RFRXD0420 datasheet(2/32 Pages) MICROCHIP

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rfRXD0420/0920

DS70090A-page 2

Preliminary

 2003 Microchip Technology Inc.

1.0

DEVICE OVERVIEW

The rfRXD0420/0920 are low cost, compact single

frequency short-range radio receivers requiring only a

minimum number of external components for a

complete receiver system. The rfRXD0420 covers the

receive frequency range of 300 MHz to 450 MHz and

the rfRXD0920 covers 800 MHz to 930 MHz. The

rfRXD0420 and rfRXD0920 share a common architec-

ture. They can be configured for Amplitude Shift Keying

(ASK), Frequency Shift Keying (FSK), or FM modula-

tion. The rfRXD0420/0920 are compatible with rfPIC™

and rfHCS series of RF transmitters.

• High frequency stability over temperature and

power supply variations

• Low spurious signal emission

• High large-signal handling capability with

selectable LNA gain control for improved dynamic

range

• Selectable IF bandwidth via external low cost

ceramic IF filter. The IF Frequency range is

selectable between 455 kHz to 21.4 MHz. This

facilitates the use of readily available low cost

10.7 MHz ceramic IF filters in a variety of

bandwidths.

• ASK or FSK for digital data reception

• FM modulation for analog signal reception

• FSK/FM demodulation using quadrature detector

(phase coincidence detector)

• Received Signal Strength Indication (RSSI) for

signal strength indication and ASK detection

• Wide supply voltage range

• Low active current consumption

• Very low standby current

The rfRXD0420/0920 is a single conversion superhet-

erodyne architecture. A block diagram is illustrated in

Figure 1-1. The rfRXD0420/0920 consists of:

• Low-noise amplifier (LNA) - Gain selectable

• Mixer for down-conversion of the RF signal to the

Intermediate Frequency (IF) followed by an IF

preamplifier

• Fully integrated Phase-Locked Loop (PLL)

frequency synthesizer for generation of the Local

Oscillator (LO) signal. The frequency synthesizer

consists of:

- Crystal oscillator

- Phase-frequency detector and charge pump

- High-frequency Voltage Controlled Oscillator

(VCO)

- Fixed feedback divider

- rfRXD0420 = divide by 16

- rfRXD0920 = divide by 32

• IF limiting amplifier to amplify and limit the IF

signal and for Received Signal Strength Indication

(RSSI) generation

• Demodulator (DEMOD) section consists of a

phase detector (MIXER2) and amplifier creating a

quadrature detector (also known as a phase

coincidence detector) to demodulate the IF signal

in FSK and FM modulation applications

• Operational amplifier (OPA) that can be config-

ured as a comparator for ASK or FSK data

decision or as a filter for FM modulation.

• Bias circuitry for bandgap biasing and circuit

shutdown

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