MC72000 Freescale Semiconductor, MC72000 Datasheet - Page 46

• Manufacturer Part Number: MC72000
• Description: Integrated Bluetooth Radio
• Manufacturer: Freescale Semiconductor

Figure 25. Crystal Start-up Time vs. Capacitor
Figure 23. Oscillator Negative Resistance vs.
Radio Functional Description
6.6 Data Clock Operation
The data clock phase lock loop is responsible for providing a constant 24 MHz reference for use
throughout the device. The MC72000 uses a simple integer-N synthesizer to derive a 24 MHz clock (CLK)
from the reference frequency. This allows the MC72000 to adapt to external reference oscillator or crystal
in the range of 12 to 26 MHz. The counter values must always be set to the appropriate values to generate
this 24 MHz clock frequency. The general model for the phase lock loop (PLL) is shown in Figure 27.
For the circuit in Figure 92, the external low pass filter has a loop filter bandwidth (LBW) of 1.0 kHz. This
proves to be adequate for any value of external reference frequency that is an integral multiple of 20 kHz.
The external low pass filter requires one capacitor. More details about PLL loop filters can be obtained
from An Improved PLL Design Method Application Note (document number AN1253/D).
The R-counter of the synthesizer (R6/9-0) is set to a value which will set the internal reference frequency
f
multiply f
reference, R = 650
46
-1000
-1200
-1400
ref
-200
-400
-600
-800
9.0
8.0
7.0
6.0
11
10
Internal to 20 kHz; thus, R = f
0
0
0
Electronic Parallel Crystal Trim (C
85°C
(Crystal Boost Enable R11/4) = 1
4.0
ELECTRONIC PARALLEL CRYSTAL TRIM (R6/14-10)
ref
See Figure 4, T
13 MHz Crystal Reference
1.0
Internal to 24 MHz; thus N = 24 MHz/f
25°C
T
A
8.0
= -20°C
CAPACITOR RATIO (C5/C8)
See Figure 4, T
Curve Measured with 13 MHz Crystal Reference
Crystal Load Capacitance Ratio = 1.8 (C15/C16)
10
A
12
and N =1200
2.0
= 25°C
Ratio
16
Freescale Semiconductor, Inc.
A
= 25°C
For More Information On This Product,
MC72000 Advance Information Data Sheet
3.0
20
ref
10
Internal/20 kHz. The N-counter of the synthesizer (R7/10-0) is set to
.
24
Go to: www.freescale.com
4.0
PT
)
28
Preliminary
5.0
32
ref
Internal. For the case of a 13 MHz external
Figure 24. Oscillator Negative Resistance vs.
-100
-110
-120
-130
-200
-400
-600
600
400
200
-40
-50
-60
-70
-80
-90
Figure 26. Crystal Frequency Pulling vs.
0
0
0
(Crystal Boost Enable R11/4) = 0
Electronic Parallel Trim Value
4.0
0.5
ELECTRONIC PARALLEL TRIM VALUE (R6/14-10)
Crystal Capacitor Ratio
See Figure 4, T
Crystal Frequency Delta measured relative to
initial frequency for R/14-10 = 12 (decimal).
8.0
1.0
See Figure 4, T
Curve Measured with 13 MHz Crystal Reference
Parallel Crystal Trim (R6/14-10) = 16 (decimal)
CAPACITOR RATIO (C5/C8)
12
1.5
A
= 25°C
16
A
= 25°C
2.0
20
2.5
MOTOROLA
24
3.0
28
3.5
32