The digital out board

This board was designed to get rid of ground-loops created by the pulse box. The board has 16 galvanically isolated grounds, each created by a DC-DC-converter. A digital isolator transfers each output signal from the common ground system of the pulse box to the signal’s seperate ground system.

The PCBs and parts list can be found on

\Anna-c704sqipPulse BoxDigital Out

Attention: This PCB cannot drive 50 Ohm. The input resistance of each connected device has to be in the order of 1kOhm or higher. So, DO NOT CONNECT 50 Ohm DEVICES TO THE DIGITAL OUTPUTS! It can’t provide enough current for 50 Ohms because the drivers are very fast and they have to drive a 5V-TTL signal. Hence, there will be rather big currents. Since we are using 50 Ohm-SMA cables and cannot terminate with 50 Ohms, there will be back-reflections. If you are using a short cable (= low load-capacitance), there may be some voltage overshoot. With a 1m cable, the overshoot can be 2V for 10ns. If that damages your circuits or try to avoid overshoots generally, you have to add a capacitor parallel to the output. To get an idea, what capacitor to use, have a look at the list below.

  • no capacitor parallel to the output, 1m coaxial cable, high-Ohm input resistance: overshoot 2V (7V in total), rise time <1ns
  • 330pF parallel to the output, 1m coaxial cable, high-Ohm input resistance: overshoot 1V (6V in total, rise time ~9ns
  • 1.5nF parallel to the output, 1m coaxial cable, high-Ohm input resistance: hardly any overshoot, rise time ~60ns

Troubleshooting

  • The cable to the breakout board is not assembled correctly
  • The supply voltage is not applied
  • A DC-DC converter is broken

Digital In board

This board was designed to get rid of ground-loops created by the pulse box. The board has 8 galvanically isolated grounds, each created by a DC-DC-converter. A digital isolator transfers each in signal from its seperate ground system to the common ground system of the pulse box.

The PCBs and parts list can be found on \Anna-c704sqipPulse BoxDigital In .

The PCBs has a high-Ohm input. This does not match 50 Ohm coaxial cable, therefore back-reflections will occur. If you have a device connected to one input channel that can drive 50 Ohm, you can put a 50 Ohm resistor parallel to your input to get rid of the reflections. BUT, if you connect a device that drives 50 Ohm to a regular high-Ohm input, the input channel might be damaged because the input voltage will then be 10V. So, don’t do that.

Troubleshooting

  • The cable to the breakout board is not assembled correctly
  • The supply voltage is not applied
  • A DC-DC converter is broken