TPIC8101: In the absence of a knock signal, the chip out pin has an integral signal output

Amy,

A little more detail would help us understand the problem.

1. Is the customer using our EVM, or their own PCB?
- If it is their PCB, can they provide a schematic & layout?
2. Can they provide their device settings?
3. What does the customer expect to see with their waveforms?

Regards,
John

Hi John,

Thank you for your response.

Below is the information provided by the customer.

1. It is their own PCB. Refer to the circuit on the datasheet:

2.Is it a setting of TPIC8101? I configured it according to the example on the datasheet.

3. I understand that the output of the TPIC8101 should be continuously high or low when the knock analog signal is not connected, and the blue waveform in the picture should be output only after the analog knock signal is introduced.

Best Regards,

Amy 

Amy,

What is the power supply voltage?

Regards,
John

Hi John,

It's 5V.

Thank you Amy.
I don't see an obvious error, and will dig into it further and update the thread by Tuesday.

Regards,
John

Amy,

Apologies for the delay.

If you have an EVM, could you configure the same as your board, and see if you see an output signal under the same conditions?

If they don't have an EVM, please have the customer try the following:

1. Is the knock sensor connected to the TPIC or is it disconnected?
2. If it is connected, does disconnecting it change the output?
3. Check the signal/noise on your open KNOCK_H and KNOCK_L pins.    
4. Check for noise on your VCC & VREF lines.
5. Short the KNOCK_H and KNOCK_L points together,
       - Does this change the output signal?

Regards,
John