S1M8821 Samsung Semiconductor, Inc., S1M8821 Datasheet - Page 18

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

S1M8821/22/23
FUNCTIONAL DESCRIPTION
•
There are synchronous and asynchronous powerdown modes for S1M8821/22/23.
Synchronous powerdown mode occurs if R18 bit is LOW, N20 bit is HIGH and charge pump output is in high
impedance state. In the synchronous power down mode, the powerdown function is activated by the charge pump
to diminish unwanted frequency jumps. Asynchronous powerdown mode occurs if R18 bit is HIGH and N20 bit is
HIGH.
When the PLL goes to either synchronous or asynchronous powerdown mode, preamp becomes debiased, R & N
counters keeps their load conditions and the charge pump becomes high impedance state. The oscillator circuitry
function becomes disabled only when both IF and RF powerdown bits are activated, i.e. N20 HIGH.
The PLL returns to an active powerup mode when N20 bit becomes LOW(either in synchronous or asynchronous
modes).
Phase Detector and Charge pump Characteristics
Phase difference detection range : -2
When R16 = HIGH
18
Powerdown mode operation
R18
0
1
0
1
CPo
LD
fp
fr
N20
0
0
1
1
fr>fp
(Continued)
to +2
PLL active
PLL active, only charge pump high impedance
Synchronous powerdown
Asynchronous powerdown
fr=fp
fr<fp
Powerdown mode status
fr<fp
fr<fp
INTERGER RF/IF DUAL PLL