Tool/software:
IC "No output "the input DC is powered on.
The pad is 24V to 12V.
When the input is powered on at 24V, the output voltage cannot rise to 12V normally, and the current does not reach the Current Limit. Why does the IC enter the hiccup state?
Please tell the reason is and how to solve it.
Hi TI AE Team,
We would like to request your support in evaluating an issue we are observing on several TPS5450-based DC-DC boards.
In some production boards (failure rate approx. 4%, 8/163 units), we observed that the 12V output fails to start when VIN is hot-plugged (24V input).
The device appears to enter Hiccup Mode immediately upon startup, and there is no output voltage.
However, when we reflow the U1 (TPS5450) — either the pins or the PowerPAD (Pin 9) — the issue disappears and the unit functions normally.
Our Investigation:After analysis, we suspect that the PowerPAD (Pin 9) may not have been properly soldered to the PCB.
Our stencil design uses 9 small dot-shaped apertures (like a star pattern) under the PowerPAD, which may result in less than 50% solder coverage.
According to IPC-7093, void area under the thermal pad should be <50% for thermal/electrical reliability.
We believe that insufficient solder coverage increases thermal impedance, which causes a rapid rise in junction temperature during the first power-up (when inrush current is high), possibly triggering thermal shutdown or protection mode.
Initial TI Feedback:We contacted our local TI support, and they responded as follows:
“Improper soldering can lead to poor thermal impedance between the device and the PCB, causing the device to overheat and trigger thermal shutdown. Since the problem seems to resolve after re-soldering, this is very likely the root cause.”
They then kindly referred us to the E2E Forum for a more formal evaluation and technical explanation by the AE team.
Our Request:Could you help confirm if insufficient PowerPAD soldering is a known cause of startup Hiccup Mode in TPS5450 under such conditions?
Are there any TI application notes, thermal protection mechanisms, or internal design guidelines you could share to help us explain this behavior to our customer?
We would appreciate any technical validation to support our understanding and guide both our layout and stencil design improvements.
Let us know if you need our schematic, PCB layout snippet, reflow profile, or X-ray images — we are happy to share.
Thank you very much for your support!
Best regardssummary-CPR251120389.pdf,
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