BL4S200 Digital Output misbehavior

We are working on implementing your BL4S200 board inside our systems.

We have found a strange issue with them. When powering both the card and the outputs(+Kx) with the same supply, and wiring Kx and a single output:

  • Using 24VDC/0.5A power supplies, both for DC output and +Kx, there is a voltage drop of around 4.5 Volts between +Kx and the onboard output when the output is set to “1”. Jumpers are set to +Kx.

  • This difference is around 0,5V when using 12V supplies (same card and load).

  • This difference only happens using onboard digital outputs. Digital IO expansion board and Hi-Current output shows no measurable drop.

This behaviour makes the used LED lamps (rated at 24V) to slightly brighten when the output is deactivated. As far as I can see in the manual, Kx goes through a BJT and a diode, so around 1,5V drop would be reasonable.

Is there anything we are missing?

Best regards,