Baseband Processor For Mixed Mode Land Mobile Radio
CMX880
1.4
External Components
Figure 2 and Figure 3 show the recommended external component configuration and power supply de-coupling
and connections.
VDD(D)
R1
FSB_SYNC_OUT
FSB_DATA_OUT
IRQN
FSB_CLOCK
FSB_SYNC_IN
FSB_DATA_IN
CLOCK_OUT
CLOCK/XTAL
VDD(D)
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Fast Serial Bus
Interface
2
3
X1
REPLY_DATA
VSS(D)
4
"C-BUS"
Interface
5
VSS(D)
SERIAL_CLOCK
CMD_DATA
CSN
6
C2
CMX880
AUDIO
R2
Loudspeaker amp
7
VSS(A)
8
VSS(A)
MOD_2
R3
R4
Modulator reference
Modulator control
FM
9
Discriminator
VBIAS
MOD_1
R5
C5
C7
10
11
12
13
14
FM_DISC
FM_DISC_FB
MIC_1
VDD(A)
C1
C3
C4
R6
R8
RSSI
MIC_2_FB
MIC_2
VSS(A)
MIC_1_FB
C9
C8
C6
R9
R7
Microphone 1
Microphone 2
R10
Figure 2 Recommended External Components
X1 15.36MHz See note 1
R1 100kW
R2 100kW
R5 See note 2
R6 100kW
R9 See note 3
R10 100kW
R3 100kW
R4 100kW
R7 See note 3
R8 100kW
C1 100pF
C2 1nF
C3 100pF
C4 100pF
C5 100pF
C6 See note 4
C7 200pF
C8 See note 4
C9 200pF
Resistors ±5%, capacitors ±20% unless otherwise stated.
Notes
1. X1 can be a crystal or a temperature compensated clock generator; this will depend on the application. The
clock drift requirement is defined in section 1.7.1. The tracks between the crystal pins and pin 24 and pin 5
should be as short as possible to ensure maximum achievable stability.
2. R5 should be selected to provide the desired dc gain of the FM discriminator input, as follows:
R5 = 100kW / ½GAINFM Disc
½
The gain should be such that the resultant output at the FM_DISC_FB pin is within the FM discriminator
input signal range specified in section 1.7.1.
3. R7 and R9 should be selected to provide the desired dc gain (assuming C6 and C8 are not present) of the
microphone inputs as follows:
R7 = 100kW / ½GAINMic1
½
R9 = 100kW / ½GAINMic2
½
The gain should be such that the resultant outputs at the MIC_1_FB and MIC_2_FB pins are within the
microphone input signal range specified in section 1.7.1.
ã 2001 Consumer Microcircuits Limited
7
D/880/1
CMLMICRO [ CML MICROCIRCUITS ]
