micrf405 Micrel Semiconductor, micrf405 Datasheet - Page 20

• Manufacturer Part Number: micrf405
• Description: Micrf405 290mhz To 980mhz Ism Band Ask/fsk Transmitter
• Manufacturer: Micrel Semiconductor

April 2006
The frequency synthesizer consists of a voltage-
controlled
prescaler, programmable frequency dividers, phase-
detector and charge pumps. Two different types of
prescalers are integrated, a pulse swallow and a
phase select prescaler. The recommended prescaler
is the phase select prescaler (Prescaler_Sel=0,
which is default). There is both a configurable on-
chip loop filter and an external loop filter. The
lengths of the N and M and A registers are 12, 12
and 6 bits respectively. The M, N and A values can
be calculated from the formula:
Micrel
Phase select prescaler (Prescaler_Sel=0):
Pulse swallow prescaler (Prescaler_Sel=1):
f
f
RF
RF
=
=
f
f
M
M
XCO
XCO
⋅
⋅
k
k
oscillator
(
(
32
31
N
N
+
+
A
2
)
A
(VCO),
)
,
crystal
oscillator,
20
There are two sets of each of the divide factors (i.e.
A0 and A1). If modulation by using the dividers is
selected Modulation1=1, Modulation0=0), the two
sets should be programmed to give two RF
frequencies, separated by two times the specified
single sided frequency deviation. For all other
modulation methods, the 0-set will be used. The
value of A is constrained to be less or equal to N,
0<=A<=N.
where:
f
f
0 < A ≤ N
k: 6: RF frequency 290-325 MHz,
XCO
RF
: RF frequency
Freq_Band[1:0]=0
4: RF frequency 430-490 MHz,
Freq_Band[1:0]=1
2: RF frequency 860-980 MHz,
Freq_Band[1:0]=2-3
: Crystal oscillator frequency
MICRF405
[phone]
M9999-041906