Delay management - Page 1
Forum section: electronics / general

author: Md_Aslam
author_rank: Contributor
timestamp: September 22, 2022, 05:05:08 am
content: I am Trying to measure the delay of 1PPS Signals of two Rb clock, and to measure the delay I want to use some ICs based TDC/TIC with smallest size possible like TDC7200. But the problem is that delays are in ms say 500ms to 700ms and the TDC/TIC which I have, has only measuring range up to 10ms.So to overcome this problem there are two solutions which I can think of:1.) Either I reduce this delay by some means and bring it to few ms, which right now, I don't know How can I do that because Delay is a constant quantity which cannot be changed.2.) or I should use the TDC/TIC with higher measuring range, but to do this, I will have to switch from ICs based TDC/TIC to some big devices like Keysight-53230A, and I don't want to use this huge device.Please suggest me some ideas to solve this problem.PS: Reducing delay by some means will be a great help for me as I already have some TDC/TIC ICs for that.PPS: Someone suggested me TAPR-TICC, which is a great device, but its size is equal to the Arduino-Mega, which is an issue for me.

author: hgl
author_rank: Regular Contributor
timestamp: September 22, 2022, 11:14:02 am
content: Maybe an AS6501 TDC in a QFP48 package will do.It has a 24 bit coarse counter and 3 channels which results in a measuring time of 0 to 1.67s at 10 MHz clock frequency using 2 channels. Additionally you need a microcontroller to read out the results. (LVDS or SPI). Resolution typical 20ps

author: Md_Aslam
author_rank: Contributor
timestamp: September 23, 2022, 06:06:21 am
content: Quote from: hgl on September 22, 2022, 11:14:02 amI used AS6500 once, and in its datasheet, the measuring range is mentioned as 0s to 16s, but when I read the datasheet carefully then I found that, in starting of the datasheet the range is 0s to 16s but in section 8.6.3 of the datasheet the max mentioned measuring range is 13ms at 5MHz and 6.5ms at 10MHz because REF_ INDEX_BITWIDTH is 16-bit only.So are you confirm that this AS6501 has no such issue?PS: Although I read the AS6501 datasheet also the measuring range is 1.6s at 10MHz, but not confirm about 24-bit of REF_ INDEX_BITWIDTH

author: hgl
author_rank: Regular Contributor
timestamp: September 23, 2022, 09:14:48 am
content: I read the datasheet again and found this:The register description says 3bytes.In section 8.1.2 Output Results it says: The maximum length of the reference index is 20 bits.In the table 8.7.3 Maximum Time Differences it says again 24bit (1.6s) at 10 MHz (LVDS only ?).My first answer was based on the table.To get longer times the microcontroller can also count the 10Mhz reference, detect index overflows and count them.Datasheet : v1-00 • 2018-May-11

author: hgl
author_rank: Regular Contributor
timestamp: September 23, 2022, 09:31:32 am
content: The index counter can count 24 bit but only in LVDS mode 24 bit can be read out.7.2.3 CFG2 Register : Bit width of reference clock index in LVDS output (not applicable to SPI data readout).101b := 24 bits

author: miro123
author_rank: Frequent Contributor
timestamp: September 24, 2022, 10:21:14 am
content: Do you have some requirement for time measurements,e.g long/short time accuracy, time resolution etc?Do you consider the reference clock for TDC circuit? It can be easily 10 times bigger than arduino mega

author: Md_Aslam
author_rank: Contributor
timestamp: September 27, 2022, 12:24:36 pm
content: Quote from: hgl on September 23, 2022, 09:31:32 amI got this point.So can I read this LVDS output using some microcontrollers like STM32? If yes then can you provide me some documentation for this.