VNH2SP30 Isolation

Hello. I recently purchased the high-current dual motor driver (VNH2SP30). I would like to isolate the +5V (IN) from the low power supply feeding my ZX-40A microcontroller ( Is it possible to connect the +5V (IN) pin to the adjacent VIN pin on the 0.1" header that resides on the left side of this picture:

In the process of tuning my PID control system (see project link below), my groundbot (GBOT) went unstable. The NiMh power supply wires to the microcontroller bubbled from heat and burned off. That power supply only powers the ZX-40A microcontroller, 1 LED, 2 IR range sensors, and PWM & +5V (IN) to the VNH2SP30 motor controller - all of these are low power signals. A separate battery pack powers the motor controller. My thought is that when the GBOT went unstable, the motor controller +5V (IN) drew too much power from the microcontroller low-power supply. This is why I want to isolate the VNH2SP30. Is this possible?


You should not connect the +5V input to the higher-voltage VIN pin. I doubt that the +5V input current was the source of your problem, but if you want it powered from the same supply as your motor supply, you could put in an extra 5V regulator from VIN to the +5V pin. This still won’t be real electrical isolation, but all the I/O pins on that board have 1k resistors on them, so the worst-case current will be quite limited.

- Jan