Philips Semiconductors

Objective specification

SA9024

900 MHz transmit modulator and 1.3 GHz

fractional–N synthesizer

1997 Aug 01

19

SR01451

R

X

P

N

REF DIVIDER

AUX/MAIN

DIVIDER

D

Q

CLK

“1”

R

D

R

CLK

“1”

X

Q

N

P

τ

GND

PH

P–TYPE

CHARGE PUMP

N–TYPE

CHARGE PUMP

R

INR

INR

Figure 9.

Phase Detector Structure With Timing

Main Output Charge Pumps and Fractional

Compensation Currents

The main charge pumps on pin PHP and PHI are driven by the main

phase detector. The current value is determined by the current at

pin RN. The fractional compensation current is linearly dependent

on the main charge pump current and its level relative to the main

charge pumps is set by an 8-bit programmable DAC. The timing for

the fractional compensation is derived from the main divider. The

shows the waveforms (not to scale) for a typical base.