TDA4887PS Datasheet, PDF (45/68 Pages) NXP Semiconductors – 160 MHz bus-controlled monitor video preamplifier

Philips Semiconductors
160 MHz bus-controlled monitor video
preamplifier
Product specification
TDA4887PS
Calculation of compensation (see Fig.22):
1. Gain adjustment is in 255 steps from 20 to 100%
which equates to 4.6 V per step at maximum contrast.
One step = ^{0----.--8----2×}---5--4--5--.-6-----V--- = 14.4 mV which is equal to
187 mV at the cathode with video gain = 13 for the
white area.
2. For 18.8% drive (used for black level adjustment) the
output changes only 2.7 mV (35 mV at the cathode)
per gain step.
3. The black level adjustment range (at feedback inputs)
is 1.9 V in 255 steps, which is 7.45 mV per step
(∆ black level of 97 mV at the cathode with feedback
gain = ¹â„₁₃). It follows that the optimum compensation
is one step black level for ^93----75-- = 2.8 or approximately
three steps of gain.
handbook, full pagewidth
0.7 V
(nom.)
FIXED
MAXIMUM
GAIN
4.6/0.7 V
CONTRAST
−40 dB
(0.5 / 100%)
255 steps
BRIGHTNESS
− 10 / 30%
of 4.6 V
255 steps
3 × GAIN
20 /100%
255 steps
4.6 V
(max.)
VIDEO GAIN
≈ 13
signal
amplitude
60 V (max.)
CRT
PREAMPLIFIER
3 × BLACK REFERENCES
range 1.9 V
255 steps
5.75
to 3.95 V
FEEDBACK GAIN
≈ 1/13
≈25 V cut-off
level variation
MHB953
Fig.22 Signal amplification and feedback references.
12.4.1.4 Example of automatic factory alignment
This procedure shows a realization of the alignment
description, it depends on disposable equipment.
Gamma = 2.25, maximum luminance = 102.8 cd/m²,
video gain = 13, feedback gain = ¹â„₁₃, white D; see Fig.23.
1. Initialization
a) Set grid 2 voltage to minimum
b) Set R, G, B gains to the centre values (80H,
subaddresses 04H, 05H, 06H)
c) Set R, G, B black references to centre values (80H,
subaddresses 07H, 08H, 09H)
d) Set contrast to maximum (FFH, subaddress 02H).
2. V_g2 and black levels
a) Set brightness to 18.8% drive (B8H,
subaddress 01H, control bit BRI=0)
b) Apply black video
c) Increase V_g2 manually until one colour appears
d) Activate the alignment computer
e) The computer will continuously adjust the R, G, B
black levels to meet the following three conditions:
x = 0.131
y = 0.329
the centre of the min/max setting remains at 80H
(this will leave some margin for the compensation
steps that follow)
f) Fine tuning of V_g2 (or V_g1) until Y = 2.4 cd/m² with
the computer still active.
2001 Oct 19
45