A very large spurious signal is observed on the logic output! If the impedance of the
logic output is reduced by adding a 1 kilohm pull-up resistor (R2 on the sample
daughterboards) to VCC2 = +5V, a smaller transient of shorter duration is observed:
Top: +1.5 kV HV pulse
Bottom: Logic out into open circuit
no DUT, R2 = 1kΩ, 100 ns/div
Top: -1.5 kV HV pulse
Bottom: Logic out into open circuit
no DUT, R2 = 1kΩ, 100 ns/div
In the above waveform photos, both channels of the oscilloscope are used
simultaneously. To eliminate the possibility of oscilloscope inter-channel interference, it
is better to record the HV pulse (typically using the oscilloscope “REF” storage
function), then full disconnect the HV probe from the HV signal, and then observe the
logic output. If this is done, the logic signal in last two images become much cleaner:
Top: +1.5 kV HV pulse
Bottom: Logic out into open circuit
no DUT, R2 = 1kΩ, 100 ns/div
Top: -1.5 kV HV pulse
Bottom: Logic out into open circuit
no DUT, R2 = 1kΩ, 100 ns/div
It becomes clear that both effects (capacitive coupling on the daughterboard, and in the
oscilloscope) are important. The oscilloscope portion is easily eliminated, at least.
62
Summary of Contents for AVRQ-5-B
Page 52: ...Bottom side 52 ...
Page 57: ...PCB 299B FOR ADUM241E0BRWZ 57 ...
Page 82: ...PCB 158R2 LOW VOLTAGE POWER SUPPLY ...
Page 87: ...DUT WIRING ON STANDARD DAUGHTERBOARD PCB 267C ...
Page 88: ...DUT WIRING ON CUSTOMIZED TLP2366 DAUGHTERBOARD PCB 298B ...
Page 89: ...DUT WIRING ON CUSTOMIZED ADUM241E0BRWZ DAUGHTERBOARD PCB 299B ...
Page 91: ...PERFORMANCE CHECK SHEET 91 ...