DC1496C-C Analog Devices

DEMO MANUAL DC1496C LTC2941/LTC2942: 2 Battery Gas Gauge with I C Interface and 14-Bit ADC DESCRIPTION Demonstration circuit 1496C-A (Figure 1) features the is exceeded, the device reports an alert using either the LTC 2941. Demonstration circuit 1496C-B features the SMBus alert protocol or by setting a flag in the internal LTC2942. Demonstration circuit 1496C-C features the status register. LTC2941-1. Demonstration circuit 1496C-D features the The LTC2941 and LTC2942 require only a single low LTC2942-1. The C, D options have parts that use an internal value sense resistor to set the measured current range. sense resistor while the A, B options rely on an external The LTC2941-1 and the LTC2942-1 have their own 50m precision sense resistor. All four devices measure battery internal resistor. The default value assembled on the charge state in handheld PC and portable product applica- DC1496 is 100m for a maximum current measurement tions. The operating range is perfectly suited for single of 500mA. Both parts have a software-configurable charge cell Li-Ion batteries. A precision analog coulomb counter complete/alert pin. When the pin is set for charge com- integrates current through a sense resistor between the plete, a jumper connects the pushbutton which simulates batterys positive terminal and the load or charger. The a logic high input to indicate a full battery. When the pin is LTC2942 adds battery voltage and on-chip temperature configured for alert, the same jumper is used to connect measurement with an internal 14-bit No Latency a red LED that indicates an alert is present. ADC. The three measured quantities (charge, voltage and The DC1496C is a part of the QuikEval system for quick temperature) are stored in internal registers accessible via 2 evaluation with a host controller through a PC. the onboard SMBus/I C interface. Design files for this circuit board are available at The LTC2941/LTC2941-1 has programmable high and DEMO MANUAL DC1496C QUICK START PROCEDURE Demonstration circuit 1496C is easy to set up to evaluate 4. Connect a DC590 to 14-pin connector J1 for evaluation 2 the performance of the LTC2941/LTC2942/LTC2941-1/ with QuikEval, or connect a host controller I C bus to LTC2942-1. Refer to Figure 2 for proper measurement the SDA, SCL and GND test turrets. equipment setup and follow the procedure below. 5. Set JP1 to QuikEval if a DC590 is present. Otherwise 1. Connect a 1-cell Li-Ion battery across V BAT and GND. set JP1 to Bat/Chrg for bus pull-up to the battery, or float JP1 and supply a bus pull-up voltage to VP. 2. Connect a load across V CHRG/LD and GND for battery 2 discharge measurement. Up to 500mA supplied from 6. Read and write to the LTC2941/LTC2942 through I C. the battery can be measured with the board default 2 7. Through I C, configure the AL/CC pin. Set JP2 100m sense resistor or 50m internal resistor. Use accordingly. + SENSE and SENSE test points to read voltage across 8 If AL/CC is set for charge complete, use pushbutton the sense resistor. switch S1 to simulate a logic high from a controller to 3. Connect a 2.7V to 5.5V battery charger supply across indicate a fully charged battery. V CHRG/LD and GND. Up to 500mA supplied to the battery can be measured with the board default 100m + sense resistor. Use SENSE and SENSE test points to read voltage across the sense resistor. V SENSE + BATTERY + CHARGER LOAD 1-CELL Li-Ion BUS PULL-UP VOLTAGE TO QuikEval TO MICROCONTROLLER Figure 2. DC1496C Basic Setup dc1496cfb 2