High-Precision Current Sensing in EV Battery Management Systems (BMS) with COS8552

In electric vehicle battery packs, precise current sensing is critical for accurate State of Charge (SoC) calculations. Standard operational amplifiers suffer from temperature-induced input offset voltage drift, leading to cumulative errors in current integration. The COS8552 zero-drift chopper architecture solves this by providing a maximum offset of 5μV and near-zero drift over the full temperature range (-40°C to +125°C).

Chopper Self-Zeroing Mechanics

By employing an internal continuous auto-calibration circuit, the COS8552 modulates low-frequency 1/f noise and input offset voltages, translating them to high-frequency bands where they are eliminated by an integrated low-pass filter.

• Input Offset (Vos): 5 μV maximum at 25°C.
• Offset Drift: 0.05 μV/°C maximum drift.
• PSRR & CMRR: High performance exceeding 110 dB.