TPS5431: TPS54318RTER Enable threshold value

Hareesh Panakkal

Part Number: TPS5431

Hi ,

We are using TPS54318RTER in our design to generate 1.8V & 3.3V . Both are power from 5V input supply. As per the datasheet, we have adjusted the Vstart and Vstop for both output voltages with a resistor divider on EN pin.\

Rtop= 10K , Rbottom = 4.3K

With above resistor values, we would get Vstop = 3.892V & Vstart= 4.124V. But this configuration the boards not at all booting. The current drawn by the board is typically 1.37A, when board is not booting.

When we change the values of Rtop & Rbottom,( As per the datasheet , 133K & 105K respectively), the board is working perfectly fine. The current drawn would go up to 1.67A (Normal).

What would be the cause for the issue? Could you please help us.

over 3 years ago

0 Young Zhao over 3 years ago

TI__Genius 9530 points

Hi ,

Seems you are using the wrong resistor divider and make devices can't be enabled .

Pls check it again.TPS54318 2.95-V to 6-V Input, 3-A Output, 2-MHz, Synchronous Step-Down SWIFT Converter datasheet (Rev. C) (ti.com)

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

Hi Young,

thanks for your reply. But as per the data sheet example, I could see Vstop should be more than 2.7V. There is not other requirements mentioned in the data sheet for selecting resistor divider.

We are providing Vstop = 3.8V. How does this make regulator not working.

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

Hi ,

Could you help check are you following below equation ?

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

Yes. Using this equation we have calculated resistor values. The same is used on data sheet for application circuit.

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

Hi ,

Vstop = 3.892V & Vstart= 4.124V

R1=(0.944*4.124-3.892)/2.59*1E6=0.4kohm

R2=0.177 kohm

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

Hi ,

But as per the resistor we have put, we should get Vstart = 4.44V & Vstop = 4.16V. We are giving 5V supply to enable pin.

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

Hi ,

Per my suggestion , pls follow the correct equation in datasheet .

If Vstart = 4.44V & Vstop = 4.16V , you should get R1=12.1K,R2=4.7K .

iF Rtop= 10K , Rbottom = 4.3K , you should get Vstart = 4.15V & Vstop = 3.892V .

This resistor value should still work well .

Pls share the sch and startup waveform for review.

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

Hi Young,

We are getting the output voltages as expected, but there are few issues when we populate the Enable voltage divider with 10K & 4.3K.

As the board is not getting booted up with above values, we have to change 4.3K resistor to different values i.e. above 5.6K. During our debugging process we have changed the current ic with new part TPS54318RTER . At that time, the board is working properly with 10K & 4.3K resister divider values.

Is there any issues with regulator IC batch? kindly let us know your thoughts on this.

Reg,

Hareesh

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

Hi ,

Just to check , which part are you talking about ? regarding "During our debugging process we have changed the current ic with new part TPS54318RTER ",

is there another PN# ?

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

Hi Young,

We have replaced the current TPS54318RTER with newer part.

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

Hi ,

got it pls let us know if there is any future question here.

BRs,

Young

0 Hareesh Panakkal over 3 years ago in reply to Young Zhao

Prodigy 210 points

could you please reply to my query ?

"Is there any issues with regulator IC batch"

0 Young Zhao over 3 years ago in reply to Hareesh Panakkal

TI__Genius 9530 points

I don't think there is any issue with the batch, as every part shipped need pass the final test before , and every spec will be guaranteed by the final test.

BRs,

Young

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TPS5431: TPS54318RTER Enable threshold value