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參數(shù)資料
| 型號： | TDA9840T |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 消費(fèi)家電 |
| 英文描述： | DIODE 1SMC28AT3 TRANSZORB 1500W SMT |
| 中文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封裝： | 7.50 MM, PLASTIC, MS-013AC, SOT-163-1, SOP-20 |
| 文件頁數(shù)： | 7/28頁 |
| 文件大?。?/td> | 200K |
| 代理商： | TDA9840T |
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1998 Jul 03
7
Philips Semiconductors
Product specification
TV and VTR stereo/dual sound processor
with digital identification and I
2
C-bus control
TDA9840
FUNCTIONAL DESCRIPTION
The TDA9840 (see Fig.1) receives the signals from the
FM-demodulators in a TV two sound-carrier system. The
circuit is realized by the H00485 bipolar process.
The IC is intended for use in economic TV and VTR
receivers. Therefore optimum relationship between
integration of functions and use of external components
has been striven for. Additionally a new type of
identification circuit has been developed.
AF signal handling
The input AF signals, derived from the two sound carriers,
are processed in analog form using operational
amplifiers.The circuit incorporates level- and
stereo-adjustment to correct the spreading in the FM
detector output levels. Dematrixing uses the technique of
two amplifiers processing the AF signals. Finally, a source
selector provides the facility to route the mono signal
through to the outputs (‘forced mono’).
De-emphasis is performed by two RC low-pass filter
networks with internal resistors and external capacitors.
This provides a frequency response with the tolerances
given in Fig.4.
A source selector, controlled via the I
2
C-bus, allows
selection of the different modes of operation in accordance
with the transmitted signal. The device was designed for a
nominal input signal (FM: 54% modulation is equivalent to
f =
±
27 kHz / AM: m = 0.54) of 250 mV RMS (V
i 1
, V
i 2
),
respectively 500 mV RMS (V
i 3
,V
i 4
). A nominal gain of
6 dB for V
i 1
and V
i 2
signals and 0 dB for V
i 3
and V
i 4
signals is built-in. By using rail-to-rail operational
amplifiers, the clipping level (THD
≤
1.5%) is 1.6 V RMS for
V
P
= 5 V and 2.65 V RMS for V
P
= 8 V at outputs V
o 1
,
V
o 2
,V
o 3
and V
o 4
. Care has been taken to minimize
switching plops. Also total harmonic distortion and random
noise are considerably reduced.
Identification
The pilot signal is fed via an external RC high-pass filter
and single tuned LC band-pass filter to the input of a gain
controlled amplifier. The external LC band-pass filter in
combination with the external RC high-pass filter should
have a loaded Q-factor of about 40 to 50 to ensure the
highest identification sensitivity. By using a fixed coil (
±
5%)
to save the alignment (see Fig.2), a Q-factor of about 12 is
proposed. This may cause a loss in sensitivity of about
2 to 3 dB. A digital PLL circuit generates a reference
carrier, which is synchronized with the pilot carrier.
This reference carrier and the gain controlled pilot signal
are fed to the AM-synchronous demodulator. The
demodulator detects the identification signal, which is fed
through a low-pass filter with external capacitor C
LP
(pin 3)
to a Schmitt-trigger for pulse shaping and suppression of
low level spurious signal components. This is a measure
against mis-identification.
The identification signal is amplified and fed through an
AGC low-pass filter with external capacitor C
AGC
(pin 2) to
obtain the AGC voltage for controlling the gain of the pilot
signal amplifier.
The identification stages consist of two digital PLL circuits
with digital synchronous demodulation and digital
integrators to generate the stereo or dual sound
identification bits which can be read out via the I
2
C-bus.
A 10 MHz quartz crystal oscillator provides the reference
clock frequency. The corresponding detection bandwidth
is larger than
±
50 Hz for the pilot carrier signal, so that
f
p
-variations from the transmitter can be tracked in case of
missing synchronisation with the horizontal frequency f
H
.
However the detection bandwidth for the identification
signal is made small (approximately
±
1 Hz) to reduce
mis-identification.
Figure 2 shows an example of the alignment-free f
p
band-pass filter. To achieve the required Q
L
of
approximately 12, the Q
0
at f
p
of the coil was chosen to be
approximately 25 (effective Q
0
including PCB influence).
Using coils with other Q
0
, the RC-network (R
FP
, C
FP
) has
to be adapted accordingly. It is assumed that the loss
factor tan
δ
of the resonance capacitor is
≤
0.01 at f
p
.
Copper areas under the coil might influence the loaded Q
and have to be taken into account. Care has also to be
taken in environments with strong magnetic fields when
using coils without magnetic shielding.
I
2
C-bus transceiver
The complete IC is controlled by a microcomputer via the
I
2
C-bus. The built-in I
2
C-bus transceiver transmits the
identification result to the I
2
C-bus and receives the control
data for the source selector and level control. The I
2
C-bus
protocol is given in Tables 2 to 12 respectively.
The data transmission between the microcontroller and
the other I
2
C-bus controlled ICs is not disturbed, when the
supply voltage of the TDA9840 is not connected or when
powering up or down. Finally, a Schmitt-trigger is built-in
the SDA/SCL interface to suppress spikes from the
I
2
C-bus.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TDA9840 | TV and VTR stereo/dual sound processor with digital identification(帶數(shù)字識別和IIC總線控制的TV和VTR立體/雙聲道處理器) |
| TDA9845T | TV and VTR stereo/dual sound processor with digital identification |
| TDA9845 | TV and VTR stereo/dual sound processor with digital identification and I 2 C-bus control(帶數(shù)字識別的TV和VTR立體/雙聲道處理器) |
| TDA9847 | TV and VTR stereo/dual sound processor with digital identification |
| TDA9847T | TV and VTR stereo/dual sound processor with digital identification |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TDA9845 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:TV and VTR stereo/dual sound processor with digital identification |
| TDA9845T | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:TV and VTR stereo/dual sound processor with digital identification |
| TDA9847 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:TV and VTR stereo/dual sound processor with digital identification |
| TDA9847T | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:TV and VTR stereo/dual sound processor with digital identification |
| TDA9850 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:I2C-bus controlled BTSC stereo/SAP decoder |
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