SMPS or LDO recommendation

Kaushik1 · ‎2024-09-23

I am trying to use STM32H7R7L8H6H working on design. So in our design we uses multiple interfaces like TFT LCD, Ethernet(RMII), RS485, Wi-Fi-BLE module. So For MCU power supply mode selection between LDO and SMPS. Which one mode ST will recommended to us.?

Can you please help to understand?

SofLit · ‎2024-09-24

Hello @Kaushik1 and welcome to the community,

That depends on your application and needs.

To summarize a comparison between the two options:

SMPS are more efficient than LDO, especially with the important input/output voltage difference.
LDO are low-cost and easy to implement, where SMPS requires a coil and more space on the PCB.
LDO generates less noise than SMPS. So if you have ADC, DAC, and other analog functions better to select LDO.
High PSRR LDO can be used on the output of a SMPS to reduce switching noise while achieving good efficiency.

You can refer to this wiki: https://wiki.st.com/stm32mcu/wiki/Basics_of_power_supply_design_for_MCU

Hope it helps.

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View solution in original post

SofLit · ‎2024-09-24

Hello @Kaushik1 and welcome to the community,

That depends on your application and needs.

To summarize a comparison between the two options:

SMPS are more efficient than LDO, especially with the important input/output voltage difference.
LDO are low-cost and easy to implement, where SMPS requires a coil and more space on the PCB.
LDO generates less noise than SMPS. So if you have ADC, DAC, and other analog functions better to select LDO.
High PSRR LDO can be used on the output of a SMPS to reduce switching noise while achieving good efficiency.

You can refer to this wiki: https://wiki.st.com/stm32mcu/wiki/Basics_of_power_supply_design_for_MCU

Hope it helps.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

Kaushik1 · ‎2024-09-24

Thanks for your suggestion.

But main difference is efficiency between LDO and SMPS, LDO has less efficiency.

I want to add few things on my question.

I am using 3x UART port, 1x SPI1 port, 1x SPI2 port, 24bit RGB TFT LCD display, and RMII interface. I am using RTC crystal and 24MHz crystal same as ST EVK.

So these are the main application for my project. I am designed the first time so it is difficult to selection between LDO and SMPS.

SofLit · ‎2024-09-24

LDO main weakness is the power efficiency / the energy dissipation.

SMPS main weaknesses are noise and BOM.

So if you have a constraints on the current consumption, SMPS is better in this case. Need to check the datasheet about the current consumption of LDO and SMPS.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

TDK · ‎2024-09-24

Both can work.

Unless power efficiency matters, which I doubt based on the number of peripherals you're using, people typically use LDO which is much simpler.

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Richard Li · ‎2024-10-08

Compare SMPS and LDO, a lot of use cases LDO power efficiency is better than SMPS.

At least these cases:

1. If power source and target voltage no big difference.

2. System continual change load even long time stand by.

3. Load change wide range, light load keep long time.

If you design for 1-2 cells battery system, you better use LDO.