AAT3688 USB Port Lithium-Ion/Polymer Battery Charger General Description Features The AAT3688 BatteryManager™ 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. BatteryManager™ 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 • • • • • • • The AAT3688 is available in a Pb-free, thermallyenhanced, space-saving 12-pin 3x3mm TDFN package and is rated over the -40°C to +85°C temperature range. Bluetooth™ 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 EN CHR USBSEL USB Hi/Lo Select RSETH RSETL BATT+ USBH BAT USBL TS AAT3688 C2 10μF BATT- GND DATA STAT1 TEMP STAT2 Battery Pack Serial Data 3688.2006.10.1.5 1 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Pin Descriptions Pin # Name Type 1 2 3 4 USB BAT GND CHR In In/Out Ground In/Out 5 6 7 8 9 10 EN TS DATA STAT2 STAT1 USBSEL In In/Out In/Out Out Out In 11 12 EP USBL USBH In/Out 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 10kΩ 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. Pin Configuration TDFN33-12 (Top View) USB BAT GND CHR EN TS 2 1 12 2 11 3 10 4 9 5 8 6 7 USBH USBL USBSEL STAT1 STAT2 DATA 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Absolute Maximum Ratings1 Symbol VP VP VN TJ TLEAD 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 Units -0.3 to 7.0 -0.3 to 6.0 -0.3 to VVP + 0.3 -40 to 150 300 V V V °C °C Value Units 50 2.0 °C/W W Thermal Information2 Symbol θJA PD Description Maximum Thermal Resistance (3x3mm TDFN) Maximum Power Dissipation 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 3 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Electrical Characteristics1 VADP = 5V, TA = -25°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C. Symbol Description Conditions Operation USB 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 ΔVBAT/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 ΔICH/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 Min Typ 4.0 Rising Edge 5.5 CC Charge Current = 500mA VBAT = 4.25V 3.0 150 0.75 0.3 VBAT = 4V, USB Pin Open 1.0 4.158 No Connection on CHR Pin 2.8 4.2 0.5 3.0 4.3 1.9 VBAT_EOC - 0.1 4.5 2.0 50 CC Mode CC Mode VIN = 5.5V 0.4 Max Units 1.5 1.0 V V mV mA µA µA 4.242 4.64 2.1 V % V V V V 500 mA 3.15 10 % 2.0 2.0 2000 2000 V V 0.5 0.65 Ω 1. The AAT3688 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C temperature range is guaranteed by design. 4 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Electrical Characteristics1 VADP = 5V, TA = -25°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C. Symbol Description 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 Pre-Charge Current Charge Termination Threshold Current Charge Termination Threshold Current Current Source from TS Pin TS1 TS Hot Temperature Fault TS2 TS Cold Temperature Fault I_DATA VDATA(H) VDATA)(L) SQPULSE tPERIOD fDATA TOVSD DATA Pin Sink Current Input High Threshold Input Low Threshold Status Request Pulse Width System Clock Period Data Output Frequency Over-Temperature Shutdown Threshold Conditions Min Typ Max 1.6 0.4 1.6 0.4 0.4 STAT Pin Sinks 4mA For For For For USBH Mode USBL Mode USBH Mode USBL Mode Threshold Hysteresis Threshold Hysteresis DATA Pin is Active Low State 70 310 2.2 8.0 4.4 10 50 7.5 35 80 330 15 2.3 10 90 350 2.4 3.0 1.6 200 50 20 145 V V V V V mA V % 0.4 Status Request Units % % µA mV V mV mA V V ns µs kHz °C 1. The AAT3688 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C temperature range is guaranteed by design. 3688.2006.10.1.5 5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics IFASTCHARGE vs. RSET Battery Voltage vs. Supply Voltage 4.242 4.221 VBAT (V) IFASTCHARGE (mA) 1000 USBL 100 USBH 10 1 10 4.200 4.179 100 4.158 1000 4.5 4.75 5 5.25 5.5 Supply Voltage (V) RSET (kΩ) Recharge Voltage vs. Temperature End of Charge Voltage vs. Temperature 4.242 4.140 4.130 4.120 4.221 4.100 VBAT (V) VRCH (V) 4.110 4.090 4.080 4.070 4.200 4.179 4.060 4.050 4.040 -50 -25 0 25 50 75 4.158 100 -50 -25 Temperature (°C) 0 25 50 75 100 Temperature (°C) Preconditioning Threshold Voltage vs. Temperature Preconditioning Charge Current vs. Temperature (USBH; USBH = 8.06kΩ Ω) 3.05 60 3.04 3.03 55 ICH (mA) VMIN (V) 3.02 3.01 3.00 2.99 2.98 50 45 2.97 2.96 2.95 40 -50 -25 0 25 50 Temperature (°C) 6 75 100 -50 -25 0 25 50 75 100 Temperature (°C) 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics Charging Current vs. Battery Voltage Fast Charge Current vs. Temperature (USBH; USBH = 8.06kΩ Ω) (USBH; USBH = 8.06kΩ) 600 540 530 500 520 400 500 ICH (A) ICH (mA) 510 490 480 300 200 470 460 100 450 0 440 -50 -25 0 25 50 75 100 2.5 3 3.5 4 4.5 Battery Voltage (V) Temperature (°C) Charging Current vs. Battery Voltage Fast Charge Current vs. Supply Voltage (USBL; USBL = 40.2kΩ Ω) (USBH; USBH = 8.06kΩ Ω) 120 600 100 500 80 400 VBAT = 3.5V ICH (mA) ICH (mA) VBAT = 3.3V 60 40 VBAT = 3.9V 300 200 100 20 0 0 2.5 3 3.5 4 4.5 4 4.25 Battery Voltage (V) 4.5 4.75 Fast Charge Current vs. Supply Voltage 5.25 5.5 5.75 6 Fast Charge Current vs. Supply Voltage (USBL; USBL = 40.2kΩ Ω) (USBH; USBH = 8.06kΩ Ω) 120 600 VBAT = 3.5V 0°C 100 500 VBAT = 3.9V 60 ICH (mA) 80 ICH (mA) 5 Supply Voltage (V) VBAT = 3.3V 40 20 70°C 400 25°C 300 200 100 0 4 4.5 5 5.5 Supply Voltage (V) 3688.2006.10.1.5 6 6.5 0 4.40 4.50 4.60 4.70 4.80 4.90 5.00 Supply Voltage (V) 7 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics VIH vs. Supply Voltage VIL vs. Supply Voltage EN Pin (Rising) EN Pin (Falling) 1.4 1.4 1.3 1.3 1.2 1.2 -40°C +25°C 1.1 1.0 VIL (V) VIH (V) 1.1 0.9 0.8 0.7 -40°C 0.9 0.8 0.7 +85°C 0.6 0.6 0.5 +85°C 0.5 0.4 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 4.2 4.4 4.6 4.8 Supply Voltage (V) 5 5.2 5.4 5.6 5.8 6 5.8 6 Supply Voltage (V) VIH vs. Supply Voltage VIL vs. Supply Voltage USBSEL (Rising) USBSEL (Falling) 1.4 1.4 1.3 1.3 1.2 -40°C 1.1 1.2 +25°C 0.9 0.8 0.7 +25°C 1.0 0.9 0.8 0.7 +85°C 0.6 -40°C 1.1 1.0 VIL (V) VIH (V) +25°C 1.0 +85°C 0.6 0.5 0.5 0.4 0.4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 4.2 4.4 4.6 4.8 Supply Voltage (V) 5 5.2 5.4 5.6 Supply Voltage (V) USB Charge Current vs. Time USB Supply Current vs. USBH Resistor (USBH; USBH = 8.06kΩ) 0.80 USB VBUS (200mV/div) 0.70 USB Charge Current (200mA/div) IQ (mA) 0.60 Constant Current 0.50 0.40 0.30 USB Peripheral Current Consumption (200mA/div) Pre-Conditioning 0.20 0.10 0.00 0 1 10 100 USBH Resistor (kΩ Ω) 8 Charge Reduction Mode Activated 2 4 6 8 10 1000 Time (sec) 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Typical Characteristics Temperature Sense Output Current vs. Temperature TS Pin CUrrent (μA) 88 86 84 82 80 78 76 74 72 -50 -25 0 25 50 75 100 Temperature (°°C) 3688.2006.10.1.5 9 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Functional Block Diagram Reverse Blocking USB USBSEL USBH USBL CHR BAT Current Compare Charge Reduction Loop Constant Current CV/ Precharge Charge Control UVLO OverTemperature Protect STAT1 STAT2 Charge Status 80µA DATA TS Serial Data 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 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Charge Complete Voltage Preconditioning Trickle Charge Phase Constant Current Charge Phase Constant Voltage Charge Phase I = Max CC 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 3688.2006.10.1.5 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 0.3µA 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 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger System Operation Flow Chart Switch On Sleep Mode No UVLO VP > VUVLO Yes USB Low Current Loop Power On Reset USB High Current Loop Fault Conditions Monitor OV, OT Battery 0 USB Detect USBSEL= ? 1 Yes No Yes USB Power Shut Down Mode No Temperature Monitor VTS1 < TS < VTS2 Battery Temp. Fault USB Voltage Regulation Enable No No Recharge Test VRCH > VBAT Yes Yes Preconditioning Test VMIN > VBAT Low Current Conditioning Charge USB Voltage Test VUSB < 4.5V Yes No Yes Current Charging Mode Yes Voltage Charging Mode Current Phase Test VEOC > VBAT USB Loop Current Reduction in USB Charging Mode No Voltage Phase Test IBAT > ITERM No Charge Completed 12 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Application Information USB System Power Charging other functions, the AAT3688 will automatically reduce USB fast charge current to maintain port integrity and protect the host system. 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. 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 10kΩ resistor from the CHR pin directly to the USB input pin. 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 The following equation may be used to approximate a USB charge reduction threshold below 4.5V: R12 Eq. 1: VUSBCHR = 2.0V ÷ R12 + R11 where R11/R12 << 1MΩ. ICC USBH Ω) RSET (kΩ USBL Ω) RSET (kΩ 50 75 100 200 300 400 500 86.6 57.6 42.2 21.0 13.7 10.2 8.06 86.6 57.6 42.2 20.5 13.7 10.2 8.06 VUSB R11 1.025M CHR R12 USB VCHR = 2.0V 825k Table 1: Recommended RSET Values. Figure 2: Internal Equivalent Circuit for the CHR Pin. 3688.2006.10.1.5 13 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger 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. 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 14 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 IFASTCHARGE (mA) 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. USBL 100 USBH 10 1 10 100 1000 RSET (kΩ) 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. 3688.2006.10.1.5 AAT3688 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 10kΩ at room temperature (25°C). The TS pin has been specifically designed to source 80µA 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 Event Description Charge Disabled or Low Supply Charge Enabled Without Battery Battery Charging Charge Completed Fault function is not required by the system, it should be terminated to ground using a 10kΩ resistor. 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. STAT1 STAT2 Off Flash1 On Off On Off Flash1 Off On On Table 2: LED Display Status Conditions. 1. Flashing rate depends on output capacitance. 3688.2006.10.1.5 15 AAT3688 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: Eq. 2: RB(STAT1/2) = (VUSB - VF(LED)) ILED(STAT1/2) Example: RB(STAT1) = (5.0V - 2.0V) = 1.5kΩ 2mA Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. 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 1.5kΩ 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: 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 16 Eq. 3: RPULL-UP ≤ VPULL-UP 3mA 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger N DATA Report Status 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 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 RPULL_UP IN DATA Pin GPIO OUT OUT μP GPIO Port Figure 4: Data Pin Application Circuit. 3688.2006.10.1.5 17 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Data Timing 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. 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, Timing Diagram SQ SQPULSE PDATA System Reset System Start CK TSYNC Data TLAT TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA TOFF > 2 PDATA TOFF N=1 N=2 Thermal Considerations Where: 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 50°C/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. PD First, the maximum power dissipation for a given situation should be calculated: N=3 = Total Power Dissipation by the Device VIN = Input Voltage Level, VUSB VBAT = Battery Voltage as Seen at the BAT Pin ICC = Maximum Constant Fast Charge Current Programmed for the Application IOP = 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 - (θJA · PD) Eq. 4: PD = [(VIN - VBAT) · ICC + (VIN · IOP)] 18 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Where: Capacitor Selection TA = Ambient Temperature in Degrees C TJ = Maximum Device Junction Temperature Protected by the Thermal Limit Control PD = Total Power Dissipation by the Device 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 1µF to 22µF 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. θJA = 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 = 500mA IOP = 0.75mA TJ = 140°C θJA = 50°C/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 = 140°C - (50°C/W · 1.00375W) = 89.81°C 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 89.81°C. 3688.2006.10.1.5 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 10µF 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 10µF 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 1µF ceramic capacitor on the BAT pin to maintain circuit stability. This value should be increased to 10µF 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 10µF may be required to prevent the device from cycling on and off when no battery is present. 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). 19 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger AAT3688 Evaluation Board Layout Figure 5: AAT3688 Evaluation Board Component Side Layout. 20 Figure 6: AAT3688 Evaluation Board Solder Side Layout. 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger AAT3688 Evaluation Board Schematic Diagram ON/OFF J1 USBSEL J2 1 2 3 1 2 3 Mini-B GND ID D+ DVBUS HI LO 5 4 3 2 1 RED GRN LED D2 LED D1 C2 TB1 USB GND 10µF R9 1 2 R2 R3 Open Open U1 1 5 BAT TS GND 2 1 2 3 TB2 USBSEL USB EN STAT2 BAT STAT1 DATA 4 C1 10µF 6 R4 10K 3688.2006.10.1.5 AAT3688 R1 Open USBL CHR TS USBH GND 3 TDFN33-12 10 R5 R6 1.5K 1.5K 1.5K 8 9 7 DATA 11 12 R8 R7 8.06K 42.2K SW1 21 AAT3688 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 22 Desig. 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 Footprint Manufacturer Part Number PAD TBLOK2 Mill-Max Phoenix Contact 6821-0-0001-00-00-08-0 277-1274-ND TBLOK3 Phoenix Contact 277-1273-ND USB-MINI-B Capacitor, Ceramic, 10µF 6.3V 10% X5R 0805 Typical Red LED, Super Bright Typical Green LED C1, C2 0805 D1 1206LED Header, 3-Pin Resistor, 10kΩ 1/16W 5% 0603 SMD Resistor, 1.5kΩ 1/16W 1% 0603 SMD Resistor, 42.2kΩ 1/16W 1% 0603 SMD Resistor, 8.06kΩ 1/16W 1% 0603 SMD Switch Tact 6mm SPST H = 5.0mm AAT3688 USB Port LithiumIon/Polymer Battery Charger J1, J2 R4 D2 Hirose Electronic H2959CT-ND Co. Ltd. MuRata 490-1717-1-ND Chicago Miniature Lamp 1206LED Chicago Miniature Lamp HEADER2MM-3 Sullins 0603 Panasonic/ECG CMD15-21SRC/TR8 CMD15-21VGC/TR8 6821-0-0001-00-00-08-0 P10KCFCT-ND R5, R6, R9 0603 Panasonic/ECG P1.5KHTR-ND R7 0603 Panasonic/ECG P42.2KHTR-ND R8 0603 Panasonic/ECG P8.06KHCT-ND SW1 SWITCH CKN9012-ND U1 TDFN33-12 ITT Industries/ C&K Div. AnalogicTech AAT3688IWP 3688.2006.10.1.5 AAT3688 USB Port Lithium-Ion/Polymer Battery Charger Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-12 PKXYY 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 2.40 ± 0.05 Detail "B" 3.00 ± 0.05 Index Area (D/2 x E/2) 0.3 ± 0.10 0.16 0.375 ± 0.125 0.075 ± 0.075 3.00 ± 0.05 1.70 ± 0.05 Top View Bottom View Pin 1 Indicator (optional) 0.23 ± 0.05 Detail "A" 0.45 ± 0.05 0.1 REF 0.05 ± 0.05 0.229 ± 0.051 + 0.05 0.8 -0.20 7.5° ± 7.5° Option A: C0.30 (4x) max Chamfered corner Side View Option B: R0.30 (4x) max Round corner Detail "B" Detail "A" All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. © 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. 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