor divider to set USB voltage regulation for charge reduction mode. Leave this pin open for default 4.5V USB regulation point. Tie to USB pin to disable this function. Enable pin. Logic high enables the IC. 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. When USB is present, use this pin to toggle between USBH and USBL charging levels. Connect resistor here to set charge current for low-current USB port. Connect resistor here to set charge current for high-current USB port. Exposed paddle (bottom); connect to GND directly beneath package.
5 6 7 8 9 10 11 12 EP
EN TS DATA STAT2 STAT1 USBSEL USBL USBH
In In/Out In/Out Out Out In In/Out In/Out
Pin Configuration
TDFN33-12 (Top View)
USB BAT GND CHR EN TS
1 2 3 4 5 6
12 11 10 9 8 7
USBH USBL USBSEL STAT1 STAT2 DATA
2
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USB Port Lithium-Ion/Polymer Battery Charger Absolute Maximum Ratings1
Symbol
VP VP VN TJ TLEAD
AAT3688
Description
USB Input Voltage, <30ms, Duty Cycle <10% USB Input Voltage, Continuous BAT, USBSEL, USBH, USBL, STAT1, STAT2, DATA, TS, CHR, EN Operating Junction Temperature Range Maximum Soldering Temperature (at leads)
Value
-0.3 to 7.0 -0.3 to 6.0 -0.3 to VVP + 0.3 -40 to 150 300
Units
V V V C C
Thermal Information2
Symbol
JA PD
Description
Maximum Thermal Resistance (3x3mm TDFN) Maximum Power Dissipation
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. 3688.2006.10.1.5
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USB Port Lithium-Ion/Polymer Battery Charger Electrical Characteristics1
VADP = 5V, TA = -25C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol
Operation USB
AAT3688
Description
Conditions
Min
4.0
Typ
Max Units
5.5 V V mV mA A A 4.242 3.15 4.64 2.1 500 V % V V V V mA % V V
Input Voltage Range Under-Voltage Lockout VUVLO Under-Voltage Lockout Hysteresis IOP Operating Current ISLEEP Sleep Mode Current Reverse Leakage Current from ILeakage BAT Pin Voltage Regulation VBAT_EOC1 End of Charge Voltage Accuracy VBAT/VBAT EOC Voltage Tolerance VMIN Preconditioning Voltage Threshold VRCH Battery Recharge Voltage Threshold VUSB_CHR USB Charge Reduction Regulation VCHR CHR Pin Voltage Accuracy Current Regulation ICH Charge Current Charge Current Regulation ICH/ICH Tolerance VUSBH USBH Pin Voltage VUSBL USBL Pin Voltage KIUH Current Set Factor: ICHARGE/IUSBH KIUL Current Set Factor: ICHARGE/IUSBL Charging Devices USB Charging Transistor RDS(ON)U On Resistance
Rising Edge CC Charge Current = 500mA VBAT = 4.25V VBAT = 4V, USB Pin Open 4.158 2.8 No Connection on CHR Pin 4.3 1.9 50
3.0 150 0.75 0.3 1.0 4.2 0.5 3.0 VBAT_EOC - 0.1 4.5 2.0
1.5 1.0
10 CC Mode CC Mode 2.0 2.0 2000 2000 0.4 0.5 0.65
VIN = 5.5V
1. The AAT3688 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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USB Port 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 Typ
1.6 0.4 1.6 STAT Pin Sinks 4mA 8.0 4.4 10 50 7.5 35 80 330 15 2.3 10 0.4 0.4
AAT3688
Max
Units
V V V V V mA V % % % A mV V mV mA V V ns s kHz C
Logic Control / Protection VUSBSEL(H) Input High Threshold VUSBSEL(L) Input Low Threshold VEN(H) Input High Threshold VEN(L) Input Low Threshold VSTAT Output Low Voltage ISTAT STAT Pin Current Sink Capability VOVP Over-Voltage Protection Threshold ITK/ICHG ITERM/ICHG ITERM/ICHG ITS TS1 TS2 I_DATA VDATA(H) VDATA)(L) SQPULSE tPERIOD fDATA TOVSD Pre-Charge Current Charge Termination Threshold Current Charge Termination Threshold Current Current Source from TS Pin TS Hot Temperature Fault TS Cold Temperature Fault DATA Pin Sink Current Input High Threshold Input Low Threshold Status Request Pulse Width System Clock Period Data Output Frequency Over-Temperature Shutdown Threshold
For For For For
USBH Mode USBL Mode USBH Mode USBL Mode 70 310 2.2 3.0 1.6
Threshold Hysteresis Threshold Hysteresis DATA Pin is Active Low State
90 350 2.4
0.4 Status Request 200 50 20 145
1. The AAT3688 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. 3688.2006.10.1.5
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USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics
IFASTCHARGE vs. RSET
1000
AAT3688
Battery Voltage vs. Supply Voltage
4.242
IFASTCHARGE (mA)
4.221
USBL
100
VBAT (V)
USBH
100 1000
4.200
4.179
10
1
10
4.158 4.5 4.75 5 5.25 5.5
RSET (k)
Supply Voltage (V)
Recharge Voltage vs. Temperature
4.140 4.130 4.120 4.110
End of Charge Voltage vs. Temperature
4.242
4.221
VRCH (V)
4.090 4.080 4.070 4.060 4.050 4.040 -50 -25 0 25 50 75 100
VBAT (V)
4.100
4.200
4.179
4.158 -50 -25 0 25 50 75 100
Temperature (C)
Temperature (C)
Preconditioning Threshold Voltage vs. Temperature
3.05 3.04 3.03 3.02
Preconditioning Charge Current vs. Temperature
(USBH; USBH = 8.06k)
60
55
VMIN (V)
3.01 3.00 2.99 2.98 2.97 2.96 2.95 -50 -25 0 25 50 75 100
ICH (mA)
50
45
40 -50 -25 0 25 50 75 100
Temperature (C)
Temperature (C)
6
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USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics
Fast Charge Current vs. Temperature
(USBH; USBH = 8.06k)
540 530 520 510 500 400 600
AAT3688
Charging Current vs. Battery Voltage
(USBH; USBH = 8.06k)
ICH (mA)
ICH (A)
500 490 480 470 460 450 440 -50 -25 0 25 50 75 100
300 200 100 0
2.5
3
3.5
4
4.5
Temperature (C)
Battery Voltage (V)
Charging Current vs. Battery Voltage
(USBL; USBL = 40.2k)
120 100 80 60 40 20 0 2.5 3 3.5 4 4.5
Fast Charge Current vs. Supply Voltage
(USBH; USBH = 8.06k)
600
VBAT = 3.5V
500
VBAT = 3.3V
ICH (mA)
ICH (mA)
400
VBAT = 3.9V
300 200 100 0 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6
Battery Voltage (V)
Supply Voltage (V)
Fast Charge Current vs. Supply Voltage
(USBL; USBL = 40.2k)
120
Fast Charge Current vs. Supply Voltage
(USBH; USBH = 8.06k)
600
VBAT = 3.5V
100 500
0C
400
VBAT = 3.9V
80
ICH (mA)
ICH (mA)
70C 25C
60 40 20 0 4 4.5
VBAT = 3.3V
300 200 100 0 4.40
5
5.5
6
6.5
4.50
4.60
4.70
4.80
4.90
5.00
Supply Voltage (V)
Supply Voltage (V)
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USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics
VIH vs. Supply Voltage
EN Pin (Rising)
1.4 1.3 1.2 1.1 1.4 1.3 1.2
AAT3688
VIL vs. Supply Voltage
EN Pin (Falling)
-40C
+25C
1.1
-40C
+25C
VIH (V)
0.9 0.8 0.7 0.6 0.5 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
VIL (V)
+85C
1.0
1.0 0.9 0.8 0.7 0.6 0.5 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
+85C
Supply Voltage (V)
Supply Voltage (V)
VIH vs. Supply Voltage
USBSEL (Rising)
1.4 1.3 1.2 1.1 1.4 1.3
VIL vs. Supply Voltage
USBSEL (Falling)
-40C
+25C
1.2 1.1
-40C
+25C
VIH (V)
0.9 0.8 0.7 0.6 0.5 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
VIL (V)
+85C
1.0
1.0 0.9 0.8 0.7 0.6 0.5 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
+85C
Supply Voltage (V)
Supply Voltage (V)
USB Supply Current vs. USBH Resistor
0.80 0.70 0.60
USB VBUS (200mV/div) USB Charge Current (200mA/div)
USB Charge Current vs. Time
(USBH; USBH = 8.06k)
IQ (mA)
0.50 0.40 0.30 0.20 0.10 0.00 1 10
Constant Current
Charge Reduction Mode Activated
Pre-Conditioning
USB Peripheral Current Consumption (200mA/div) 0 2 4 6 8 10
100
1000
USBH Resistor (k)
Time (sec)
8
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USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics
Temperature Sense Output Current vs. Temperature
88
AAT3688
TS Pin CUrrent (A)
86 84 82 80 78 76 74 72 -50 -25 0 25 50 75 100
Temperature (C)
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USB Port Lithium-Ion/Polymer Battery Charger Functional Block Diagram
Reverse Blocking
AAT3688
USB USBSEL USBH USBL CHR
Charge Reduction Loop
BAT
Current Compare CV/ Precharge
Constant Current
Charge Control
UVLO
OverTemperature Protect
STAT1 STAT2
Charge Status
80A
DATA
Serial Data
TS
Window Comparator
IC enable EN GND
Functional Description
The AAT3688 is a highly integrated single cell lithium-ion/polymer battery charger IC designed to operate from USB port VBUS supplies, while requiring a minimum number of external components. The device precisely regulates battery charge voltage and current for 4.2V lithium-ion/polymer battery cells. The AAT3688 is specifically designed to be powered from a USB port VBUS supply, but it can also be powered from any input voltage source capable supplying 4.5V to 5.5V for loads up to 500mA. Depending on the USB port type, the AAT3688 constant charge current can be externally programmed for two levels, USB high and USB low, for maximum constant current charge levels up to 500mA. Typically, the USB charge levels are set at 500mA and 100mA for the USBH and USBL modes; however, the user may program either mode to any level they desire below 500mA. The USBH/L mode has an automatic Charge Reduction Loop control to allow users to charge the battery with limited available current from a USB port while 10
maintaining the regulated port voltage. This system assures the battery charge function will not overload a USB port while charging if other system demands also share power with the respective port supply. 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 14 various charge states to a 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 AAT3688 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.
3688.2006.10.1.5
USB Port Lithium-Ion/Polymer Battery Charger
Preconditioning Trickle Charge Phase Constant Current Charge Phase I = Max CC Constant Voltage Charge Phase
AAT3688
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 AAT3688 has four basic modes for the battery charge cycle and is powered from the USB input: pre-conditioning/trickle charge; constant current/fast charge; constant voltage; and end of charge. For reference, Figure 1 shows the current versus voltage profile during charging phases. Battery Preconditioning Before the start of charging, the AAT3688 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. In addition, 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 AAT3688 checks the state of the battery. If the cell voltage is below the Preconditioning Voltage Threshold (VMIN), the AAT3688 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 500mA, then the preconditioning mode (trickle charge) current will be 50mA. Cell preconditioning is a safety precaution for a deeply discharged battery 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 AAT3688
begins the constant current fast charging phase. The fast charge constant current (ICC) amplitude is determined by the selected charge mode USBH or USBL and is programmed by the user via the RSETH and RSETL resistors. The AAT3688 remains in 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 output charge regulation threshold (VBAT) during the constant current, fast charge phase. The regulation voltage level is factory programmed to 4.2V ( 1%). The 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 also automatically enter power-saving sleep mode. Only consuming an ultra-low 0.3A in sleep mode, the AAT3688 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 AAT3688 input voltage drops, the device will enter the sleep mode and automatically resume charging once the input supply has recovered from its fault condition. 11
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USB Port Lithium-Ion/Polymer Battery Charger
System Operation Flow Chart
Switch On
AAT3688
Sleep Mode
No
UVLO VP > VUVLO
Yes
USB Power
Power On Reset
USB Low Current Loop
0
USB Detect USBSEL= ?
USB High Current Loop Fault Conditions Monitor OV, OT No Yes
1
Shut Down Mode No Battery Temp. Fault
Yes
Battery
Temperature Monitor
VTS1 < TS < VTS2
USB Voltage Regulation Enable
No Recharge Test VRCH > VBAT Yes Preconditioning Test VMIN > VBAT No Yes Current Phase Test VEOC > VBAT Current Charging Mode Yes Low Current Conditioning Charge USB Voltage Test VUSB < 4.5V
No
Yes USB Loop Current Reduction in USB Charging Mode
No Yes Voltage Charging Mode
Voltage Phase Test IBAT > ITERM No Charge Completed
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USB Port Lithium-Ion/Polymer Battery Charger Application Information
USB System Power Charging
The USB charge mode provides two programmable fast charge levels up to 500mA for each, USB high and USB low, USBH and USBL, respectively. The USBH or USBL modes may be externally selected by the USB select pin (USBSEL). When the USBSEL pin is connected to a logic high level, the USBH level will be active. Conversely, when USBSEL is pulled to a logic low level (ground), the USBL level will be used for fast charging. Typically USBH is set for 500mA and USBL is set for 100mA. However, these two USB charge levels may be user programmed to any level between 50mA and 500mA by selecting the appropriate resistor values for RSETH and RSETL. Refer to Table 1 for recommended RSETH and RSETL values for the desired USB input constant current charge levels. USB Charge Reduction In many instances, product system designers do not know the real properties of a potential USB port to be used to supply power to the battery charger. Typical powered USB ports commonly found on desktop and notebook PCs should supply up to 500mA. In the event a USB port being used to supply the charger is unable to provide the programmed fast charge current, or if the system under charge must also share supply current with other functions, the AAT3688 will automatically reduce USB fast charge current to maintain port integrity and protect the host system. The USB charge reduction system becomes active when the voltage on the USB input falls below the USB charge reduction threshold (VUSBCHR), which is typically 4.5V. Regardless of which USB charge function is selected (USBH or USBL), the charge reduction system will reduce the fast charge current level in a linear fashion until the voltage sensed on the USB input recovers above the charge reduction threshold voltage. The USB charge reduction threshold (VUSBCHR) may be externally set to a value lower than 4.5V by placing a resistor divider network between VUSB and ground with the center connected to the CHR pin. The USB charge reduction feature may be disabled by connecting a 10k resistor from the CHR pin directly to the USB input pin. The following equation may be used to approximate a USB charge reduction threshold below 4.5V:
AAT3688
R12 Eq. 1: VUSBCHR = 2.0V / R12 + R11
where R11/R12 << 1M.
ICC
50 75 100 200 300 400 500
USBH RSET (k)
86.6 57.6 42.2 21.0 13.7 10.2 8.06
USBL RSET (k)
86.6 57.6 42.2 20.5 13.7 10.2 8.06
VUSB
USB
R11
1.025M
CHR
VCHR = 2.0V
825k
R12
Table 1: Recommended RSET Values. Figure 2: Internal Equivalent Circuit for the CHR Pin.
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USB Port Lithium-Ion/Polymer Battery Charger
USB Input Charge Inhibit and Resume The AAT3688 UVLO and power on reset feature will function when the USB input pin voltage level drops below the UVLO threshold. At this point, the charger will suspend charging and shut down. When power is re-applied to the USB pin or the UVLO condition 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. for 500mA and 100mA USB fast charge levels. However, these two charge levels may be set to any level between 50mA and 500mA, depending upon the system design requirements for a given USB charge application. Refer to Table 1 and Figure 3 for recommended RSETH and RSETL values.
1000
AAT3688
IFASTCHARGE (mA)
USBL
100
Enable / Disable
The AAT3688 provides an enable function to control the charger IC on and off. The enable (EN) pin is an active high. When pulled to a logic low level, the AAT3688 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 re-enabled, 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.
USBH
10
1
10
100
1000
RSET (k)
Figure 3: IFASTCHARGE vs. RSET.
Protection Circuitry
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 AAT3688 charge control will shut down the device until voltage on the BAT pin drops below the over-voltage protection threshold (VOVP). The AAT3688 will resume normal charging operation after the over-voltage condition is removed. During an over-voltage event, the STAT LEDs will report a system fault; the actual fault condition may also be read via the DATA pin signal. Over-Temperature Shutdown The AAT3688 has a thermal protection control circuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold.
Programming Charge Current
The fast charge constant current charge level for the USB input is programmed with set resistors placed between the USBH and USBL pins and ground. The accuracy of the fast charge, as well as the preconditioning trickle charge current, is dominated by the tolerance of the set resistors used. For this reason, 1% tolerance metal film resistors are recommended for programming the desired constant current level. The USB input fast charge constant current charge control provides for two current set levels, USBH and USBL. The USBSEL pin is used to select the high or low charge current levels in the USB charge mode. When the USBSEL pin is pulled to a voltage level above the VUSBSEL(H) threshold, the USBH current level will be selected. Conversely, this pin should be pulled below the VUSBSEL(L) to enable the USBL charge level. Typically, the two RSETH and RSETL for the USBH and USBL functions are fixed
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USB Port Lithium-Ion/Polymer Battery Charger
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 AAT3688 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 negative temperature coefficient (NTC) thermistors which are typically integrated into the battery package. Most commonly used NTC thermistors used in battery packs are 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 that results from the resistive load should stay within a window from 335mV to 2.32V. If the battery becomes too hot during charging due to an internal fault, the thermistor will heat up and reduce in value, thus pulling the TS pin voltage lower than the TS1 threshold, and the AAT3688 will halt charging and 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.
AAT3688
Battery Charge Status Indication
The AAT3688 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 AAT3688 also provides a bi-directional data reporting function so that a system microcontroller may interrogate the DATA pin and read any one of 14 system states. Status Indicator Display Simple system charging status may be displayed using one or two LEDs in conjunction with the STAT1 and STAT2 pins on the AAT3688. These two pins are simple switches to connect the display LED cathodes to ground. It is not necessary to use both display LEDs if a user simply wants to have a single lamp to show "charging" or "not charging." This can be accomplished by just using the STAT1 pin and a single LED. Using two LEDs and both STAT pins simply gives the user more information for charging states. Refer to Table 2 for LED display definitions.
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 2: LED Display Status Conditions.
1. Flashing rate depends on output capacitance. 3688.2006.10.1.5
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USB Port Lithium-Ion/Polymer Battery Charger
The LED anodes should be connected to VUSB. The LEDs should be biased with as little current as necessary to create reasonable illumination; therefore, a ballast resistor should be placed between each of the LED cathodes and the STAT1/2 pins. LED current consumption will add to the over-thermal power budget for the device package, hence it is recommended to keep the LED drive current to a minimum. 2mA should be sufficient to drive most low-cost green, red, or multi-color LEDs. It is not recommended to exceed 8mA for driving an individual status LED. The required ballast resistor value can be estimated using the following formulas: regarding the state 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 14 possible return pulse counts in which the microcontroller can look up based on the serial report shown in Table 3. The DATA pin function is active low and should normally be pulled high to VUSB. This data line may 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 value of the pull-up resistor used is too high, the strobe pulse from the system microcontroller may 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 at the VUSB input. If the data line is pulled high to a voltage level less than 5.0V, the pull-up resistor may be calculated based on a recommended minimum pull-up current of 3mA. Use the following formula:
AAT3688
Eq. 2: RB(STAT1/2) =
(VUSB - VF(LED)) ILED(STAT1/2)
Example:
RB(STAT1) =
(5.0V - 2.0V) = 1.5k 2mA
Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. Table 2 shows the four status LED display conditions.
Digital Charge Status Reporting
The AAT3688 has a comprehensive digital data reporting system by use of the DATA pin feature. This function can provide detailed information
Eq. 3: RPULL-UP
VPULL-UP 3mA
16
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USB Port Lithium-Ion/Polymer Battery Charger
AAT3688
N
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
DATA Report Status
Chip Over-Temperature Shutdown Battery Temperature Fault Over-Voltage Turn Off Not Used Not Used Not Used Not Used Not Used Not Used Not Used Not Used Not Used USBH Battery Condition Mode USBH Charge Reduction in Constant Current Mode USBH Constant Current Mode USBH Constant Voltage Mode USBH End of Charging USBL Battery Condition Mode USBL Charge End of Charging Reduction in Constant Current Mode USBL Constant Current Mode USBL Constant Voltage Mode USBL End of Charging Data Report Error
Table 3: Serial Data Report Table.
1.8V to 5.0V
IN
AAT3688 Status Control
OUT
RPULL_UP DATA Pin
GPIO
IN
OUT
P GPIO Port
Figure 4: Data Pin Application Circuit.
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USB Port Lithium-Ion/Polymer Battery Charger
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 AAT3688 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 the TDATA specification.
AAT3688
Timing Diagram
SQPULSE System Reset System Start PDATA
SQ
CK
TSYNC TLAT TOFF
Data
TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA TOFF > 2 PDATA
N=1
N=2
N=3
Thermal Considerations
The AAT3688 is packaged in a Pb-free, 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 affect 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. 4: PD = [(VIN - VBAT) * ICC + (VIN * IOP)]
Where: PD = Total Power Dissipation by the Device VIN = Input Voltage Level, VUSB 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
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. 5: TA = TJ - (JA * PD)
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USB Port Lithium-Ion/Polymer Battery Charger
Where: TA TJ PD = Ambient Temperature in Degrees C = Maximum Device Junction Temperature Protected by the Thermal Limit Control = Total Power Dissipation by the Device
AAT3688
Capacitor Selection
Input Capacitor In general, it is good design practice to place a decoupling capacitor between the VUSB 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 AAT3688 USB input is to be used in a system with an external power supply source rather than a USB port VBUS, 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 bounce effects when the power supply is "hot plugged" in. Likewise, a 10F or greater input capacitor is recommended for the USB input to help buffer the effects of USB source power switching noise and input cable impedance. Output Capacitor The AAT3688 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 AAT3688 is to be used in applications where the battery can be removed from the charger, such as in the case of 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.
JA = Package Thermal Resistance in C/W Example: For an application where the fast charge current is set to 500mA, VUSB = 5.0V and the worst case battery voltage at 3.0V, what is the maximum ambient temperature at which the thermal limiting will become active? Given: VADP = 5.0V VBAT = 3.0V ICC IOP TJ = 500mA = 0.75mA = 140C
JA = 50C/W Using Equation 4, calculate the device power dissipation for the stated condition: Eq. 6: PD = (5.0V - 3.0V)(500mA) + (5.0V * 0.75mA)
= 1.00375W
The maximum ambient temperature before the AAT3688 thermal limit protection will shut down charging can now be calculated using Equation 5: Eq. 7: TA = 140C - (50C/W * 1.00375W)
Printed Circuit Board Layout Considerations
For the best results, it is recommended to physically place the battery pack as close as possible to the AAT3688 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. For maximum power dissipation of the AAT3688 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 AAT3688 evaluation board for a good layout example (see Figures 5 and 6).
= 89.81C
Therefore, under the stated conditions for this worst case power dissipation example, the AAT3688 will suspend charging operations when the ambient operating temperature rises above 89.81C.
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USB Port Lithium-Ion/Polymer Battery Charger
AAT3688 Evaluation Board Layout
AAT3688
Figure 5: AAT3688 Evaluation Board Component Side Layout.
Figure 6: AAT3688 Evaluation Board Solder Side Layout.
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USB Port Lithium-Ion/Polymer Battery Charger
AAT3688 Evaluation Board Schematic Diagram
ON/OFF J1 Mini-B GND ID D+ DVBUS
5 4 3 2 1 123
AAT3688
USBSEL J2
123
HI
LO
C2 TB1 USB GND
1 2
RED GRN LED D2 LED D1 R9 R2 R3 Open Open
1 5
10F R5
10 8 9 7 11 12
U1
USB EN BAT
AAT3688
USBSEL STAT2 STAT1 DATA
R6 1.5K
1.5K
1.5K
BAT TS GND TB2
1 2 3
2
DATA
C1 10F
4
CHR TS GND
3
USBL USBH
6
R8 8.06K
R7 42.2K
R4 10K
R1 Open
TDFN33-12
SW1
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USB Port Lithium-Ion/Polymer Battery Charger
AAT3688 Evaluation Board Bill of Materials (BOM)
Quantity Description
1 1 1 1 2 1 1 2 1 3 1 1 1 1
AAT3688
Desig.
Footprint
PAD TBLOK2 TBLOK3 USB-MINI-B 0805 1206LED
Manufacturer
Mill-Max Phoenix Contact Phoenix Contact
Part Number
6821-0-0001-00-00-08-0 277-1274-ND 277-1273-ND
Test Pin DATA Connecting Terminal Block, USB,GND 2.54mm, 2 Pos Connecting Terminal Block, BAT, GND, TS 2.54mm, 3 Pos USB 2.0 Receptacle, 5 Pos USB Capacitor, Ceramic, 10F 6.3V 10% X5R 0805 Typical Red LED, Super Bright Typical Green LED Header, 3-Pin Resistor, 10k 1/16W 5% 0603 SMD Resistor, 1.5k 1/16W 1% 0603 SMD Resistor, 42.2k 1/16W 1% 0603 SMD Resistor, 8.06k 1/16W 1% 0603 SMD Switch Tact 6mm SPST H = 5.0mm AAT3688 USB Port LithiumIon/Polymer Battery Charger C1, C2 D1 D2 J1, J2 R4 R5, R6, R9 R7 R8 SW1 U1
Hirose Electronic H2959CT-ND Co. Ltd. MuRata 490-1717-1-ND CMD15-21SRC/TR8 CMD15-21VGC/TR8 6821-0-0001-00-00-08-0 P10KCFCT-ND P1.5KHTR-ND P42.2KHTR-ND P8.06KHCT-ND CKN9012-ND AAT3688IWP
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
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USB Port Lithium-Ion/Polymer Battery Charger Ordering Information
Package
TDFN33-12
AAT3688
Marking1
PKXYY
Part Number (Tape and Reel)2
AAT3688IWP-4.2-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
All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.
(c) Advanced Analogic Technologies, Inc.
Detail "A"
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
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0.23 0.05
0.45 0.05
Detail "A"
3.00 0.05
1.70 0.05
23

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