TDA6650TT; TDA6651TT
NXP Semiconductors
5 V mixer/oscillator and low noise PLL synthesizer
Table 12. Charge pump current…continued
CP2
CP1
CP0
Charge pump current
number
Typical current (absolute
value in µA)
1
1
1
0
1
1
1
0
1
6
7
8
254
400
580
8.1.6 Automatic Loop Bandwidth Control (ALBC)
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 Figure 27 and 28. This feature is activated by setting bits T[2:0] = 011 after
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 13 and 14. When ALBC is active, bit ALBC = 1.
Table 14 summarizes the programming of the band selection and the charge pump
current when ALBC is active.
Table 13. ALBC settings
Bit
Band
selected current
Charge pump Port
BS3
ALBC
0
BS3
BS2
BS1
BS2
BS1
X
0
0
high
see Table 14
follows off
bit BS3
off
0
0
X
X
0
1
1
0
low
see Table 14
see Table 14
follows off
bit BS3
on
off
mid
follows on
bit BS3
0
1
X
X
1
1
forbidden
X
X
depends on LO program, shown in Table 14
Table 14. ALBC band selection and charge current setting
LO frequency
Band
Charge pump current
number
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
low
low
low
low
low
2
3
4
5
6
TDA6650TT_6651TT_5
© NXP B.V. 2007. All rights reserved.
Product data sheet
Rev. 05 — 10 January 2007
12 of 54
NXP [ NXP ]
