TPS92611-Q1: Disconnect the GND of chip, LED will light on

Xiong JIANG

Prodigy 180 points

Part Number: TPS92611-Q1

Tool/software:

Hi export,

In our design, LED driver is on 1 board, LED is on another board.

When disconnect the GND of driver, connect 12V battery, connect LED board GND. Like below figure

The LED will be light up, current is about 15mA.

What is the reason? How can we solve it?

Thanks a lot!

over 1 year ago

0 Hailee Xu over 1 year ago

TI__Genius 10140 points

Hi Xiong,

Do you mean the GND of the Driver Board is not connected, but the GND of the LED board is connected to GND of the Driver Board via the connector, then you can see a 15mA current, is my understanding correct? Why do you create this situation? and what is your expectation for this case?
Please provide the waveforms of Vsupply, Vout, and Iout.. and please provide the full schematic, including the LED board.

Many thanks!

BR,

Hailee.

0 Xiong JIANG over 1 year ago in reply to Hailee Xu

Prodigy 180 points

Hi Hailee,

It's a abnormal condition test. Like figure below, driver board not connect GND.

0 Xiong JIANG over 1 year ago in reply to Xiong JIANG

Prodigy 180 points

In this setup why there is a small current through LED board?

0 Hailee Xu over 1 year ago in reply to Xiong JIANG

TI__Genius 10140 points

Hi Xiong,

I can't reproduce your phenomenon on our EVM board, please tell me your test steps, and also provide the material that I mentioned.

And could you provide a clear photo of the IC's marking? Many thanks!

BR,

Hailee.

0 Xiong JIANG over 1 year ago in reply to Hailee Xu

Prodigy 180 points

Hi Hailee,

Please see the material in attached file, thanks.

LED test.pptx

0 Xiong JIANG over 1 year ago in reply to Xiong JIANG

Prodigy 180 points

Hi Hailee,

Would you please help to have a review of the materials? Thanks a lot.

+1 Hailee Xu over 1 year ago in reply to Xiong JIANG

TI__Genius 10140 points

Hi Xiong,

Thanks for your material, it is clear for me to see this issue, now I can reproduce this phenomenon when I use two EVM boards. this is a corner case; we don't recommend you disconnect the GND of the driver board and leave it floating. please keep a stable GND connection.

The LED can be turned on, it is supposed to be a current path from the Battery side -- > SUPPLY --> OUT --> LED --> GND. If the GND is floating on the Driver board, since the internal connection of the IC, the GND would be pulled to an unknown state.

BR,

Hailee.

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TPS92611-Q1: Disconnect the GND of chip, LED will light on