TPS61032: Burns out when the 5V output loading increased from 400mA to 600mA while using 2 x AA as power source

Philip Hwa

Part Number: TPS61032

We have a PCB circuit design that uses TPS61032.

Designed output is 5V/1A for two output loadings. 1st loading is 5V/400mA, 2nd loading is 5V/200mA.

This is for a 3 stage switch (0,1,2) power supply system. 
SW1=0, All off;
SW1=1, Only 1st loading (5V/400mA) is on
SW1=2, both 1st (5V/400mA) and 2nd loading (5V/200mA) are on

=== PROBLEM ENCOUNTERED WHEN USING 2 x AA BATTERIES AS POWER SOURCE ===

The PCB worked fine when SW1=1.  But when SW1=2, U2 (TPS61032RSAR) immediately burned out.

--- NOTE ---

The previous versions of this circuit design uses TPS61023, which supports both output loadings (total 5V/600mA) from the same 2 x AA power source without issue.  
We modified the circuit according to the guidance in your TPS61032 spec.

*** PLEASE HELP,   THANK YOU! ***

over 3 years ago

0 Wenhao Wu over 3 years ago

TI__Genius 9046 points

Hi Philip,

Let me check their schematic and PCB layout and give feedbacks later.

-Wenhao

0 Philip Hwa over 3 years ago in reply to Wenhao Wu

Prodigy 15 points

Hi Wenhao,

Thank you for helping out. Please advise how we can make our designed circuit supports more than 5V/700mA output using 2 x AA batteries as power source?

Best regards,

0 Wenhao Wu over 3 years ago in reply to Philip Hwa

TI__Genius 9046 points

Hi Philip,

I think the layout has main issue here. Also their schematic does not have enough output caps. I sent you message to you already.

-Wenhao

0 Philip Hwa over 3 years ago in reply to Wenhao Wu

Prodigy 15 points

Hi Wenhao,

Many thanks for your suggestions. The engineer used a larger capacitor (186uF) for testing but still not working. Can you kindly provide more guidance on what else we should try (circuit components and/or pcb layout) when you have a chance?

Thank you again and best regards,

Philip

0 Wenhao Wu over 3 years ago in reply to Philip Hwa

TI__Genius 9046 points

Hi Philip,

Schematic

1.Output capacitor, please ask them change output capacitor especially with >30mOhm ESR. Without ESR the loop is hard to be stable; Please make sure 186uF is effective capacitance instead of capacitor.

2.If area available, they can add snubber place holder (R+C in series, 0603 package) between SW and GND;

PCB layout

1.The most effective way to reduce parasitic inductance in VOUT loop is reduce its loop length instead of width. They can solder 22uF between PGNDs PIN5,6,7 to VOUT PIN1, 15, 16 directly onto IC to shorten loop distance, and check if this works.

2.It is not recommended as 2-layer PCB that does not place a solid GND in bottom layer. Please strictly follow datasheet recommendation for PCB layout reference, especially for VOUT PINS->COUT->PGND PINS connections. They should be wide and short.

Test

They need to test VOUT voltage when switching the load, SW-PGND spikes before switching the load and when load is switching. Please use minimum loop method to carry out this test.

www.ti.com/.../slvaf30

0 Philip Hwa over 3 years ago in reply to Wenhao Wu

Prodigy 15 points

Hi Wenhao,

Really appreciate your detailed recommendation. We will try them and provide update asap.

Best regards,

Philip

0 Wenhao Wu over 3 years ago in reply to Philip Hwa

TI__Genius 9046 points

Hi Philip,

Any updates from customer now?

-Wenhao

0 Wenhao Wu over 3 years ago in reply to Wenhao Wu

TI__Genius 9046 points

Hi Philip,

Since no further reply. I closed the thread, if you have any update you can post here. Thanks!

-Wenhao

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TPS61032: Burns out when the 5V output loading increased from 400mA to 600mA while using 2 x AA as power source