From 4632c72a9be66139f0ce71690172fe6e6f7c600e Mon Sep 17 00:00:00 2001 From: architeuthis Date: Wed, 29 Jan 2025 14:53:26 +0100 Subject: [PATCH] 2118-2128: revise noise/jitter note --- 2118-2128.tex | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/2118-2128.tex b/2118-2128.tex index 0e09029..3600d4c 100644 --- a/2118-2128.tex +++ b/2118-2128.tex @@ -36,7 +36,7 @@ Each channel supports 50\textOmega~terminations, individually controllable using DIP switches. Outputs tolerate short circuits indefinitely. Both cards are capable of a minimum pulse width of 3ns. - Note that isolated TTL cards are less suited to low-noise applications as the isolator itself injects noise between primary and secondary sides. Cable shields may also radiate EMI from the isolated grounds. For low-noise applications, use non-isolated cards such as 2238 MCX-TTL or 2245 LVDS-TTL. + Isolated TTL cards are not well suited to low-noise or low-jitter applications due to interference from isolation components. For low-noise applications, use non-isolated cards such as 2238 MCX-TTL or 2245 LVDS-TTL. % Switch to next column \vfill\break @@ -359,6 +359,8 @@ \end{threeparttable} \end{table} + Low-jitter applications should note carefully the jitter introduced by the signal isolator. Noise is also introduced between the primary and secondary domains by the DC/DC convertor. Where noise or jtter are crucial, it is instead recommended to use non-isolated cards such as 2238 MCX-TTL or 2245 LVDS-TTL. + Minimum pulse width was measured by generating pulses of progressively longer duration through a DDS generator and using them as input for a BNC-TTL card. The input BNC-TTL card was connected to another BNC-TTL card as output. The output signal is measured and shown in Figure \ref{fig:pulsewidth}. \begin{figure}[ht]