MICRF505BML TR Micrel Inc, MICRF505BML TR Datasheet - Page 17

• Manufacturer Part Number: MICRF505BML TR
• Manufacturer: Micrel Inc

Specifications of MICRF505BML TR

• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Modulation Type: FSK
• Lead Free Status / Rohs Status: Not Compliant

0000011
RF freq.
850MHz
868MHz
915MHz
950MHz
A6..A0
If an external reference is used instead of a crystal,
the signal shall be applied to pin 24, XTALOUT. Due
to internal DC setting in the XCO, an AC coupling is
recommended to be used between the external
reference and the XTALOUT-pin.
VCO
The VCO has no external components. If has three
bit to set the bias current and two bit to set the VCO
frequency. These five bit are set by the RF
frequency, as follows:
October 2006
D7
‘1’
Table 7. Typical values with C
VCO_IB2
D6
‘1’
XCOtune
1
0
0
0
16
31
D5
0
1
2
4
8
‘0’
VCO_IB2 VCO_IB1 VCO_IB0 VCO_freq1 VCO_freq0
VCO_IB1
D4
1
1
0
0
Start-up Time (µs)
D3
VCO_IB0
1
1
1
0
1140
2050
590
590
700
700
810
D2
EXT
VCO_freq1 VCO_freq0
= 1.5pF
0
0
1
1
D1
0
1
0
1
D0
17
The bias bit will optimize the phase noise, and the
frequency bit will control a capacitor bank in the
VCO. The tuning range, the RF frequency versus
varactor voltage, is dependent upon the VCO
frequency setting, and can be shown in Figure 7.
When the tuning voltage is in the range from 0.9V to
1.4V, the VCO gain is at its maximum, approximately
65-70MHz/V. It is recommended that the varactor
voltage stays in this range.
The input capacitance at the varactor pin must be
taken into consideration when designing the PLL
loop filter. This is most critical when designing a loop
filter with high bandwidth, which gives relatively
small component values. The input capacitance is
approximately 6pF.
Figure 7. RF Frequency vs. Varactor Voltage
1000
980
960
940
920
900
880
860
840
820
800
and VCO Frequency bit (V
0
0.5
Table 8. VCO Bit Setting
Varactor voltage (V)
1
Tuning range
1.5
2
DD
[phone]
= 2.25V)
2.5
M9999-103106
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'01'
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