TMP451-Q1: TMP451 random OPEN false fault after device initialization

Scarlett Cao

Part Number: TMP451-Q1
Other Parts Discussed in Thread: TMP451

Hi team,

My customer is using TMP451-Q1 in project and met two cases of random false open fault issue. The OPEN bit assert after initialization, after restart the system the issue is gone. Could you help suggest possible reason? Thank you

Below is the initialization

WriteReg(TMP451_REG_W_LOCAL_TEMP_HIGH_LIMIT);

WriteReg(TMP451_REG_W_LOCAL_TEMP_LOW_LIMIT);

WriteReg(TMP451_REG_W_REMOTE_TEMP_HIGH_LIMIT_HIGH_BYTE);

WriteReg(TMP451_REG_W_REMOTE_TEMP_HIGH_LIMIT_LOW_BYTE);

WriteReg(TMP451_REG_W_REMOTE_TEMP_LOW_LIMIT_HIGH_BYTE);

WriteReg(TMP451_REG_W_REMOTE_TEMP_LOW_LIMIT_LOW_BYTE);

WriteReg(TMP451_REG_W_LOCAL_TEMP_THERM_LIMIT);

WriteReg(TMP451_REG_W_REMOTE_TEMP_THERM_LIMIT);

WriteReg(TMP451_REG_W_CONFIGURATION

WriteReg(TMP451_REG_W_CONVERSION_RATE);

ReadReg (TMP451_REG_R_STATUS);

After above instruction, customer read TMP451 status register bit2 and it asserts.

Thanks

Scarlett

over 1 year ago

0 Ren Schackmann over 1 year ago

TI__Mastermind 43785 points

Could you share the schematic? What is the remote junction? The OPEN bit indicates a fault with the remote junction.

thanks,

ren

0 Bingyan Gu over 1 year ago in reply to Ren Schackmann

Prodigy 20 points

0 Ren Schackmann over 1 year ago in reply to Bingyan Gu

TI__Mastermind 43785 points

Are you seeing this failure on one sample? It may be possible the PMBTA56 or TMP451 have EOS damage.

PMBTA56 may not be a suitable junction; TI has no experience with it. 3904 NPN and 3906 PNP transistor variants are used industry wide as temperature sensing junctions. You can find further information about junctions for temperature sensing in the app note Remote Temperature Sensor Transistor Selection Guide.

Does the TMP451 report the expected Remote Temperature in register 0x02?

Could you show me oscilloscope capture of the D+ signal? I need to see a zoomed in picture of the 34ms active conversion time on the D+ pin. The voltage level will alternate through 3 states repeatedly during this active conversion time.

thanks,

ren

0 Bingyan Gu over 1 year ago in reply to Ren Schackmann

Prodigy 20 points

I don't think it's EOS damage, since it can't reproduce the phenomenon after the DUT reset.

We can't find any failure about PMBTA56 in DV and PV test.

Software engineer said that he can read value expected remote temperature in register 0x02 when issue occurred.

D+ signal is as below screenshot, please refer to.

0 Ren Schackmann over 1 year ago in reply to Bingyan Gu

TI__Mastermind 43785 points

The signal is noisy, but otherwise acceptable. The OPEN error may be caused by system noise. If the OPEN bit is cleared and does not return, it could be ignored.

thanks,

ren

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TMP451-Q1: TMP451 random OPEN false fault after device initialization