TPS4800-Q1: TPS4800-Q1, abnormal fault, FLT, oscillation

Hi Jin-Suk,

Do you mean does this device protect against short circuit conditions - output shorted to ground? If so, yes using ISCP and TMR pins for configuring the threshold and response time respectively. The SCP_TEST pin can also be used to check the internal SCP comparator operation. I saw the system uses CTMR configuration in the slides.

Can you please provide a schematic of the system?

Best Regards,

Rishika Patel 

Hi~ Rishika. What I mean was protection from input short circuit case. 

You can refer customer schematic as below link. (mobed_ti.pdf)

https://e2e.ti.com/support/power-management-group/power-management---internal/f/power-management---internal-forum/1475031/tps4811-q1-tps4811-q1-current-limit/5664653?tisearch=e2e-sitesearch&keymatch=tps4811-q1%2520jin%2520suk#5664653

Thanks.

Hi Jin-Suk,

It seems that you are talking more about a reverse battery condition where the output sees some voltage and the input is connected to ground causing reverse current. If so, please see below for the integrated reverse polarity protection that this device has.

Best Regards,

Rishika Patel 

Hi~ Rishika. No, My main question is why FLT signal trigger during start up and reason of FLT signal repeat with 1.3ms period. This is main question as attached waveform. Can't expect 1.3ms period FLT repeat reason and need your help to understand root cause.

Thanks.

Hi Jin-Suk,

For the TPS4800-Q1, is R93 populated in the actual test or no? The two waveforms on the right side of the slide seem to be an actual fault whereas the waveform with a quick fault trigger does not. Is the repeated fault with 1.3ms period expected based on test conditions or no? Which way is the current flowing in this system?

I want to mention here that a filter capacitor across the ISCP and CS- pins of at least 1 nF is recommended to eliminate nuisance short circuit trips where large di/dt and layout parasitic inductances are involved. Please see below. 

Best Regards,

Rishika Patel 

Hi~ Rishika.R93 is just for test purpose. Current flowing from left to right in schematic and waveforms are during start up. BTW, your filter capacitor comment is TPS4811 datasheet not TPS4800. Would you please check on this? I also requested to test add some filter Y filter cap on CS ISCP node of TPS4800 will check test result. Thanks.

Hi Jin-Suk,

So, it is populated when these waveforms were taken? We need this to know what the expected overcurrent response behavior of the device is. Yes, I will double check on this.

Best Regards,

Rishika Patel