Maxim’s MAX40056: Bi‑Directional Current Sense Amplifier with Superior PWM Rejection

Designers can now boost motor efficiency and cut vibration with Maxim Integrated’s MAX40056, a bi‑directional current sense amplifier that features patented PWM rejection.

Accurate measurement of motor winding currents is essential for high‑performance motor control. While most systems infer winding currents via ground or supply‑referenced bridge measurements, direct current sensing delivers superior precision—though it has been hampered by the high common‑mode swings of PWM signals. Existing solutions suffer from inadequate PWM rejection and sluggish settling times, limiting their usefulness.

The MAX40056 eliminates these constraints. It rejects PWM slew rates exceeding 500 V/µs and settles within just 500 ns, delivering 0.3 % full‑scale accuracy in winding‑current measurement. The patented PWM‑rejection architecture provides a four‑fold faster settling time than comparable products, enabling designers to raise drive frequency or lower the minimum duty cycle without compromising measurement fidelity.

Higher PWM frequencies smooth current flow, reducing torque ripple and improving overall motor efficiency. Precise winding‑current readouts at low duty cycles also help eliminate vibration during low‑speed operation.

With a wide common‑mode voltage range of –0.1 V to +65 V and a protection window of –5 V to +70 V, the MAX40056 withstands inductive kickback without damage. Its bi‑directional sensing makes it ideal for DC‑motor control, base‑station power supplies, data‑center power systems, battery‑stack management, and any application that demands reliable current measurement in noisy environments.