KB8821 Datasheet, PDF (10/21 Pages) Samsung semiconductor – FREQUENCY SYNTHESIZER

PRELIMINARY SPECIFICATION (V1.5)
FREQUENCY SYNTHESIZER
KB8821/22/23
FUNCTIONAL DESCRIPTION
The Samsung KB882x are dual PLL frequency synthesizer ICs. KB882x combined with external LPFs andexter-
nal VCOs form PLL frequency synthesizers. They include serial data control, R counter, N counter, prescaler,
phase detector, charge pump, and etc.(Figure 1).
Serial data is moved into 20-bit shift register on the rising edge of the clock(Figure 2). These data enters MSB
first. When LE becomes HIGH, data in the shift register is moved into one of the 4 latches(by the 2-bit control).
The divide ratios of the prescaler and the counters are determined by the data stored in the latches. The external
VCO output signal is divided by the prescaler and the N counter. External reference signal is divided by the R
counter. These two signals are the two input signals to the phase detector. The phase detector drives the charge
pump by comparing frequencies and phases of the above two signals.The charge pump and the external LPF
make the control voltage for the external VCO and finally the VCO generates the appropriate frequency signal.
Serial Data Input Timing
MSB
DATA ^N20(R20)
N19(R19)
N10(R10) N9(R9)
LSB
C2 C1
CLOCK
t_DS
LE
t_CWL
t_CWH
t_LEW
t_DH
t_CLE
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