1 . Use 5V is not recommend by richtek in recent batch of regulator ... Using 4V is one thing that can be consider ...Originally Posted by EMC2
Yes, a problem with higher Vmem if you used the 3.3V rail... you could use either the Vmem regulator's first stage output (you said it was limitted to ~4.2V) or the 5V rail.
Spec allows for up to 6V on Vctrl:
If you go back and look at the scope shots in post #47, the "regular" drops are 60mV from the nominal center condition, which is 2x the spec'd 30mV as shown in the transient response ratings for the RT9173A.
But the bigger Q is why the 200mV+ drops like shown in post #62 under some operating conditions? Looks like either current limitting is kicking in or the RT9173A is going unstable...
2 . The nominal center of actual board is different from dummy load testing like the richtek datasheet ... The patter in memtest8# already cover the full current sinking/sourcing mode of this regulator , I will only check the peak-to-peak range of the result of actual board ...
3 . 94mv in my original measurement is not very good , but acceptable when you consider that the VTT is 1.45V but not 1.25V in the richtek datasheet ... And this is the TCCD/300MHz/1T case , if the DRAM is BH5/CH5 type or the DRAM frequency is much lower , the value will be smaller ...
4 . I don't know what happened to your board , but I have tried 4 different board(different batch/model) ... All of them act very close to the pic I post ...
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