参数资料
型号: MSK645B
厂商: MS KENNEDY CORP
元件分类: 音频/视频放大
英文描述: HIGH PERFORMANCE, HIGH VOLTAGE VIDEO DISPLAY DRIVER
中文描述: 1 CHANNEL, VIDEO AMPLIFIER, BFM9
封装: HEAT SINK, SIP-9
文件页数: 3/6页
文件大小: 217K
代理商: MSK645B
APPLICATION NOTES
BLACK LEVEL CONTROL
Unlike many currently available video amplifiers, the MSK 645
is a D.C. coupled device. D.C. coupling affords the user direct
black level control.
A video input voltage of approximately
0.85 volts will set the output voltage to 50VDC (black level for
+VHV=60VDC). Black level control grants the user flexibility
in the application of the amplifier. For example, the user could
apply a 0.85VDC level to the video input to bias the output at
the black level (approximately 50V for VHV=60V) and have
input video information swing from 0.85 to 1.5V causing the
output to swing from the black level towards white (zero).
This configuration would dissipate the least amount of power
and is most common. Another possible circuit configuration
could be to D.C. bias the video input pin so that the output is
at 1/2VHV. The output video signal could then swing linearly
from (+VHV-10V) to (ground + 10V). Careful consideration
must be paid to device power dissipation in this configuration
since it will be very high.
VBIAS INPUT
The VBIAS pin is connected to the base of the cascode tran-
sistor in the equivalent schematic. The purpose of the cascode
transistor is to isolate the input transistor from the high volt-
age supply. The input transistor must have a very high transi-
tion frequency specification and this is difficult to find in high
voltage transistors. By using the cascode transistor to relieve
the input transistor of its high BVceo requirement, high speed,
low breakdown transistors can be used. The voltage applied
to pin three minus a base to emitter voltage drop of approxi-
mately 0.6 volts is the voltage present at the collector of the
input transistor that acts as the voltage to current convertor.
The voltage applied to the VBIAS pin has a practical upper limit
of 10.0 volts. Above 10.0 volts the device may not be able to
reach white level without going into cutoff. The practical lower
limit for this pin is approximately 2.0 volts. Below 2.0 volts
the input transistor will be dangerously close to cutoff. The
MSK 645 functions best with VBIAS set to 5.0 volts ±1.0 volt.
OUTPUT CONSIDERATIONS
The output of the MSK 645 is driven by a complimentary
push-pull buffer. The output stage isolates the capacitive load
from the amplifier thereby making rising and falling edges rela-
tively load independent. The bandwidth of the MSK 645 is
limited by the RC time constant made up of the resistance
from +VHV to the base of the NPN buffer and the capacitance
from the NPN buffer base to ground. The coils in the equiva-
lent schematic are chosen at the factory to moderately peak
the amplifiers response (10%). For application specific user
adjustable peaking, see the Typical Connection Circuit page.
OUTPUT PROTECTION
High voltage arcing can occur in the CRT being driven and
cause severe damage to the MSK 645 output unless certain
precautions are taken. The clamp diodes D1 and D2 (see fig-
ure 1) will keep the voltage at the output at a safe level. These
diodes should have a low series resistance and shunt capaci-
tance as well as a high surge rating (FDH400 is recommended).
In the event of an arcover, Rb limits the current flowing through
the clamp diode and Ra limits the current into the MSK 645
output. The recommended values shown in figure 1 should
not be deviated from without checking the monitor performance
since increasing these values will adversely affect transistion
times.
HEAT SINK SELECTION
To calculate what size heat sink is needed for a particular ap-
plication, the following formula must be used:
Tj = Pd (R
θjc + Rθsa) + Ta
where:
Tj=junction temperature = 150°C max.
R
θjc=30°C/W max.
Ta is the ambient temperature and Pd is the device power dis-
sipation. R
θsa is the heat sink thermal resistance.
EXAMPLE:
In an application an MSK 645 is dissipating 4 watts of power
and the ambient temperature is +25°C. Plugging in all the
known variables and rearranging the equation it can be seen
that:
R
θsa = ((150°C - 25°C)/4W) - 30°C/W
= 1.2°C/W
A heat sink with a thermal resistance of no more than 1.2°C/W
must be used to maintain a junction temperature of 150°C max.
POWER DISSIPATION
The most efficient method to reduce device power dissipa-
tion when using the MSK 645 is to fix the black level at a point
as close to +VHV as possible and maintain the peak to peak
video output voltage to as small an excursion as possible. The
case of the MSK 645 is electrically isolated from internal cir-
cuitry and therefore the user should attach the heat sink di-
rectly to the case of the device.
POWER SUPPLY DECOUPLING
Both the +VHV and the VBIAS input pins are decoupled inter-
nally with 0.1F capacitors to contain line noise. However it is
good practice to decouple the MSK 645 externally with at least
a 4.7F electrolytic capacitor placed as close as possible to
the associated device pins.
Rev. D 10/05
3
相关PDF资料
PDF描述
MSL400C-NKB6HD SINGLE COLOR LED, BLUE
MS400-NWW28H SINGLE COLOR LED, COOL WHITE
MS400-NKA60H SINGLE COLOR LED, AMBER
MS400C-NKA120DC SINGLE COLOR LED, AMBER
MS400-NKG2 SINGLE COLOR LED, GREEN
相关代理商/技术参数
参数描述
MSK690 制造商:MSK 制造商全称:M.S. Kennedy Corporation 功能描述:HIGH VOLTAGE AMPLIFIER
MSK690B 制造商:MSK 制造商全称:M.S. Kennedy Corporation 功能描述:HIGH VOLTAGE AMPLIFIER
MSK707 制造商:MSK 制造商全称:M.S. Kennedy Corporation 功能描述:ULTRA-ACCURATE/HIGH SLEW RATE INVERTING OPERATIONAL AMPLIFIER
MSK707E 制造商:MSK 制造商全称:M.S. Kennedy Corporation 功能描述:ULTRA-ACCURATE/HIGH SLEW RATE INVERTING OPERATIONAL AMPLIFIER
MSK707H 制造商:MSK 制造商全称:M.S. Kennedy Corporation 功能描述:ULTRA-ACCURATE/HIGH SLEW RATE INVERTING OPERATIONAL AMPLIFIER