LDOLDOs if output voltage is greater than output

[joanvicient]

Hi,

I'm working on a custom board with an iMX6 Solo processor.

VDDARM_IN, and VDDSOC_IN are powered at 1.2V by a DCDC with less than 5% Vpp ripple.

My doubt is about the difference between bypassing LDOs or setting them with an output voltage greater than output.

As Igor said:

> but since in your case output voltage is set greater than input,

> LDO transistor is fully "closed"

in LDO turning from 0x1F to 0x1E cause i.MX6DL hang 

I understand that the "power" part of LDOs work in exactly same way and the only difference is that when bypassing the control/analog part of LDO is disabled. Am I wrong?

Which LDOs configuration do you recommend us in case we want to use Arm at 972MHz and GPU as well?

Thanks in advance!

[igorpadykov]

Hi joan

ldo bypass allows less processor heating, so it may be recommended

when using gpu/vpu. Linux ldo bypass configuration can be found in function
regulator_allow_bypass() in linux/drivers/regulator/core.c :
Bypass mode means that the regulator is simply passing the input directly to the output with no regulation.
also please check sect.50.7.4 Digital Regulator Core Register (PMU_REG_CORE),

i.MX6DQ RMREG_TARG description
http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------