tda18219hn NXP Semiconductors, tda18219hn Datasheet - Page 7

• Manufacturer Part Number: tda18219hn
• Description: Silicon Tuner For Terrestrial And Cable Digital Tv Reception
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA18219HN_1
Objective data sheet
9.4 Low-pass filter (LPF)
9.5 High-pass filter (HPF)
In the circuit, the Take Over Point (TOP) are programmable to offer the optimal
noise/linearity compromise during reception. The TOP are carefully selected not to
overload following stages nor to have too weak signal to noise ratio. They correspond to
decision points where the gain distribution changes inside the tuner.
In order to avoid instability of gain chain while working around level decision point a
hysteresis has been implemented to avoid gain toggling. This is the reason why there are
different values for TOP-up / TOP-down. Its main purpose is to make sure gain switch
occurs to prevent signal distortion along the gain chain.
The TOP values are considered as tuner settings and could cause performances
degradations if wrongly set.
Table 5.
The programmable LPF avoids aliasing of demodulators Analog-to-Digital converters. In
addition, it suppresses the remaining signals. The programming allows to receive signal
bandwidth of 1.7 MHz, 6 MHz, 7 MHz and 8 MHz.
The HPF helps removing residual adjacent (N + 1) channel power after image rejection
has been performed.
AGC number
AGC1
AGC2
AGC3
AGC4
AGC5
Fig 3.
Remark: to get a 0 dB gain on the loop-through, then only steps from 6 dB to 15 dB are available.
AGC1 TOP description example
AGC number / block correspondence
corresponding AGC block
LNA AGC
RF Filter AGC
RF AGC
Mixer AGC
LPF AGC
LNA gain
(dB)
−12
Rev. 01 — 3 February 2010
15
12
−3
−6
−9
9
6
3
0
Silicon Tuner for terrestrial and cable digital TV reception
91
94
HIST = 6 dB
97
comment
Not described, handled internally by tuner
100
TOP = 100 dBμV
LNA output level (dBμV)
TDA18219HN
001aak488
© NXP B.V. 2010. All rights reserved.
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