为什么TPS3808 RESET输出一直为低？

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In the figure, after power, VCC_1V_RESET_N goes high, enabling VCC_2.5V output, but VCC_2.5V_RESET_N has been low, resulting VCC3V3 no output, would like to ask why this is? Thank you!

yes!Thank you!

Who can help me resolve this problem?Thanks!

Hi Shidong,

I apologize for the delay.  I am not sure I fully understand your question; however, I do notice that you do not have any pull-up resistors in the schematic.  TPS3808 should have a pull-up resistor on the /RESET.

Very Respectfully,

Ryan

Thank you!The Tps3808(u44) /reset output is connected to the track of power module PTH08T240W and there is not a pull-up resistor on the /reset,but the /reset output work fine. so i think this is not the reason,thank you very much!

Hi Shidong,

I must not understand the question then.  If the /RESET is operating as intended, what is your question?  Could you please try and restate it?

Very Respectfully,

Ryan

MY question is why U44 /reset output can work well,but U48 /reset output is always stay at low?Thank you very much

!

Hi Shidong,

Thank you for restating your question.  TPS3808 requires a pull-up resistor.  Without using a pull-up resistor, you are not using the device as designed.  There could be something on the U44 /RESET line satisfying the pull-up requirement that is not on the U48 /RESET line; however, to ensure proper operation, you need to add a pull-up resistor from 10k to 1M ohm as stated in the datasheet.

Very Respectfully,

Ryan

Thank you very much!Ryan.But I don't think this is the reason,I design my schematic follow the reference design "slva408",you can see it.1321.slva408.pdf

Having looked further at the PowerTrain modules and given that the same module is connected to both TPS devices and U44 works then either a TPS3808 with the wrong sense voltage is in location U48 or the power module isn't outputing a level high enough to reach the valid threshold of the TPS3808 sense input.

I have measured the power moudle output which is U48 sense input,it is 2.5v,the p-p ripple is about 120mv.At the same time I have checked  the tps3808 chip mark and make sure it is tps3808g25.Thank you very much!