We are using PMIC of STPMIC1A, here Buck2 input is 5V and ouput is 1.1v (default value) as mentioned in datasheet. In LDO3 input is VDD_DDR i.e,1.1v and output is VTT_DDR i.e,1.8v(Default value). How is it possible when using LDO?

PS.5 · ‎2019-08-01

Olivier GALLIEN · ‎2019-08-28

Hi @PS.5

Indeed LDO3 can not generate 1.8V with an 1.1V input.

But please note that both BUCK2 and LDO3 are not started by default (Rank 0). This is because STPMIC1 let the application manage those specific regulators to fit the used DDR.

Then, to match the typical application schematics with DDR3 fly by topology, the boot process will start BUCK2 with 1.35V and set LDO3 in BUCK2/2 mode in order to provide VTT at 0.675V.

Can you confirm you are using STPMIC1 with an STM32MP1 ?

Thanks and BR

Olivier

Olivier GALLIEN
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PS.5 · ‎2019-08-28

Hello,

Thanks for your reply.

1. We are using STPMIC1APQR PMIC with Processor of STM32MP157AAD3. We are referring page no 5 of 157 processor development board (refer the attached file mp_schematic.pdf). Our package is TFBGA257 and referred package is LFBGA354 we are connecting appropriately.

2. Also we have another question regarding PMIC, We are referring the page no 2 of PMIC, in that Output voltage from LDO3 is 1.8v by default. but we require any voltage between 3.4v to 4.3V. Can we program to get this voltage? Attached the datasheet of PMIC as well.

Thanks and Regards

Priya S

Hi @priya.s1.5647228846566692E12

Indeed LDO3 can not generate 1.8V with an 1.1V input.

But please note that both BUCK2 and LDO3 are not started by default. This is because STPMIC1 let the application manage those specific regulators to fit the used DDR.

Then, to match the typical application schematics with DDR3 fly by topology, the boot process will start BUCK2 with 1.35V and set LDO3 in BUCK2/2 mode in order to provide VTT at 0.675V.

Can you confirm you are using STPMIC1 with an STM32MP1 ?

Thanks and BR

Olivier

Hi

Indeed LDO3 can not generate 1.8V with an 1.1V input.

But please note that both BUCK2 and LDO3 are not started by default. This is because STPMIC1 let the application manage those specific regulators to fit the used DDR.

Then, to match the typical application schematics with DDR3 fly by topology, the boot process will start BUCK2 with 1.35V and set LDO3 in BUCK2/2 mode in order to provide VTT at 0.675V.

Can you confirm you are using STPMIC1 with an STM32MP1 ?

Thanks and BR

Olivier

We are using PMIC of STPMIC1A, here Buck2 input is 5V and ouput is 1.1v (default value) as mentioned in datasheet. In LDO3 input is VDD_DDR i.e,1.1v and output is VTT_DDR i.e,1.8v(Default value). How is it possible when using LDO?

Hi

Indeed LDO3 can not generate 1.8V with an 1.1V input.

But please note that both BUCK2 and LDO3 are not started by default. This is because STPMIC1 let the application manage those specific regulators to fit the used DDR.

Then, to match the typical application schematics with DDR3 fly by topology, the boot process will start BUCK2 with 1.35V and set LDO3 in BUCK2/2 mode in order to provide VTT at 0.675V.

Can you confirm you are using STPMIC1 with an STM32MP1 ?

Thanks and BR

Olivier