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TH7107

315/433MHz FSK/FM/ASK Transmitter

Melexis Microelectronic Systems  

TH7107

315/433MHz

FSK/FM/ASK Transmitter

1 Theory of Operation

1.1 General

As depicted in Fig.1, the TH7107 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. An external loop filter

at pin LF determines the dynamic behavior of the PLL and suppresses reference spurious signals. The

VCO’s output signal feeds the power amplifier (PA). RF signal power Po can be adjusted in six steps from

Po = –12 dBm to +2 dBm either by changing the value of resistor RPS or by varying the voltage VPS at pin

PS. The open-collector differential output (OUT1, OUT2) can be used to either directly drive a loop antenna

or to be converted to a single-ended impedance by means of a balanced-to-unbalanced (balun) transformer.

For maximum available output power, the differential output should be matched to a load of about 1 kΩ.

Bandgap biasing ensures stable operation of the IC at a power supply range of 2.2 V to 5.5 V.

1.2 Block Diagram

VCC 10

CKOUT

8

div 4

RO1

5

XTAL

RO2

CX2 4

CX1

XOSC

3 DATA

VCC 15

div32

PFD

charge

pump

RPS

PS 9

PA

VCO

mode

control

VEE

14

OUT1

13

OUT2

12

VEE

11

antenna

or

balun VCC

ENCK

7

ENTX

6

1 LF1

CF1

RF1

16 LF2 2 SUB

CF2

Fig. 1: Block diagram with external components

3901007107

Rev. 008

Page 3 of 16

Data Sheet

May/03

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