TH72002

315MHz

ASK Transmitter

3901072002

Page 3 of 20

Data Sheet

Rev. 007

June/07

1

Theory of Operation

1.1

General

As depicted in Fig.1, the TH72002 transmitter consists of a fully integrated voltage-controlled oscillator

(VCO), a divide-by-32 divider (div32), a phase-frequency detector (PFD) and a charge pump (CP). An inter-

nal loop filter determines the dynamic behavior of the PLL and suppresses reference spurious signals. A

Colpitts crystal oscillator (XOSC) is used as the reference oscillator of a phase-locked loop (PLL) synthe-

or to be matched to a 50Ohm load. Bandgap biasing ensures stable operation of the IC at a power supply

range of 1.95 V to 5.5 V.

1.2

Block Diagram

Fig. 1:

Block diagram with external components

VEE

XOSC

PA

XBUF

VCO

PLL

CP

PFD

32

PSEL

RPS

ROI

XTAL

8

5

3

2

antenna

matching

network

OUT

7

CX1

1

ASKDTA

6

VCC

mode

control

ENTX

4

low

voltage

detector