Hybrid Electric Vehicles
Electric vehicles need monitors and controls for battery stack, motors and inverters. Breakthrough products from ADI are automotive qualified to support the challenges of designing electric vehicles. The tough EMI and temperature environment, coupled with the expectation of extremely low defect rates, require thoroughly tested systems to manage the multi-hundred volts of the battery stack, measuring and correcting to millivolt and single degree sensing. KV isolation and multi-hundred ampere to milliamp currents require enhanced communications, protection and instrumentation accuracy over the life of the vehicle.
The AD7280A contains all the functions required for general-purpose monitoring of stacked lithium ion batteries as used in hybrid electric vehicles, battery backup applications, and power tools. The part has multiplexed cell voltage and auxiliary ADC measurement channels for up to six cells of battery management. An internal ±3 ppm reference is provided that allows a cell voltage accuracy of ±1.6 mV. The ADC resolution is 12 bits and allows conversion of up to 48 cells within 7 μs.
The AD7280A operates from just one VDD supply that has a range of 8 V to 30 V (with an absolute maximum rating of 33 V). The part provides six differential analog input channels to accommodate large common-mode signals across the full VDD range. Each channel allows an input signal range, VIN(+) − VIN(−), of 1 V to 5 V. The input pins assume a series stack of six cells. In addition, the part includes six auxiliary ADC input channels that can be used for temperature measurement or system diagnostics.
The AD7280A includes on-chip registers that allow a sequence of channel measurements to be programmed to suit the applications requirements.
The AD7280A also includes a dynamic alert function that can detect if the cell voltages or auxiliary ADC inputs exceed an upper or lower limit defined by the user. The AD7280A has cell balancing interface outputs designed to control external FET transistors to allow discharging of individual cells.
The AD7280A includes a built in self-test feature that internally applies a known voltage to the ADC inputs.
There is a daisy-chain interface that allows up to eight parts to be stacked without the need for individual device isolation.
The AD7280A requires only one supply pin that takes 6.5 mA under normal operation, while converting at 1 MSPS.
All this functionality is provided in a 48-lead LQFP package operating over a temperature range of −40°C to +105°C.
- Lithium ion battery monitoring
- Electric and hybrid electric vehicles
- Power supply back up
- Power tools
The part functions independently from a primary monitor, such as the AD7280, containing its own reference and LDO, both of which are powered completely from the battery cell stack. The reference, in conjunction with external resistor dividers, is used to establish trip points for the over/under-voltages. Each cell channel contains programmable de-glitching (D/G) circuitry to avoid alarming from transient input levels.
The AD8280 also has two digital pins that can be used to select various combinations of the inputs in the case where there are less than six cells to be monitored. Most importantly, it has a self-test feature making it suitable for high-reliability applications, such as automotive hybrid electric vehicles. It can function over a temperature range of -40°C to +105°C.Applications
- Lithium Ion Battery Back-up Monitor
- Ideally Suited for companion to AD7280 Primary Monitor
- Lithium Ion Battery Threshold Detection