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<Astralix1>
Hi guys!
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<Astralix1>
Can someone try to get me a datasheet of a DC/DC chip in SOT32-5 housing. It is marked S1525 and many of these are used in my RK3066 tablet.
<Astralix1>
I'd like to figure out the correct PWM values for the RK3066 PWM DC/DC controller drivers. But the original code was ripped, functions where cleared and no schematics available...
<karlp>
sure it's dc/dc?
<karlp>
and you mean sot23/5 right?
<Astralix1>
yes
<karlp>
it's a super super common footpritn for LDOs, that's all.
<Astralix1>
It is connected to inductor, diode and caps
<karlp>
sounds like dcdc then sure :)
<Astralix1>
and its output is controlled by an input, so SOC can control voltage. Standby 1.12V, medium usage 1.25V
<karlp>
what's the input voltage range?
<Astralix1>
About 4.xV constant
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<Astralix1>
one pin is changing 600..650mV when the output is changing from 1.12V to 1.25V
<karlp>
that's probably the reference pin for the feedback
<Astralix1>
Could be a chinese trick to fake a PWM-input DC/DC controller with a tiny little cheap standard DC/DC.
<Astralix1>
Just put an offset to the ref-input
<Astralix1>
Unfortunately I still could not identify the PWM signal.
<karlp>
some of the people in ##stm32 might know, it's not the sort of part I normally have much need to use
<karlp>
does it just cahnge from 2 levels?
<karlp>
it might just be a bypassable regulator
<karlp>
so it's just switching from regulated 1.12 to a passtrhough 1.25 from upstream?
<Astralix1>
It is a bit complicated to drive the tablet into several different loads on the touch, while holding a scope probe into a mss of SMD parts where 5V and 1.1V are close together
<karlp>
:)
<Astralix1>
I need a third hand and another pair of eyes that look throught the table what is going on on the screen :)
<Astralix1>
Ok, before I do standby for the night, one test
<Astralix1>
I start some game or so to produec some load
<Astralix1>
Ok, tested with some game running and the two DC/DCs that change their voltages are just spinning between 1.12 and 1.25V.
<Astralix1>
But I had my kernel running and it creates much more voltages on these two DC/DCs, but it is always a bit too high. Not that it is dagerous, but too high.
<Astralix1>
In the assembler code the original kernel uses more steps too, but who knows what governor is active there and how it was limited in this RK code.
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