
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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
Solved! Go to Solution.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Dear Naoum,
Thank you for your reply.
I think that case1 does not have any problem from your answer.
Does case2 not have any problem?
Best regards,
Keisuke Watanabe

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Dear Keisuke,
Case 2 cannot happen - 1.2V is generated from 3.3V (see attachment).
Sincerely yours, Naoum Gitnik.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Dear Keisuke,
Yes, it is right.
Best regards, Naoum.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Dear Naoum,
I mistake, case1 and case2 was the reverse.
Does case1 not have any problem?
Best regards,
Keisuke Watanabe

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
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.
