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TH7111: DescriptionFSK /FM/ASK Receiver; File Size706KB，20 Pages; ManufacturerETC

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TH7111 Overview

FSK /FM/ASK Receiver

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TH7111

868/915MHz

FSK/FM/ASK Receiver

Features

Double superhet architecture for high degree of image rejection

FSK for digital data and FM reception for analog signal transmission

FM/FSK demodulation either with phase-coincidence or PLL demodulator

Low current consumption in active mode and very low standby current

Switchable LNA gain for improved dynamic range

AFC feature allows wide carrier frequency acceptance range

RSSI allows signal strength indication and ASK detection

Surface mount package LQFP44

Ordering Information

Part No.

TH7111

Temperature Range

-40 °C to 85 °C

Package

LQFP44

Application Examples

General digital and analog 868 MHz or 915 MHz ISM band usage

Low-power telemetry

Alarm and security systems

Keyless car and central locking

Pagers

Technical Data Overview

Input frequency range: 800 MHz to 930 MHz

Power supply range: 2.5 V to 5.5 V for double conversion and 3.3 V to 5.5 V for single conversion

Temperature range: -40 °C to +85 °C

Operating current: 7.5 mA at low gain and 9.2 mA at high gain mode

Standby current: < 100 nA

with 40 kHz second IF filter BW (incl. SAW front-end filter loss)

Sensitivity: -109 dBm

Sensitivity: -102 dBm with 150 kHz second IF filter BW (incl. SAW front-end filter loss)

Range of first IF: 10 MHz to 80 MHz

Range of second IF: 455 kHz to 21.4 MHz

Maximum input level: –10 dBm at ASK and 0 dBm at FSK

Image rejection: > 65 dB (e.g. with SAW front-end filter and at 10.7 MHz 2 IF)

Spurious emission: < -70 dBm

Input frequency acceptance:

±50

kHz (with AFC option)

RSSI range: 70 dB

Frequency deviation range:

±5

kHz to

±120

kHz

Maximum data rate: 80 kbit/s NRZ

Maximum analog modulation frequency: 15 kHz

8 kHz FSK deviation, BER = 3⋅10 and phase-coincidence demodulation

-3

50 kHz FSK deviation, BER = 3⋅10 and phase-coincidence demodulation

-3

TH7111 Data Sheet

3901007111

Page 1 of 20

Nov. 2001

Rev. 005

TH7111

868/915MHz

FSK/FM/ASK Receiver

General Description

The TH7111 receiver IC consists of the following building blocks:

PLL synthesizer (PLL SYNTH) for generation of the first and second local oscillator signals LO1 and LO2

Parts of the PLL SYNTH are the high-frequency VCO1, the feedback dividers DIV_16 and DIV_2,

a phase-frequency detector (PFD) with charge pump (CP) and a crystal-based reference oscillator (RO)

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

First mixer (MIX1) for down-conversion of the RF signal to the first IF (IF1)

second mixer (MIX2) for down-conversion of the IF1 to the second IF (IF2)

IF amplifier (IFA) to amplify and limit the IF2 signal and for RSSI generation

Phase coincidence demodulator (DEMOD) with third mixer (MIX3) to demodulate the IF signal

Operational amplifier (OA) for data slicing, filtering, ASK detection and automatic-frequency control (AFC)

Bias circuitry for bandgap biasing and circuit shutdown

With the TH7111 receiver chip, various circuit configurations can be arranged in order to meet a number of

different customer requirements. For FM/FSK reception the IF tank used in the phase coincidence demodu-

lator can be constituted either by a ceramic resonator or an LC tank (optionally with varactor to create an AFC

circuit). In PLL demodulator configuration, the multiplier MIX3 forms a phase comparator. In ASK configurati-

on, the RSSI signal is feed to an ASK detector, which is constituted by the operational amplifier. The second

VCO (VCO2) can be used either as the VCO of a PLL demodulator or as the LO2 source of a second exter-

nal PLL in a multi-channel system. The following table briefly summarizes the various configurations.

Single-conversion configuration

FM/FSK

ASK

RX with RSSI-based demodulation

narrow-band RX with ceramic demodulation

tank

wide-band RX with LC demod. tank and AFC

Double-conversion configuration

narrow-band RX with ceramic demodulation

tank

wide-band RX with LC demod. tank and AFC

multi-channel RX with ceramic demodulation

tank and external channel synthesizer

RX with RSSI-based demodulation

RX with RSSI-based demodulation and exter-

nal channel synthesizer

extended sensitivity RX with PLL demodulator extended sensitivity RX with PLL demodulator

The preferred superheterodyne configuration is

double conversion

where MIX1 and MIX2 are driven by the

internal local oscillator signals LO1 and LO2, respectively. This allows a

high degree of image rejection,

achieved in conjunction with an RF front-end filter. Efficient RF front-end filtering is realized by using a SAW,

ceramic or helix filter in front of the LNA and by adding a LC filter at the LNA output.

It is also possible to use the TH7111 in

single-conversion

configuration. This can be achieved by switching

the LO2 input of MIX2 from the on-chip PLL synthesizer to the pin IN_MIX2 by means of an internal switch

(done via pin SW_MIX2). Now MIX2 operates as an amplifier for the IF1 signal if an external pull-down re-

sistor at pin IN_MIX2 is added.

The same setting of MIX2 can be used for

multi-channel applications.

In this situation IN_MIX2 must be

driven by an external LO2 signal. This signal can be generated by the VCO2, which is mainly a bipolar tran-

sistor that can be configured as a varactor-tuned VCO. Furthermore, a second external PLL for channel

selection via LO2 tuning is required. This may be arranged by using a PLL synthesizer chip that can be con-

trolled through a 3-wire bus serial interface. The reference signal for the external PLL synthesizer can be

directly taken from the crystal-based reference oscillator RO.

TH7111 Data Sheet

3901007111

Page 2 of 20

Nov. 2001

Rev. 005

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