LMX2485_08 Datasheet, PDF (37/40 Pages) National Semiconductor (TI) – 50 MHz - 3.0 GHz High Performance Delta-Sigma Low Power Dual PLLatinum™ Frequency Synthesizers with 800MHz Integer PLL

2.8 R7 REGISTER
RE 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
GI
ST
ER
Data[19:0]
R7 0 0 0 0 0 0 0 0 0 0 DIV 0 1 0 0
4
876543210
C3 C2 C1 C0
1 IF_ RF IF_ RF 1 1 1 1
RS _R CP _C
T ST T PT
2.8.1 DIV4 -- RF Digital Lock Detect Divide By 4
Because the digital lock detect function is based on a phase error, it becomes more difficult to detect a locked condition for larger
comparison frequencies. When this bit is enabled, it subdivides the RF PLL comparison frequency (it does not apply to the IF
comparison frequency) presented to the digital lock detect circuitry by 4. This enables this circuitry to work at higher comparison
frequencies. It is recommended that this bit be enabled whenever the comparison frequency exceeds 20 MHz and RF digital lock
detect is being used.
2.8.2 IF_RST -- IF PLL Counter Reset
When this bit is enabled, the IF PLL N and R counters are reset, and the charge pump is put in a Tri-State condition. This feature
should be disabled for normal operation. Note that a counter reset is applied whenever the chip is powered up via software or CE
pin.
IF_RST
0 (Default)
1
IF PLL N and R Counters
Normal Operation
Counter Reset
IF PLL Charge Pump
Normal Operation
Tri-State
2.8.3 RF_RST -- RF PLL Counter Reset
When this bit is enabled, the RF PLL N and R counters are reset and the charge pump is put in a Tri-State condition. This feature
should be disabled for normal operation. This feature should be disabled for normal operation. Note that a counter reset is applied
whenever the chip is powered up via software or CE pin.
RF_RST
0 (Default)
1
RF PLL N and R Counters
Normal Operation
Counter Reset
RF PLL Charge Pump
Normal Operation
Tri-State
2.8.4 RF_TRI -- RF Charge Pump Tri-State
When this bit is enabled, the RF PLL charge pump is put in a Tri-State condition, but the counters are not reset. This feature is
typically disabled for normal operation.
RF_TRI
0 (Default)
1
RF PLL N and R Counters
Normal Operation
Normal Operation
RF PLL Charge Pump
Normal Operation
Tri-State
2.8.5 IF_TRI -- IF Charge Pump Tri-State
When this bit is enabled, the IF PLL charge pump is put in a Tri-State condition, but the counters are not reset. This feature is
typically disabled for normal operation.
IF_TRI
0 (Default)
1
IF PLL N and R Counters
Normal Operation
Normal Operation
IF PLL Charge Pump
Normal Operation
Tri-State
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