BL2040 Mini Alpha V3 - Brushless Servo Driver

NOTE: A board layout error was discovered with regards to the hall effect current sensors, and we'll release a revised design to correct this soon.

Hardware

• RP2040 32-bit microcontroller, with 4MB of flash
• 2x Hall effect current sensors, ±20A range
• 14-bit hall effect angle sensor on the back (requires soldering)
• All IO broken out to headers, including allocated pins (helpful for debugging)

Power

• 5 - 24V DC input to VCC (with reverse polarity protection)
• 5V DC at USB port can also be used to power the motor
• Power OR-ing to allow use of VCC and USB simultaneously
• Upstream device USB protection IC limits drawn current to 1A (resistor programmable)

Errata

• The USB impedance controlled traces in this version are not quite correctly defined, but they still work ok. Definitely need to fix before the next release.
• The green LED for +5V power rail is a bit too bright, might want to add a slightly higher resistor value.
• The hall effect current sensors have no filtering caps, and they currently pick up some PWM switching noise. The PCB has some 0402 pads where a capacitor can be installed, and I am currently investigating the best value.
• Before next release, need to slightly increase the spacing between the the three diode triplets above the mosfets.
• The hall effect current sensors should be powered from the +3V3 rail instead of the +5V rail, and the voltage divider on the sensor output should be removed.
• Need to add a way to detect when VCC is present regardless of USB power input status (ensure enough current is available).
• Add DC bus current sensing or some OCP strategy.

Ordering

• Several non-critical components may not be available from JLCPCB any more (i.e. the exact LEDs that are specified in the schematic), in which case you will need to pick equivalent alternatives manually.
• JLCPCB DFM review comes back fine, except for the three triplets of diodes above the mosfets, which are slightly too close together in the board layout.
• Total approximate cost of 5pcs order: $2.50 for PCBs, $95 for PCBA + components, and $12.60 for the hall angle sensors from LCSC. This comes to about $22 per board, not inclusive of shipping.