參數(shù)資料
型號(hào)： TDA4884
廠商： NXP SEMICONDUCTORS
元件分類： 音頻／視頻放大
英文描述： Advanced monitor video controller for OSD
中文描述： 3 CHANNEL, VIDEO PREAMPLIFIER, PDIP20
封裝： 0.300 INCH, PLASTIC, SOT-146-1, DIP-20
文件頁(yè)數(shù)： 11/28頁(yè)
文件大?。?/td> 189K
代理商： TDA4884
1997 Nov 26
11
Philips Semiconductors
Product specification
Three gain control video pre-amplifier for OSD
TDA4884
Notes to the characteristics
1.
Definition of levels:
a)
Artificial black level
: internal signal level behind input emitter follower during input clamping and signal clipping.
This level is inserted instead of the input signal during blanking.
b)
Reference black level
: DC voltage during output clamping at voltage outputs, not influenced by contrast or gain
setting, adjustable by cut-off stabilization.
c)
Cut-off level
: corresponding DC voltage at CRT cathode in closed feedback loop.
d)
Black level
: actual signal black level at either voltage outputs or cathode. At voltage outputs the black level is
equal to reference black level because there is no brightness control via TDA4884. At cathode the black level is
equal to cut-off level. Brightness can be adjusted via grid 1.
e)
Ultra-black level
,
switch-off level
: lowest adjustable reference black level, lowest signal level at voltage outputs.
f) The minimum guaranteed control range for reference black level is 0.1 to 1 V.
The ultra-black level is dependant on the external resistor R
O
at pins 13, 16 and 19 (voltage outputs) to ground.
g)
h) Signal processing see Fig.4.
Linear control range is 1 to 6 V for V
i(CC)
, independent of supply voltage. Open pin 6 leads to absolute maximum
contrast setting. It is recommended not to exceed V
i(CC)
= V
P
1 V to avoid saturation of internal circuitry. For
V
i(CC)
< V
i(CC)(min)
≈
0.7 V a small negative signal (
≈
40 dB) will appear. For frequency dependency of contrast
control see note 14. Typical contrast characteristic see Fig.5.
Definition for nominal output signals: input V
i(b-w)
= 0.7 V, gain pins 3, 1 and 11 open-circuit, contrast control
V
i(CC)
= V
i(CC)(nom)
.
log
A
10
2.
3.
4.
A
x
: signal output amplitude in channel x at any contrast setting between 1 and 6 V.
A
x0
: signal output amplitude in channel x at nominal contrast and same gain setting.
Typical step in contrast voltage and response at signal outputs for nominal input signal V
i(b-w)
= 0.7 V. Typical OSD
fast blanking input/output see Fig.7.
Linear control range is 1 to 6 V for V
i(GC)
, independent of supply voltage. Typical gain characteristic see Fig.6.
The internal reference voltage can be measured at pins 18, 15 and 12 during output clamping (V
i(HBL)
= 2 V) in closed
feedback loop. Typical variation of V
ref(int)
with temperature and power supply voltage see Fig.8.
Slow variations of video supply voltage V
CRT
(see Fig.1) will be suppressed at CRT cathode by cut-off stabilization.
Change of V
CRT
by 5 V leads to specified change of cut-off voltage.
The test mode allows testing without input and output clamping pulses. The signal inputs (pins 2, 5 and 8) have to
be biased via resistors to the previously measured clamp voltages of approximately 3 V (artificial black level + V
BE
).
Signal blanking is not possible during test mode.
5.
6.
7.
8.
9.
10. The signal-to-noise ratio is calculated by the formula (frequency range 1 to 70 MHz):
S
N
RMS value of the noise output voltage
11. Large output swing e.g. I
o(b-w)
= 50 mA leeds to signal depending power dissipation in output transistors.
Thermal V
BE
variation is compensated.
12. Composite signals will not disturb normal operations because an internal clipping circuit cuts all signal parts below
black level. Typical sync clipping see Fig.10.
V
bl SO
)
R
3.5 k
R
O
+
-------------------------------
4.65 V
×
≈
G
track
20
maximum of
A
1
A
10
--------
A
A
2
--------
×
1
A
A
A
3
--------
×
log
A
2
A
20
--------
A
A
3
--------
×
log
;
;
×
dB
=
---
20
peak-to-peak value of the nominal signal output voltage
log
×
=
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