Part Number: LMZ31707
We have a problem with a 12V to 1.8V design using the LMZ31707.
Below I will share a detailed description of what we see, signal measurements, etc.
Any assistance will be highly appreciated.
See below our design:
We are unable to get the required output. Instead we get ~1.2V.
And zooming in:
1. AGND and PGND are connected together on the pcb (opposed to TI layout instructions which ask to separate it).).
2. INH gets an open drain output of a voltage monitoring device. The first pulse you see on this pin is a side effect of the same issue we see on a device which precedes this one (power sequencing wise).
3. The average load on the 1.8V is ~200mA (the board is still not fully active).
We think the issue is with the saw-tooth signal we see on the SS (slow-start) pin. We don't know the origin of it.
Any thoughts/ideas will be highly appreciated.
Thank you all,
In reply to Michael Daimer:
We discovered that PH is shorted to VOUT and that caused this behavior.
Removing the short fixed it.
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