DRV8332 OTW and FAULT PIN are always low

ashish kumar41

Hi,

I have DVR8432 chips on my board and it seems to have a problem with OTC and FAULT . The voltage on the fault and OTW pins is always around 1.5-2V. I don't believe I have any overcurrent condition or overtemperature conditions as - no motors connected, no PWM input active..... and from starting these pins are low

I have isolated the pins from the board and still show in that 1.5V - 2.0V range. Any ideas ?

this is my schematic which is similar to one that is in datasheet.

over 8 years ago

0 Wilson Zuo over 8 years ago

TI__Mastermind 26065 points

Hi Ashish,

This nOTW is open drain output and need external pull up. So if you MCU input is a HiZ input state, you may see a voltage like that.

Best regards,

0 ashish kumar41 over 8 years ago in reply to Wilson Zuo

Prodigy 60 points

hi sir,

thanks for your reply, now i understand what was the problem. and at last i get correct.

Thanks sir

0 ashish kumar41 over 8 years ago in reply to ashish kumar41

Prodigy 60 points

one more thing i have used 10k resistor as pull up . but still not getting fair amount of voltage. would u pls suggest value of resistor

0 Rick Duncan over 8 years ago in reply to ashish kumar41

TI__Guru** 114905 points

Hi Ashish,

What voltage are you measuring at FAULT and OTW? What voltage is the top of the pullup resistor?

A 10k pullup resistor should be sufficient. Please check that the GPIO is set to an input with pulldowns disabled. If set properly and the voltage is still low, a fault could exist.

0 ashish kumar41 over 8 years ago in reply to Rick Duncan

Prodigy 60 points

i am getting around 1.5-2 V. and my pull up resistor is connect to 3.3 V which is the voltage of vreg. i am using volt meter to measure the voltage.

0 Rick Duncan over 8 years ago in reply to ashish kumar41

TI__Guru** 114905 points

Hi Ashish,

Is power applied to DRV8332 when the voltage at FAULT and OTW is measured? If not, please apply power to GVDD, VDD, and PVDD (this may be optional) and re-measure.

0 ashish kumar41 over 8 years ago in reply to Rick Duncan

Prodigy 60 points

hi sir

actually i am using a led which is connected OTW and FAULT . and when i measure voltage in this condition then the output voltage is low . but yesterday i accidentally disconnect the led from OTW and FAULT and then measure the voltage btw OTW and FAULT then it is showing 3.3 volts. and when i reconnect led to OTW and FAULT it shows again low . my led is in good state and glow when i provide external voltage .i have powered all GVDD, VDD, and PVDD and then i have measured the values.

pls reply as soon as possible

thanks

0 Rick Duncan over 8 years ago in reply to ashish kumar41

TI__Guru** 114905 points

Hi Ashish,

Can you provide a quick schematic of the LED connection and the point where you made the measurement?

The forward voltage of the LED is sometimes 1 to 1.5V which could explain the lower voltage.

0 ashish kumar41 over 8 years ago in reply to Rick Duncan

Prodigy 60 points

Hi sir ,
sry for replying so late , sir have used same schematic as given in data sheet and for LED I have connected it to OTW and GROUND.
sir , when i pull up OTW and FAULT to 3.3 volts to get 5V across OTW and FAULT then also in this case i am not getting accurate values and leds are not blinking.
sir we ran out of drv8332 , so will u pls send ur schematic with led on it .

0 Wilson Zuo over 8 years ago in reply to ashish kumar41

TI__Mastermind 26065 points

Hi Ashich,

If you connect LED from OTW to GND, so in normal state, the OTW internal is off state open drain. The LED is lited on by your external 10k. The voltage you found is the turn-on voltage dropping of the LED. The voltage could be about 1.5V for red and green LED, and 2V to 3V for blue and white LED. Also in this configuration, LED is OFF when in fault condition which is not a normal way to report fault.

Below is normally how we design the nfault/nOTW in our EVM, FYI.

Best regards,

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DRV8332 OTW and FAULT PIN are always low