MICRF610 Micrel Inc, MICRF610 Datasheet - Page 12

• Manufacturer Part Number: MICRF610
• Manufacturer: Micrel Inc

Specifications of MICRF610

• Operating Temperature (min): -20C
• Operating Temperature Classification: Commercial
• Modulation Type: FSK
• Lead Free Status / Rohs Status: Not Compliant

Frequency Synthesizer
The frequency synthesizer consists of a voltage-controlled
oscillator (VCO), a crystal oscillator, phase select
prescaler, programmable frequency dividers and a phase-
detector. The length of the N, M, and A registers are 12,
12 and 6 respectively. The N, M, and A values can be
calculated from the formula:
f
f
f
f
There are two sets of each of the divide factors (i.e. A0
and A1). Storing the ‘0’ and the ‘1’ frequency in the 0- and
the 1 registers respectively, does the 2-FSK. The receive
frequency must be stored in the ‘0’ registers.
Crystal Oscillator (XCO)
0001001
The crystal oscillator is a reference for the RF output
frequency and the LO frequency in the receiver. It is
possible to tune the internal crystal oscillator by switching
in internal capacitance using 5 tune bits XCOtune4 –
XCOtun0. The benefit of tuning the crystal oscillator is to
eliminate the initial tolerance and the tolerance over
temperature and aging. By using the crystal tuning feature
the noise bandwidth of the receiver can be reduced and a
higher sensitivity is achieved.
XCOtune0 = 0 no internal capacitors are connected to the
crystal pins. When XCOtune4 – XCOtune0 = 1 all of the
internal capacitors are connected to the crystal pins.
Figure 5 shows the tuning range.
PHD
XCO
VCO
RF
Micrel, Inc.
July 2006
Adr
: Input/output RF frequency
0001010
0001011
0001100
0001101
0001110
0001111
0010000
0010001
0010010
0010011
A6…A0
: Phase detector comparison frequency
: Crystal oscillator frequency
: Voltage controlled oscillator frequency
f
PhD
D7
‘0’
=
M0_7
M1_7
N0_7
N1_7
D6
‘0’
D7
f
-
-
-
-
-
-
XCO
M
D5
‘1’
M0_6
M1_6
N0_6
N1_6
D6
=
-
-
-
-
-
-
XCOtune4
(
16
D4
A0_5
N0_5
M0_5
A1_5
N1_5
M1_5
D5
×
-
-
-
-
1 ≤ A < N
N
f
M ≠ 0
VCO
XCOtune3
+
M0_4
M1_4
A0_4
N0_4
A1_4
N1_4
D4
D3
-
-
-
-
A
)
×
N0_11
M0_11
N1_11
M1_11
A0_3
N0_3
M0_3
A1_3
N1_3
M1_3
2
D3
XCOtune2
When XCOtune4 –
=
D2
(
16
M0_10
M1_10
N0_10
N1_10
N0_2
M0_2
N1_2
M1_2
A0_2
A1_2
D2
×
XCOtune1
f
N
RF
D1
M0_9
M0_1
M1_9
M1_1
A0_1
N0_9
N0_1
A1_1
N1_9
N1_1
D1
+
A
)
XCOtune0
N0_8
N0_0
M0_8
M0_0
N1_8
N1_0
M1_8
M1_0
A0_0
A1_0
,
D0
D0
12
The typical start up time for the crystal oscillator (default
XCO_tune=13) is ~750us. If more capacitance is added
(higher XCO_tune value), then the start-up time will be
longer.
To save current in the crystal oscillator start-up period, the
XCO is turned on before any other circuit block. When the
XCO has settled, rest of the circuit will be turned on. No
programming should be made during this period.
The current consumption during the prestart period is
approximately 280µA.
VCO
The VCO has no external components. It has three bit to
set the bias current and two bit to set the VCO frequency.
These five bits are set by the RF frequency, as follows:
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 on the VCO frequency setting, and can be
shown in Figure 6.
0000011
A6..A0
RF freq.
868MHz
D7
‘1’
-15.0
-25.0
-35.0
-45.0
55.0
45.0
35.0
25.0
15.0
-5.0
5.0
VCO_IB2
D6
‘1’
0
0
4
D5
‘0’
Table 7. VCO Bit Setting
Figure 5. XCO Tuning
8
VCO_IB2 VCO_IB1 VCO_IB0 VCO_freq1 VCO_freq0
VCO_IB1
[XCO_tune value]
12
D4
1
16
20
VCO_IB0
D3
24
1
MICRF610/MICRF610Z
28
D2
VCO_freq1 VCO_freq0
32
0
M9999-120205
D1
1
D0