MC13211 Datasheet, PDF (66/70 Pages) Freescale Semiconductor, Inc – ZigBee™- Compliant Platform - 2.4 GHz Low Power Transceiver for the IEEE® 802.15.4 Standard plus Microcontroller

• When the MCU is used in low power modes, be sure that all unused IO are programmed properly
for low power operation (typically best case is as outputs in the low state). The MC1321x is
commonly used with the Freescale MC9S08GT/GB 8-bit devices. For these MCUs:
— Use only STOP2 and STOP3 modes (not STOP1) with these devices where the GPIO states are
retained. The MCU must retain control of the MC1321x IO during low power operation.
— As stated above all unused GPIO should be programmed as outputs low for lowest power and
no floating inputs.
— The MCU has IO signals that are not pinned-out on the package. These signals must also be
initialized (even though they cannot be used) to prevent floating inputs.
7.3 RF Single Port Application with an F Antenna
Figure 35 shows a typical single port RF application topology in which part count is minimized and a
printed copper F antenna is used for low cost. Only the RFIN port of the MC1321x is required because the
differential port is bi-directional and uses the on-chip T/R switch. Matching to near 50 Ohms is
accomplished with L1, L2, L3, and the traces on the PCB. A balun transforms the differential signal to
single-ended to interface with the F antenna.
The proper DC bias to the RFIN_x (PAO_x) pins is provided through the balun. The CT_Bias pin provides
the proper bias voltage point to the balun depending on operation, that is, CT_Bias is at VDDA voltage for
transmit and is at ground for receive. CT_Bias is switched between these two voltages based on the
operation. Capacitor C2 provides some high frequency bypass to the dc bias point. The L3/C1 network
provides a simple bandpass filter to limit out-of-band harmonics from the transmitter.
NOTE
Passive component values can vary as a function of circuit board layout as
required to obtain best matching and RF performance.
U1
44
GPIO1
39
PAO_M
PAO_P
38
RFIN_P
RFIN_M
CT_Bias
36
35
34
MC1321x
L1
1.5nH
L4
1.5nH
L2
3.9nH
Z1
3
1
2
5
4
6
LDB212G4005C-001
L3
3.9nH
C1
1.0pF
R1
0R
R2
0R
Not Mounted
ANT1
F_Antenna
C2
10pF
Figure 35. RF Single Port Application with an F-Antenna
2
3
J1
4
SMA_edge_Receptacle_Female
5
MC13211/212/213 Technical Data, Rev. 1.5
66
Freescale Semiconductor