TPS3700: UVOV test problem

simmy2010

Part Number: TPS3700

Dear all,

When I actual test UVOV value to TPS3700, I find a problem.

1.The monitor voltage is 4.706V(The output state 1 change to 0), When the monitor voltage form under voltage to normal;(There is no floating)

2.The output state is floating when monitor voltage form normal to under voltage;(Monitor voltage range:[4.649V,4.669V]

3.The monitor voltage is 5.399V(The output state 1 change to 0),when monitor voltage form normal to over voltage;(There is no floating)

4.The monitor voltage is 5.321V(The output state 0 change to 1),when monitor voltage from over voltage to normal.(There is no floating).

I want to know why is there floating state when the monitor voltage form normal to under voltage?? And there is no floating state at the other transfer.

Thanks!

over 5 years ago

0 Michael_DeSando over 5 years ago

TI__Genius 12630 points

Simmy Zheng,

Please provide the part number for the device you are using and a schematic to show how the device is configured. We will try to get this figured out asap. Thanks!

-Michael

0 simmy2010 over 5 years ago in reply to Michael_DeSando

Prodigy 80 points

Dear,

I used the part number:TPS3700-Q1.

The schematic:

When resistor configuration--Group1:91K,1K,0.82K,7.68K, The function is OK.

When resistor configuration--Group2:91K,1.3K,1.1K,7.5K. When monitor voltage from normal to undervoltage, The output is floating state.

Please tell me why? Group1 is ok, but group2 is not ok!!

Floating state waveform:

Thanks!

0 Michael_DeSando over 5 years ago in reply to simmy2010

TI__Genius 12630 points

Simmy Zheng,

I believe the issue is either the pull-up resistor at the output or the transistor configuration at the output.

What is the pull-up resistor value to the RESET supply?

-Michael

0 simmy2010 over 5 years ago in reply to Michael_DeSando

Prodigy 80 points

Dear Michael,

The pull-up resistor value is 10K.

But I think maybe the reason is not the pull-up resistor. And I doubt the use method that monitor voltage and IC supply voltage is same.

Because when I use monitor voltage and IC supply voltage is different, there is no problem.

Please help me analysis it.

Thank you very much!

0 simmy2010 over 5 years ago in reply to Michael_DeSando

Prodigy 80 points

Hello Michael,

When you have time, please help me!
Because I change the pull-up resistor value and take out the transistor, the floating state still exist.
Thanks!

-Simmy

0 Michael_DeSando over 5 years ago in reply to simmy2010

TI__Genius 12630 points

Simmy,

I will ask for you to double check the expected monitor range to cause the UV and OV faults. If the problem still continues, try to use a known good and working good device to eliminate the possibility that the board is the issue. Let me know if you are still having issues. Thanks!

-Michael

0 simmy2010 over 5 years ago in reply to Michael_DeSando

Prodigy 80 points

Hi Michael,

Thanks.

The floating state will be appear when the IC supply voltage is (4.6V--4.7V) and UV threshold value also is (4.6V--4.7V). And I test 3 PCBs all have this problem.

But now we have a way to avoid the problem. The output will be OK if we set the UV threshold value greater than 4.7V.

So ,now I just want to know why? Why has the phenomenon for this IC when the supply voltage is (4.6V--4.7V)??

Thanks!!

0 Michael_DeSando over 5 years ago in reply to simmy2010

TI__Genius 12630 points

This seems like the issue could be the pull up resistor value. I notice in Figure 14 when the outputs are tied together for the Window Voltage Supervisor application they have 50k ohm for the pull-up resistor and you are using 10kohm. Maybe you can try to increase your pull-up resistor value to prevent the floating output. Please let me know how this works for you. Thanks!

-Michael

0 simmy2010 over 5 years ago in reply to Michael_DeSando

Prodigy 80 points

Dear Michael,

I changed the resistor value before. But there was no effect. I changed to 3.3K or 50K, but the floating state is still exist.

Thanks for you support!!

--Simmy

0 Michael_DeSando over 5 years ago in reply to simmy2010

TI__Genius 12630 points

Simmy,

Please let me know if this item requires additional support. Thanks!

-Michael

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TPS3700: UVOV test problem