big fluctuations of the outputs

user1289523

Prodigy 180 points

I am using the DRV8432EVM. I tested it , but I can see big fluctuations of the outputs:

When I disconnect its outputs with anything , I can see many fluctuations. Please see Figure1.

When I connect its outputs with a coil (resistance=11Ω)， I can see many fluctuations. Please see Figure1.

When I connect its outputs with a 200Ω resistor, the number of fluctuations can be reduced to one. Please see Figure2.

When I connect its outputs with a 100Ω resistor, the fluctuations disappear. Please see Figure3

Why the turning on and stabilazing time is not so short as the datasheet says?

figure1

figure2

figure3

Thanks!

over 8 years ago

0 Wilson Zuo over 8 years ago

TI__Mastermind 26065 points

Hi

Let's reproduce the waveform on bench and get back later. Some question, do you have long wire or caps for the load? only EVM board or any change?

Best regards,

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

TI__Mastermind 26065 points

Hi,

I check that it is because you may test the output after the on board inductor which induce the ring (Caused by this L and the C n R from the loading ). If you test the waveform right on the out pins, you will not see it.

Best regards,

0 user1289523 over 8 years ago in reply to Wilson Zuo

Prodigy 180 points

Hi,

I did not use long wire or caps for the load. The load are open circuit, small resistor, coil, respectively. But I use the oscilloscope to connect the OUTA to see the output.

Best regards,

Xinjing