High-voltage automotive battery-stack monitor achieves 0.04% measurement accuracy

A drop-in replacement for the LTC6804 with higher performance and 25% lower price - the LTC6811, a new high-voltage battery-stack monitor has been introduced by Linear Technology. The LTC6811 is a complete battery measuring IC for hybrid/electric vehicles that incorporates a deep buried Zener voltage reference, high voltage multiplexers, 16-bit delta-sigma ADCs and a 1Mbps isolated serial interface. An LTC6811 can measure up to 12 series-connected battery cell voltages with better than 0.04% accuracy. With 8 programmable 3rd order low pass filter settings, the LTC6811 provides outstanding noise reduction. In the fastest ADC mode, all cells can be measured within 290µsec. For large battery packs, multiple LTC6811s can be interconnected and operated simultaneously, using Linear Technology’s proprietary 2-wire isoSPI interface. This built-in interface provides electrically isolated, high RF noise immune communication for data rates up to 1Mbps. Using twisted pair, many LTC6811s can be connected in a daisy chain to one host processor, enabling the measurement of hundreds of cells in high voltage battery stacks. The LTC6811 follows three generations of road-proven battery monitor ICs, designed to surpass the environmental, reliability and safety demands of automotive and industrial applications. The LTC6811 is fully specified for operation from -40C to 125C. It has been engineered for ISO 26262 (ASIL) compliant systems with extensive fault coverage via its redundant voltage reference, logic test circuitry, cross-channel testing, open wire detection capability, a watchdog timer and packet error checking on the serial interface. For existing designs using Linear Technology's LTC6804 battery stack monitor, the LTC6811 is a drop-in replacement with additional filter cut-off frequencies, added passive and active balancing control features, new ADC commands and enhanced fault coverage for functional safety. The LTC6811 is fully supported by Linear's Linduino technology, an Arduino-based microcontroller board and software library. The microcontroller board includes an electrically isolated USB port and directly connects to the LTC6811 demonstration board, providing a simple platform for evaluating and developing the LTC6811. The LTC6811 is offered in a 8mm x 12mm surface-mount SSOP package.