DRV8432: DRV8432 drive TEC

dengshan yang

Prodigy 155 points

Part Number: DRV8432

hi，

I'm using DRV8432 to drive TEC-XLT2418, the flow chart is below

1. heat TEc to 90℃ by PWMing PWM_A(buty cycle 100%) and PWM_B(buty cycle 0%),

2. then cooling it down by PWMing PWM_B 100%(buty cycle 100%) and PWM_A(buty cycle 0%)

but we found one question, at the moment of cooling down from 90℃, the TEC+ is still high while PWM_A is 0%, and hold up 1s above.

why it happened? when PWM_A low, why TEC+ can't drop down to low instantaneously with PWM_A?

the design is below.

BR
Jerry

over 2 years ago

0 Wang5577 over 2 years ago

TI__Guru 56650 points

Jerry,

This is a duplicated thread. I just replied the original one. BTW, the post would be replied in one business day. If the thread is posted on Saturday or Sunday, it will be replied on Monday.

Regards,

Wang Li

0 dengshan yang over 2 years ago in reply to Wang5577

Prodigy 155 points

hi Wang,

to be clear,heating and cooling down the TEC respectively, it's normal, but when cycling from heating it to 90℃ to cooling down, it's abnormal,

just cycling TEC, it happened.

0 Wang5577 over 2 years ago in reply to dengshan yang

TI__Guru 56650 points

Dengshan,

If you want to discuss here, I will close the other duplicated thread.

Regards,

Wang

0 dengshan yang over 2 years ago in reply to Wang5577

Prodigy 155 points

hi Wang,

OK, BTY, one more question related, we set up PWM_A high and PWM_B low directly to heat the TEC, but we found DRV8432 could not work, the output TEC+ respected to TEC- is low. is it normal?

Jerry

0 Wang5577 over 2 years ago in reply to dengshan yang

TI__Guru 56650 points

Jerry,

I would think the output capacitance is too high and make DRV8432 trigger the over current protection.

Would you remove all output capacitor on the output to confirm the issue? And then, we can work on the solution.

Regards,

Wang Li

0 dengshan yang over 2 years ago in reply to Wang5577

Prodigy 155 points

hi Wang,

what do you mean the output capacitance, all 47uf capacitance? BTY, about the issue of heat and cool down cycle, do you have any idea?

Jerry

0 dengshan yang over 2 years ago in reply to dengshan yang

Prodigy 155 points

hi Wang,

I removed all 47uf capacitance, and change C40,C48,C58,C66 from 47uf to 0.22uf, the ouput TEC+ high and TEC- low while PWM_A high, PWM B low,

but when I PWM PWM_A 50 duty cycle(@100KHz), PWM_B low, the TEC+ and TEC- is abnormal, the waveform is below,BTY, the output TEC+ is high, TEC- is low with C40,C48,C58,C66@47uf and PWM_A 50 duty cycle(@100KHz), PWM_B low. please help check out why.

PWM_A 50 duty cycle(@100KHz), PWM_B low

TEC+ and TEC-

Jerry

0 Wang5577 over 2 years ago in reply to dengshan yang

TI__Guru 56650 points

Jerry,

"but when I PWM PWM_A 50 duty cycle(@100KHz), PWM_B low, the TEC+ and TEC- is abnormal, the waveform is below,BTY, the output TEC+ is high, TEC- is low with C40,C48,C58,C66@47uf and PWM_A 50 duty cycle(@100KHz), PWM_B low. please help check out why."

What is the voltage waveform on R31 (between AGND and PGND)? What is about OUT_A/B and OUT_C/D voltage?

Regards,

Wang Li