12-cell battery-monitoring IC does not require isolators when daisy-chained together

The Maxim 11068,The Maxim 11068, a high-voltage battery-monitoring IC, simplifies the design of large HEV or EV battery packs. A 12-cell measurement system, this device employs a capacitor-isolated SMBus-laddered communication bus to reduce component count and cost (isolators are not required). This architecture allows up to 31 devices to be connected in a series stack to monitor as many as 372 cells.

The capacitor-based interface provides low-cost isolation from one bank of batteries to the next,

eliminating cascading electrical failures. Maxim's solution is said to consume 75% less space than discrete designs. Altogether, it can reduce the expense of a typical battery-management system from $250 to $50, according to the company.

The MAX11068's analog front-end combines a 12-channel voltage-measurement data-acquisition system with a high-voltage, fault-tolerant switch bank input. A 12-bit ADC is used to digitize the cell voltages. The MAX11068 employs a two-phase scanning approach to collect cell measurements and correct them for errors. This technique delivers cell-measurement simultaneity, allowing all cell-measurement samples of a 120-cell pack to be co-sited within 10µs.

The MAX11068 is said to deliver less than ±0.25% error over normal battery temperature ranges and ±20mV error over the full AEC-Q100 Type 2 temperature range.