Bidirectional Current Sense Amplifier Features PWM Rejection

Maxim Integrated has introduced the MAX40056, a bidirectional current sense amplifier with patented pulse-width modulation (PWM) rejection. This high speed, wide-bandwidth amplifier extends Maxim’s family of precision, high-voltage current sense amplifiers into motor control applications.

Creating a motor control system requires precise current sensing and measurement of motor winding currents, says Maxim. A commonly used approach is to infer winding currents by performing ground or supply referenced measurements in the bridge circuit. Direct winding current measurement is a simpler and more accurate method, but the implementation is challenging due to the high common mode swing of the PWM signal. Adoption of this approach has been limited by poor PWM rejection and slow settling speed of existing solutions.

MAX40056 rejects PWM slew rates of greater than 500 V/µs and settles within 500 ns to provide 0.3 percent accurate, full-scale winding current measurement. The patented PWM rejection scheme achieves 4 times faster settling time than competitive offerings, allowing motor control designers to increase drive frequency or decrease minimum duty cycle without sacrificing measurement accuracy. Higher PWM frequency smooths out the current flow and reduces torque ripple, resulting in more efficient motor operation.

Accurate winding current measurement at low duty cycle helps reduce or virtually eliminate vibration when the motor is running at a slow speed. MAX40056 has a wide common mode voltage range of -0.1 V to +65 V and a protection range of -5 V to 70 V to ensure the inductive kickback does not damage the IC. With bi-directional sensing capability, it is well suited for DC motor control, base station, datacenter, battery stack and many other applications which require precise current measurements in noisy environments.

The MAX40056 is available at Maxim’s website for $1.19 (1000-up, FOB USA), also available from authorized distributors. The MAX40056EVKIT evaluation kit is available for $69.

Maxim Integrated | www.maximintegrated.com

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