The TADD-2 output drivers exhibit significant ringing and crosstalk due
to ground and Vcc bounce.
To minimise crosstalk dedicate each 74AC04 output device to a single
frequency and load.
Because of the ringing setting the trigger threshold is more critical
than usual.
No damage occurs when driving the 5370A/B 1x inputs with 5V logic levels
however various protection diodes will turn on and the preamp input
stage becomes nonlinear.
Bruce
Dave hartzell wrote:
Today I have been trying to drive a 5370B directly from a TADD-2, with
little luck (other HP freq counters seem to work OK). I was about to ask
about it on this list, but noticed this thread.
I guess this could explain why I am getting erroneous, random readings?
Dave
On Sat, Feb 27, 2010 at 4:01 PM, Bruce Griffiths<bruce.griffi...@xtra.co.nz
wrote:
The attached excerpts from the 5370A and 5370B manuals indicate that for
best performance, that the common practice of driving the 5370A/B 1x inputs
directly from a 5V CMOS logic signal is a bad idea.
For the 5370A attenuating the 5V CMOS signal to a 1V swing with the
threshold set to 0.5V is close to optimum.
An input signal with limits of 0V and +1.4V with a trigger threshold of
0.7V is the maximum usable (for high performance).
An input signal with limits of 0V and +0.3V with a trigger threshold of
0.15V is the minimum usable (for high performance).
For the 5370A attenuating the 5V CMOS signal to a 2V swing with the
threshold set to 1V is close to optimum.
An input signal with limits of 0V and +3.5V with a trigger threshold of
0.7V is the maximum usable (for high performance).
An input signal with limits of 0V and +0.3V with a trigger threshold of
0.15V is the minimum usable (for high performance).
Bruce
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