CDC3S04 Powered by its own LDO?

Steve Lyon

Other Parts Discussed in Thread: CDC3S04

Hi,

I am using the CDC3S04YFFR quad clock fanout buffer and I am wondering if it is an ok plan to power the digital and analog supply pins by the internal LDO.

It seems like the internal LDO is controlled by logic supplied by the digital supply so it might not not work to connect VLDO to VDD_ANA and VDD_DIG.

If this is the case and the internal LDO is not otherwise needed, then is it necessary to supply VBAT and bypass VLDO?

Thanks,

Steve

over 12 years ago

0 Michael Wagner (Intern) over 12 years ago

Intellectual 390 points

Hi,

i hope i understand your plan to supply the whole device without external LDO, by using the 1.8V from VLDO of the CDC3S04.
but the internal LDO is only for a low-noise TCXO supply.
The LDO output is enabled when VDD_DIG and VBAT are supplied and RESET(or REQ-Signal) is active.
In every case you`ll need a supply for VDD_DIG & VDD_ANA.

Best Regards
Michael

0 Steve Lyon over 12 years ago in reply to Michael Wagner (Intern)

Prodigy 50 points

I see. In my case I gave the TCXO its own even better LDO so wanted to use the CDC3S LDO for something.

Since I will not be using the internal LDO for anything do you think it is still necessary to connect Vbat and bypass VLDO?

Thanks for the reply,

Steve

0 Michael Wagner (Intern) over 12 years ago in reply to Steve Lyon

Intellectual 390 points

Hi,

it`s no problem to use the CDC3S04 internal LDO for something different, but keep in mind that it is controlled by the device and provides only a small amount of current.
If you don`t want to use the internal LDO you also don`t need to supply the VBAT pin, the device will aslo work without VBAT.
(http://www.ti.com/lit/ds/symlink/cdc3s04.pdf) <-link to datasheet..

best regards
Michael

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CDC3S04 Powered by its own LDO?