TPS62133: 5V rail drop to 4.6V and lower

Kamran

Intellectual 270 points

Part Number: TPS62133

Hello,

I am using the TPS62133 for a 5V / 2.5A supply.5V_PSU.pdf

With no load, I measure 5V, howerver with approximately 250 mA, the voltage rail drops down to 4.6 V.

It keeps dropping down with higher current demand.

Is there any error in the attached design?

Parts P/N:

C87: CL31A106KAHNNNE Description: CAP CER 10UF 25V X5R 1206

C89: CC0603KRX7R9BB104 Description: CAP CER 0.1UF 50V X7R 0603

C90: C0603C102K3RACTU Description: CAP CER 1000PF 25V X7R 0603

L4: PA4341.822ANLT Description: INDUCTOR 8.2 UH Current rating 4.5A Saturation Current 6A

The layout is attached 4237.5V_PSU Layout.pdf. Note that C101 that appears in the layout is Aluminium 68uF/16V (P/N: EEE-FP1C680AP)

Thank you for your help!

Kamran

over 6 years ago

0 Jason Wang (BSR-MV) over 6 years ago

TI__Genius 9550 points

Hi Kamran,

We are looking into your request, and will give you feedback on Monday.

0 Zhao Ma over 6 years ago

TI__Genius 15135 points

Hi, Kamran

I think the problem is the VOS connecting point is incorrect, which makes the converter regulate 5V left point to 5V, not 5V output to 5V.

VOS should be connected to 5V output, see below.

You can do some test to verify this:

1. Measure 5V left voltage to check if it would drop down with loading.

2. Connect VOS to 5V output by flying wire, then test again.

0 Kamran over 6 years ago in reply to Zhao Ma

Intellectual 270 points

Hello Zhao,

I will try it. But L3 is only there to choke noise. The output inductor is L4.

What do you think.

Kamran

0 Kamran over 6 years ago in reply to Kamran

Intellectual 270 points

Hello Zhao,

I did the suggested correction and it worked. But I did not go all the way up to 2.5 Amps yet, my load was about 350 mA. I will try to increase the load tomorrow.

Could you please explain to me why it worked with VOS connected to the output directly? L3 is only a choke.

Thank you!

0 Zhao Ma over 6 years ago in reply to Kamran

TI__Genius 15135 points

Hi, Kamran

VOS is output voltage sense pin, the control loop detects its voltage and regulate it to 5V, see below diagram.

So VOS should be connected to output capacitor in shortest way.

0 Kamran over 6 years ago in reply to Zhao Ma

Intellectual 270 points

This resolved my issue

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TPS62133: 5V rail drop to 4.6V and lower