Today, we receive Nicolas who has been concentrating on the development of the Trigger IC that has been implemented on the M9703A. This circuit was developed as part of a trigger circuitry which includes others elements as you will discover in this interview.
Hello Nicolas, tell us a bit more about yourself. Have you always been working in the development of IC?
Actually, I started my career in an automotive company, mainly doing software coding as well as CPLD firmware but this was not my cup of tee. I changed job and worked for a DSO company and was mainly involved in the design of Front-end, multi-chip-modules and also GaAs IC design. After this I completed a PhD at the Swiss federal institute of technology in the field of IC design in the area of RF power amplifier efficiency improvement. Since then, I have been working for Agilent mainly on IC design for time base, trigger circuit and vertical signal conditioning. Incidentally, I am also in charge of the full time base circuitry development, implementing our own IC. Having to implement a circuit in a real application always gives new ideas for improvement. READ MORE
The trigger circuit you developed is part of a trigger circuitry which is also made of several different blocks. Tell us a bit more about this circuitry. What is the influence of this dedicated trigger IC on the timing precision of a trace positioning (a precision of 12ps rms as a reminder) ?
This target of some pico seconds would most probably be very difficult to reach with a full discrete design. As mentioned in your question, the trigger system is made of several blocks, based on ultra-fast analog comparators, commercial Analog-to-Digital Converter (ADC) and a Field Programmable Gate Array (FPGA) (cf figure 1). The trigger chip integrates a lot of functionalities including fast and low jitter logic and a time-to-analog converter (TAC) to precisely place the trigger event. The advantage of using this dedicated trigger chip is to dramatically reduce the occupied PCB area and above everything power dissipation compared to a full discrete design.
Figure 1 Trigger circuitry timing diagram
What is the added-value of your in-house design trigger circuit?
The added value of the trigger chip is quite straightforward. Definitely, without this trigger chip, we could not propose our customers good trigger capability and precision because we would be limited by the available PCB area and the dissipated power. The edge trigger provides a marker which determines the exact moment the trigger source signal crosses the chosen threshold. Furthermore, the edge trigger information is propagated in real-time to a configurable area of the Digital Processing Unit (DPU) FPGA where customers could potentially implement their own processing algorithms.
The next figure summarizes the flexibility and synchronization offered by this trigger technology:
Note from the editor: We can provide you with further details on the trigger circuitry functioning and possibilities upon the reception of an email from you. A figure showing the standard M9703A trigger position standard deviation is also available upon request.
Nicolas as a last word: Do you still see room for improvement in trigger circuit design? What is your feeling about it?
The trace positioning precision depends on the slope of the signal one wants to trigger on. When the slope is very steep, the ultimate precision limitation is the TAC repeatability. The room of improvement would be mainly based on finding new architecture for the TAC with better repeatability.Tags: FPGA programming m9703a share trigger circuitry