CMX838D1 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838D1' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
6.4.4 Synthesizer and Charge Pump
The Synthesizer and Charge Pump section reduces component cost and size when compared with non-
integrated alternatives. It also provides a simpler programming interface because it is focused on FRS
applications. When combined with an external VCO and related circuits its features include:
• Pre-programmed support for FRS, PMR446 and GMRS RF standard frequencies via simple ‘channel
select’ commands.
• Lock detect function with IRQ indication, if enabled.
• Direct control of synthesizer values for more flexible operation, if desired.
• Support for several REFIN reference clock frequencies.
• Charge pump programmed via a combination of a two state internal selection and an external charge
current setting resistor.
• Charge pump polarity control via serial command.
• Integrated voltage reference provides constant charge pump current without requiring an external voltage
regulator.
REFIN 11
+RFIN 9
+
-RFIN 8
-
divide
32/33
12 bit programmable
reference counter
programmable divider
phase
detect
lock
detect
voltage ref
charge
pump
CPOUT 5
ISET 6
Figure 39: Synthesizer and Charge Pump
6.4.5 Clock Generation
The Clock Generation section develops internal clocks to operate the Audio Processing,
Tone Signaling Processor and Level Control sections. The clock source can be externally supplied or
internally developed from an external crystal (attached to pins 12 and 13) or from a REFIN clock signal applied
to the Synthesizer & Charge Pump. When the latter is used, the external crystal can be omitted to save cost
and space. Several crystal and REFIN clock frequencies are supported.
Clock generation also includes a timer that is used in both RX and TX modes. In RX mode it operates as a
Notone timer to qualify when a received subaudio tone has been removed. In TX mode it serves to time a
transmission’s duration.
attach
optional
crystal
XTAL 12
XTAL 13
RX Notone / TX Duration
timer
Baseband timing generation
internal
clocks
REFIN via Synthesizer
and Charge Pump section
Figure 40: Clock Generation
2003 CML Microsystems Plc
54
D/838/8
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