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DRV8800: Overcurrent protection

na na78
Guru 16770 points
Part Number: DRV8800

Hi

The customer want to operate their DC motor under following condition.

VM=8V

Iout(normal)=100mA

Iout(start)=500mA 

Iout (motor lock) = 360mA 

Iout (start) and Iout (motor lock) were obtained by motor unit test.

They want to turn off the driver when motor is locked.

1.

Is it possible to stop H bridge of driver and report nfault when output current reaches Itrip set by Rsense?

2.

Is the motor start-up current also affected by overcurrent setting by Itrip?

3.

According to datasheet, nFAULT is asserted under a motor fault, undervoltage, and over temperature.

SLVS855J, P12 9.3.8 

"The nFAULT pin signals a problem with the chip via an open-drain output. A motor fault, undervoltage condition, or TJ > 160°C drives the pin low"

What is motor fault?  Motor lock condition is implied?

BestRegards

  • 0
    TI__Prodigy 190 points
    1. When an overcurrent condition is observed, the full-bridge outputs are turned off and nFAULT is driven low. A 1.2 ms fault timer occurs after which the device will turn on only if the fault condition is no longer present. Refer to section 9.3.10 in the datasheet for more information.

    2. Startup current may trigger I_TRIP if it occurs for longer than the overcurrent deglitch time which is 3 uS (Table 7.5). To prevent false trips, the I_TRIP must be configured to be higher than regular operating current. Refer to section 10.2.2.3 in the data sheet for more info.

    3. When a fault is detected (undervoltage lockout, charge pump undervoltage, overcurrent protection, overtemperature shutdown) the outputs of the motor will shut down until the fault is removed. Refer to section 9.3.5 for more information.