NTE1890 Datasheet, PDF (4/6 Pages) NTE Electronics – Integrated Circuit NTSC Decoder for TV

Electrical Characteristics (Cont’d): (V_P = V_1–23 = 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 –
Signal–to–Noise Ratio of Output Signals (Note 5)
S/N
62 –
– dB
Residual 7.1MHz Signal and Higher Harmonics at the RGB Outputs
(Peak–to–Peak Value)
– 75 150 mV
Output Impedance of RGB Outputs
|Z_{13, 14, 15–23}|
–
50
–
Ω
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
Level at which Burst Gate and Clamping Pulse are Separated
Delay Bteween Black Level Clamping and Burst Gate Pulse
Input Current at V_8–23 = 0 to 1V
Input Current at V_8–23 = 1V to 8.5V
Input Current at V_8–23 = 8.5V to 12V
V_8–23
V_8–23
t_d
–I₈
I₈
I₈
1.0 1.5 2.0 V
6.5 7.0 7.5 V
– 0.4 – µs
–
–
1 mA
– 20 – µA
–
–
2 mA
Note 5. The signal–to–noise ratio is defined as peak–to–peak signal with respect to RMS noise.
Functional Description:
Luminance Amplifier
The luminance amplifier is voltage driven and requires an input signal of 450mV peak–to–peak (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 peak–to–peak. The gain control stage has a control range
in excess of 30dB, the maximum input signal should not exceed 1.1V peak–to–peak, 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.