© 2008 Microchip Technology Inc. Advance Information DS70329B-page 7
MRF24J40MA
2.0 CIRCUIT DESCRIPTION
The MRF24J40MA is a complete 2.4 GHz IEEE
Std. 802.15.4™ compliant surface mount module with
integrated crystal, internal voltage regulator, matching
circuitry and PCB antenna. The MRF24J40MA module
interfaces to many popular Microchip PIC micro-
controllers via a 4-wire serial SPI interface, interrupt,
wake, Reset, power and ground. Data communications
with the MRF24J40MA module are documented in the
“MRF24J40 IEEE 802.15.4™ 2.4 GHz RF Transceiver
Data Sheet” (DS39776). Refer to the MRF24J40 Data
Sheet for specific serial interface protocol and register
definitions.
2.1 Schematic
A schematic diagram of the module is shown in
Figure 2-1 and the Bill of Materials (BOM) is shown in
Table 2-1.
The MRF24J40MA module is based on the Microchip
Technology MRF24J40 IEEE 802.15.4™ 2.4 GHz RF
Transceiver IC. The serial I/O (SCK, SDI, SDO and
CS
), RESET, WAKE and INT pins are brought out to
the module pins. The SDO signal is tri-state buffered by
IC2 to solve a silicon errata, where the SDO signal
does not release to a high-impedance state, after the
CS pin returns to its inactive state. Crystal, X1, is a
20 MHz crystal with a frequency tolerance of
±10 ppm @ 25°C to meet the IEEE Std. 802.15.4
symbol rate tolerance of ±40 ppm. A balun is formed by
components: L1, L3, C2 and C14. L2 is an RF choke
and pull-up for the RFP and RFN pins on the
MRF24J40. C15 is a DC block capacitor. A low-pass
filter is formed by components: L4, C16 and C17. The
remaining capacitors provide RF and digital bypass.
