Help reading a schematic

Hello would it be possible to get a little help reading this schematic?

I’m trying to work out the overhead I have when drawing amps on the AOZ1282CI DCDC converter.

I see it’s taking the 24V/12V and supplying the board with 5V, but having trouble working out what onboard parts are using the 5V and the taking up some of the 1.2A continuous output current, as I plan to power some neopixles from the 5v header, but don’t want to exceed the output current of the AOZ1282CI

BTT SKR mini E3 V1.2sch (1).pdf (100 KB)

Well the main current consumption will be the processor, stm32f103rct6, which is rated for 70mA max
at 72MHz clock.

The TMC2209's will take their main power from VBB being motor drivers, but each is 4.5mA from its 5V supply.

Its usually simplest to measure the current, that go through all the datasheets and tot up the current consumptions.

Thank you MarkT.

So I'm looking at max 4.5mA from the STM32, and with 4 stepper motors 22.5mA. How about the LCD screen assume that's running off the 5V too? So should probably measure the power draw from that too and add to the 27mA?

Anything else I'm missing?

Hello n00b,
I would advice you to look at datasheet of chip , for example here https://www.tme.eu/Document/61ae6352e3794ec021f5272be7addd54/AOZ1282CI-DTE.pdf . Everything is important, but I would definitely understand well input voltage vs current limit diagram, and carefully read detailed description about usage. I suppose you do not try to build your own power supply for this project, but you buy one pcb ready for use . It is important to do not miss the power dissipation of module of power supply, and think about heat exchanger of chip, if you push it to the limit....
Ohhh, I saw detailed schematics attached - you have your supply built in . Well if I were in your shoes I would use another power supply for display with 5 Volts, or 3.3 Volts . This load would always draw current from 5Volts regulator, and maximum current might be not enough. I would use LM2596 regulator for other loads , drawing current from 5 Volts line... Of course and good output capacitor....

n00b:
Thank you MarkT.

So I’m looking at max 4.5mA from the STM32, and with 4 stepper motors 22.5mA. How about the LCD screen assume that’s running off the 5V too? So should probably measure the power draw from that too and add to the 27mA?

Anything else I’m missing?

No, the processor is 70mA max at full speed. 4.5mA per stepper driver from the logic rail.

MarkT:
No, the processor is 70mA max at full speed. 4.5mA per stepper driver from the logic rail.

Got it, sorry should've had my glasses on! :slight_smile: