REV. B

ADF4252

–5–

PIN FUNCTION DESCRIPTIONS

Mnemonic

Function

RF Charge Pump Output. This is normally connected to a loop filter that drives the input to an external VCO.

RF Charge Pump Ground.

Input to the RF Prescaler. This small signal input is normally taken from the VCO.

MUXOUT

This multiplexer output allows either the RF or IF lock detect, the scaled RF or IF, or the scaled reference fre-

quency to be accessed externally.

100 k

Ω. This input can be driven from a TTL or CMOS crystal oscillator.

Reference Output.

Digital Ground for the Fractional Interpolator.

CLK

Serial Clock Input. This serial clock is used to clock in the serial data to the registers. The data is latched into the

shift register on the CLK rising edge. This input is a high impedance CMOS input.

DATA

Serial Data Input. The serial data is loaded MSB first with the three LSBs being the control bits. This input is a

high impedance CMOS input.

LE

Load Enable, CMOS Input. When LE goes high, the data stored in the shift registers is loaded into one of the

seven latches, the latch being selected using the control bits.

Connecting a resistor between this pin and ground sets the minimum charge pump output current. The relationship

I

R

CP

SET

1 6875

.

Input to the IF Prescaler. This small signal input is normally taken from the IF VCO.

Positive Power Supply for the Fractional Interpolator Section. Decoupling capacitors to the ground plane should

IF Charge Pump Output. This is normally connected to a loop filter that drives the input to an external VCO.

Positive Power Supply for the RF Digital Section. Decoupling capacitors to the ground plane should be placed as close

± 10%. V

Positive Power Supply for the RF Analog Section. Decoupling capacitors to the ground plane should be placed as close

RF Charge Pump Power Supply. Decoupling capacitors to the ground plane should be placed as close as possible