MSK645 MSK | Alldatasheet
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The MSK 645 is an amplifier designed specifically to suit the needs of todays high resolution CRT display moni- tors. With a typical bandwidth of 150 MHz and transition times typically under 3.0nS the MSK 645 can easily drive monitors with resolutions of up to 1280 x 1024. The output can swing up to 65 Vpp and gain is internally set to minimize external component count. The MSK 645(B) is available screened to MIL-PRF-38534 and comes in a space efficient pack- age that is electrically isolated from the internal circuitry and can be attached directly to a heat sink for efficient thermal dissipation. FEATURES: 4707 Dey Road Liverpool, N.Y. 13088 M.S.KENNEDY CORP. (315) 701-6751 HIGH PERFORMANCE, HIGH VOLTAGE VIDEO DISPLAY DRIVER 645 ISO-9001 CERTIFIED BY DSCC EQUIVALENT SCHEMATIC
65 Vpp Output Voltage
150 MHz Typical Bandwidth
Transition Times Typically <3.0 nS Cost and Space Efficient Package Electrically Isolated Case Gain Fixed Internally DESCRIPTION: MIL-PRF-38534 CERTIFIED CRT Driver for SVGA Display Driver for Systems with up to 1280 x 1024 Display Resolution High Voltage Fixed Gain Amplifier PIN-OUT INFORMATION TYPICAL APPLICATIONS Video Input Ground VBIAS Ground Video Output Ground +VHV Ground Ground Rev. D 10/05
2.0 0.5 1.3 ±3.0 5.0 STATIC CHARACTERISTICS Quiescent Current (VHV) Quiescent Current (+VBIAS) VHV Power Supply Range VBIAS Power Supply Range Video Input Voltage DYNAMIC CHARACTERISTICS Video Gain Video Gain Flatness 2 Video Output Rise/Fall Time Video Output Overshoot 2 Bandwidth -3dB 2 mA mA V V V V V V/V dB nS MHz Storage Temperature Range Lead Temperature Range (Solder 10 Seconds) Junction Temperature Case Operating Temperature MSK645 MSK645(B) +VHV +VIN +VBIAS IOUT High Voltage Supply Input Voltage Bias Input Voltage Peak Output Current ○+80V ±5V +10V 200mA TST TLD TJ TC ABSOLUTE MAXIMUM RATINGS -65°C to +150°C +300°C +175°C -40°C to +85°C -55°C to +125°C ELECTRICAL SPECIFICATIONS Min. Typ. Max. VIN=No Connect RL=∞ VIN=No Connect RL=∞ VOUT=+50VDC Output Stage Junction to Case @ 125°C High Level Low Level F=1MHz;VOUT=+15Vto+45V F=10Hz to 60MHz;VOUT=30VPP VOUT=+15Vto+45V VOUT=10VPP VINTR=10nS 0.4 100 0.6 0.01 0.85 ±1.0 3.0 150 0.5 100 0.6 0.01 0.85 ±1.0 3.0 150 1,2,3 1,2,3 1,2,3 Min. Typ. Max. MSK 645(B) MSK 645 Video Output Voltage 2.0 0.5 1.2 ±2.0 4.0 NOTES: +VHV=60V; +VBIAS=5V; RL=10KΩ; unless otherwise specified. Parameter is guaranteed by design but not tested. Typical specifications are representative of actual device performance at 25°C but are for reference only. Military grade devices ('B' suffix) shall be 100% tested to subgroups 1,2,3 and 4. Subgroup 5 and 6 testing available upon request. Subgroup 1,4 TA=TC=+25°C Subgroup 2,5 TA=TC=+125°C Subgroup 3,6 TA=TC=-55°C Refer to the video clip point curve on the Typical Performance Curves page. Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle. Parameter Test Conditions Group A Subgroup Units Rev. D 10/05 Thermal Resistance 2 °C/W
Unlike many currently available video amplifiers, the MSK 645 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 (Rθjc + Rθsa) + Ta where: Tj=junction temperature = 150°C max. Rθjc=30°C/W max. Ta is the ambient temperature and Pd is the device power dis- sipation. Rθsa 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: Rθsa = ((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 0.1µF capacitors to contain line noise. However it is good practice to decouple the MSK 645 externally with at least a 4.7µF electrolytic capacitor placed as close as possible to the associated device pins. Rev. D 10/05
TYPICAL PERFORMANCE CURVES Rev. D 10/05
Figure 1. Keep in mind that as the value of load capacitance increases, so will the overshoot. Starting with 499Ω resistors for RD1 and RD2 and 150pF for CA, the overshoot can be minimized by adjusting RD1 and RD2 up or down.
ORDERING INFORMATION
The information contained herein is believed to be accurate at the time of printing. MSK reserves the right to make changes to its products or specifications without notice, however, and assumes no liability for the use of its products. Please visit our website for the most recent revision of this datasheet. MECHANICAL SPECIFICATIONS M.S. Kennedy Corp.
4707 Dey Road, Liverpool, New York 13088
Phone (315) 701-6751 FAX (315) 701-6752 www.mskennedy.com ALL DIMENSIONS ARE ±0.010 INCHES UNLESS OTHERWISE LABELED Part Number Industrial MSK645 MSK645B Rev. D 10/05 ESD Triangle indicates Pin 1 Mil-PRF-38534 CLASS H