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CVA2405T Datasheet(PDF) 3 Page - Calogic, LLC |
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CVA2405T Datasheet(HTML) 3 Page - Calogic, LLC |
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3 / 4 page 
CVA2405T CORPORATION CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025 APPLICATION INFORMATION The CVA2405T is a high voltage triple CRT driver suitiable to drive 69kHz, 1280 x 1024 CRT displays. It features a high impedance input to match any pre-amplifier. The CVA2405T has a true class AB output stage that results in excellent gray scale linearity and consistent EMI performance. As with any high speed amplifier used in CRT display applications, specific precaution should be taken to get the required performance. Power supply should be by pass as close to the device pin as possible. Use 0.01 µf very near to the device and a large capacitor of 10 µf or more (preferable 100 µf) near the device. A 0.1µf and 10µf should be connected near the Vbias pin (#10). Arc protection is very essential. Fast diodes together with the spark gap will achieve sufficient protection. However, in certain applications depends on the tubes a high value of resistor is required to reduce the current into the CVA2405T during arcing. This will result in less than desireable performance some of which can be restored by using a peaking inductor at the output pin, Figure 2. Another way to achieve this is by using a RC network at the output of the device and use a peaking inductor at the tube, Figure 3. The rise and fall time of the CVA2405T may suffer due to stray capacitances associated with the PC Board and other components. It can be improved by carefully designing the PC Board where the output stage and input stage ground path are seperated. Calogic will assist customers in the layout of the PC Board that will result in quick EMI passage and better performance. The output peaking should be used only to restore the performance loss due to stray capacitances. Over peaking will cause excessive ringing that will have better results but poor EMI. The DC restore circuit is also important when considering the high frequency performance. Using CVA4501, DC Bias IC, better results can be obtained and high frequency performance can be maximixed. THERMAL CONSIDERATIONS Power supply current increases as the input signal increases and consequently power dissipation also increases. The CVA2405T cannot be used without heat sinking. Figure 4 shows the power dissipated in each channel over the operating voltage range of the device. Under white screen conditions, i.e.: 25V output, dissipation increases to 10.8W total. The CVA2405T case temperature must be maintained below +100 oC. If the maximum expected ambient temperature is +50 oC, then a heat sink is needed with thermal resistance equal to or less than: Rth = ( 100 − 50oC) 10.8W = 4.6oC/W The CVA2405T maximum load is 600 Ω to ground or V+. The output of CVA2405T is not short circuit proof. Any resistance to V + or Ground should be > 600Ω. FIGURE 2. 1P-15 VBIAS VIDEO CVA2405T +80V L R 91 Ω SPARK GAP 33 Ω FIGURE 3. 1P-16 VBIAS VIDEO CVA2405T +80V 1K SPARK GAP 33 Ω C CVA4501 BIAS DC BIAS I.C. Vcc L R |
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