AD8451 Low Cost Precision Analog Front End and Controller for Battery Test/Formation Systems

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. 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 and the DA gain is 0.8.

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, low for discharge). An analog output, VCTRL, interfaces directly with the Analog Devices, Inc., ADP1972 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 mm LQFP package and is rated for an operating temperature of −40°C to +85°C.

APPLICATIONS

Battery cell formation and testing
Battery module testing

Features and Benefits

Integrated constant current and voltage modes with automatic switchover
Charge and discharge modes
Precision voltage and current measurement
Integrated precision control feedback blocks
Precision interface to PWM or linear power converters
Fixed gain settings
Current sense gain: 26 V/V (typ)
Voltage sense gain: 0.8 V/V (typ)

Excellent ac and dc performance
Maximum offset voltage drift:
0.9 μV/°C
Maximum gain drift: 3 ppm/°C
Low current sense amplifier input voltage noise: >9 nV/√Hz typ
Current sense CMRR:
108 dB minimum
TTL compliant logic