[time-nuts] Trimble Thunderbolt 1pps
Javier Herrero
jherrero at hvsistemas.es
Mon Jan 27 14:43:25 EST 2014
On 27.01.2014 19:33, Robert Atkinson wrote:
> All the receiver chips I've looked at, ancient and modern, have only positive thresholds. Most have single supplies and clamp the input at 1 diode drop negative WRT common after an input current limiting resistor, see the MC1489 datasheet.
>
Hello,
Not exactly. If you check the MC1489 datasheet from On Semiconductor,
the thresholds can be programmed with the response control resistor and
can in fact be negative. (Figures 6 and 7 in the datasheet). The serial
input resistor forms part of a resistive divider with the feedback
resistor and the external resistor - not simply a current limiter to the
diode.
Regards,
Javier
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