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2.5A brushed motors driver IC
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3dgeo:
Hello,

I'm making driver for 2 2.5A (MAX) 24V brushed motors and found DRV8412 (2x3A). Motors will be on for a short period of time (max 20s) and only few times a day if at all (indoors). I need to limit current and chop 38V, so DRV8412 looks very suitable, but cos I'm not an expert in this field I wanted to get input from others. Mostly I'm concern about thin PCB traces near IC.
It's one off, so price is not an issue. Controller – ESP32.

Should I be worried about thin traces or heat? Is there anything else I'm missing?

Also recommendation on adequate PCB to wire plugs are very welcome.

Thanks in advance.
Siwastaja:
On a quick glance, the IC datasheet looks OK. It's an actual motor driver IC, meaning it can provide you with a proper current (torque) limiting, although slightly inaccurate.

The fact it has internal MOSFETs simplifies the layout work a lot. Still, be careful with DC link bypass capacitors - minimize distance to the IC power pins and ground plane, use a combination of MLCCs (say something like a bunch of 0.47uF 50V in 0805) and traditional crappy and lossy aluminum electrolytic capacitors (for ESR, damping).

Thin traces usually aren't a problem in tight integration - make them short. Standard 1oz copper has resistance of 0.5 mOhm per square (Google for this if you don't know the concept and the unit sounds weird - Dave has a video about it). This means, even if you had a tiny trace with 0.3mm width, if it's also 0.3mm long, the resistance is 0.5 mOhm! Or if it's 0.3mm x 0.6mm, it's 1mOhm. This means, minimize the distance between parts, and your wiring loss problem disappears.
3dgeo:
Thank you for your reply.


--- Quote from: Siwastaja on September 10, 2019, 07:23:03 pm ---On a quick glance, the IC datasheet looks OK. It's an actual motor driver IC, meaning it can provide you with a proper current (torque) limiting, although slightly inaccurate.

--- End quote ---
Yes, it looks very nice on a paper, exactly what I need. What do you mean by "slightly inaccurate"? Motors should be synced, tho they have a hall effect sensors for rotary encoding, so it's possible to resync them with microcontroller.


--- Quote from: Siwastaja on September 10, 2019, 07:23:03 pm ---The fact it has internal MOSFETs simplifies the layout work a lot. Still, be careful with DC link bypass capacitors - minimize distance to the IC power pins and ground plane, use a combination of MLCCs (say something like a bunch of 0.47uF 50V in 0805) and traditional crappy and lossy aluminum electrolytic capacitors (for ESR, damping).

--- End quote ---
This IC eliminates a lot of extra components in original circuit – relays, fets, fet drivers, flyback diodes.
In datasheet, on pages 28,29 there is a wiring circuit/PCB layout example that I'm going to follow, but I will be using 100V rated 0603 (not 0805) components cos I just prefer 0603. As far as I know there is no disadvantage using smaller components (if they are rated for the same voltage), or I'm missing something?


--- Quote from: Siwastaja on September 10, 2019, 07:23:03 pm ---Thin traces usually aren't a problem in tight integration - make them short. Standard 1oz copper has resistance of 0.5 mOhm per square (Google for this if you don't know the concept and the unit sounds weird - Dave has a video about it). This means, even if you had a tiny trace with 0.3mm width, if it's also 0.3mm long, the resistance is 0.5 mOhm! Or if it's 0.3mm x 0.6mm, it's 1mOhm. This means, minimize the distance between parts, and your wiring loss problem disappears.

--- End quote ---
Traces will be up to 3cm (I'm good at making traces as short as possible), also I will make them as wide as I can.
3dgeo:
Made ruff high current side PCB layout, GND input will be on top and there will be tones of GND vias around.
I changed design from datasheet example to reduce trace length.

Any feedback is welcome:
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