Hardware Errata

This page lists some issues with the hardware.

Holes for current sense resistors should be slightly larger
- Datasheet specifies 1.5mm ±0.12mm
Increase spacing between heatsink and MOSFET/resistor slightly
- Right now, the legs need to be bent at a bit of an angle, which makes fitting everything a huge pain in the ass
Zero offset resistor (R307, ???) is too large
- 4M7 is too large and doesn’t let us trim out the entire DC offset (~4.5mV)
- 1M was also too large (~3.5mV)
- 200k works (able to trim to ~1µV remaining offset)
  - This is probably too low, maybe something like 330k or 500k is better
  - The trimming range is quite small

MOSFET gate drive voltage too low
- V_Gs, with the current configuration can only drive to max +3V3. This is not sufficient to turn on the MOSFETs selected (IXTH80N075L2) with a V_Gs(th) of 4.5V max
- May be salvageable by rework (op-amp powered from 5V instead) and selecting a different MOSFET
- Future work
  - Select a MOSFET driver opamp that can be powered from ±12V
  - Update power section to generate isolated 12V (replace PS201 with PDSE1-S12-S12-S)
  - Generate 5V locally (switching supply off 12V)
I²C isolator (U203, ADuM1250) has the output SCL/SDA swapped
- The I²C bus is swapped for all devices downstream of the EEPROM