DRV11873: DRV11873 DON'T WORK

Hi Qiwu,

Thanks for posting your question in MD forum. Do you see stable 5V output on the V5 pin? We recommends a 2.2-µF ceramic capacitor to connect closely on the PCB layout between the V5 pin and ground. If you see a stable 5V on V5 then the issue might be due to something else and not the 5V power supply. Did you refer to section section 8.3.7 in the datasheet to choose the Rcs resistor? Also, did you try pulling FS pin High and low? This is Motor parameter adjustment pin. This pin should be pulled low for lower-speed motor and pulled high for high-speed motor.

Regards,

Vishnu

HI Vishnu，

Thanks for your reply.The output voltage of V5 pin is 5V，Is there a startup time requirement for the internal LDO?

Motor will not spin unless power is applied again，At this time, the RD pin is high.

I've seen a lot of similar situations on e2e forums, but none of them have a definitive answer, is there a flaw in DRV11873 itself?

HI Vishnu，

Thank you for your reply.

Vcc is 5V.This is the waveform of V5 at power up，V5 is not connected to any load.how long is‘ few ms’?do you have any specific data？If I use a smaller capacitor at the V5 pin, say 1uf，the rising edge time will be shorter,is there any problem？

Hi Qiwu,

I see that the V5 takes 2.5 ms to ramp up. Is your motor starting after this time? 

Regards,

Vishnu. 

yes，the motor PWM control signal is far behind the power-on time

HI Vishnu，

When the motor is not spinning，the RD PIN is high,and sometimes the high level is 5V,sometimes the high level is about 2.2V,does this matter?

Qiwu,

I think we are seeing this issue because Vcc is at 5V. Can you check if the issue still exists at higher Vcc say 12V? 

Regards,

Vishnu

Hi Qiwu, 

Do you still need assistance? If not please mark as Resolved. 

Thanks,
Aaron