Bi-directional current sense amplifier quadruples speed

Motor efficiency can be improved and vibration reduced, using the MAX40056 bi-directional current sense amplifier with patented pulse width modulation (PWM) rejection from Maxim Integrated Products.

The high speed, wide-bandwidth amplifier uses direct winding current measurement, a simpler and more accurate method than to infer winding currents by performing ground or supply referenced measurements in the bridge circuit. The drawbacks are the high common mode swing of the PWM signal and slow settling speeds.

MAX40056 rejects PWM slew rates of greater than 500V/micro seconds and settles within 500 nano seconds to provide 0.3 per cent accurate, full-scale winding current measurement. The patented PWM rejection scheme achieves four times faster settling time than competitive offerings, claims Maxim, 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 and 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 to +65V and a protection range of -5.0 to 70V to ensure the inductive kickback does not damage the IC. Bi-directional sensing is also a characteristic that makes it particularly suitable for DC motor control, base station, data centre, battery stack and other applications which require precise current measurements in noisy environments.

The MAX40056 is available now directly from Maxim or from authorised distributors, The company also offers the MAX40056EVKIT evaluation kit.

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