tda6651tt/c3/s3 NXP Semiconductors, tda6651tt/c3/s3 Datasheet - Page 12

• Manufacturer Part Number: tda6651tt/c3/s3
• Description: 5 V Mixer/oscillator And Low Noise Pll Synthesizer For Hybrid Terrestrial Tuner Digital And Analog
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA6650TT_6651TT_5
Product data sheet
8.1.6 Automatic Loop Bandwidth Control (ALBC)
Table 12.
In a PLL controlled VCO in which the PLL reduces phase noise close to the carrier, there
is an optimum loop bandwidth corresponding to the minimum integrated phase jitter. This
loop bandwidth depends on different parameters like the VCO slope, the loop filter
components, the dividing ratio and the gain of the phase detector and charge pump.
In order to reach the best phase noise performance it is necessary, especially in a
wideband system like a digital tuner, to set the charge pump current to different values
depending on the band and frequency used. This is to cope with the variations of the
different parameters that set the bandwidth. The selection can be done in the application
and requires for each frequency to program not only the divider ratios, but also the band
and the best charge pump current.
The TDA6650TT; TDA6651TT includes the ALBC feature that automatically sets the band
and the charge pump current, provided the IC is used in the DVB-T standard application
shown in
power-on reset. This feature is disabled when the same bits are set again. When ALBC is
activated, the output ports BS1, BS2 and BS3 are not programmed by the corresponding
BS bits, but are set according to
Table 14
current when ALBC is active.
Table 13.
Table 14.
CP2
1
1
1
Bit
ALBC
0
0
0
0
1
LO frequency
80 MHz to 92 MHz
92 MHz to 144 MHz
144 MHz to 156 MHz
156 MHz to 176 MHz
176 MHz to 184 MHz
summarizes the programming of the band selection and the charge pump
Figure 27
BS3
X
X
X
X
X
Charge pump current
ALBC settings
ALBC band selection and charge current setting
CP1
0
1
1
BS2
0
0
1
1
X
and 28. This feature is activated by setting bits T[2:0] = 011 after
Rev. 05 — 10 January 2007
CP0
1
0
1
BS1
0
1
0
1
X
…continued
Table 13
Charge pump current
number
6
7
8
5 V mixer/oscillator and low noise PLL synthesizer
Band
selected
high
low
mid
forbidden
depends on LO program, shown in
Band
low
low
low
low
low
TDA6650TT; TDA6651TT
and 14. When ALBC is active, bit ALBC = 1.
Charge pump
current
see
see
see
Table 14
Table 14
Table 14
Typical current (absolute
value in A)
254
400
580
Port
BS3
follows
bit BS3
follows
bit BS3
follows
bit BS3
Charge pump current
number
2
3
4
5
6
Table 14
© NXP B.V. 2007. All rights reserved.
BS2
off
off
on
BS1
off
on
off
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