
Micrel
MICRF405
April 2006
26
M9999-041906
(408) 955-1690
Modulation
type
Fphd
[kHz]
BW
[kHz]
CP
[uA]
CP_CUR
C1
[pF]
C2
[pF]
LF_CAP
R1
[k
Ω
]
LF_RES1
R3
[k
Ω
]
LF_RES3
Open loop
VCO
500
22.5
3.125/31.25 1 32.4
10.8
3 96 7 57 8
Open loop
VCO
1000
45
6.25/62.5 2 32.4
10.8
3 48 2 28 3
ASK
≤
4.8kbps
1000
32
3.125/31.25 1 32.4
10.8
3 68 4 40 5
ASK
≤
9.6kbps
2000
64
6.25/62.5 2 32.4
10.8
3 34 1 20 2
ASK
>9.6kbps
2000 220 12.5/125
3
5.4 1.8
0
76
5
5
0
Table 18. Internal Dual Path Filter Settings.
The design of the PLL filter will strongly affect the
performance of the frequency synthesizer. Input
parameters, when designing the loop filter for the
MICRF405, are mainly the modulation method and
the bit rate. Internal loop filter, which have relative
high bandwidths, is recommended for ASK. The
external filter must be used when the bandwidth
must be low. These choices will also affect the
switching time and phase noise.