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PDF NTE1890 Data sheet ( Hoja de datos )
| Número de pieza | NTE1890 | |
| Descripción | Integrated Circuit NTSC Decoder for TV | |
| Fabricantes | NTE | |
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NTE1890
Integrated Circuit
NTSC Decoder for TV
Description:
The NTE1890 is a monolithic integrated decoder for the NTSC color television standards. It combines
all functions required for the demodulation of NTSC signals. Further more it contains a luminance
amplifier, an RGB–matrix and amplifier. These amplifiers supply output signals up to 5V peak–to–
peak (picture information) enabling direct drive of the discrete output stages.
Absolute Maximum Ratings:
Maximum Supply Voltage (Pin1), VP = V1–23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2V
Maximum Total Power Disipation, Ptot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7W
Operating Ambient Temperature Range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –25° to +65°C
Storage Temperature Range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –25° to +150°C
Thermal Resistance, Junction–to–Ambient, RthJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50K/W
Electrical Characteristics: (VP = V1–23 = 12V, TA = +25°C unless otherwise specified)
Parameter
Symbol
Min Typ Max
Supply (Pin1)
Supply Voltage
Supply Current
Total Power Dissipation
Luminance Amplifier (Pin9)
VP = V1–23
IP = I1
Ptot
8.0 12.0 13.2
– 85 –
– 1.0 –
Input Voltage (Peak–to–Peak Value, Note 1)
Input Level Before Clipping
Input Current
Contrast Control Range
V9–23(p–p)
V9–23
I9
– 450 –
––2
– 0.15 1.0
–17 – +3
Control Voltage for an Attenuation of 40dB
– 1.2 –
Input Current Contrast Control
Peaking of Luminance Signal
I7 – – 15
Output Impedance (Pin10)
Ratio of Internal/External Current when Pin10 is Short–Circuited
|Z10–23|
– 200 –
–3–
Control Voltage for Peaking Adjustment (Pin11)
Input Impedance (Pin11)
V11–23
|Z11–23|
– 2.4 –
– 10 –
Note 1. Signal with the negative–going sync; amplitude includes sync amplitude.
Unit
V
mA
W
mV
V
µA
dB
V
µA
Ω
V
kΩ
1 page  
Functional Description (Cont’d):
Oscillator and ACC Detector
The 7.16MHZ reference oscillator operates at twice the subcarrier frequency. The reference signals
for the (R–Y) and (B–Y) demodulators, the burst phase detector, and ACC detector are obtained via
the divide–by–2 circuit, which provides a 90° phase shift. The oscillator is controlled by the burst
phase detector, which is gated with the narrow part of the sandcastle pulse (Pin8). As the burst phase
detector has an asymmetrical output the oscillator can be adjusted by changing the voltage of the out-
put (Pin21) via a high–ohmic resistor. The capacitor in series with the oscillator crystal must then have
a fixed value. When Pin6 (saturation control) is connected to the positive supply line the burst signal
is suppressed and the color killer is overruled. This position can therefore be used for adjustment of
the oscillator. The adjustment is visible on the screen.
The hue control is obtained by changing the phase of the input signal of the burst phase detector with
respect to the chrominance signal applied to the demodulators. This phase shift is obtained by gener-
ating a 90° shift sine–wave via a Miller integrator (biased via Pin19) which is mixed with the original
burst signal. A control circuit is required in the 90° phase shift circuit to make the chrominance voltage
independent of the hue setting. This control circuit is decoupled by a capacitor connected to Pin5.
As the shifted burst signal is synchronously demodulated in a separate ACC detector to generate the
ACC voltage, it is not affected by the hue control. The output pulses of this detector are peak detected
(Pin4) to control the gain of the chrominance amplifier, thus preventing blooming–up of the color dur-
ing weak signal reception. This ensures reliable operation of the color killer. During color killing the
color channel is blocked by switching–off saturation control and the demodulators.
Demodulators
The (R–Y) and (B–Y) demodulators are driven by the chrominance signal (Pin24) and the reference
signals from the 7.16MHZ divider circuit. The phase angle between the two reference carriers is 115°.
This is achieved by the (R–Y) demodulator receiving an additional phase shift by mixing the two sig-
nals from the divider circuit. The phase shift of 115° can be varied between 90° and 140° by changing
the bias voltage at Pin18. The demodulator output signals are fed to R and B matrix circuits and to
the (G–Y) matrix to provide the (G–Y) signal which is applied to the G matrix. The demodulator circuits
are killed and blanked by bypassing the input signals.
RGB Matrix and Amplifiers
The three matrix and amplifier circuits are identical and only one circuit will be described. The lumi-
nance and the color difference signals are added in the matrix circuit to obtain the color signal. Output
signals are 5V (p–p) (black–white) for the following nominal input signals and control settings.
D Luminance 450mV(p–p)
D Chrominance 550mV(p–p) (burst–to–chrominance ratio of the input 1: 2.2)
D Contrast–3dB max
D Saturation–6dB max
The maximum output voltage is approximately 7V(p–p). The black level of the blue channel is com-
pared with a variable external reference level (Pin12), which provides the brightness control. The
brightness control range is 1V to 3.2V. The control voltage is stored in a capacitor (connected to
Pin16) and controls the black level at the output (Pin15) between 2V and 4V, via a change of the level
of the luminance signal before matrixing.
Note
Black levels of up to approximately 6V are possible, but amplitude of the output signal is reduced to
3V(p–p).
If the output signal surpasses the level of 9V the peak–white limiter circuit becomes active and re-
duces the output signal via the contrast control.
5 Page | ||
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| PDF Descargar | [ Datasheet NTE1890.PDF ] | |
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