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[SOLVED] Oscillation start on programmable pulse generator

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Junior Member level 3
Jan 18, 2011
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Hi Folks

Im looking at Data delay devices' 3d7622 22-bit programmable pulse gen.

I hope to use to of them to create an oscillator with dual edge variable pulse in a range around 50MHz.

However, fig5 in the datasheet **broken link removed** shows an example of a simpler oscillator, but I do not understand the startup of oscillation...

Also, looking at the timing formula and diagram, it seems confused about if its using a NAND gate or a NOR gate... am I missing something??


EDIT just realised there are two figure 5's in this sheet, I am refering to the second one on page 6.

EN stands for enable. When you bring the EN line low, it starts the device operating.
Bring EN high to stop.

Are you asking about the gate that looks like a triangle with a circle at the output? One line in, one line out.
That's an inverter.
You can make one from a NAND gate or a NOR gate. Just connect both inputs.

Oh, figure 5. The one having 2 inputs going to 2 circles. Not sure about that. It may be an AND gate working on reverse logic. Not the same as a NAND gate.

Hi Brad, thanks for your reply

I get that the reset signal enables the device, but how does this mean a pulse is generated without a trigger?

thanks for the idea on the NAND/NOR gate. :)

Figure 5 on page 6 shows a wire going from the output pin to the trigger pin. (Not directly but rather through that unfamiliar gate.)

Thus the one-shot generator becomes self-triggering. This is a typical method used to turn a one-shot pulse generator into a continuous pulse generator.

It's up to you to experiment with combinations of gates and enable signals, inverters, etc., in order to achieve desired operation.

As to that odd gate... I wouldn't be surprised if a newly hired graphics layout person had a hard time trying to figure out what symbol the electronics engineer had drawn by hand.

Most likely it's a NAND gate.
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