Technical Guide: Width & Delay
Quantum Composers pulse generators can provide an array of output pulse trains with precise timing and unparalleled flexibility. Each channel can provide independent width and delay control within some specific settings. This technical document explains the required settings of width and delay and how those settings affect the channel output.
The period setting (called To) will generate an internal pulse at the desired period from the system to the individual channels. The channels then use this pulse to start calculating the set delay and width.
The width and delay are limited by the intended output period To. The delay time plus the width time must be less than the intended output period by approximately 75 ns in order to generate a pulse output at the set period. If the delay and width settings exceed the unit’s To period, the channel will still generate an output pulse just not with the intended period.
As an example, let’s say that the output period of the pulse generator is set to 10 us. This can be represented as a pulse output with a rate between rising edges of 10 us. Figure 1 shows an example of the output on Channel A with a delay and width setting total that exceeds the 10 us internal rate. The delay setting is 9 us and the width is set to 4 us for a total of 13 us. When the 2nd To pulse reaches the channel, the channel is in the middle of generating the 4 us output. When this situation happens, the channel ignores the 2nd To pulse and finishes the output operation.
Figure 2 shows how this behavior affects the output over a longer period of time.
Since the output was busy when the second To pulse arrived at the channel, the To pulse is ignored and the channelwon’t start the next output generation (delay and width) until the 3rd To pulse. This causes the output to generate an output pulse every 20 us, from rising edge to rising edge, instead of the intended 10 us. This limitation is one way multiple rates can be generated out of two different channels. By setting the delay on one channel to match the To period, that channel will be in synch with any non-delayed channel but running at ½ the period as show in Figure 3.
The important point to remember when attempting to operate the unit with a specific period is to always allow approximately 75 ns of “dead time” at the end of the pulse event. Leaving that little bit of time at the end of the pulse will ensure that the pulses will be generated with the intended period.