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 RGBmatrix and amplifier. These amplifiers supply output signals up to 5V peakto
peak (picture information) enabling direct drive of the discrete output stages.
Absolute Maximum Ratings:
Maximum Supply Voltage (Pin1), V
P
= V
123
13.2V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Total Power Disipation, P
tot
1.7W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Ambient Temperature Range, T
A
25
to +65
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage Temperature Range, T
stg
25
to +150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Resistance, JunctiontoAmbient, R
thJA
50K/W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Characteristics: (V
P
= V
123
= 12V, T
A
= +25
C unless otherwise specified)
Parameter
Symbol
Min
Typ
Max
Unit
Supply (Pin1)
Supply Voltage
V
P
= V
123
8.0
12.0
13.2
V
Supply Current
I
P
= I
1
85
mA
Total Power Dissipation
P
tot
1.0
W
Luminance Amplifier (Pin9)
Input Voltage (PeaktoPeak Value, Note 1)
V
923(pp)
450
mV
Input Level Before Clipping
V
923
2
V
Input Current
I
9
0.15
1.0
A
Contrast Control Range
17
+3
dB
Control Voltage for an Attenuation of 40dB
1.2
V
Input Current Contrast Control
I
7
15
A
Peaking of Luminance Signal
Output Impedance (Pin10)
|Z
1023
|
200
Ratio of Internal/External Current when Pin10 is ShortCircuited
3
Control Voltage for Peaking Adjustment (Pin11)
V
1123
2.4
V
Input Impedance (Pin11)
|Z
1123
|
10
k
Note 1. Signal with the negativegoing sync; amplitude includes sync amplitude.
Electrical Characteristics (Cont'd): (V
P
= V
123
= 12V, T
A
= +25
C unless otherwise specified)
Parameter
Symbol
Min
Typ
Max
Unit
Chrominance Amplifier (Pin3)
Input Voltage (PeaktoPeak Value, Note 2)
V
323(pp)
55
550
1100
mV
Input Impedance
|Z
323
|
8
k
Input Capacitance
C
323
4
6
pF
ACC Control Range
30
dB
Change of the Burst Signal at the Output over the Whole Control Range
1
dB
Gain at Nominal Contrast/Saturation Pin3 to Pin24 (Note 3)
13
dB
Output Voltge (PeaktoPeak Value at Burst Signal of 300mV
(pp)
,
(Note 3)
V
2423(pp)
240
mV
Maximum Output Voltage Range (Pin24, PeaktoPeak Value)
V
2424(pp)
1.7
V
Distortion of Chrominance Amplifier at V
2423(pp)
= 0.5V (Output)
up to V
323(pp)
= 1V (Input)
d
3.0
5.0
%
Frequency Response Between 0 and 5MHz
243
2
dB
Saturation Control Range
50
dB
Input Current Saturation Control (Pin6)
I
6
20
A
Tracking Between Luminance and Chrominance Contrast Control
2
dB
CrossCoupling Between Luminance and Chrominance Amplifier
(Note 4)
46
dB
SignaltoNoise Ratio at Nominal Input Signal (Note 5)
S/N
56
dB
Phase Shift Between Burst and Chrominance at Nominal
Contrast/Saturation
5
deg
Output Impedance of Chrominance Amplifier
|Z
2423
|
25
Output Current
I
24
10
mA
Reference Part (PhaseLocked Loop)
Catching Range (Note 6)
f
500
700
Hz
Phase Shift for
400Hz Deviation for f
OSC
(Note 6)
5
deg
Reference Part (Oscillator)
Temperature Coefficient of Oscillator Frequency (Note 6)
TC
OSC
1.5
Hz/K
Frequency Variation when Supply Voltage Increases from
10V to 13.2V (Note 6)
f
OSC
40
Hz
Input Resistance (Pin22)
R
2223
300
Input Capacitance (Pin22)
C
2223
10
pF
Note 2. Indicated is a signal for a color bar with 75% saturation; chrominance to burst ratio is 2.2:1.
Note 3. Nominal contrast is specified as the maximum contrast 3dB and nominal saturation as the
maximum saturation 6dB.
Note 4. Cross coupling is measured under the following conditions:
S
Input signals nominal.
S
Contrast and aturation such that the nominal output signals are obtained.
S
The signals at the output at which no signal should be available must be compared
with the nominal output signal at that output.
Note 5. The signaltonoise ratio is defined as peaktopeak signal with respect to RMS noise.
Note 6. All frequency variations are referred to 3.58MHz carrier frequency.
Electrical Characteristics (Cont'd): (V
P
= V
123
= 12V, T
A
= +25
C unless otherwise specified)
Parameter
Symbol
Min
Typ
Max
Unit
Reference Part (ACC Generation, Pin22)
Control Voltage at Nominal Input Signal
V
223
5.3
V
Control Voltage without Chrominance Input
V
223
2.8
V
ColorOff Voltage
V
223
3.4
V
ColorOn Voltage
V
223
3.6
V
Change in Burst Amplitude with Supply Voltage
Independent
Voltage at Pin4 at Nominal Input Signal
V
423
5.2
V
Reference Part (Hue Control)
Control Range
50
deg
Demodulator Part
Input Burst Signal Amplitude (PeaktoPeak Value, Pin17)
V
1723(pp)
320
mV
Input Impedance (Pin17, Note 7)
|Z
1723
|
2
k
Ratio of Demodulated Signals (BY)/(RY)
V
1523
/V
1323
1.1
Ratio of Demodulated Signals (GY)/(RY); No (BY) Signal
V
1423
/V
1323
0.26
Ratio of Demodulated Signals (GY)/(BY); No (RY) Signal
V
1423
/V
1523
0.22
Frequency Response Between 0 and 1MHz
3
dB
Crosstalk Between Color Difference Signals
40
dB
RGB Matrix and Amplifiers
Output Voltage at Nominal Input Signal
(PeaktoPeak value, BlacktoWhite, Note 3)
V
13, 14, 1523(pp)
5
V
Output Voltage at Pin13 at Nominal Contrast/Saturation and
No Luminance Signal to (RY) (PeaktoPeak Value)
V
1323(pp)
5.25
V
Maximum PeakWhite Level (Note 8)
V
13, 14, 1523
9.0
9.3
9.6
V
Maximum Output Current (Pin13, Pin14, Pin15)
I
13, 14, 15
10
mA
Output Black Level Voltage for a Brightness Control Voltage
at Pin12 of 2V
V
13, 14, 1523
2.7
V
Black Level Shift with Vision Contents
40
mV
Brightness Control Input Current
I
12
5
A
Variation of Black Level with Temperature
V/
T
0.35
1.0
mV/K
Variation of Black Level with Contrast
V
10
100
mV
Relative Spread Between the R, G and B Output Signals
10
%
Relative BlackLevel Varition Between the Three Channels During
Variation of Contrast, Brightness and Supply Voltage
0
20
mV
Differential BlackLevel Drift Over a Temperature Range of 40
C
0
20
mV
Note 3. Nominal contrast is specified as the maximum contrast 3dB and nominal saturation as the
maximum saturation 6dB.
Note 7. These signal amplitudes are determined by th ACC circuit of the reference part.
Note 8. If the typical voltage for this white level is exceeded, the output voltage is reduced by dis-
charging the capacitor at Pin7 (contrast control); discharge current is 1.5mA.
Electrical Characteristics (Cont'd): (V
P
= V
123
= 12V, T
A
= +25
C unless otherwise specified)
Parameter
Symbol
Min
Typ
Max
Unit
RGB Matrix and Amplifiers (Cont'd)
Blanking Level at the RGB Outputs
1.9
2.1
2.3
V
Difference in Blanking Level of the Three Channels
0
mV
Differential Drift of the Blanking Levels over a
Temperatue Range of 40
C
0
mA
Tracking of Output Black Level with Supply Voltage
1.1
SignaltoNoise Ratio of Output Signals (Note 5)
S/N
62
dB
Residual 7.1MHz Signal and Higher Harmonics at the RGB Outputs
(PeaktoPeak Value)
75
150
mV
Output Impedance of RGB Outputs
|Z
13, 14, 1523
|
50
Frequency Response of Total Luminance and RGB Amplifier Circuits
for f = 0 to 5MHz
3
dB
Sandcastle Input (PIn8)
Level at which the RGB Blanking is Activated
V
823
1.0
1.5
2.0
V
Level at which Burst Gate and Clamping Pulse are Separated
V
823
6.5
7.0
7.5
V
Delay Bteween Black Level Clamping and Burst Gate Pulse
t
d
0.4
s
Input Current at V
823
= 0 to 1V
I
8
1
mA
Input Current at V
823
= 1V to 8.5V
I
8
20
A
Input Current at V
823
= 8.5V to 12V
I
8
2
mA
Note 5. The signaltonoise ratio is defined as peaktopeak signal with respect to RMS noise.
Functional Description:
Luminance Amplifier
The luminance amplifier is voltage driven and requires an input signal of 450mV peaktopeak (posi-
tive video). The luminance delay line must be connected between the IF amplifier and the decoder.
The input signal must be AC coupled to the input Pin9.
The black level at the output of the preamplifier is clamped to a fixed DC level by the black level clamp-
ing circuit. The high input impedance of the luminance amplifier minimizes disturbance of the input
signal black level by the source impedance (delay line matching resistors).
During clamping the low input impedance reduces noise and residual signals. After clamping the sig-
nal is fed to a peaking stage. The overshoot is defined by the capacitor connected to Pin10 and the
peaking is adjusted by the control voltage at Pin11.
The peaking stage is followed by a contrast control stage. The contrast control voltage range (Pin7)
is nominally 17 to +3dB.
Chrominance Amplifier
The chrominance amplifier has an asymmetrical input. The input signal must be AC coupled (Pin3)
and have a minimum amplitude of 55mV peaktopeak. The gain control stage has a control range
in excess of 30dB, the maximum input signal should not exceed 1.1V peaktopeak, otherwise clip-
ping of the input signal will occur. From the gain control stage the chrominance signal is fed to the
saturation and contrast control stages. Chrominance and luminance control stages are directly
coupled to obtain good tracking. Saturation is linearly controlled via Pin6. The control voltage range
is 2V to 4V, the input impedance is high and the saturation control range is in excess of 50dB. The
burst signal is not affected by saturation control. The output signal at Pin24 is AC coupled to the demo-
dulators via Pin17.
Functional Description (Cont'd):
Oscillator and ACC Detector
The 7.16MH
Z
reference oscillator operates at twice the subcarrier frequency. The reference signals
for the (RY) and (BY) demodulators, the burst phase detector, and ACC detector are obtained via
the divideby2 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 highohmic 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 sinewave 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 bloomingup 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 switchingoff saturation control and the demodulators.
Demodulators
The (RY) and (BY) demodulators are driven by the chrominance signal (Pin24) and the reference
signals from the 7.16MH
Z
divider circuit. The phase angle between the two reference carriers is 115
.
This is achieved by the (RY) 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 (GY) matrix to provide the (GY) 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
(pp)
(blackwhite) for the following nominal input signals and control settings.
D
Luminance 450mV
(pp)
D
Chrominance 550mV
(pp)
(bursttochrominance ratio of the input 1: 2.2)
D
Contrast3dB max
D
Saturation6dB max
The maximum output voltage is approximately 7V
(pp)
. 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
(pp)
.
If the output signal surpasses the level of 9V the peakwhite limiter circuit becomes active and re-
duces the output signal via the contrast control.
PDF 
ZIP