TS3DV421DGVR supply (VSS) issue

Sunil Patel1

Other Parts Discussed in Thread: TS3DV421

We are facing a problem in one of our project with HDMI switch from TI. The switch part No is #TS3DV421DGVR.
We have used 3.3V as VCC and 1.5V as VSS as we are doing HDMI switching with the switch.

We have adjusted VSS for the device at 1.5V (VCC_1V5). When we connect this supply to HDMI switch we get higher voltage then applied at the switch input.
I.E. when we connect the VCC_1V5 supply to HDMI switch TS3DV421DGVR it becomes 2.12V. When we removed the HDMI switch from our board we are getting proper voltage i.e. 1.5V.

We are not giving 1.5V supply in our board to any other device except TS3DV421DGVR. Can you please help us to resolve the issue.

over 12 years ago

0 Andrew_Mason over 12 years ago

TI__Expert 6395 points

Hello Sunil,

Can you provide a schematic showing all connections to the TS3DV421 pins?

Regards,

Andrew

0 Sunil Patel1 over 12 years ago in reply to Andrew_Mason

Prodigy 90 points

Hi Andrew,

Please find below schematic for TS3DV421.

0 Andrew_Mason over 12 years ago in reply to Sunil Patel1

TI__Expert 6395 points

Hello Sunil,

I cannot view the schematic in any of the browsers I have tried. Can you attach it to your post as a PDF?

Regards,

Andrew

0 Sunil Patel1 over 12 years ago in reply to Andrew_Mason

Prodigy 90 points

Hi Andrew

I have attached the schematic.

4628.Schematic_HDMISwitch.pdf

0 Andrew_Mason over 12 years ago in reply to Sunil Patel1

TI__Expert 6395 points

Hello Sunil,

I believe that the triple LDO ADP323 is having issues sinking current instead of supplying it. From my research it appears the output voltage is set by this formula:

VOUT2 = 0.5 V(1 + R3/R4) + (FBIN)(R3)

For a Vout of 2.12 with the same resistor combination the FBIN pin would have to be drawing 250 uA which is near the Icc value of the TS3DV421. However I don't know that this formula assumes the LDO is supplying current not sinking and don't know if it will remain valid in our use case.

Could you provide the following measurements to confirm this suspicion? Also are the measurements taking with an oscilloscope or a multimeter?

Voltage at FB pin without DV421
Voltage at FB pin with DV421

Regards,

Andrew

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TS3DV421DGVR supply (VSS) issue