
Limitation is not listed in a datasheet, is the constitution of power supply such as follows possible?
Case1 VDD=1.2V OFF VDD33=3.3V OFF SDRAMC_VDD1P5=1.5V ON
Case 2 VDD=1.2V ON VDD33=3.3V ON SDRAMC_VDD1P5=1.5V OFF
已解决! 转到解答。

Dear Keisuke,
Regarding "Case 2: VDD=1.2V ON, VDD33=3.3V ON, SDRAMC_VDD1P5=1.5V OFF".
Yes, the case when SDRAMC_VDD1P5 is not applied (but VDD and VDD33 are) is possible.
I replied "impossible" and sent the scope screenshots because I thought you also meant the sequence:
- first VDD=1.2V is applied,
- second VDD33=3.3V is applied,
- third SDRAMC_VDD1P5=1.5V is applied.
That is why I replied "1.2V is generated from 3.3V".
If you only meant their presence, without sequence, then this case is indeed possible.
Best regards, Naoum.

Dear Keisuke,
- VDD33=3.3V is applied to Vybrid first in the power-up sequence.
- VDD=1.2V is generated by Vybrid itself, without any user's intervention.
- SDRAMC_VDD1P5=1.5V - is applied to Vybrid with arbitrary timing with respect to the above rails.
- Regarding the mutual timing of the 3.3V rail and the transistor collector voltage (if different than VDD33) – to not overload the BCTRL output pin, the transistor collector voltage should appear no later than 3.3V.
Sincerely yours, Naoum Gitnik.

Dear Keisuke,
Case 2 cannot happen - 1.2V is generated from 3.3V (see attachment).
Sincerely yours, Naoum Gitnik.

Dear Naoum,
In figure 4.Power supply, "SDRAMC_VDD1P5" seems to be provided from external power supply.
Therefore I think the case2 can happen.
Please correct me if I am missing some point.
Best regards,
Keisuke Watanabe

Dear Keisuke,
Regarding "Case 2: VDD=1.2V ON, VDD33=3.3V ON, SDRAMC_VDD1P5=1.5V OFF".
Yes, the case when SDRAMC_VDD1P5 is not applied (but VDD and VDD33 are) is possible.
I replied "impossible" and sent the scope screenshots because I thought you also meant the sequence:
- first VDD=1.2V is applied,
- second VDD33=3.3V is applied,
- third SDRAMC_VDD1P5=1.5V is applied.
That is why I replied "1.2V is generated from 3.3V".
If you only meant their presence, without sequence, then this case is indeed possible.
Best regards, Naoum.

Dear Naoum,
Thank you for your reply.
Even a state of regular case1 (or case2) does not have any problem.
Is it right by the interpretation mentioned above ?
Best regards,
Keisuke Watanabe

Dear Keisuke,
Regarding "Case1: VDD=1.2V OFF, VDD33=3.3V OFF, SDRAMC_VDD1P5=1.5V ON".
No problem with Case1 because the SDRAMC_VDD1P5 power rail order is NA (Not Applicable = Do not care = Arbitrary) in the sequence table.
Best regards, Naoum.
