LMX2335TM datasheet(10/18 Pages) NSC

10 / 18 page

Functional Description (Continued)

TABLE 1. Programmable Modes

R16

R17

R18

R19

R20

RF2 Phase

Detector Polarity

RF2 I

CPo

RF2 D

TRI-STATE

RF2 LD

RF2 F

RF1 Phase

Detector Polarity

RF1 I

CPO

RF1 D

TRI-STATE

RF1 LD

RF1 F

N19

N20

RF2

Prescaler

Pwdn

RF2

RF1

Prescaler

Pwdn

RF1

TABLE 2. Mode Select Truth Table

Phase Detector Polarity

(Note 7)

oTRI-STATE

CPo

(Note 5)

RF1

Prescaler

RF2

Prescaler

Pwdn

(Note 6)

Negative

Normal Operation

LOW

64/65

pwrd up

Positive

TRI-STATE

HIGH

128/129

pwrd dn

Note 5: The ICPo LOW current state = 1/4xICPo HIGH current.

Note 6: Activation of the RF2 PLL or RF1 PLL powerdown modes result in the disabling of the respective N counter divider and debiasing of its respective fIN inputs

(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

both RF2 and RF1 powerdown bits are activated. The OSCin is connected to VCC through 100 kΩ resistor and the OSCout goes HIGH when this con-

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

oLD Output Truth Table

RF1 R[19]

(RF1 LD)

RF2 R[19]

(RF2 LD)

RF1 R[20]

(RF1 F

RF2 R[20]

(RF2 F

oLD

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)

RF2 Reference Divider Output

RF1 Reference Divider Output

RF2 Programmable Divider Output

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

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