LM2451 NSC | Alldatasheet
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Absolute Maximum Ratings (Notes 1, If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VCC) +250V Bias Voltage (VBB) +16V Input Voltage (VIN) −0.5V to VBB +0.5V Storage Temperature Range (TSTG) −65˚C to +150˚C Lead Temperature (Soldering, <10 sec.) 300˚C ESD Tolerance, Human Body Model 2 kV Machine Model 200V Junction Temperature 150˚C θJC (typ) 4.0˚C/W Operating Ratings (Note 2) VCC +100V to +230V VBB +7V to +13V VIN +0V to +5V VOUT +40V to +215V Case Temperature (10W max power) 110˚C Do not operate the part without a heat sink and thermal grease. Heat sink must have a thermal resistance under 5.0˚C/W. (Note 7)
Electrical Characteristics
(See Figure 3 for Test Circuit). Unless otherwise noted: VCC = +220V, VBB = +12V, VDAC = +0.5V, CL = 10 pF, TC = 50˚C. DC Tests: VIN = +2.7VDC. AC Tests: Output = 130VPP (60V – 190V) at 1 MHz. Symbol Parameter Conditions LM2451 Units Min Typ Max ICC Supply Current No Input Signal, No Video Input, No Output Load mA IBB Bias Current mA VOUT, 1 DC Output Voltage No AC Input Signal, VIN = 2.7VDC 122 127 132 VDC VOUT, 2 DC Output Voltage No AC Input Signal, VIN = 1.2VDC 200 205 210 VDC VOUT, 3 DC Output Voltage No AC Input Signal, VIN = 1.2VDC, VDAC = 1.2VDC 192 198 204 VDC VOUT, 4 DC Output Voltage No AC Input Signal, VIN = 1.2VDC, VDAC = 2.7VDC 154 160 166 VDC AV DC Voltage Gain No AC Input Signal −51 −54 −57 V/V ADAC DAC Input DC Voltage Gain No AC Input Signal −23 −26 −29 V/V ∆AV Gain Matching (Note 4), No AC Input Signal 1.0 dB LE Linearity Error (Notes 4, 5), No AC Input Signal tr Rise Time (Note 6), 10% to 90% ns +OS Overshoot tf Fall Time (Note 6), 90% to 10% ns −OS Overshoot (Note 6) BWL Large Signal Bandwidth VOUT AC = 130 VP-P, VOUT DC = 125 V MHz BWM Medium Signal Bandwidth VOUT AC = 100 VP-P, VOUT DC = 125 V MHz BWS Small Signal Bandwidth VOUT AC = 60 VP-P, VOUT DC = 125 V MHz IkERROR Current Output Error Output Current = 0 µA to 200 µA −52 µA ∆IkERROR Current Output Difference Between Channels Output Current = 0 µA to 200 µA NA µA Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Note 2: Operating ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may change when the device is not operated under the listed test conditions. Note 3: All voltages are measured with respect to GND, unless otherwise specified. Note 4: Calculated value from Voltage Gain test on each channel. Note 5: Linearity Error is the variation in DC gain from VIN = 1.10V to VIN = 4.30V. Note 6: Input from signal generator: tr, tf < 10 ns. Note 7: Running the 1 MHz to 30 MHz test pattern at 1080i this part will dissipate approximately 10 W. This is the commonly accepted test pattern that is representative of the worst case high frequency content for normal television viewing. This is the pattern used to estimate the worst case power dissipation of the LM2451 in its normal application. It is recommended to use a heat sink with a thermal resistance of 5.0˚C/W or better. LM2451 www.national.com
(Continued) NSC DEMONSTRATION BOARD Figure 15 shows the routing and component placement on the NSC LM2451 demonstration board. This board provides a good example of a layout that can be used as a guide for future layouts. Note the location of the following compo- nents: C26—VCC bypass capacitor, located very close to pin 12 and ground pins C27—VBB bypass capacitor, located close to pin 7 and ground C28, C30, C33—VCC bypass capacitors, near LM2451 and VCC clamp diodes. Very important for arc protection. The routing of the LM2451 outputs to the CRT is very critical to achieving optimum performance. Figure 16 shows the routing and component placement from pin 13 (VOUT3) of the LM2451 to the blue cathode. Note that the components are placed so that they almost line up from the output pin of the LM2451 to the blue cathode pin of the CRT connector. This is done to minimize the length of the video path between these two components. Note also that D1, D8 and R36 are placed to minimize the size of the video nodes that they are attached to. This minimizes parasitic capacitance in the video path and also enhances the effectiveness of the pro- tection diodes. The anode of protection diode D1 is con- nected directly to a section of the ground plane that has a short and direct path to the CRT ground and the LM2451 ground pins. The cathode of D8 is connected to VCC very close to decoupling capacitor C28 which is connected to the same area of the ground trace as D1. The diode placement and routing is very important for minimizing the voltage stress on the LM2451 during an arc over event. This demonstration board uses large PCB holes to accom- modate socket pins, which function to allow for multiple insertions of the LM2451 in a convenient manner. To benefit from the enhanced LM2451 package with thin leads, the device should be secured in small PCB holes to optimize the metal-to-metal spacing between the leads. CURRENT OUTPUT FOR IK FEEDBACK SYSTEMS The LM2451 can be used in DTV applications that use an IK feedback system. Figure 14 shows an example of an inter- face circuit used to feed back the IK output of LM2451 to a preamplifier with an ac coupled IK input. This feedback system consists of the preamp, LM2451, and interface circuit, forming a closed loop to automatically ad- just the black level of the drive signals to the cutoff point of the RGB cathodes. Following is a description of the interface circuit operation used for AVPs that have a voltage input for their IK sense input. The output at pin 8 of the LM2451 is filtered of high fre- quency noise by C14. D7 is used to limit the peak voltage at pin 8. Without this clamp diode the voltage would easily exceed 12V during active video when the cathode currents are much greater than the small currents being detected during vertical blanking. Exceeding 12V could damage Q4 and result in improper operation of the driver. R35 is essential to convert the IK current to voltage. Choos- ing the value of R35 sets the gain of the feedback voltage, and consequently, the operating point of the tube. Once a stable operating point is established, this point can be fine- tuned using the adjustment range of the feedback system or standard preamp controls. Changing the value of R35 will change the cutoff voltage at the cathode. A smaller value of R35 requires more IK current to maintain the feedback loop. The cutoff voltage set at the cathode will be lower to adjust to the higher IK current. This additional current must come from the cathode; therefore, the cathode voltage is set lower to meet higher current requirement. A higher value of R35 will do the opposite, raising the cathode voltage because less IK current is needed to maintain the same voltage at R35. The emitter follower, Q7, isolates R35 from the input imped- ance of the preamp. R21 and R39 bias the emitter of Q7 to limit the maximum voltage to the preamp. These resistor values should be chosen to limit the maximum voltage at the emitter and protect the preamp from any large voltages that would otherwise occur during active video. C9 is used to AC couple the IK signal to the preamp. The advantage of AC coupling is that any DC component (leakage current from the driver) of the IK signal is not detected by the IK sense input of the preamp. Some AVPs do have a direct current input for their IK sense input. For interfacing to these AVPs the only components to be used in the IK sense section are D7 and R41. To com- plete the signal path a jumper must be used to replace R34, C9 and the base-emitter junction of Q7. C14 can still be used for high frequency filtering. LM2451 www.national.com
FIGURE 14. LM2451 DTV Applications Circuit
FIGURE 15. LM2451 DTV Demonstration Board Layout
FIGURE 16. Trace Routing and Component Placement for Blue Channel Output
inches (millimeters) unless otherwise noted NOTE: Available only with lead free plating Order Number LM2451TB National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. Leadfree products are RoHS compliant. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 www.national.com LM2451 220V Monolithic Triple Channel 12 MHz DC Coupled CRT DTV Driver