TPS61025 powerpad not connected.

Q: TPS61025 powerpad not connected. by 493921

My customer is using TPS61025 and he suspects that he subcontractor may have not soldered the powerpad.  The device is not working and they would like to know if complete inoperation is the likely result of not connecting it.  They are planning to get the boards reworked but would like to know in the short term if this is the root of the problem.  Do we have any experience of this please?


A: RE: TPS61025 powerpad not connected. by 10449

The TPS61025 IC has both an analog and power ground pin.  These two pins must be properly connected to their respective grounds and the two grounds must be connected together on the PWB.  As always, we suggest following the EVM layout for these connections.  If you do not electrically connect the exposed thermal pad to ground, the IC will still work properly.  However, please note that the exposed thermal pad MUST be soldered to the PWB.  We strongly reommend making the thermal pad connection to the ground plane.

I must agree with Chris that we have no way of knowing what might be the problem.  Please work with the customer to reconfirm their schematic and layout meets datasheet requirements.  Then compare customer's PWB waveforms with the EVM waveforms.  This analyis will provide the required information to help resolve this problem.  With their incomplete layout, this could be as simple as that they left the EN pin floating or incorreclty connected it to ground.


Q: RE: TPS61025 powerpad not connected. by 10449

Gary, I'm sorry I don't have a more exact answer, but without more information all we can do is guess at potential causes.  I'm sure you've already validated these basic troubleshooting steps, but it's important that we confim this.  If I were troubleshooting, I would

1.  Cofirm there is an input voltage applied to input of the IC.  Check both the input capacitor side and the switch node to make sure the inductor is soldered properly.

2.  The EN voltage is high enough for the IC to detect the voltage as a logic H and turn on the IC.

3.  Confirm there is not a short circuit from Vout to GND.

4.  Confirm the TPS61025 GND and PGND pins are electrically connected to the input capacitor and output capacitor grounds.

5.  Confirm the TPS61025 is propery soldered and not rotated 180 deg.

6.  Confirm all pins are properly soldered to the PWB.

If all this is correct and the exposed thermal pad is floating, I still expect the TPS61025 to function properly.

Please provide confirmation of the above and when we get the results, we'll be able to narrow down the cause.  You might also consider swapping out ICs to make sure the one on the board was not damaged during assembly.


Q: RE: TPS61025 powerpad not connected. by 493921

Hi there

 

It means there is no output – zero volts

 

Regards

 

Gary

 Q: RE: TPS61025 powerpad not connected. by 1090425

Typically, the requirement to be soldered is for mechanical reliability of the package.  But it may also be used electrically as a GND connection.  I am not aware of any tests being done without it being soldered down.

Could you elaborate on what 'not working' means for your customer?


Q: RE: TPS61025 powerpad not connected. by 493921

Hi there

 

I appreciate that it has to be soldered but can you comment on what the likely effect of it not being connected would be please?  I appreciate that this a difficult question to answer so if you don’t know that’s fine.

 

Regards

 

Gary

 
Q: Re: TPS61025 powerpad not connected. by 1090425

Per the packaging information at the end of the datasheet, this IC actually contains an exposed thermal pad which must be soldered to the PCB.

Once they have their boards reworked, do the usual debug of their circuit, checking the usual things--SW node, output cap placement, etc.