Precision battery monitor front-end and supervisory controller

April 14, 2014 // By Graham Prophet
Analog Devices has posted details of the AD8451, a precision analogue 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, optimising 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 I SET and V SET 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, V CTRL, interfaces directly with Analog Devices’ ADP1972 PWM controller.

The AD8451 simplifies designs by providing accuracy, performance over temperature, flexibility with functionality, and overall reliability in a space-saving package. It comes in an 80-lead, 14 × 14 × 1 mm LQFP package and is rated for an operating temperature of −40°C to +85°C.

The device features;

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

Excellent ac and dc performance

Maximum offset voltage drift of 0.9 μV/°C

Maximum gain drift of 3 ppm/°C

Current sense amplifier input voltage noise of under 9 nV/√Hz typ

Current sense CMRR of 108 dB minimum

Analog Devices;