AAT3681

USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger General Description The AAT3681 BatteryManager is an integrated single cell lithium-ion/polymer battery charger IC, designed to operate from a DC power source or USB port up to an input voltage of 6.5V. It requires just one external component. The AAT3681 precisely regulates battery charge voltage and current for 4.2V (4.375V option) lithiumion/polymer battery cells. When charged from an AC adapter or USB port, the battery charging current can be set by an external resistor up to 300mA. Battery charge state is continuously monitored for fault conditions. In the event of an over-voltage, short-circuit, or over-temperature failure, the device will automatically shut down, thus protecting the charging device, control system, and the battery under charge. A status monitor output pin is provided to indicate the battery charge status by directly driving an external LED. The AAT3681 is available in a Pb-free, thermally enhanced, space-saving 8-pin 2.0x2.1mm SC70JW package and is specified for operation over the -40°C to +85°C temperature range. AAT3681 Features • • • • • • • • • • • • BatteryManager™ USB or AC Adapter System Power Charger — Programmable from 15mA to 300mA 4.0V ~ 6.5V Input Voltage Range High Level of Integration with Internal: — Charging Device — Reverse Blocking Diode Automatic Current Sensing Automatic Recharge Sequencing Full Battery Charge Auto Turn Off/Sleep Mode/Charge Termination Shutdown Current VUVLO Yes Shut Down Yes Fault Conditions Monitoring OV, OT Charge Control No (AAT3681) No (AAT3681-1) Preconditioning Test V MIN > VBAT Yes Preconditioning (Trickle Charge) No No Recharge Test V RCH > VBAT Yes Current Phase Test V IN > VBAT Yes Constant Current Charge Mode No Voltage Phase Test IBAT > ITERM Yes Constant Voltage Charge Mode No Charge Completed 10 3681.2007.01.1.2 USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Application Information Adapter or USB Power Input Constant current charge levels up to 300mA may be programmed by the user when powered from a sufficient input power source. The AAT3681 will operate from the adapter input over a 4.0V to 6.5V range. The constant current fast charge current for the adapter input is set by the RSET resistor connected between ISET and ground. Refer to Table 1 for recommended RSET values for a desired constant current charge level. Adapter Input Charge Inhibit and Resume The AAT3681 has a UVLO and power on reset feature so that if the input supply to the ADP pin drops below the UVLO threshold, the charger will suspend charging and shut down. When power is reapplied to the ADP 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. Nominal ICHARGE (mA) 300 250 200 150 100 50 40 30 20 15 AAT3681 Set Resistor Value (kΩ) 5.36 6.49 8.06 10.7 16.2 31.6 38.3 53.6 78.7 105 Table 1: RSET Values. 1000 ICH (mA) 100 10 Enable / Disable The AAT3681 provides an enable function to control the charger IC on and off. The enable (EN) pin is internally pulled down. When pulled to a logic high level, AAT3681 is enabled. When left open or pulled to a logic low level, the AAT3681 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 on the BAT pin. 1 1 10 100 1000 RSET (kΩ) Figure 2: Constant Charging Current vs. Set Resistor Values. 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 overvoltage condition occurs, the AAT3681 charge control will shut down the device until voltage on the BAT pin drops below VOVP. The AAT3681 will resume normal charging operation after the overvoltage condition is removed. Over-Temperature Shutdown The AAT3681 has a thermal protection control circuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold. Once the internal die temperature falls below the thermal limit, normal operation will resume the previous charging state. 11 Programming Charge Current The fast charge constant current charge level is user programmed with a set resistor placed between the ISET 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 15mA to 300mA may be set by selecting the appropriate resistor value from Table 1. 3681.2007.01.1.2 USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Charge Status Output The AAT3681 provides battery charge status via a status pin. This pin is internally connected to an Nchannel open drain MOSFET, which can be used to drive an external LED. The status pin can indicate the following conditions: Event Description No battery charging activity Battery charging via adapter or USB port Charging completed AAT3681 Status OFF ON OFF 160°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 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: Table 2: LED Status Indicator. The LED should be biased with as little current as necessary to create reasonable illumination; therefore, a ballast resistor should be placed between the LED cathode and the STAT pin. 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: PD(MAX) = Where: (TJ(MAX) - TA) θJA PD(MAX) = Maximum Power Dissipation (W) θJA = Package Thermal Resistance (°C/W) TJ(MAX) = Maximum Device Junction Temperature (°C) [135°C] TA = Ambient Temperature (°C) Figure 3 shows the relationship of maximum power dissipation and ambient temperature of AAT3681. 1000 800 R 1= (VADP - VF(LED)) ILED PD(MAX) (mW) 600 400 200 0 0 20 40 60 80 100 Example: (5.5V - 2.0V) = 1.75kΩ R1 = 2mA Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. TA (°C) Figure 3: Maximum Power Dissipation. Next, the power dissipation can be calculated by the following equation: Thermal Considerations The AAT3681 is offered in a SC70JW-8 package which can provide up to 687mW of power dissipation when it is properly bonded to a printed circuit board and has a maximum thermal resistance of PD = [(VIN - VBAT) · ICH + (VIN · IOP)] 12 3681.2007.01.1.2 USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Where: PD = Total Power Dissipation by the Device VIN = Input Voltage VBAT = Battery Voltage as Seen at the BAT Pin ICH IOP = Constant Charge Current Programmed for the Application = Quiescent Current Consumed by the Charger IC for Normal Operation [0.5mA] AAT3681 Capacitor Selection Input Capacitor In general, it is good design practice to place a decoupling capacitor between the ADP pin and GND. 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. If the AAT3681 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 10µF 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 AAT3681 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 AAT3681 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 10µF may be required to prevent the device from cycling on and off when no battery is present. By substitution, we can derive the maximum charge current before reaching the thermal limit condition (thermal cycling). The maximum charge current is the key factor when designing battery charger applications. ICH(MAX) = (PD(MAX) - VIN · IOP) VIN - VBAT (TJ(MAX) - TA) - V · I IN OP θJA ICH(MAX) = VIN - VBAT In general, the worst condition is the greatest voltage drop across the charger IC, when battery voltage is charged up to the preconditioning voltage threshold. Figure 4 shows the maximum charge current in different ambient temperatures. 300 250 TA = 25°C TA = 45°C Printed Circuit Board Layout Considerations For the best results, it is recommended to physically place the battery pack as close as possible to the AAT3681 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. Refer to the AAT3681 evaluation board for a good layout example (see Figures 5 and 6). 6.75 ICH(MAX) (mA) 200 150 100 50 0 4.25 TA = 60°C TA = 85°C 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 VIN (V) Figure 4: Maximum Charging Current Before Thermal Cycling Becomes Active. 3681.2007.01.1.2 13 USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger AAT3681 Figure 5: AAT3681 Evaluation Board Top Layer. Figure 6: AAT3681 Evaluation Board Bottom Layer. VBAT VIN(ADP) JP2 AAT3681 1 2 3 4 C1 10µF R8 8.06K EN ISET BAT ADP GND GND GND STAT 8 7 6 5 C2 2.2µF U1 (SC70JW-8) JP1 0Ω D1 RED LED R1 1K Figure 7: AAT3681 Evaluation Board Schematic Diagram. Component U1 R1 R8 JP1 C1 C2 JP2 LED1 Part Number AAT3681IJS-T1 Chip Resistor Chip Resistor Chip Resistor GRM21BR61A106KE19L GRM21BR71A225KA01L PRPN401PAEN CMD15-21SRC/TR8 Description USB/ADP Battery Charger; SC70JW-8 Package 1kΩ, 5%, 1/4W; 0603 8.06kΩ, 1%, 1/4W; 0805 0Ω, 5%, 1/4W; 0603 CER 10µF 10V 10% X5R 0805 CER 2.2µF 10V 10% X7R 0805 Connecting Header, 2mm Zip Red LED; 1206 Manufacturer AnalogicTech Vishay Vishay Vishay Murata Murata Sullins Electronics Chicago Miniature Lamp Table 3: AAT3681 Evaluation Board Bill of Materials. 14 3681.2007.01.1.2 USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Ordering Information Trickle Charge Yes No AAT3681 Package SC70JW-8 SC70JW-8 Marking1 REXYY STXYY Part Number (Tape and Reel)2 AAT3681IJS-4.2-T1 AAT3681IJS-4.2-1-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 0.50 BSC 0.50 BSC 0.50 BSC SC70JW-8 1.75 ± 0.10 0.225 ± 0.075 2.00 ± 0.20 2.20 ± 0.20 0.048REF 0.85 ± 0.15 1.10 MAX 0.15 ± 0.05 0.100 7 ° ± 3° 0.45 ± 0.10 2.10 ± 0.30 4° ± 4° 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. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737- 4600 Fax (408) 737- 4611 3681.2007.01.1.2 0.05 ± 0.05 15