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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?
Qiwu,
Is Vcc 5V? Internal LDO should power up within few ms after Vcc powers up. Did you try at higher Vcc (say 12V) and check if there is any delay? Is V5 connected to any load?
Regards,
Vishnu.
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.
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