PE3335
Product Specification
Enhancement Register
The functions of the enhancement register bits are shown below with all bits active “high”.
Table 9. Enhancement Register Bit Functionality
Bit Function
Description
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Reserved**
Reserved**
Reserved**
Power down
Counter load
Power down of all functions except programming interface.
Immediate and continuous load of counter programming as directed by the Bmode and
Bit 5
Bit 6
Bit 7
MSEL output
Prescaler output
fp, fc OE
Drives the internal dual modulus prescaler modulus select (MSEL) onto the Dout output.
Drives the raw internal prescaler output onto the Dout output.
fp, fc outputs disabled.
** Program to 0
Phase Detector
The phase detector is triggered by rising edges
from the main Counter (fp) and the reference
counter (fc). It has two outputs, PD_U, and PD_D.
If the divided VCO leads the divided reference in
phase or frequency (fp leads fc), PD_D pulses
“low”. If the divided reference leads the divided
VCO in phase or frequency (fc leads fp), PD_U
pulses “low”. The width of either pulse is directly
proportional to phase offset between the two input
signals, fp and fc.
CP. The current pulses from pin CP are low pass
filtered externally and then connected to the VCO
tune voltage. PD_U pulses result in a current
source, which increases the VCO frequency;
PD_D pulses result in a current sink, which
decreases VCO frequency (for a positive Kv
VCO).
A lock detect output, LD is also provided, via the
pin Cext. Cext is the logical “NAND” of PD_U and
PD_D waveforms, which is driven through a series
2 kohm resistor. Connecting Cext to an external
shunt capacitor provides low pass filtering of this
signal. Cext also drives the input of an internal
inverting comparator with an open drain output.
Thus LD is an “AND” function of PD_U and PD_D.
The signals from the phase detector couple
directly to a charge pump. PD_U controls a
current source at pin CP with constant amplitude
and pulse duration approximately the same as
PD_U. PD_D similarly drives a current sink at pin
Document No. 70-0049-02 │ www.psemi.com
©2005 Peregrine Semiconductor Corp. All rights reserved.
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