Procedure for configuring VDD=1.8V

[Aedan Cullen]

What is the recommended procedure for configuring the OSD32MP1 for a system using 1.8V IO? I know that Buck3 should be set to 1.8V for the VDD supply, but I am not sure about BYPASS_REG1V8. Should it still be tied to ground? Is there any other configuration that must be done to operate with 1.8V VDD? (Documentation from ST says that the internal 1.8V LDO must be bypassed, but I’m not sure whether this must be done using the bypass pin or if a certain register setting (PWR_CR3?) can achieve the same effect even if BYPASS_REG1V8 is low.

tl;dr Will just changing the Buck3 setting be sufficient to enable 1.8V operation or are there any other changes to be made?

[Neeraj Dantu]

Aeden,

Based on the documentation, in addition to the VDD setting, REG1V8 configuration should be changed.

BYPASS_REG1V8(M10) needs to be connected to VDD.

VDDA1V8_REG (R7) needs to be connected to VDD instead of being a test point.

Note that we have not tested this configuration. But, according to the documentation, this is all the changes you need to make for 1.8V operation. We will report back once we verify.

Best,

Neeraj

[Aedan Cullen]

Thank you, that makes sense. The only thing I am not sure about is the initial configuration of Buck3. If the SiP is on a board with VDD tied to VDDA1V8_REG, at first wouldn’t 3.3V be applied to VDDA1V8_REG as that is the default setting of Buck3?

[Neeraj Dantu]

Aedan,

BUCK3 can be set at TF-A or the PMIC can be reprogrammed to set BUCK3 to 1.8V at power up(see https://octavosystems.com/app_notes/stpmic1-non-volatile-memory-programming-guide/).

The connection for VDDA1V8_RED is per recommendation of STM32MP1 datasheet(see section 3.8.1 of datasheet: https://www.st.com/resource/en/datasheet/stm32mp157c.pdf) as well as section 10.1.5 of Hardware Getting Started Guide for STM32MP1 (https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf).

Best,

Neeraj

[mlarkin]

Hello,

Can someone from Octavo provide any insight on whether or not this was ever tested -> 1.8V I/O?

“Note that we have not tested this configuration. But, according to the documentation, this is all the changes you need to make for 1.8V operation. We will report back once we verify.”

Essentially, does the latest comment on this thread imply it was verified and works accordingly?

Thank you!

[Erik Welsh]

Yes, 1.8V I/O operation of the OSD32MP1 was verified and added to the datasheet (https://octavosystems.com/docs/osd32mp15x-datasheet/).  See sections:  6.1.1 on I/O voltages and 7.6.3 on the discussion about the VDD power rail.

You will need to modify the device tree to set the I/O voltage and PMIC outputs appropriately.  Additionally, see Section 10 of:

https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf

for examples of 1.8V operation of different interfaces.  Please let us know if you have any additional questions.

[mlarkin]

Thanks Erik,

To confirm, this cannot be tested with a BRK or RED board? The below items do not appear accessible for modification.

BYPASS_REG1V8(M10) needs to be connected to VDD.
VDDA1V8_REG (R7) needs to be connected to VDD instead of being a test point.

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