2.8 R7 REGISTER

REGISTER 23 22 21 20 19 18 17 16 15 14

13

12 11 10 9 8

7

6

5

4

3210

Data[19:0]

C3 C2 C1 C0

R7

0000000000 DIV4 0

1

0 0 0 IF_RST RF_RST IF_CPT RF_CPT

1111

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

IF PLL N and R Counters

IF PLL Charge Pump

0 (Default)

Normal Operation

Normal Operation

1

Counter Reset

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

RF PLL N and R Counters

RF PLL Charge Pump

0 (Default)

Normal Operation

Normal Operation

1

Counter Reset

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

RF PLL N and R Counters

RF PLL Charge Pump

0 (Default)

Normal Operation

Normal Operation

1

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

IF PLL N and R Counters

IF PLL Charge Pump

0 (Default)

Normal Operation

Normal Operation

1

Normal Operation

Tri-State

www.national.com

36