LVE bit Pad control Register

[satyavenkatasan]

Dear freescale,

I have few peripherals which is of 1.8V on our custom board and we are using IMX6SoloLite. there are few peripherals that which works on 1.8V, for that i'm generating the 1.8V using PMIC which I could able to do. know I'm trying make the GPIO's to 1.8V for that I have Enabled the LVE bit in pad control register. but instead of the 1.8V output we are getting 3.15V (Core voltage that we are using) tested by generating a square wave. can you help me on this to generate the 1.8V on that GPIO's.

Thanks & Regards,

Satya.

[Yuri]

   The i.MX6 SL has special recommendations, when using so called low voltage

design, in particular it relates to 1.8V SD cards. Please refer to section 7.2.4 (Power-up

sequence in low voltage system design) of the “Hardware Development Guide for i.MX

6SoloLite - User Guide”

http://cache.freescale.com/files/32bit/doc/user_guide/IMX6SLHDG.pdf 

  Also, from the next thread

"i.MX6SL : power up sequence for NVCC33_IO"

< https://community.freescale.com/message/339021 >

   In MX6SL, the I/O Gate Keeper circuit is enabled and is powered by NVCC33_IO (LVE bit is "0")

by default.

There is a "potential" issue if the following conditions are matched in customer's design.

1. A MX6SL I/O is connected to external chip with 1.8V powered I/O AND

2. No 47k ohm (or smaller resistance) pull-low resistor on that I/O AND

If both the above two conditions are matched, the I/O pin voltage may kick-up to ~2V before setting

the LVE bit to "1" in uBoot.

Thus the following guidelines should be followed -

1. Add 47k (or smaller) pull-low resistors on all 1.8V I/Os

2. Power the external chip 1.8V I/O supply using NVCC18_IO to make sure both MX6SL and external

     chip I/O supplies would be turned-on at the same time.

Have a great day,
Yuri

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