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The LTC6804 high voltage battery monitor from Analog Devices Power by Linear has been designed for use in high voltage, stacked-battery systems such as those used in hybrid and electric vehicles and energy storage systems.
The LTC6804 can measure up to 12 series connected battery cells at voltages up to 4.2V with 16 bit resolution and better than 0.04% accuracy. This high precision is maintained over time, temperature and operating conditions by a sub-surface Zener voltage reference similar to references used in precision instrumentation. When stacked in series, the LTC6804 enables the measurement of every battery cell voltage in large high voltage systems. Six operating modes are available to optimize update rate, resolution and the low pass response of the built-in 3rd order noise filter. In the fastest mode, all cells can be measured within 290µsec.

Multiple LTC6804s can be interconnected over long distances and operated simultaneously, using Analog Devices Power by Linear proprietary 2-wire isoSPI^™ interface. Integrated into every LTC6804, the isoSPI interface provides high RF noise immunity up to 1Mbps and up to 100 meters of cable, using only twisted pair. Two communication options are available: with the LTC6804-1, multiple devices are connected in a daisy chain with one host processor connection for all devices; with the LTC6804-2, multiple devices are connected in parallel to the host processor with each device individually addressed.

The LTC6804 has been designed to minimize power consumption, especially during long-term storage where battery drain is unacceptable. In sleep mode, the LTC6804 draws less than 4µA from the batteries. General purpose I/O pins are available to monitor analog signals, such as current and temperature, and can be captured simultaneously with the cell voltage measurements. Additional features include passive balancing for each cell with a programmable balancing timer for up to 2 hours, even when the LTC6804 is in sleep mode. The LTC6804 interfaces with external I2C devices such as temperature sensors, ADCs, DACs and EEPROM. Local EEPROM can be used to store serialization and calibration data, enabling modular systems.

The LTC6804 was designed to surpass the environmental, reliability and safety demands of automotive and industrial applications. The LTC6804 is fully specified for operation from –40°C to 125°C. It has been engineered for ISO 26262 (ASIL) compliant systems and a full set of self-tests ensure that there are no latent fault conditions. To accomplish this, the LTC6804 includes a redundant voltage reference, extensive logic test circuitry, open wire detection capability, a watchdog timer and packet error checking on the serial interface.

Click below for an overview of the LTC6804 12 Channel Multicell Battery Monitor

Along with the LTC6804, Analog Devices has the LTC6820 isoSPI transceiver. The LTC6820 enables bidirectional transmission of the Serial Peripheral Interface bus (SPI) across an isolated barrier up to 100 meters. With the LTC6820 , the SPI data is encoded into a differential signal, which is then transmitted via twisted pair and a simple, inexpensive Ethernet transformer. The LTC6820 supports SPI data rates up to 1MHz, using matched source and sink currents to eliminate the need for a transformer centre tap and to reduce EMI. The drive currents and the comparator thresholds are set with two resistors, allowing the system to be optimized for cable length and signal-to-noise performance. The LTC6820 is a companion to the LTC6804, high voltage battery monitor with its built-in isoSPI interface. The LTC6820 enables battery management systems using the LTC6804 to interface to external components, such as microcontrollers.

The LTC6804, is offered in a small 8mm × 12mm surface mount device and the LTC6820 is offered in an option of MSOP or a tiny QFN package

Demo Boards

The Demonstration Circuit DC2100B-D is a stackable, bidirectional cell balancer slave board using the LTC6804-2 and the LTC3300-1 ICs to achieve active balancing of up to 12 Li-Ion cells. It requires the DC2100B-C for proper operation. The DC2100B-D uses a single LTC6804-2 Multi-Cell Addressable Battery Stack Monitor IC to measure cell voltages and two LTC3300-1 Synchronous Flyback ICs to provide active cell balancing. The DC2100B-C controller board contains a microcontroller, the LTM2884 isolated USB transceiver, the LTC6804-2 two LTC3300-1 ICs, and the LTC6820 isoSPI Interface IC to facilitate isolated communication. Up to seven DC2100B-D boards can be connected to a DC2100B-C to build a stacked system of eight total boards.

Anglia are offering customers FREE Evaluation boards and samples of the LTC6804 battery monitor and LTC6820 isoSPI transceiver from Analog Devices, please fill in the form below to register your interest now.