TABLE 1. Programmable Modes

C1

C2

R16

R17

R18

R19

R20

0

0

RF2 Phase

Detector Polarity

RF2 I

CPo

RF2 D

o

TRI-STATE

RF2 LD

RF2 F

o

0

1

RF1 Phase

Detector Polarity

RF1 I

CPO

RF1 D

o

TRI-STATE

RF1 LD

RF1 F

o

C1

C2

N19

N20

10

RF2

Prescaler

Pwdn

RF2

11

RF1

Prescaler

Pwdn

RF1

TABLE 2. Mode Select Truth Table

Phase Detector Polarity

(Note 7)

D

I

CPo

(Note 5)

RF1

Prescaler

RF2

Prescaler

Pwdn

(Note 6)

0

Negative

Normal Operation

LOW

64/65

64/65

pwrd up

1

Positive

TRI-STATE

HIGH

128/129

128/129

pwrd dn

(to a high impedance state). The powerdown function is gated by the charge pump to prevent unwanted frequency jumps. Once the powerdown program mode is

loaded, the part will go into powerdown mode when the charge pump reaches a TRI-STATE condition. The R counter and Oscillator functionality does not become

disabled until

dition exists. The MICROWIRE control register remains active and capable of loading and latching data during all of the powerdown modes.

Note 7: PHASE DETECTOR POLARITY

Depending upon VCO characteristics, the R16 bits should be set accordingly:

When VCO characteristics are positive like (1), R16 should be set HIGH;

When VCO characteristics are negative like (2), R16 should be set LOW.

Note 8:

TABLE 3. The F

RF1 R[19]

(RF1 LD)

RF2 R[19]

(RF2 LD)

RF1 R[20]

(RF1 F

RF2 R[20]

(RF2 F

F

Output State

0000

Disabled (Note 9)

0100

RF2 Lock Detect (Note 10)

1000

RF1 Lock Detect (Note 10)

1100

RF1/RF2 Lock Detect (Note 10)

X

0

0

1

RF2 Reference Divider Output

X

0

1

0

RF1 Reference Divider Output

X

1

0

1

RF2 Programmable Divider Output

X

1

1

0

RF1 Programmable Divider Output

0011

Fastlock (Note 11)

0111

For Internal use only

1011

For Internal use only

1111

Counter Reset (Note 12)

X — don’t care condition

VCO Characteristics

DS012332-7

www.national.com

10