[time-nuts] Achieving maximum performance when driving 5370A/B inputs

[Bruce Griffiths]

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.griffiths at 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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