How to calculate the current of a MCU and CAN BUS circuit?

Question

I have a circuit which uses a STM32F205RGY MCU, and two SN65HVD230 CAN Bus transceivers, one 20mA LED with a 100Ω resistor and a USB port.

The MCU will run a 24MHz crystal.

Each CAN Bus Transceiver will run at 1Mbps

The USB is standard speed.

The circuit is 3v3 and the working input voltage is 8-30v.

I'm struggling to work out what current my regulator needs to supply. Due to size constraints I will probably use a LDO regulator.

I have a similar circuit built but with 4 LEDs, and a STM32F105 and that uses 0.04A-0.1A with no data on the CAN Bus as I have no CAN analyser at my current location, this seems awfully low though.

What current can I expect my circuit to use? Will a 300mA LDO be ok?

Answer 1

Power budget:

1. SN65HVD23 datasheet table 8.3 - maximum current value 48mA (times two)

2. STM32F205RGY datasheet table 12 - maximum total current 120mA. This value probably assumes that totally everything is running at the same time. Your real consumption will be lower than that.

3. LED - 20mA

Total 236mA. 300mA LDO should be fine.