LM2432 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 (V CC) +250V Bias Voltage (VBB) +16V Input Voltage (VIN) -0.5V to V BB+0.5V IK Voltage (VIK) -0.5V to +16V 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 θ JC (typ) 4.5˚C/W Operating Ranges(Note 2) VCC +130V to +230V VBB +7V to +13V VIN 0V to +4.25V VIK 0V to VBB+1V VOUT +40V to VCC–5V Case Temperature See Figure 11. Derate power for TC above 110˚C. Do not operate the part without a heat sink. Electrical Characteristics (See Figure 3 for Test Circuit) Unless otherwise noted: V CC = +220V, VBB = +12V, CL = 10 pF, T C = 40˚C. DC Tests: VIN = 2.75VDC AC Tests: Output = 110V PP (80V - 190V) at 1 MHz Symbol Parameter Conditions LM2432 UnitsMin Typical Max ICC Supply Current No AC Input Signal, No Output Load 12 17 mA IBB Bias Current 81 1 m A VOUT, 1 DC Output Voltage No AC Input Signal, V IN = 2.75VDC 121 126 131 V DC VOUT, 2 DC Output Voltage No AC Input Signal, V IN = 1.25VDC 199 204 209 V DC AV DC Voltage Gain No AC Input Signal –50 –53 –56 LE Linearity Error (Note 4), No AC Input Signal 5 % t R Rise Time (Note 5), 10% to 90% 10 ns +OS Overshoot (Note 5) 21 % t F Fall Time (Note 5), 90% to 10% 8 ns –OS Overshoot (Note 5) 8 % IKERROR IK Current Output Error (Notes 6, 7) –37 0 +37 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 analy sis. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may change when the device is not operated under the list ed test conditions. Note 3: All voltages are measured with respect to GND, unless otherwise specified. Note 4: Linearity Error is the variation in DC gain from V IN = 1.15V to V IN = 4.35V. Note 5: Input from signal generator: t r,t f < 2 ns. Slower inputs to the LM2432 will change the transient response characteristics and reduce power dissipation. Note 6: IKERROR =I K –I OUT, where IK is the IK current output from pin 5 (IK) and I OUT is the cathode current into pin 2 (V OUT). IK is calculated by measuring VIK across a known resistor value between pin 5 and GND. Note 7: Refer to the RGB Video Processor data sheet for IK leakage compensation, feedback operation, and adjustment range information. LM2432 www.national.com 2
The LM2432 is a high voltage monolithic single channel CRT driver suitable for HDTV applications. The LM2432 typically operates with 220V and 12V power supplies. The part is housed in a staggered 7-lead TO-220 molded plastic power package. The circuit diagram of the LM2432 is shown in Figure 2. The PNP emitter follower, Q5, provides input buffering. Q1 and Q2 form a fixed gain cascode amplifier with resistors R1 and R2 setting the gain at −53. Emitter followers Q3 and Q4 isolate the high output impedance of the cascode stage from the capacitance of the CRT cathode which decreases the sensitivity of the device to load capacitance. Q6 provides biasing to the output emitter follower stage to reduce cross- over distortion at low signal levels. The LM2432 has an IK current output (pin 5) that produces a replica of the actual cathode current into V OUT (pin 2). The IK output pin is internally connected to the collector of Q4. If IK feedback is not used in the application, the IK pin should be connected to the same ground as pin 3 (GND). Otherwise, the IK output can interface with a RGB video processor with IK feedback for automatic cathode calibration. Note: During the non-blanking period, video current levels can be as high as several mA, which is much higher than the reference currents (in µA range) produced during the IK measurement interval. These high currents have the potential to produce large voltages at the IK output pin. To avoid damage to Q4, the IK output voltage, V IK, must not exceed +16V (V IKMAX). Please see the section “Cathode Current Output for IK Feed- back Systems” for more information on the usage and pro- tection of the IK output. Application Hints INTRODUCTION National Semiconductor (NSC) is committed to provide ap- plication information that assists our customers in obtaining the best performance possible from our products. The fol- lowing information is provided in order to support this com- mitment. The reader should be aware that the optimization of performance was done using a specific printed circuit board designed at NSC. Variations in performance can be realized due to physical changes in the printed circuit board and the application. Therefore, the designer should know that com- ponent value changes may be required in order to optimize performance in a given application. The values shown in this document can be used as a starting point for evaluation purposes. When working with high bandwidth circuits, good layout practices are also critical to achieving maximum per- formance. IMPORTANT INFORMATION The LM2432 performance is targeted for the HDTV market. The application circuits shown in this document to optimize performance and to protect against damage from CRT ar- cover are designed specifically for the LM2432. If another member of the NSC DTV CRT Driver family is used, please refer to its data sheet. POWER SUPPLY BYPASS Since the LM2432 is a wide bandwidth amplifier, proper power supply bypassing is critical for optimum performance and for robustness against arcover. Improper power supply bypassing can result in large overshoot, ringing or oscilla- tion, and even arcover failure. 0.1 µF capacitors should be connected from the supply pins, V CC and V BB, to ground using very short traces. Additionally, a 10 µF or larger elec- trolytic capacitor should be connected from both supply pins to ground reasonably close to the LM2432. ARC PROTECTION During normal CRT operation, internal arcing may occasion- ally occur. This fast, high voltage, high energy pulse can damage the LM2432 output stage since it is DC coupled to the cathode. In a DC coupled application, an external spark gap with an arcover voltage rating of 200 to 300V DC on the cathode is NOT recommended. The internal CRT socket spark gap (1 to 2 kV DC rating) can sufficiently reduce the initial arcover voltage seen at the cathode. The output circuit shown in Figure 13is designed to help clamp the voltage at the output of the LM2432 to a safe level during an arcover. External arc protection clamp diodes, D1 and D2, should have a fast transient response, high peak current rating, low series impedance and low shunt capacitance. 1SS83 or equivalent diodes like BAV21 are recommended. D1 and D2 should have short, low impedance connections to V CC and ground respectively. The cathode of D1 should have a very short connection to a separate V CC bypass capacitor, C3. The ground connection of D2 and the C3 should have a short, direct path to ground. This will significantly reduce the high frequency voltage transients that the LM2432 would be subjected to during an arcover. Resistor R2, which limits the arcover current that is seen by the diodes, should be a 1⁄2W solid carbon type resistor. R1 limits the current into the LM2432 as well as the voltage stress at the outputs of the device and can be a 1⁄4W metal or carbon film type resistor. Having large value resistors for R1 and R2 would be desirable, but this has the effect of increas- ing rise and fall times. Inductor L1 is critical to reduce the initial high frequency voltage levels that the LM2432 would be subjected to. The inductor will not only help protect the device but it will also help minimize rise and fall times as well as minimize EMI. For proper arc protection, it is important to not omit any of the arc protection components shown in Figure 13. LM2432 www.national.com 6
Application Hints (Continued) ever, it was decided to preserve the TV’s original RGB mainboard circuitry (the PNP buffer) and use two NPN tran- sistors on the neck board. The input stage from the RGB processor to the LM2432 will be determined by the system designer for his specific appli- cation. The input stage required depends mainly on the following system parameters: Nominal CRT cut-off voltage Nominal black level output voltage of the RGB processor VCC &V BB supply voltages of the LM2432 (determines DC transfer characteristic) Once the nominal black level input to the LM2432 estab- lishes a cathode black level near the CRT cut-off voltage, it can be fine-tuned using the processor’s cut-off adjustment or calibrated automatically using the IK feedback system, if applicable. Lastly, some RGB processor video outputs can- not adequately drive the capacitive load introduced by the cabling between the RGB mainboard and neck boards. To prevent loading the processor’s output, a NPN or PNP buffer stage can be applied close to the output on the mainboard to sufficiently drive the video signal through cabling to the neck board. It is important to bias the buffer stage(s) properly to obtain optimal video performance and maintain the full video adjustment range of the RGB processor. Video Output and Arc Protection The routing of the LM2432 output to the CRT is very critical to achieve optimal video performance and robustness against arcover. Figure 17shows the routing and component placement from V OUT (pin 2) of the LM2432 to the cathode pin of the CRT socket. The components are placed so that there is a short, direct path from the LM2432 output to the cathode. This is done to reduce the PCB parasitic capaci- tance on the LM2432 output and minimize EMI. Note also that L3, D3, D4, and R6 are placed to minimize the size of the video nodes that they are attached to. This enhances the effectiveness of the arc protection diodes. The anode of protection diode D3 is connected directly to a section of the ground plane that has a short, direct path to ground. The cathode of D4 is connected to V CC very close to decoupling capacitor C7, which is connected to the same section of the ground plane as D3. The diode placement and routing is very important to shunt arcover current away from the output and minimize the voltage stress on the LM2432. The internal CRT socket spark gap is essential to significantly reduce the initial arcover voltage seen at the cathode. The DAG con- nector should be connected to CRT ground for arc return current. IK Feedback Circuit The NSC demonstration neck board was made so that no modifications to the existing TV circuitry were necessary (except for replacing the original neck boards). Therefore, the video interface and IK feedback circuits are designed to be compatible with those original TV circuits. Referring to Figure 16, the LM2432 IK output (pin 5) is connected to protection circuitry before the IK current signal is routed to pin 4 of connector J8. Diode D1 protects the LM2432 IK pin from excessive voltage during normal video by clamping to the V BB supply. Diode D2 isolates the IK output from the other channels during the active IK measurement interval. Resistors R17 and R12 limit the current through D1 and D2, and C12 is used for filtering. From connector J8, the IK current signal is passed through cabling and combined with the other two IK signals on the RGB mainboard. Note: The following paragraph describes circuitry that is not part of the NSC demonstration neck board. The RGB pro- cessor, which operates with a voltage feedback IK topology, uses a single “IK resistor” on the RGB mainboard to convert all three IK currents into a voltage signal. The IK voltage signal is then buffered through a PNP transistor before it is filtered and AC coupled to the RGB processor’s IK input. This is one implementation of the IK feedback circuit based on this TV’s specific RGB processor. The system designer should refer to the RGB processor data sheet to determine the appropriate feedback circuit implementation for his ap- plication. Supply Decoupling Note the location of the following components: C 5—V CC bypass capacitor with short traces to the V CC and GND pins of LM2432. C 7—V CC bypass capacitor with short traces to the V CC arc protection diode and ground. This capacitor is very important for arc protection. C 9—V BB bypass capacitor with short traces to the V BB and GND pins. C10 and C11 — V CC and V BB electrolytic capacitors placed near supply pins of LM2432. Other Items Connector J1 and switches JP2 & JP4 can be used to bypass the TV’s internal 200V and 12V supplies and evalu- ate the LM2432 with external V CC and VBB supplies. Also, this demonstration board uses medium-sized PCB holes to accommodate socket pins, which function to allow for mul- tiple insertions of the LM2432 in a convenient manner. To benefit from the enhanced LM2432 package with thin leads, the device should be secured with solder in small PCB holes to optimize the metal-to-metal spacing between the leads. LM2432 www.national.com 10
FIGURE 16. LM2432 Demonstration Board Schematic
FIGURE 17. LM2432 Demonstration Board Layout
Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM2432TE 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. 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 LM2432 220V Monolithic Single Channel 37 MHz HDTV CRT Driver