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For the design of the PCB nets I need to know the current consumption of a TFT screen and an SD module. The display microcontroller is the ST7735. In its datasheet I have found the following table:

enter image description here

The current to be aware of is the IDD in the "Maximum" column I imagine. But what is the difference between them? It seems that both "IDDI" and "VDDI" refer to an interface but I don't know what it means exactly.

About the SD module I can't find the data sheet. Does anyone know how much it can consume more or less?

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  • \$\begingroup\$ Doubt the SD module really has much stuff on it. Probably the SD module is just an adapter for the SD card which is where all the interesting stuff is! Some (more expensive) SD cards come with datasheets... \$\endgroup\$
    – user253751
    Aug 5 at 15:08

2 Answers 2

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enter image description here

VDDI is used for the logic (e.g., GPIO), whereas VDD is the main source of power to the IC.

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According to the Wikipedia page on SD cards, they can consume up to 2.9W which would be almost 900mA from 3.3V. The maximum current will be during write operations.

The controller chip on the LCD module is likely insignificant in current draw in comparison to other things on the module. You should find specs on the entire module. Most likely everything sans backlight will be 10mA or less, so not important for reasonable trace widths. The backlight is probably in the 100mA or more range for a 3”-ish LCD display, so worth finding the specs.

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  • \$\begingroup\$ But, if I supply the components with the VCC pin of the microcontroller, they couldn't consume more than the pin can give, right? \$\endgroup\$
    – Libegria
    Aug 10 at 16:19
  • \$\begingroup\$ The Vcc pin on the microcontroller does not supply the SD card. They both drain current individually from the power supply. \$\endgroup\$ Aug 10 at 16:33

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