DS8615 Datasheet, PDF (4/6 Pages) National Semiconductor (TI) – Low Power Dual Modulus Prescalers

Application Hints
OPERATING NOTES
The signal source is usually capacitively coupled to the in-
put At higher frequencies a 0 001 mF input capacitor (C1) is
usually sufficient with larger values used at the lower fre-
quencies If the input signal is likely to be interrupted it may
be desirable to connect a 100 kX resistor between one in-
put and ground to stabilize the device In the single-ended
mode it is preferable to connect the resistor to the unused
input In the differential mode the resistor can be connected
to either input The addition of the 100 kX pulldown resistor
causes a loss of input sensitivity but prevents circuit oscilla-
tions under no signal (open circuit) conditions In addition in
the single ended mode a capacitor of 0 001 mF (C2) should
be connected between the unused input and the ground
plane to provide a good high frequency bypass The capaci-
tor should be made larger for lower frequencies
The input waveform may be sinusoidal but below about
20 MHz the operation of the circuit becomes dependent on
the slew rate of the input rather than amplitude A square
wave input with a slew rate of greater than 20 V ms will
permit correct operation down to lower frequencies provid-
ed the proper input coupling capacitor is provided
For regulated mode operation connect V_S to V_REG to en-
sure proper operation (see Typical Application diagram)
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