Tool/software:
Dear Team,
We are using the TPSM82902SISR in our design. The input to the module is 12 V, and the output is regulated to 5 V. This 5 V rail is also routed to an HDMI port.
We are facing an issue with backdrive when the board is powered off but the HDMI cable is still connected. Specifically:
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When the board is off and HDMI is connected, the 5 V rail is pulled up to ~3.2 V.
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At the same time, the 12 V input rail also rises (to ~2.8–3.2 V), even though the main 12 V supply is off.
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To debug this, we isolated the 12 V input using a ferrite bead. After doing this:
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The 12 V side (upstream of the bead) is no longer backdriven.
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However, the TPSM82902 input pin side (downstream of the bead, toward the IC) still rises to ~3.2 V.
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From this observation, it seems that the backdrive current from the HDMI 5 V rail is enabling the voltage at 12V.
Could you please clarify:
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Does the TPSM82902SISR have an internal path that allows backfeeding from VOUT to VIN when the device is unpowered?
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If so, what is the expected backfeed current/voltage behavior?
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What is the recommended method to prevent this reverse conduction in our application.
