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PDF TDA8295 Data sheet ( Hoja de datos )
| Número de pieza | TDA8295 | |
| Descripción | Digital global standard low IF demodulator | |
| Fabricantes | NXP Semiconductors | |
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TDA8295
Digital global standard low IF demodulator for analog TV and
FM radio
Rev. 01 — 4 February 2008
Product data sheet
1. General description
The TDA8295 is an alignment-free digital multistandard vision and sound low IF signal
PLL demodulator for positive and negative video modulation including AM and FM mono
sound processing. It can be used in all countries worldwide for M/N, B/G/H, I, D/K,
L and L-accent standard. CVBS and SSIF/mono audio is provided via two DACs. FM radio
preprocessing is included for simple interfacing with demodulator/stereo decoder
backends.
The IC is especially suited for the application with the NXP Silicon Tuner TDA8275A or
TDA1827x.
All the processing is done in the digital domain.
The chip has an ‘easy programming’ mode to make the I2C-bus protocol very simple. In
principle, only one bit sets the proper standard with recommended content. However, if
this is not suitable, free programming is always possible.
2. Features
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I Digital IF demodulation for all analog TV standards worldwide (M/N, B/G/H, D/K, I,
L and L-accent standard)
I Multistandard true synchronous demodulation with active carrier regeneration
I Alignment-free
I 16 MHz typical reference frequency input (from low IF tuner) or operating as crystal
oscillator
I Internal PLL synthesizer which allows the use of a low-cost crystal (typically 16 MHz)
I Especially suited for the NXP Silicon Tuner TDA8275A or TDA1827x
I No SAW filter needed
I Low application effort and external component count in combination with the
TDA8275A or TDA1827x
I Pin compatible with predecessor TDA8290
I Simple upgrade of TDA8290 possible
I 12-bit IF ADC on chip running with 54 MHz or 27 MHz
I Two 10-bit DACs on chip for CVBS and SSIF or audio
I Easy programming for I2C-bus
I High flexibility due to various I2C-bus programming registers
I I2C-bus interface and I2C-bus feed-through for tuner programming
I Four I2C-bus addresses selectable via two external pins
1 page  
NXP Semiconductors
TDA8295
Digital global standard low IF demodulator for analog TV and FM radio
Table 1. Quick reference data …continued
Power supplies 3.3 V, 1.2 V; Tamb = 25 °C; PC / SC1 for L and M = 10 dB, all others 13 dB; residual picture carrier for L = 3 %,
all others 10 %; FM/AM modulation = 54 %, 1 kHz modulation frequency; measured in application PCB (see Figure 12) with
16 MHz crystal frequency, loaded with 75 Ω (CVBS) and 1 kΩ (SSIF/audio). Values are meant for ‘easy programming’
settings (recommended) except internal mono audio and IF demodulation. The low IF spectrum is delivered by a professional
downconverter.
Symbol Parameter
Conditions
Min Typ
Max Unit
BAF(−3dB)
−3 dB AF bandwidth
AM
FM
20 27
40 50
- kHz
- kHz
(S/N)w(AF) AF weighted
signal-to-noise ratio
via internal mono sound demodulator;
“ITU-R BS.468-4”; FM mode related to
27 kHz deviation before pre-emphasis;
10 % residual PC; SC1
color bar picture
54 58
- dB
via internal mono sound demodulator;
“ITU-R BS.468-4”; AM; m = 54 %; 3 %
residual PC; SC1
color bar picture
43 46
- dB
[1] 50 % ADC current; 100 % video DAC current; 50 % sound DAC current.
[2] 50 % ADC current; 50 % video DAC current; 25 % sound DAC current.
[3] The pull-in range can be doubled to ±1660 kHz by I2C-bus register like described in Table 16. Then the AFC read-out has 256 steps.
5. Ordering information
Table 2. Ordering information
Type number
Package
Name
Description
TDA8295HN
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HVQFN40 plastic thermal enhanced very thin quad flat package; no leads;
40 terminals; body 6 × 6 × 0.85 mm
Version
SOT618-1
TDA8295_1
Product data sheet
Rev. 01 — 4 February 2008
© NXP B.V. 2008. All rights reserved.
5 of 77
5 Page 
NXP Semiconductors
TDA8295
Digital global standard low IF demodulator for analog TV and FM radio
Next comes the equalizer circuit to remove the transmitter group delay predistortion.
A video leveling stage follows, which brings the output within the SCART specification
( 3dB overall), despite heavy overmodulation. The response time is made very slow.
Finally, a video equalizer allows to compensate the perhaps non-flat frequency response
from the tuner or to change the overall video response according to customer wish (i.e.
peaking or early roll-off).
8.5 Upsampler and video DAC
The filtered and compensated CVBS signal is connected to the oversampled 10-bit video
DAC (fs = 108 MHz) via an interpolation stage. The strong oversampling replaces a former
complicated LCR postfiltering by a simple first-order RC low-pass filter to remove the DAC
image frequencies sufficiently. This holds also for the sound DAC, described in
Section 8.6.
8.6 SSIF/mono sound processing
The complex signal is routed via a band-pass and interpolation filter to the 10-bit sound
DAC for the recovery of the second sound carriers (SSIF). A very sharp band-pass filter at
5.5 MHz is added in the FM Radio mode to remove neighbor channels. This also eases
the dynamic burden on the following ADC in the demodulator/decoder chip. The
afore-mentioned high-selectivity band-pass, which replaces the former ceramic filter, is
located behind a frequency shifter. In there, the incoming wanted FM radio channel from
the Silicon Tuner is changed from 1.25 MHz to 5.5 MHz.
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Moreover, the complex signal is demodulated in a linear CORDIC detector and low-pass
filtered to attenuate the video spectrum and the second sound carrier, respectively other
disturbers above the intercarrier. The output of the linear CORDIC (phase information) is
differentiated for getting the demodulated FM audio. The AM demodulation is executed in
a synchronous fashion by using a narrow-band PLL demodulator.
A de-emphasis filter is implemented for FM standards, before the audio is interpolated to
108 MHz as in the CVBS case.
The mono audio is made available in the sound DAC via an I2C-bus controlled selector in
case the intercarrier path is not used for driving an external stereo demodulator.
However, if the mono audio output has to meet the SCART specification, an external
cheap operational amplifier with 12 dB gain becomes necessary, because the low supply
voltage for the TDA8295 doesn’t allow such high levels like 2 V (RMS) maximum.
8.7 Tuner IF AGC
This AGC controls the tuner IF AGC amplifier in the TDA8275A or TDA1827x in such a
way, that the IF ADC is always running with a permanent headroom of 3 dB for the sum of
all signals present at the ADC input. This ensures an always optimal exploitation of the
dynamic range in the IF ADC.
The detection is done in peak Search mode during a field period. The attack time is made
much faster than the decay time in order to avoid transient clipping effects in the IF ADC.
This can happen during channel change or airplane flutter conditions.
TDA8295_1
Product data sheet
Rev. 01 — 4 February 2008
© NXP B.V. 2008. All rights reserved.
11 of 77
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