SA9025 データシートの表示（PDF） - Philips Electronics

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SA9025

900 MHz transmit modulator and 2.2 GHz fractional–N synthesizer

Philips Electronics 

Philips Semiconductors

900 MHz transmit modulator and 2.2 GHz

fractional–N synthesizer

Objective specification

SA9025

CLOCK

DATA

STROBE

TEMPORARY REGISTER

TXEN

WORKING REGISTER

SE

(2)

DQ

CLK

Q

R

D RQ

CLK

Q

(1)

VCC

D

CLK

R

(2)

QQ

SYNEN

Figure 6. Transmit Offset Synthesizer Reset Circuit

SR01449

In Figure 6, the falling edge of the strobe and address, inverted,

toggles the Q output of flip-flop (1) to a ‘1’ state, enabling the phase

detector, VCO, divide by M, TXIF buffer and SSB up-converter.

Approximately 80µs after the synthesizer is locked, the TXEN signal

(enabled = 1) turns on the modulator and variable gain amplifier.

The rising edge of TXEN has no effect on SYNEN, however, the

falling (rising inverted) edge toggles the Q output of D flip-flop (2) to

a ‘0’ state. This disables the synthesizer, modulator and variable

gain amplifier. To insure that slow edges on TXEN do not cause

improper operation, the TXEN is a Schmitt trigger design.

The address decoder for program word ‘D’ ANDed together with the

strobe is used to load the contents of the temporary register into the

working registers. D flip-flop (3) is used to prevent multiple strobe

and address pulses in the event the address decoder output toggles

on garbage bits during the time the strobe remains in a ‘1’ state.

The temporary register is common to the transmit offset synthesizer,

main channel synthesizer and auxiliary synthesizer.

1997 Aug 01

13

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