[SOLVED] Oscillation start on programmable pulse generator

[Wolf99]

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??

Thanks

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

 

[BradtheRad]

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.

 

[Wolf99]

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.

 

[BradtheRad]

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.