S1M8821 Samsung Semiconductor, Inc., S1M8821 Datasheet - Page 13

• Manufacturer Part Number: S1M8821
• Description: Interger Rf/if Dual Pll Frequency Synthesizer
• Manufacturer: Samsung Semiconductor, Inc.

INTERGER RF/IF DUAL PLL
S1M8821/22/23
FUNCTIONAL DESCRIPTION
The Samsung S1M8821/22/23 are dual PLL frequency synthesizer ICs. S1M8821/22/23 combined with external
LPFs and external VCOs form PLL frequency synthesizers. They include serial data control, R counter, N counter,
prescaler, phase detector, charge pump, and etc.
Serial data is moved into 20-bit shift register on the rising edge of the clock. 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
LSB
N20(R20)
N19(R19)
N10(R10)
N9(R9)
C2
C1
DATA
CLOCK
t
LEW
t
t
t
CWL
CWH
DS
LE
t
t
CLE
DH
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