Author Topic: Does it make any sense to put power switching/small motor PWM on a second PCB?  (Read 648 times)

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Offline newtoTopic starter

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With how cheap 100x100mm 2 and 4 layer boards are from JLC, would it make sense to separate all the voltage switching/motor pwm/battery charging/BMS on a second PCB?

My project is already going to have two PCBs, one with some sensitive analog components and the MCU, and the other PCB with a 2s2p battery charging and management circuit, and I'm trying to figure out if it would help or hurt noise to put some of the switching based components onto the battery PCB instead of the main board.

Specifically:

6V pump motor PWM control
+3.3V buck
-3.3V charge pump
+5V buck
24-30V boost

95% of the board will be running on 3.3V, with one set of sensors needing 5V, and another needing 24-30V (both very low current). Intuitively, it feels like the 6V pump PWM can be on the other board, since none of the main components will be running on 6V, but would putting the other power stuff on the second board screw with return paths and make things noisier than just having them sort of close on the same small board?
 

Offline thm_w

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Its all trade-offs. You can have the same circuitry on one board and just put it very far apart, but then that means more horizontal space taken up.
If currents are very high it may make sense to have a power board that uses thicker copper (2oz).
Then you get into the connectors and wiring between the two boards.

What kind of currents are we talking about?

If this is a hobby project I would focus more on what makes it easier to design and build for you. Off the shelf 2s BMS PCBs are commonly available.
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Offline newtoTopic starter

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What kind of currents are we talking about?

If this is a hobby project I would focus more on what makes it easier to design and build for you. Off the shelf 2s BMS PCBs are commonly available.

Fairly low, the pump is <500mA if it ran at full speed and pressure (so likely closer to 200mA in use), the 24-30V sensor is a few mA, and the 5V sensor is <100mA.

For the BMS, it's half as a practice/experience type of thing, and half not wanting to deal with aliexpress parts. I'm sure they're perfectly safe, but the constant appearing and disappearing dealers and designs makes me not want to deal with it, and shipping these days is an absolute mess.
 


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