2.5A brushed motors driver IC - Page 1
Forum section: electronics / projects

author: 3dgeo
author_rank: Frequent Contributor
timestamp: September 10, 2019, 04:15:19 pm
content: Hello,I'm making driver for 2 2.5A (MAX) 24V brushed motors and foundDRV8412(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.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 10, 2019, 07:23:03 pm
content: 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 themshort. 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.

author: 3dgeo
author_rank: Frequent Contributor
timestamp: September 10, 2019, 08:34:59 pm
content: Thank you for your reply.Quote from: Siwastaja on September 10, 2019, 07:23:03 pmYes, 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 pmThis 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 pmTraces 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.

author: 3dgeo
author_rank: Frequent Contributor
timestamp: September 11, 2019, 05:20:14 pm
content: 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: