F1TDC Dynamic Range (fwd)

[Elton Smith <elton@jlab.org>]

---------- Forwarded message ----------
Date: Mon, 15 Apr 2002 13:53:40 -0400
From: Fernando J. Barbosa <barbosa@jlab.org>
To: Elliott Wolin <wolin@jlab.org>
Cc: Stephen Wood <saw@jlab.org>, Chris Cuevas <cuevas@jlab.org>,
     Ed Jastrzembski <jastrzem@jlab.org>, Elton Smith <elton@jlab.org>
Subject: F1TDC Dynamic Range

Hi, Elliot. 

You have shown interest in having a TDC with a wide dynamic range and with
a relaxed LSB resolution. According to F1 chip specs, the reference clock
can range from 500 KHz to 40 MHz. For the highest resolution, the
reference clock is set at 40 MHz and an LSB resolution of about 120 pS is
attained in low res mode (8 channels per chip) and 60 pS in high res mode
(4 channels per chip). The dynamic ranges are 7.86 uS and 3.93 uS,
respectively. As you may recall, the F1TDC board has an internal
oscillator (40 MHz) and external inputs on both the front panel and the
backplane. The oscillator chip can be easily replaced if needed as it is
surface mounted. Thus, you can use the F1TDC as is for your wide dynamic
range application.

    The LSB resolution in low res (8 channels per chip) mode is
LSB=K*Tref, where K is a constant (can be programmed) and Tref is the
reciprocal of the reference clock; the dynamic range (DR) is DR=65535*LSB
because the readout counter is 16 bits wide. Therefore, the dynamic range
at 500 KHz is about 629 uS at a resolution of 4.8 nS in low res . Halve
these numbers for the high res mode. The constant K can be easily adjusted
to increase the dynamic range further but we have to wait until we have
the prototype running as I have no details on the practical limits of this
constant. K depends on two internal clock dividers and on the gate delays
on the delay locked loop which ultimately depend on the fabrication
process of the chip.

    I hope this helps. Best regards,
        Fernando
BEGIN:VCARD
VERSION:2.1
N:Barbosa;Fernando;J
FN:Fernando J Barbosa
ORG:Jefferson Lab
ADR;WORK:;757-269-7433;12000 Jefferson Ave.;Newport News;VA;23606;USA
LABEL;WORK;ENCODING=QUOTED-PRINTABLE:757-269-7433=0D=0A12000 Jefferson Ave.=0D=0ANewport News, VA 23606=0D=0AUSA
EMAIL;PREF;INTERNET:barbosa@jlab.org
REV:20020415T175340Z
END:VCARD