Part Number: DRV8873-Q1
Hi,
When the power supply voltage is stable, changing nSLEEP from High to Low causes nFAULT to become Low. Could you tell me why nFAULT becomes Low?
I measured the waveform, but it didn't seem like a FAULT was occurring. A motor of about 26 Ω is connected to the load.
Best Regards,
Nishie
Hey Nishie-san,
Does this also occur if you repeat the test with no load attached?
It looks like the driver was driving the load at the time you put it into sleep mode, correct? Please retry this test after the motor has stopped spinning (Set OUT1 and OUT2 to HI-Z and wat for motor to stop).
It also might be related to the Open-Load detection - try connecting the nOL pin to 5V if this is the hardware version of the device.
Best,
Jacob
Hi Jacob-san,
We measured the waveform of each item, but there was no change in the symptoms. Do you have any other concerns?
Does this also occur if you repeat the test with no load attached?
->I did the measurement with no load.
Please retry this test after the motor has stopped spinning (Set OUT1 and OUT2 to HI-Z and wat for motor to stop).
->After setting the output to the BREAK state, the motor was stopped and the nSLEEP was lowered.
It also might be related to the Open-Load detection - try connecting the nOL pin to 5V if this is the hardware version of the device.
->External 5V connected to nOL.
In addition, the voltage of nOL was confirmed in the existing circuit. After nSLEEP went low, nOL decreased.
Best Regards,
Nishie
Hi Nishie-san,
What is the VCP voltage and the VM voltage in this capture:
In sleep mode the expectation is for the charge pump to be disabled:
Does this happen on all devices or is it only on a select few?
Does it always recover from the fault?
I am going to check on my end as well.
Best,
Keerthi
Hello Nishie-san,
In this capture below you can see after 40 us, nFAULT goes low, which is the same time DVDD starts to discharge. When it is fully discharged, the nFAULT goes high again. Can you also try capturing DVDD on your end as well?
Best,
Keerthi
Hi Keerthi-san,
According to your test results, nFAULT becomes Low about 40us after nSLEEP changes to Low.
Also, 7.4.1.4 nSLEEP Reset Pulse on the datasheet shows the difference in IC operation depending on the Low time of nSLEEP.
I have additional question. Is DRV8873-Q1 correct in understanding that if nSLEEP goes Low for more than 30us, then nFAULT also goes Low?
If there is a pulse time for nSLEEP that nFAULT does not go Low, please let me know.
Best Regards,
Nishie
Hi Nishie-san,
If there is a pulse nFAULT shouldn't go low. It should be only the case when the device goes to sleep. After 30us, the device might be in sleep, and the min time to sleep is 50 us.
Best,
Keerthi
Hi Keerthi-san,
1) Is it correct to understand that if the Low time of nSEELP is shorter than 30us, nFAULT will not become Low? (Case 1 in the figure below)
2) Also, if nFAULT becomes Low after the Low time of nSLEEP becomes 30us or more as in Case 2, is it correct to understand that nFAULT also becomes High by changing nSLEEP back to High?
3) Also, is it possible to measure the waveform of the above two movements?
Best Regards,
Nishie
Hi Nishie-san,
I was able to capture one of the waveforms:
This matches what was expected as nFAULT stays high for a pulse of less than 30us. However, the EVM has been modified, so I have to check if the driver is still functional before continuing to collect data. Please give me till tomorrow EOD for all the waveforms.
Best,
Keerthi
Hi Nishie-san,
Remaining waveforms yellow- nSLEEP, purple - nFAULT:
Best,
Keerthi
