MSK1900 Datasheet, PDF (4/6 Pages) M.S. Kennedy Corporation – HIGH PERFORMANCE, HIGH VOLTAGE VIDEO DISPLAY DRIVER

APPLICATION NOTES CON'T
VOFF
VOFF is the output offset (brightness) control used to set the
output quiescent current and consequently the DC output volt-
age (black level). Output quiescent current adjustment range is
from several µA to 100mA nominal (80 to 130 mA actual).
Normally a 5K potentiometer is connected between VREF and
GND to this input, but any 0 - 5.5V external DC source may be
used. A 0.1µF capacitor should be connected from this pin to
signal ground to improve the amplifier's stability.
BLANK INPUT
The video input can be electrically disconnected from the
amplifier by applying a TTL high input to the blank pin. When
this occurs, the output will be set to approximately +VHV. The
VGAIN and VOFF control pins have little or no effect on the output
when it is in blank mode.
When the TTL compatible blank input is not used, the pin
must be connected to ground to enable the amplifier. The blank
input will float high when left unconnected which will disable
the video.
VREF OUTPUT
The MSK 1900 has an on board buffered DC zener reference
output. The VREF output is nominally 5.5V DC and has full
temperature test limits of 5.2V to 5.8V DC. This output is
provided for gain and offset adjustment and can source up to
4mA of current.
BLACK LEVEL
The voltage developed across the external load resistor with a
0V video input to the MSK 1900 is the black level. This voltage
may be changed by adjusting the load resistor or by varying the
output quiescent current of the MSK 1900 as described in VOFF
above. The black level could also be effected by the VGAIN con-
trol voltage if the video input has a DC component. AC coupling
of the video input will prevent this phenomenon from occurring.
THERMAL MANAGEMENT
The MSK 1900 package is electrically isolated from the inter-
nal circuitry, allowing direct connection to a heat sink.
The power dissipation of the amplifier depends mainly on
the load requirements, bandwidth, pixel size, black level and the
value of the external Rp. Refer to the following table for typical
power levels for selected video conditions:
POWER DISSIPATION TABLE
(TC = 25°C, VHV = 70V, RP = 200Ω)
VO - VBLACK
Duty
Cycle %
IC PD
Watts
PLOAD
Watts
TOTAL
PD Watts
0
0
1.6
0
1.6
35
100
7.8
6.1
13.9
35
80
6.5
4.9
11.4
50
80
5.6
10
15.6
4
Rev. B 9/99