cx24118a NXP Semiconductors, cx24118a Datasheet - Page 20

• Manufacturer Part Number: cx24118a
• Description: Advanced Modulation Digital Satellite Tuner
• Manufacturer: NXP Semiconductors

NXP Semiconductors
2.6
2.6.1
CX24118A_N_2
Product data sheet
Automatic Tuning System
Auto-tuning Procedure
During Initialization
Table 5.
The CX24118A uses an automatic tuning system to select the VCO and band during channel
change. The system selects among the 12 virtual VCOs (VCO1–VCO6, each with a high and
low band) based on preload values that are programmed during initialization. The automatic
tuning system does not require time-consuming calibration during initialization or channel
change. The procedure for using the automatic tuning system is given in
Frequency
Mode
Frequency tolerance at 25 ºC
Frequency tolerance over
temperature
Maximum equivalent series
resistance (ESR)
Aging
Load Capacitance
Maximum Drive Level
Operating Temperature Range
FOOTNOTES:
(1)
(2)
(3)
1.
2.
– Register 0x14 also contains the tuning system enable bits, TUNAutoEn[1:0], which
This is the maximum crystal series resistance for reliable startup at low energy levels. Compliance with
this spec at 10 nW is required. This number is also required at operating power levels.
The power dissipated across the crystal will depend on the ESR of the crystal and the bias level of the
oscillator. Leaving the XTAL_BIAS pin open will create a lower bias current than if it were shorted to
ground.
A 40.444 MHz crystal is only needed when DVB symbol rates of 44–45 MSps are required for the
CX24116 DVB-S2 demodulator.
Program the tuning system preload values with the values provided by Conexant and
enable the automatic tuning system.
a.
b.
c.
d.
Program automatic charge pump levels with the values provided by Conexant. These
values are selected based on the VCO tuning voltage.
a.
b.
c.
should be programmed to 00b at the same time.
Set register field TUN1[5:0] (0x14[5:0]) to 0x0F.
Set register TUN2[7:0] (0x15[7:0]) to 0xFF.
Set register TUN3[7:0] (0x16[7:0]) to 0xFF.
Set register TUN4[7:0] (0x17[7:0]) to 0xF0.
Set register field CPLevel1[1:0] (0x11[7:6]) to 11b.
Set register field CPLevel2[1:0] (0x11[5:4]) to 11b.
Set register field CPLevel3[1:0] (0x11[3:2]) to 10b.
Parameter
Crystal Requirements
(1)
(2)
Rev. 02 — 8 September 2009
40.000 MHz (40.444 MHz
Parallel resonant, 3rd overtone
80
18 pF
1 mW
0 ºC to 70 ºC
25 ppm
50 ppm
5 ppm/Year
(3)
Chapter 2: Functional Descriptions
Specification
)
CX24118A
© NXP B.V. 2009. All rights reserved.
Section
2.6.1.
20