MPC5xxx中的主题 VSTBY

VSTBY

pwok2004 — Wed, 15 May 2019 03:42:06 GMT

I am designing the hardware circuit of spc5644A.
SRAM standby functionality is required, but I do not know how to handle VSTBY pins.
I don't know if I need an external power supply or not.

now, only an external RC circuit is connected to the processing, and there is no power supply.
I don't know if it's right.

Re: VSTBY

davidtosenovjan — Wed, 15 May 2019 08:55:29 GMT

Hi, SRAM can be backed up directly by 1V power rail or “indirectly” from 2-5.5V when standby regulator derives 1V from that automatically. It removes the need of separate 1V rail. 1-2V and 0.2V-0.95V voltage are forbidden areas.

When

VSTBY = 0-0.2V then standby function is disabled completely

VSTBY = 0.95-1.2V then standby regulator is disabled and standby RAM is fed directly

VSTBY = 2-5.5V then standby regulator is enabled and standby RAM is fed by 1V output of this regulator (internally).

I guess the screenshot is wrong.

Re: VSTBY

pwok2004 — Fri, 17 May 2019 00:44:16 GMT

Hi,Thanks for your reply.

Does whether it mean that in my circuit, I need to connect the external power supply of 2-2.5v to the VSTBY pin?

As shown in the figure below:

thanks very much.

Re: VSTBY

davidtosenovjan — Fri, 17 May 2019 05:11:10 GMT

Not 2-2.5V but 2-5.5V, typically 5V.

See AN4291, section 3.3:

https://www.nxp.com/docs/en/application-note/AN4291.pdf

Re: VSTBY

pwok2004 — Mon, 20 May 2019 09:20:37 GMT

ok,thanks very much.