TPS65131 VNEG Output Problem.

I am using the TPS65131 regulator in my design.(To drive 5 AMP as shown below)

reference design : TPS65131 Datasheet typical application

Please see the attachment configuration of the circuit.(tps65131.pdf)

1. Positive Output Voltage : no problem

2. Negative Output Voltage :

    - no load  or 1 AMP connect: -5V

    - all amp connect : -5V --> -0.2V

please help..

let me know what is wrong.

tps65131.pdf

Hello Bjkong,

Can you post the schematic once more, as there might have been a problem with the conversion.
Can you as well send me the part number of the opamps you are using.

Thank you,
Best Regards,
Ilona

hello ilona,

I've attached a shematic.

please review looked answers.

thanks.

tps65131.pdf

Hello Bjkong,

Thanks for the schematic, it fairly looks ok from the component selection. Although I noticed that the schematic relates to the TPS65130, so which part are you really referring to? You need to be aware that at this input voltage the output current capability of the TPS65130 is almost half of the TPS65131. Can you share some scope plots with the VNEG/OUTN and the output current of VNEG?

Additionally I noticed that the output voltage of the positive rail is 5 V as well as the input voltage. I wonder why you say that this rail does not have a problem because the minimum output voltage that this converter can deliver is VIN + 0.5 V...

Thank you,
Best Regards,
Ilona

hello, Ilona

An input voltage supplied to 3.3V(unlike schematic)

The remaining parts are the same as in the schematic.

TPS65130 and TPS65131 are same symptons.

In order to measure the current consumption.

All 5 AMP Power : Commercial Power supply (+/- 5V)

Positive 5V Current : about 60mA

Negative 5V Current : about 60mA

==> the current is not much consumed.

Attached file is a scope waveform of -5V.

please advice.

thanks.

Hello Bjkong,

Please excuse the late reply, I assume you still have this problem?
Although the output load is quite low i would like to check if the inductor does really not went into saturation. Can you please make another scope plot showing the inductor current of L1 and L6 and the FBN- pin ?

Thanks,
Best Regards,
Ilona

Hello Bjkong,

Can you give me the complete circuit with the circuitry of the opamps ? I want to replicate this circuit in the lab and see if i can reproduce the issue.

Thank you,
Best Regards,
Ilona

Hello Ilona.

I've attached a schematic.

please review.

thank you.

SIGNAL_DISTRIBUTOR_VER.pdf

Hello Bjkong,

I could not evaluate the board but I have another idea. Can you try to disable the Power Safe Mode and see if it still fails?

Thanks.
Best Regards,
Ilona

Hello Ilona,

I tried to disable the Power Save Mode of N5V side.
but, Symptoms were the same.
I do not know what to do anymore.

please help..

Thanks..

Hello Bjkong,

Is it possible that you measure the inductor current as well as the output current of the negative rail? What I want to check is whether it is related to current limit of the device.
So please send a scope plot with V(OUTN), V(N5V) and I(L6) and I(N5V).

Thank you.
Best Regards,
Ilona

Hello Bjkong,

Do you have any update for me?

Thanks.
Best Regards
Ilona

Hello Ilona,

I using a commercial Power Supply to measure the current of the N5V.
N5V Current consumption: 60mA

I have attached a file that measure N5V and OUTN.

please review.

Thank you.

Best Regards,

bjkong.

N5V_Capture.zip