The AD8451 is a precision analog front end and controller for testing and monitoring battery cells. A precision fixed gain instrumentation amplifier （IA） measures the battery charge/ discharge current， and a fixed gain difference amplifier （DA） measures the battery voltage （see Figure 1）。 Internal laser trimmed resistor networks set the gains for the IA and the DA， optimizing the performance of the AD8451 over the rated temperature range. The IA gain is 26 V/V and the DA gain is 0.8 V/V.

　　Voltages at the ISET and VSET inputs set the desired constant current （CC） and constant voltage （CV） values. CC to CV switching is automatic and transparent to the system.

　　A TTL logic level input， MODE， selects the charge or discharge mode （high for charge， and low for discharge）。 An analog output， VCTRL， interfaces directly with the Analog Devices， Inc.， ADP1972 pulse-width modulation （PWM） controller.

　　The AD8451 simplifies designs by providing excellent accuracy， performance over temperature， flexibility with functionality， and overall reliability in a space-saving package. The AD8451 is available in an 80-lead， 14 mm × 14 mm × 1.40 mm LQFP and is rated for an operating temperature of ?40°C to +85°C.