TPS27SA08: using the TPS27SA08 to drive a TEC

Hi Li,

Such leakage can be present when diagnostics is enabled due to the internal pull up resistor for open load detection.

This may be why there is a level shift but should not have an effect on the functionality of the device. Can you please provide a schematic and where you are probing?

Thanks,

Rishika Patel 

Hi

   The following is the schematic diagram. Please help to further confirm whether rectification is needed. Thank you!

Hi Li,

I see no issues on the schematic but to clarify, PWMing the DIA_EN pin does not turn the switch on and off; PWMing the EN pin does though. What is the customer trying to achieve here? When diagnostics is off, is the output voltage able to be pulled down to 0V?

Thanks,

Rishika Patel

Hi

The above PWM is incorrectly marked, and the following is the actual schematic diagram. At present, the test of DIA_EN on and off, the above problems will still occur, when the PWM control of EN foot is low, the load theory is 0V, the actual 2V+

Hi Li,

Are you using an e-load on the output? If so, is it in constant current mode or constant resistance mode?

Thanks,

Rishika Patel 

Hi

I use a pure resistive load and the above problems do not occur, and the above problems will occur when driving the TEC. The PWM frequency is 1KHz, and we have tried to reduce the frequency, but the problem still exists，thanks

Red: TEC current
Blue: TEC voltage

Hi Li,

Just to be clear, EN and DIAG_EN are off and you still see a 2V level shift when the TEC is connected?

Thanks,

Rishika Patel 

Hi

  Yes, the red circles in the picture are EN off and DIAG_EN off