EV-124 AAT3681: USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Introduction The AAT3681 evaluation board demonstrates single-cell lithium-ion/polymer battery charging from either a USB or ADP port. The AAT3681 precisely regulates battery charge voltage and current for 4.2V (4.375V option) lithium-ion/polymer battery cells. This device operates at an input voltage range from 4V to 6.5V. The charging current can be set up to 300mA by an external resistor. This document describes the evaluation board and the value for the set resistor. In addition, a schematic of the complete evaluation board's circuit (Figure 1) and the board layout (Figures 2 and 3) are provided. For additional information, please refer to the AAT3681 product datasheet. Schematic VBAT VCC JP2 Enable C1 10µF U1 R8 8.06K 1 2 3 4 EN ISET VBAT VCH GND GND GND STAT 8 7 6 5 C2 2.2µF AAT3681 D1 R1 1K JP1 RED LED Figure 1: Evaluation Board Schematic. Printed Circuit Board Figure 2: Top Layer (not to scale). EV-124.2006.03.1.1 Figure 3: Bottom Layer (not to scale). 1 EV-124 AAT3681: USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger Programming Charge Current The charging current level is programmed with a resistor placed between the ISET pin and ground. The accuracy of the constant charge current and preconditioning trickle charge current is dominated by the resistor tolerance. A 1% tolerance resistor is recommended. The constant charge current can be programmed from 15mA to 300mA. Table 1 provides resistor values for commonly used constant charge current levels. Figure 4 shows the relationship between ICC and RSET. ICC (mA) Ω) Set Resistor Value RSET (kΩ 300 250 200 150 100 50 40 30 20 15 5.36 6.49 8.06 10.7 16.2 31.6 38.3 53.6 78.7 105 Table 1: Recommended RSET Values. 1000 ICC (mA) 100 10 1 1 10 100 1000 RSET (kΩ Ω) Figure 4: ICC vs. RSET. 2 EV-124.2006.03.1.1 EV-124 AAT3681: USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger LED Status Output The AAT3681 status pin function provides a visual indication of the status of a battery under charge. The status LED is turned on by an internal MOSFET switch which connects the status pin to ground when the AAT3681 is in the pre-conditioning trickle charge, constant current charge, or constant voltage charge modes. The LED status indicator is turned off when there is no battery charging or when the charge cycle is complete. A series resistor (R1) is placed with the status indicator LED (D1) to limit the forward current through the LED. The nominal value of R1 is 1kΩ; this value may be adjusted by the following formula: ILED = VCC - VF R1 Use of the LED status indicator is optional. To disable this function, remove jumper JP1 which connects the LED to the input supply. Enable The AAT3681 enable pin should be pulled to a logic high level to turn on the device. EV-124.2006.03.1.1 3 EV-124 AAT3681: USB Port or AC Adapter Lithium-Ion/Polymer Battery Charger AAT3681 EVAL Component Listing Component U1 R1 R8 JP1 C1 C2 JP2 LED1 Part# Description AAT3681IJS-T1 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 Chip Resistor Chip Resistor Chip Resistor GRM21BR61A106KE19L GRM21BR71A225KA01L PRPN401PAEN CMD15-21SRC/TR8 Manufacturer AnalogicTech Vishay Vishay Vishay Murata Murata Sullins Electronics Chicago Miniature Lamp Table 3: Component Listing. © 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. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 4 EV-124.2006.03.1.1