Question about TPS51487

[Francisco.s]

Hi, have a question about the pwm TPS51487 output voltage.

Have a UX425IA motherboard that have no image.
All voltages are present, and power consumption is 600 mA from power supply.
A good bios have been programmed but nothing change.
DDR4 voltage is only 1.1 volts, and I think It should be 1.2volts
It has 4 lpddr4 memory chips type OVE77 D9WLQ, and datasheet says this chip needs 1.2v.

Probably the chip and sorrounding components all are good and 1.1v is ok in this board, but need someone that confirm that.

I know that TPS51486 is almost identical, but not found datasheet for comparing them.

Thanks for your comments.

[Sephir0th]

Re: Question about TPS51487

There is no point to dig in the dark right now.

Simply measure resistance to GND of the
1.2V rail to rule out a (partial) shorted power rail.

[SMDFlea]

Re: Question about TPS51487

Heres some schematics with these IC`s.Some of the pin descriptions are not the same,if you look carefully

Quanta DAG7HAMB8E0 https://www.badcaps.net/forum/showpo...80&postcount=2 TPS51486RJER - PU8700

HuaQin NB8511 https://www.badcaps.net/forum/showthread.php?t=105702 TPS51487XRJER - PU701

[Francisco.s]

Re: Question about TPS51487

Thanks SMDFlea, this information solves the question.

From the schematic "Floris Yebisu NB8511 NB8512PU701 MB V4 FINAL" I can see that PU701 (TPS51487XRJER) outputs the +V1P1U_VDDQ for LPDDR4 chips.

So, in this board probably the cpu is damaged and is not able to fulfil the POST.

Another board for the trash can.

Forgot to say that kbc have been programmed wit new data extracted from last bios update.

[Sephir0th]

Re: Question about TPS51487

I still haven't noticed any resistance measurement. It is a bid odd to dismiss a repair attempt without even doing a few simple checks. But it's your repair attempt, so feel free to get eid of it.