10.25 MHz
NOTE 8
R1
+5V
MCU
SPECIAL DIGITAL
INPUT WITH
GENERAL-PURPOSE
DIGITAL INPUT
SWITCHPOINT AT
33% OF VDD
ANALOG INPUTS
(SIGNAL LEVEL, ETC.)
AM SECOND I.F. (450 kHz)
FM I.F. (10.7 MHz)
NOTE 5
+5V
NOTE 7
MC145173
1 OSCin
OSCout 24
2 ENB
REFout 23
3 Din
4 CLK
5
Dout
6
INPUT D
7
INPUT C
8
INPUT B
9
INPUT A
10
HF IFin
11
VHF IFin
12
OUTPUT A
OUTPUT D 22
21
VHF PDout
20
Rx
VSS 19
HF PDout 18
VDD 17
HFin 16
VHFin 15
OUTPUT C 14
OUTPUT B 13
NOTE
6
+5V
+5V
RBIAS
10.25 MHz
BUFFERED
OUTPUT
(AM SECOND L.O.)
GENERAL-PURPOSE
DIGITAL OUTPUT
LOW–PASS
FILTER
0.1 µF + 5 V
NOTE 3
OPTIONAL
GAIN
BLOCK
15 kΩ
LOW-PASS
FILTER
NOTE 3
OPTIONAL GAIN BLOCK
HF
VCO
AM FIRST L.O.
VHF
VCO
FM L.O.
GENERAL PURPOSE DIGITAL OUTPUTS
NOTES:
1. The HF PDout and VHF PDout pins require different low-pass filters. See the Phase-Locked Loop – Low-Pass Filter Design page for
more information.
2. For optimum performance, bypass the VDD pin to VSS with a low-inductance capacitor.
3. The gain blocks can be simple one-transistor circuits. See Figures 28 and 29.
4. For the AM band, an R counter divide ratio of 1,025 is used for 10 kHz tuning resolution. The FM band uses an R counter ratio of 205 for
50 kHz tuning resolution.
5. I.F. (intermediate frequency) signals are fed to pins 10 and 11 only if seek or scan feature is included in radio.
6. Diode string is used to limit voltage swing at pin 23; additional or fewer diodes may be used. For full rail-to-rail swing, tie R1 to VSS
(GND) and delete the diodes and the RBIAS resistor. Caution: this large signal swing may cause a high level of EMI (electromagnetic
interference).
7. Pull-up voltage must be at the same potential as the VDD pin or less. Pull-up device other than a resistor may be used.
8. A 10.25 MHz crystal facilitates design of the AM upconversion scheme shown. This results in double conversion for the AM receiver. Op-
tionally, single-conversion designs may be used which offer more flexibility on reference crystal values. For example, a 10.0 MHz crystal
could be used which would allow higher-performance 200 kHz tuning resolution for FM.
Figure 26. AM-FM Broadcast Receiver Subsystem — USA
MC145173
28
MOTOROLA