MRF24J40_08 Datasheet, PDF (7/152 Pages) Microchip Technology – IEEE 802.15.4™ 2.4 GHz RF Transceiver

2.0 HARDWARE DESCRIPTION
2.1 2.1 Overview
The MRF24J40 is an IEEE 802.15.4 Standard
compliant 2.4 GHz RF transceiver. It integrates the
PHY and MAC functionality in a single chip solution.
Figure 2-1 is a block diagram of the MRF24J40
circuitry.
A frequency synthesizer is clocked by an external
20 MHz crystal and generates a 2.4 GHz RF frequency.
The receiver is a low-IF architecture consisting of a Low
Noise Amplifier (LNA), down conversion mixers, poly-
phase channel filters and baseband limiting amplifiers
with a Receiver Signal Strength Indicator (RSSI).
The transmitter is a direct conversion architecture with
a 0 dBm maximum output (typical) and 36 dB power
control range.
An internal Transmit/Receive (TR) switch combines the
transmitter and receiver circuits into differential RFP
and RFN pins. These pins are connected to impedance
matching circuitry (balun) and antenna. An external
Power Amplifier (PA) and/or LNA can be controlled via
the GPIO pins.
MRF24J40
Six General Purpose Input/Output (GPIO) pins can be
configured for control or monitoring purposes. They
can also be configured to control external PA/LNA RF
switches.
The power management circuitry consists of an
integrated Low Dropout (LDO) voltage regulator. The
MRF24J40 can be placed into a very low-current (2 μA
typical) Sleep mode. An internal 100 kHz oscillator or
32 kHz external crystal oscillator can be used for Sleep
mode timing.
The Media Access Controller (MAC) circuitry verifies
reception and formats for transmission IEEE 802.15.4
Standard compliant packets. Data is buffered in Trans-
mit and Receive FIFOs. Carrier Sense Multiple
Access-Collision Avoidance (CSMA-CA), superframe
constructor, receive frame filter and security engine
functionality are implemented in hardware. The
security engine provides hardware circuitry for
AES-128 with CTR, CCM and CBC-MAC modes.
Control of the transceiver is via a 4-wire Serial Peripheral
Interface (SPI), interrupt, wake and Reset pins.
© 2008 Microchip Technology Inc.
Preliminary
DS39776B-page 5