micrf507ymltr Micrel Semiconductor, micrf507ymltr Datasheet - Page 15

• Manufacturer Part Number: micrf507ymltr
• Description: 470mhz To 510mhz Low-power Fsk Transceiver With +10dbm Power Amplifier
• Manufacturer: Micrel Semiconductor

Clock Generation
The MICRF507’s crystal oscillator:
March 2010
Micrel, Inc.
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•
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Serves as the reference for the synthesizer that is
the carrier and local oscillator source.
Is divided down to clock the switched-capacitor IF
filter.
Is divided down to generate three other clocks: bit
rate
modulator clock
clock,
Field Name
XCOtune
RefClk_K
BitRate_clkS
Mod_clkS
BitSync_clkS
bit
synchronization
Number
of bits
5
6
3
3
3
Table 3. Register Bit Fields for Clock Generation
Reg9[4:0]
Reg7[5:0]
Reg7[7:6]
Reg6[6:4]
Reg6[3:1]
Location
Reg6[0],
of bits
Figure 6. MICRF507 Clock Sources
clock,
Crystal oscillator trimming.
Reference clock divider.
Transmitter Bit rate clock setting. See Figure 9 and “Data
Interface and Bit Synchronization” section for more details.
VCO Modulator clock setting, set the modulator clock to
either 8x or 16x the bit rate clock.
Receiver Bit Synchronization clock setting, always set bit
synchronization clock to 16x the bit rate clock. See Figure 9
and “Data Interface and Bit Synchronization” section for more
details.
and
15
Figure 6 shows the oscillator with its frequency-shifting
capacitor bank (controlled by the register field XCOtune)
and the frequency dividers that derive the latter three
clocks from its output. This division occurs in two stages.
First, the XCO output is divided by the 6-bit field Refclk_K,
which has allowable values between 1 and 63. Then, for
each of the three clocks, another field (BitSync_clkS,
BitRate_ClkS, and ModClkS, respectively) selects the
number of further divisions by 2. Complete relationships of
field values and resultant frequencies are given below for
each clock.
Description
M9999-032210-B
MICRF507