I have this setup: HV507 output -- 300k ohm resistor -- 30pF capacitor -- 100k ohm resistor -- 300k ohm resistor -- hv507 output. The hv507 both output pulses, except they are phased 180 degrees from one another. Essentially this setup forms a different square wave. I wanted to understand why the voltage is reduced by roughly 10%. For instance, I ran a pulse setup where I run from 50v to 0v and the rms of that pulse is 21.5v when it should be 25v. What is the math behind this?

1. When I did a test where I removed both the 300k resistors, the waveform possessed more squared edges and the RMS that is displayed the top right corner was closer to 25v. This is the chip data sheet that is driving this setup (https://ww1.microchip.com/downloads...-Push-Pull-Outputs-Data-Sheet-DS20005843B.pdf). Also there are two HV3418 outputs, one at each end. The waveforms (pulses) produced from each of these outputs are phased 180 degrees from another. I want to understand what the reason is for the reduced RMS and how to calculate it. Also is there any way to somehow use these results and understand what the RMS would look like for another chip with slightly different characteristics (ex: less current sourcing/sinking from each output), specifically the HV507 (https://ww1.microchip.com/downloads...OTH/ProductDocuments/DataSheets/20005845A.pdf)





2. Also a another question, I want to be able to gauge how many outputs being active the chip can handle. For instance this what the circuit would look like, except instead of 4 outputs going into the output 5 (going to be referred to as the ref pin) with maybe 10 - 20 outputs. What are the calculations behind this?

 

rms of that pulse is 21.5v when it should be 25v

The 300k resistor and the 1meg resistor inside the scope probe will reduce the signal. (voltage divider)

, the waveform possessed more squared edges

Look at only one side of the circuit. 300k resistor, next there is a 100k and a 30pf. If the 30pF went to ground, it would short out some of the high frequencies. (RC low pass filter.) I know the cap does not go to ground. Because the cap goes to (1/signal) the cap acts like it is twice as big. The 30pF cap is removing some of the high frequency signal from getting to the scope.

 

That makes a lot more sense as to why the RMS is reduced at that point, thanks for the help on that. Thank you Ron.

 

Always use a x10 probe in preference to a x1, it generally has less impact on the circuit under test.

 

Now I wanted to understand how this circuit setup would behave. For context, each output is a separate output channel on the high voltage switching IC HV507 and each channel can handle +-1mA and the max voltage it reaches is 300v. What would the current going into hv507 output 5 (ref) look like; would it be only 1mA or would it be however many channels are outputting into the reference output. Also how would the setup change is some branches had 100k ohm resistors and some didn't. By the way, the number of outputs going into the reference output can change; I want to be able to find how many outputs, one hv507 output can handle based on this RC network.

 

The output acts as a voltage divider between the impedance of the high inputs, and the impedance of all the low inputs in parallel.
So the output voltage will vary, depending upon how many inputs are high and how many are low.

 

We can not tell you what the output will look like without knowing what the four inputs look like.
Example. If "HV507 Output 1" has the inverse of "HV507 Output 2" the two signals will cancel each other out and there will be no change in output.

 

The branch outputs or the outputs going into the reference output possess a pulse phased 180 degrees from the reference output pulse. The branch outputs in conjunction with the reference output form square waves. I wanted to understand what the current flow is like. Is it more like the current from every branch equals 1mA because the reference output is producing 300v with 300k ohm resistor so 1mA current draw or is it different?