Current-sense amp for motor drives

November 12, 2016 // By Graham Prophet
Texas Instruments' latest device for the motor-drive sector is a current-shunt monitor that improves efficiency and accuracy for motor and solenoid control applications.

This current-sense amplifier for in-line motor phase current measurement, TI says, can improve overall motor efficiency compared to existing current-sense amplifiers. The INA240 offers enhanced pulse-width modulation (PWM) rejection for systems running at up to 80V to support a variety of applications such as motor control, solenoid control and power delivery systems.

The INA240's enhanced PWM rejection improves transient suppression and gives designers the ability to reduce their blanking time, optimize the motor-control algorithm and ultimately improve motor efficiency. It operates at PWM rates in excess of 100 kHz, with switching-edge rates as high as 10 V/nsec while enabling system voltages as high as 80V. To address the needs for a wide range of systems, this device supports the negative voltages (-4 V) induced by the inductive kickback of the motor.

The INA240 has low offset voltage (5 µV), offset drift (50 nV/°C), gain error and drift performance (0.05% and 0.5 ppm/°C, respectively). The device also provides an AC common-mode rejection ratio (CMRR) of 93 dB at 50 kHz. The INA240 delivers performance over a wide range of operating conditions.

The INA240's precision is showcased in a 48-V 10-A In-Line Three-Phase High-Frequency Gallium Nitride (GaN) Inverter for Brushless Motors Reference Design; This BoosterPack plug-in module reference design is paired with a C2000 LaunchPad kit, demonstrating how designers can use the INA240 and LMG5200 GaN half-bridge power stage to reduce switching losses over an extended temperature range up to 125°C, facilitate the use of higher PWM frequencies and reduce heat sinking requirements.