LM73100EVM: Startup Test Issue (Section 5.1 of user guide)

Tyler Holmvik

Part Number: LM73100EVM

Customer is trying to use LM73100EVM and perform first test with device. They are trying to follow section 5.1 of the user guide but not seeing the output voltage they expect.

Here is what we know about the setup

Power supply connected to Vin1 at 20V/5A (Vin2 left disconnected)
Load connected to Vout1
All the jumpers set as default
Oscilloscope connected to the Vout1. Expected to get 20V at the output but don't see any output voltage (power supply showing 4V/3.6A)

Also tried 12V input (to match user guide) after originally trying 20V input, but has the same results.

Do you have any recommendations on what to check? Can Vin2 and Vout2 be left empty?

I don't have details on what type of load is connected, but I do know there is one connected.

over 1 year ago

0 Rakesh over 1 year ago

TI__Guru** 102711 points

Hi Tyler,

Thanks for reaching out!

Are they able to power-on without any load - Vout1 reaching 20V ? Can you share startup waveforms (VIN, VOUT and input current) and load details.

Both channels are independent. Vin2 and Vout2 can be left empty

Best Regards

Rakesh

0 Tyler Holmvik over 1 year ago in reply to Rakesh

TI__Prodigy 661 points

They cannot power on, even with no-load. Customer noted the following:

In the Power supply I set 12V/5A out, but only see the about 4 V, and I can’t see any output.

Here are three pictures of the setup:

Thanks,

Tyler

0 Rakesh over 1 year ago in reply to Tyler Holmvik

TI__Guru** 102711 points

May be Vin1 channel might have damaged.

Can they check on Vin2 channel.

How much input impedance the EVM is showing up on Vin1 terminals ?

Regards,

Rakesh

0 Tyler Holmvik over 1 year ago in reply to Rakesh

TI__Prodigy 661 points

Both Vin1 and Vin2 are measuring only a few ohms. What do you expect the impedance to be?

Customer hasn't tested Vin2 specifically yet.

0 Kunal Goel over 1 year ago in reply to Tyler Holmvik

TI__Guru 58910 points

Hi Tyler,

Default OVLO setting for EVM channel 1 is 5.7V. So device maybe in OVLO. Have they modified anything on EVM? Lets put J4 in 5-6 position and apply 12V at ch1 and see output voltage.

Regards

Kunal Goel

0 Tyler Holmvik over 1 year ago in reply to Kunal Goel

TI__Prodigy 661 points

Hi Kunal. No, the customer hasn't modified anything on the device. Maybe it was damaged due to ESD or other event.

Can you confirm what the expected impedance should be from your earlier comment?

0 Kunal Goel over 1 year ago in reply to Tyler Holmvik

TI__Guru 58910 points

Hi Tyler,

But OVLO setting they do need to select accordingly such that OVLO threshold is above VIN operating. VIN-GND Impedance should be like 100-400K ohm with no supply connected.

They can try removing these components from input side, may be they are damaged.

Regards

Kunal Goel

0 Tyler Holmvik over 1 year ago in reply to Kunal Goel

TI__Prodigy 661 points

Kunal,

Turns out the customer found a short across D2, so this may be damaged due to ESD. We've gone ahead and sent another board to the customer to test with. Thanks for your help.

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LM73100EVM: Startup Test Issue (Section 5.1 of user guide)