Time to amplitude converter - Page 1
Forum section: electronics / projects

author: Sankha
author_rank: Newbie
timestamp: January 21, 2022, 10:50:21 am
content: Hi,Im Sankha from university of Colombo, Sri Lanka. To measure nanosecond scale [1 to 5 ns] pulse width we need to make a time to amplitude convertor (TAC). Can anyone help me to find a circuit diagram of such a device or any alternative solution to this problem is highly appreciated..!

author: Christe4nM
author_rank: Unknown
timestamp: January 21, 2022, 01:14:19 pm
content: I'm not sure if you are looking for help with an assignment, or rather working in a lab and needing a circuit to assist you with the research you are working on.In the case of it being an assignment, I'll give you something to help you on your way. I think you'll learn a lot more from it than just finding a circuit. So think about this: what happens to the voltage on a capacitor when a constant current flows into it? And how could that principle be used to make what you are looking for?If the latter, I'm sure others will tune in with something that will get you to what you need.

author: ch_scr
author_rank: Frequent Contributor
timestamp: January 21, 2022, 01:17:39 pm
content: I guess you would want to measure the voltage afterwards, to get a digital value proportional to the pulse?If yes, then there is an integrated solution called "Time to Digital Converter" TDC from TIhttps://www.ti.com/product/TDC7200This has been used in an open source project:https://github.com/TAPR/TICC/tree/master/TICCYou can also buy this:https://tapr.org/product/tapr-ticc/

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 21, 2022, 01:19:25 pm
content: Other than just using a (fast) scope, the only way I can think of that doesn't require complex RF design is to use a FPGA with a fast SERDES block.That TI chip, while quite interesting, can only go down to 12ns.

author: ch_scr
author_rank: Frequent Contributor
timestamp: January 21, 2022, 01:36:20 pm
content: Quote from: NiHaoMike on January 21, 2022, 01:19:25 pmI am not sure where you get this from, the datasheet says under application information "measurement range of 0.25ns to 8ms and accuracy of 28ps" and "single shot resolution of 55ps"Edit: Scrolling down I see now, they manage the shorter pulse width but with a pre-trigger you have to generate yourself....

author: Sankha
author_rank: Newbie
timestamp: January 22, 2022, 02:24:58 pm
content: Thank you very much for that information. Im currently working in a project to measure phase difference of two pulses which has a pulse separation of few nanoseconds.Hope your idea of using a TDA will work for me. If you have a better idea, please let me know.

author: mino-fm
author_rank: Regular Contributor
timestamp: January 22, 2022, 06:17:16 pm
content: Quote from: ch_scr on January 21, 2022, 01:36:20 pmMode 1: 12 ns to 500 nsMode 2: 250 ns to 8 msYou can use mode 1. Leading edge of 1. signal triggers "START". Leading edge of 2. signal has to be delayed by 100 ns (10 MHz clock) to trigger "STOP". So results are from 100 ns to 200 ns. All you need are three D-FFs.Another TDC is AS6500/6501 which works from 0 ns phase difference directly.To realize a time-to-voltage-converter you need some analog stuff or one fast XOR gate and an integrating circuit.I wouldn't do so.