Author Topic: S25FL256 serial Flash Voltage rail sequence  (Read 380 times)

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Offline rakeshm55

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S25FL256 serial Flash Voltage rail sequence
« on: October 27, 2019, 05:57:41 am »
Hi ,
I happen to raise a query regarding voltage rail of serial FLASH S25FL256 via this thread in cypress forum

https://community.cypress.com/thread/45499
thread response specified using system 1.8V for pullups input pins.

Data sheet: https://www.cypress.com/file/448601/download

For S25FL256 VIO volatge can be 1.8V or 3.3V and I want to operate VIO in 1.8V. It also has a sequencing requirement VIO should follow VCC. Since my system voltage rail does not follow this sequence I have used a separate LDO to generate the voltage needed.

The Input pin voltages have an absolute max specification of
""Input voltage with respect to Ground (VSS)::    ( –0.5V to +(VIO + 0.5V)).....

My query was which voltage rail I need to pull up input pins to....If the response is correct then how this absolute max rating is surmounted...please help
 

Offline rakeshm55

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Re: S25FL256 serial Flash Voltage rail sequence
« Reply #1 on: October 27, 2019, 06:11:34 am »
Attached is the schematics page
 

Offline SiliconWizard

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Re: S25FL256 serial Flash Voltage rail sequence
« Reply #2 on: October 27, 2019, 03:08:20 pm »
The Input pin voltages have an absolute max specification of
""Input voltage with respect to Ground (VSS)::    ( –0.5V to +(VIO + 0.5V)).....

My query was which voltage rail I need to pull up input pins to....

To VIO, what else?

If the response is correct then how this absolute max rating is surmounted...please help

I may have missed something, but how would pulling up to VIO violate the specs?
 

Offline rakeshm55

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Re: S25FL256 serial Flash Voltage rail sequence
« Reply #3 on: October 28, 2019, 03:06:17 pm »
Hi,
""signals HOLD, WP and CS to power rail B_1V8_D. ""
 Is the response I received ...
B_1V8_D is system supply voltage and not VIO....
VIO is sequenced after VCC where as B_1V8_D is sequenced before VCC.... So for a short period I guess input pins will be raised above VIO... This is my concern
 

Offline SiliconWizard

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Re: S25FL256 serial Flash Voltage rail sequence
« Reply #4 on: October 28, 2019, 03:24:58 pm »
They may have gotten confused by your multiple 1.8V rails.

As I said, I would personally pull up to VIO, which after looking at your schematic would be B_1V8_SF.
 

Offline voltsandjolts

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Re: S25FL256 serial Flash Voltage rail sequence
« Reply #5 on: October 28, 2019, 03:35:12 pm »
The FLASH IC has internal pullups on Write Protect and Hold signals, presumably to VIO.
Leave your pullups unpopulated and relax, it'll be fine.
 


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