CF5072 series
FUNCTIONAL DESCRIPTION
Oscillator Equivalent Circuit
The oscillator can be represented by the equivalent circuit shown below. The crystal unit is connected to XIN,
and the other terminal is connected to the L and R network. A varicap is added with cathode connected to
S
P
XR, and anode connected to XC.
The control voltage is applied to the VC pin, with high-resistance element connected between VC and XR
built-in.
X'tal
RP
LS
XIN
XC
To differential
converter
100pF
HVC350B
RVC
C2
XR
RS
C1
VC
VC input
VSS1
Oscillator internal capacitors
Recommended external constants
Internal capacitance [pF] (design value)
Oscillator
frequency
1
L
[nH]
R
[kΩ]
P
S
Version
C1
C2
220
180
2.2
1.8
CF5072AA
11.2
14.4
155.52MHz
1. R is a damping resistor to prevent parasitic oscillation due the
P
combined effects of the external inductor (expander coil) and varicap
capacitance/internal capacitance. It is recommended that R be
P
connected in parallel with L .
S
Output Circuit
The output is enabled/disabled using the OE pin. Outputs are high impedance when disabled. The OE pin logic
is shown in the following table.
OE
HIGH or open
LOW
OUT
OUTN
CLK output
CLK output
High impedance
High impedance
VDD1
OE = HIGH: ON
OE = LOW: OFF
From pre-buffer
OUTN
OUT
OE = HIGH: OFF
OE = LOW: ON
NIPPON PRECISION CIRCUITS INC.—2
SEIKO [ SEIKO EPSON CORPORATION ]
