TH7120

300 to 930MHz

FSK/FM/ASK Transceiver

3901007120

Page 2 of 28

Data Sheet

Rev. 005

Jan. 2002

PR

EL

IM

INA

RY

General Description

The TH7120 is a single chip FSK/FM/ASK transceiver IC. It is designed to operate in low-power multi-channel

programmable or single-channel stand-alone, half-duplex data transmission systems. It can be used for ISM,

SRD or any other application operating in the frequency ranging of 300 MHz to 930 MHz.

The TH7120 transceiver IC consists of the following building blocks:

"

Low-noise amplifier (LNA) for high-sensitivity RF signal reception with switchable gain

"

Mixer (MIX) for RF-to-IF down-conversion

"

IF amplifier (IFA) to amplify and limit the IF signal and for RSSI generation

"

Phase-coincidence demodulator with external ceramic discriminator (FSK Demodulator)

"

Operational amplifier, connected to demodulator output (OA1)

"

Operational amplifier, integrator circuit at FSK-AFC mode (OA2)

"

Control logic with 3wire bus serial control interface (SCI)

"

Reference oscillator (RO) with external crystal

"

Reference divider (R counter)

"

Programmable divider (N/A counter)

"

Phase-frequency detector (PFD)

"

Charge pump (CP)

"

Voltage control oscillator (VCO) with internal varactor

"

Power amplifier (PA) with adjustable output power

The transceiver can be used either as a 3wire-bus-controlled programmable or as a stand-alone fixed-

frequency device. After power up, the transceiver is set to fixed-frequency mode. In this mode, pins

The logic levels at pins FS0/SDEN and FS1/LD must not be changed after power up in order to remain in

fixed-frequency mode.

Channel frequency

433.92 MHz

868.3 MHz

315.0 MHz

915.0 MHz

FS0/SDEN

10

1

0

FS1/LD

00

1

1

After the first logic level change at pin FS0/SDEN, the transceiver enters into programmable mode while pin

FS1/LD is now a PLL lock detector output. In this mode, the user can set any PLL frequency or mode of op-

eration by the SCI.

In the fixed-frequency mode, the user can set the transceiver to Standby, Receive, Transmit or Idle (only PLL

synthesizer active) mode via control pins RE/SCLK and TE/SDTA.

Operation mode

Standby

Receive

Transmit

Idle

RE/SCLK

01

0

1

TE/SDTA

00

1

1