National Semiconductor Application Note 2067 Terry Allinder June 15, 2010 Introduction Theory of Operation The LM5027A evaluation board is designed to provide the design engineer with a fully functional power converter based on the Active Clamp Forward topology to evaluate the LM5027A controller. The evaluation board is provided in an industry standard quarter-brick footprint. The performance of the evaluation board is as follows: Input Operating Range: 36 to 78V (100V peak) Output Voltage: 3.3V Output Current: 0 to 30A Measured Efficiency: 90.5% @ 30A, 92.5% @ 15A Frequency of Operation: 250 kHz Board Size: 2.3 X 1.45 x 0.5 inches Load Regulation: 1% Line Regulation: 0.1% Line UVLO, Hiccup Current Limit A 70% Maximum Duty Cycle The printed circuit board consists of 6 layers of 2 ounce copper on FR4 material with a total thickness of 0.050 inches. The unit is designed for continuous operation at rated load at <40°C and a minimum airflow of 200 CFM. Power converters based on the Forward topology offer high efficiency and good power handling capability in applications up to several hundred Watts. The operation of the transformer in a forward topology does not inherently self-reset each power switching cycle; a mechanism to reset the transformer is required. The active clamp reset mechanism is presently finding extensive use in medium level power converters in the 50 to 200W range. The Forward converter is derived from the Buck topology family, employing a single modulating power switch. The main difference between the topologies are, the Forward topology employs a transformer to provide input / output ground isolation and a step down or step up function. Each cycle, the main primary switch turns on and applies the input voltage across the primary winding, which has 12 turns. The transformer secondary has 2 turns, leading to a 6:1 stepdown of the input voltage. For an output voltage of 3.3V the required duty cycle (D) of the main switch must vary from approximately 60% (low line) to 25% (high line). The LM5027A limits the PWM duty cycle output to a maximum of 70% (typical). The maximum duty cycle limits the voltage stress on the Active Clamp Forward converter MOSFETs. The clamp capacitor along with the reset switch reverse biases the transformer primary each cycle when the main switch turns off. This reverse voltage resets the transformer. The clamp capacitor voltage is Vin / (1-D). Feedback from the output is processed by an amplifier and reference, generating an error voltage, which is coupled back to the primary side control through an optocoupler. The LM5027A voltage mode controller pulse width modulates the error signal with a ramp signal derived from the input voltage. Deriving the ramp signal slope from the input voltage provides line feed-forward, which improves line transient rejection. The LM5027A also provides a controlled delay necessary for the reset switch. The evaluation board can be synchronized to an external clock with a recommended frequency range of 275 to 300 kHz. LM5027A Evaluation Board LM5027A Evaluation Board AN-2067 © 2010 National Semiconductor Corporation 301263 www.national.com 30126301 AN-2067 Schematic www.national.com 2 AIR FLOW An appropriate electronic load, with specified operation down to 3.0V minimum, is desirable. The resistance of a maximum load is 0.11Ω. You need thick cables! Consult a wire chart if needed. If resistor banks are used there are certain precautions to be taken. The wattage and current ratings must be adequate for a 30A, 100W supply. Monitor both current and voltage at all times. Ensure there is sufficient cooling provided for the load. When applying power to the LM5027A evaluation board certain precautions need to be followed. A failure or mis-connection can present itself in a very alarming manner. PROPER CONNECTIONS When operated at low input voltages the evaluation board can draw up to 3.5A of current at full load. The maximum rated output current is 30A. Be sure to choose the correct connector and wire size when attaching the source supply and the load. Monitor the current into and out of the evaluation board. Monitor the voltage directly at the output terminals of the evaluation board. The voltage drop across the load connecting wires will give inaccurate measurements; this is especially true for accurate efficiency measurements. POWERING UP Using the shutdown pin provided will allow powering up the source supply with the current level set low. It is suggested that the load be kept quite nominal during the first power up. Set the current limit of the source supply to provide about 1.5 times the wattage of the load. As you remove the connection from the shutdown pin to ground, immediately check for 3.3 volts at the output. A most common occurrence, that will prove unnerving, is when the current limit set on the source supply is insufficient for the load. The result is similar to having the high source impedance referred to earlier. The interaction of the source supply folding back and the evaluation board going into undervoltage shutdown will start an oscillation, or chatter, that may have highly undesirable consequences. A quick efficiency check is the best way to confirm that everything is operating properly. If something is amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be incorrect in a switching power supply without creating losses and potentially damaging heat. SOURCE POWER The evaluation board can be viewed as a constant power load. At low input line voltage (36V) the input current can reach 3.5A, while at high input line voltage (78V) the input current will be approximately 1.5A. Therefore too fully test the LM5027A evaluation board a DC power supply capable of at least 80V and 4A is required. The power supply must have adjustments for both voltage and current. An accurate readout of output current is desirable since the current is not subject to loss in the cables as voltage is. The power supply and cabling must present a low impedance to the evaluation board. Insufficient cabling or a high impedance power supply will droop during power supply application with the evaluation board inrush current. If large enough, this droop will cause a chattering condition upon power up. This chattering condition is an interaction with the evaluation board undervoltage lockout, the cabling impedance and the inrush current. OVER CURRENT PROTECTION The evaluation board is configured with hiccup over-current protection. In the event of an output overload (approximately 33A) the unit will discharge the softstart capacitor, which disables the power stage. After a delay the soft-start is released. The shutdown, delay and slow recharge time of the softstart capacitor protects the unit, especially during short circuit event where the stress is highest. LOADING An appropriate electronic load, with specified operation down to 3.0V minimum, is desirable. The resistance of a maximum load is 0.11Ω. You need thick cables! Consult a wire chart if needed. If resistor banks are used there are certain precautions to be taken. The wattage and current ratings must be adequate for a 30A, 100W supply. Monitor both current and 30126302 Typical Evaluation Setup 3 www.national.com AN-2067 voltage at all times. Ensure there is sufficient cooling provided for the load. Powering and Loading Considerations AN-2067 Start-Up Power supplies have a soft-start circuit(s) to control their output voltage when input power is applied. The soft-start sequence limits the peak inrush current as the output capacitors are charged, and prevents the output voltage from overshooting. In most power supplies there are primary side and secondary side soft-start circuits. The primary side soft-start circuit is generally in a primary side controller and the soft-start time is set with an external capacitor. The function of the primary side soft-start circuit is to slowly increasing the duty cycle of the controller from zero to the maximum duty cycle. The maximum duty cycle varies based on the controller and the circuit topology. The secondary side soft-start circuit connects a resistor/capacitor from the secondary side voltage reference to the positive input of the error amplifier. The soft-start time is set by the resistor/capacitor time constant and works by ramping up the voltage reference on the secondary side error amplifier. The output of the error amplifier is fed across the isolation boundary to the primary side controller compensation input which is connected to the controller PWM input. The voltage at the compensation input increases to a value required for regulation as determined by the voltage feedback loop. The secondary side soft-start along with the primary side soft-start work together to control the duty cycle on start-up to controling the power supplies output start-up time, and limit the stress on the power components. Figure 1 shows the primary and secondary side soft-start sequence using the LM5027A into an electronic load. After Vin is applied the primary side soft-start ramps up. When the voltage on the LM5027A SS pin reached 1.0 V the output drives start and power is delivered to the secondary of the transformer. The power supply output rises and the secondary side soft-start circuit begins to ramp-up. The output of the DC-DC converter monotonically increased with no overshoot to 3.3 V out. www.national.com 30126303 FIGURE 1. Soft-Start Pre-Bias Load Start-Up Figure 2 below shows a typical Forward Converter topology with an active clamp using self-driven synchronous rectification. It’s simple and very efficient; however there are some disadvantages when starting this topology into a pre-biased load. The first occurs because the synchronous rectification is on the secondary side of the transformer and without adding intelligence the output current will flow into the converter via the output choke and the free wheeling MOSFET when the converter starts-up or shut down with pre-bias voltage. 4 AN-2067 30126304 FIGURE 2. Typical Forward Converter 5 www.national.com AN-2067 soft-start reaches approximately 4.0V. The OUTSR delay was added to ensure that the power supply output voltage is up and in regulation prior to the freewheeling MOSFET being turned-on, refer to Figure 4 and Figure 5. The OUTSR drive is soft-started; a capacitor on the SSSR pin is released and is charged with a 25 µA current source, slowly increasing the duty cycle of the freewheeling FET’s duty cycle. OUTSR Drive The LM5027A has a dedicated pin (OUTSR) to drive the synchronous rectifier free wheeling MOSFET through a drive transformer as shown in Figure 3. When the converter startsup, the OUTSR drive is held low and the freewheeling MOSFET is turned-off. As a result, no output current will sink into the converter. The OUTSR is enabled after the primary side 30126301 FIGURE 3. LM5027A Synchronous Rectifier Drive Output (OUTSR) www.national.com 6 AN-2067 30126306 FIGURE 4. LM5027A Drive Timing 30126307 FIGURE 5. LM5027A Soft-Start Waveforms 7 www.national.com AN-2067 Secondary Side Soft-Start Secondary Side Soft-Start Reset In a typical DC-DC converter with a 3.3 V output the voltage reference for the error amplifier is 1.2V. Prior to the power supply being turned-on and if there is a pre-bias load, the secondary side soft-start capacitor (CSS) will be pre-charged to the voltage reference level of 1.2 V (if the pre-bias load > 1.2V), refer to Figure 7. On start-up the primary side soft-start begins and the output voltage rises from the pre-bias voltage level to 3.3 V, refer to Figure 6. At the end of the primary side soft-start period the controller will be at maximum duty cycle and the output voltage will overshoot until the feedback error amplifier has a chance to respond and reduce the output voltage to the regulation set point. When input power is supplied to the LM5027A Evaluation Board the LM5027A’s internal VCC Regulator turns-on providing power to the VCC pin, the primary side soft-start voltage increases, and the output drives are enabled. When the drive outputs are enables the voltage on the transformer secondary increases, the Secondary Bias rises supplying voltage to the reference and error amplifier, refer to Figure 8. During this time FET Q1 is turned-on holding the reference voltage at the positive input to the error amplifier low (zero volts). When the voltage on the secondary bias capacitor (CBIAS) rises above the Zener diode> 3.6 V, the Secondary Bias Power Good (the collector of Q2) goes high. This turns-off FET Q1 allowing the secondary soft-start capacitor to charge up. This solution of reseting the soft-start capacitor to zero (0 V) on start-up works for pre-bias loads as well as loads that do not need to start into a pre-biased condition. This allows for a monotonic start-up under both operating modes. 30126308 FIGURE 6. Pre-bias Secondary Side Soft-Start www.national.com 8 AN-2067 30126309 FIGURE 7. VREF with Pre-Bias Load 9 www.national.com AN-2067 30126310 FIGURE 8. Pre-Bias Schematic the pre-bias source will conduct current through the output inductor and the self driven gate drive resistors R1 and R2. If the pre-bias voltage is greater than the Vgs of the synchronous MOSFET (M1), the MOSFET will be turned-on sinking current into the power supply. Pre-Bias Load-Synchronous Forward MOSFET Enabled The self driven synchronous rectification topology has an issues starting into a pre-bias load. When a pre-bias load is connected across the power supply output, refer to Figure 9, www.national.com 10 AN-2067 30126311 FIGURE 9. Self Driven with Pre-Bias Load Where: Vin = 100 V under transient conditions n is the transformer turns ratio = 6 A diode D1 is connected from the collector to the emitter of Q3 to handle any voltage spikes as a result of circuit inductance. Without this diode inductive voltage spike may damage the Cascod amplifier Q3. An NPN transistor was use instead of an N-Channel MOSFET because the Vgs drop, typically 4 to 5 volts; this would reduce the gates drive voltage to M1. Under minimum input line conditions M1 may not be fully turned-on and there would be an increase in the I2 x RDS(ON) losses. Figure 11 shows the start-up waveforms for the Evaluation board. After the input power is supplied to the Evaluation board the secondary bias voltage rises, when the secondary bias is greater than 3.6 V, the Secondary Power Good output goes high. This turns-on M1 and enables the secondary side soft-start circuit allowing the output voltage to increase after Vout > Vpre-bias. Synchronous Forward MOSFET Enabled For the LM5027A Evaluation board we used the Secondary Bias Power Good signal as a flag to indicate that the primary sides MOSFETs are switching providing power to the secondary of the transformer T1. When the flag goes high this indicates that it is time to turn-on the forward conducting MOSFET M1. The Secondary Bias Power Good signal drives the base of an NPN transistor (Q3), refer to Figure 10. The NPN transistor is configured as a Cascod amplifier; when it is turned-on, the voltage on the secondary of the transformer T1 drives the gate of the synchronous MOSFET, M1. The MOSFET gate drive voltage is: V-GATE_DRIVE_M1 = V_Secondary_Bias_Power_GoodVBE_Q3 An NPN transistor needs to be selected so that the transistors collector to emitter voltage under the worst case operating condition does not exceed it’s VCE ratings, and that the collector current (Icc) can handle the maximum peak current to drive the gate of MOSFET M1. For the LM5027A Evaluation board the transistor is a 30 V, 1.5 ampere transistor. The maximum VCE is: 11 www.national.com AN-2067 30126313 FIGURE 10. Isolated Synchronous MOSFET www.national.com 12 AN-2067 30126314 FIGURE 11. Pre-Bias Load Waveforms An alternative to using the circuit in Figure 10 is shown in Figure 12; an additional winding can be added to the power transformer which can be used to drive the Forward Syn- chronous Rectifier MOSFET (M1). This is a simple solution and should not add a lot of complexity to the transformer design. 13 www.national.com AN-2067 30126315 FIGURE 12. Isolated Synchronous MOSFET Drive Using a Transformer Pre-Bias Load Test Set-Up Pre-Bias Load Start-Up Requirements For the Pre-bias start-up test, the circuit in Figure 13 was used. An external bias supply, through a 1.0 ohm resistor, was connected across the output terminals of the Evaluation Board. www.national.com The Evaluation board Pre-Bias start-up requirements are: During converter start-up the output shall rise monotonically and not sink current (into the converter) of more than 50 mA . 14 AN-2067 30126316 FIGURE 13. Isolated Synchronous MOSFET Drive Using a Transformer is less than 50 mA. When the output voltage rise above the pre-bias voltage there is approximately 400 mA of current out of (sourced) the Evaluation Board to charge the external 220 µF capacitor. After the external capacitor is charge to 3.3 V the current out of the power supply drop to approximately 50 mA. Evaluation Board Results Figure 14 shows the output of the Evaluation Board starting with a pre-bias voltage of 2.7 V. Under these conditions the output voltage starts at 2.7 V and then increases monotonically to 3.3 V. The current into the Evaluation board (sinking) 30126317 FIGURE 14. Pre-Bias StartUp 15 www.national.com www.national.com 16 Application Schematic: Input 36-76, Voutput 6.3A, 30A 30126318 AN-2067 AN-2067 Performance Characteristics TURN-ON WAVEFORMS When applying power to the LM5027A evaluation board a certain sequence of events occurs. Soft-start capacitor values and other components allow for a minimal output voltage for a short time until the feedback loop can stabilize without overshoot. Figure 15 shows the output voltage during a typical start-up with a 48V input and a load of 5A. There is no overshoot during startup. OUTPUT RIPPLE WAVEFORMS Figure 16 shows the transient response for a load of change from 2A to 25A. The lower trace shows minimal output voltage droop and overshoot during the sudden change in output current shown by the upper trace. 30126321 Conditions: Input Voltage = 48VDC Output Current = 30A Bandwidth Limit = 25 MHz Trace 1: Output Voltage Volts/div = 50 mV Horizontal Resolution = 2 µs/div FIGURE 17. Figure 17 shows typical output ripple seen directly across the output capacitor, for an input voltage of 48V and a load of 30A. This waveform is typical of most loads and input voltages. Figure 18 and Figure 19 show the drain voltage of Q1 with a 25A load. Figure 18 represents an input voltage of 38V and Figure 19 represents an input voltage of 78V. Figure 20 shows the gate voltages of the synchronous rectifiers. The drive from the main power transformer is delayed slightly at turn-on by a resistor interacting with the gate capacitance. This provides improved switching transitions for optimum efficiency. The difference in drive voltage is inherent in the topology and varies with line voltage 30126319 Conditions: Input Voltage = 48VDC Output Current = 5A Trace 1: Output Voltage Volts/div = 1.0V Horizontal Resolution =1 ms/div FIGURE 15. 30126322 Conditions: Input Voltage = 38VDC Output Current = 25A Trace 1: Q1 Drain Voltage volts/Div = 20V Horizontal Resolution = 1 µs/div 30126320 Conditions: Input Voltage = 48VDC Output Current = 2A to 25A Trace1: Output Voltage Volts/div = 0.2V Trace 2: Output Current Amps/Div = 5.0 A Horizontal Resolution = 1 ms/div FIGURE 18. FIGURE 16. 17 www.national.com AN-2067 30126323 30126324 Conditions: Input Voltage = 78VDC Trace 1: Q1 Drain Voltage Volts/Div = 20V Horizontal Resolution = 1 µs/div Conditions: Input Voltage = 48VDC Output Current = 5A Trace 3: (gate) Synchronous Rectifier, Q3/Q4 Volts/Div = 2V Trace 2: (gate) Synchronous Rectifier, Q5/Q6 Volts/Div = 2V Horizontal Resolution = 1 µs/div FIGURE 19. FIGURE 20. 30126336 FIGURE 21. Efficiency www.national.com 18 PART NUMBER DESCRIPTION VALUE C ITEM 1 C4532X7R2A225M CAPACITOR, CER, TDK 2.2µ, 100V C 2 C4532X7R2A225M CAPACITOR, CER, TDK 2.2µ, 100V C 3 C4532X7R2A225M CAPACITOR, CER, TDK 2.2µ, 100V C 4 C4532X7R2A225M CAPACITOR, CER, TDK 2.2v, 100V C 5 APXE4R0ARA681MH80G CAPACITOR, CER, United Chemi-Con 680µ, 4V C 6 C1210C476M8PACTU CAPACITOR,CER,KEMET 47µ, 10V C 7 C1210C476M8PACTU CAPACITOR,CER,KEMET 47µ, 10V C 8 C0603C471J5GAC CAPACITOR, CER, KEMET 470p, 50V C 9 C0603C103K3RAC CAPACITOR, CER, KEMET 0.01µ, 25V C 10 C0603C223K3RAC CAPACITOR, CER, KEMET 0.022µ, 25V C 11 C0603C473K3RAC CAPACITOR, CER, KEMET 0.047µ, 25V C 12 C1608X7R1H104K CAPACITOR, CER, TDK 0.1µ, 50V C 13 C0603C101J5GAC CAPACITOR, CER, KEMET 100p, 50V C 14 C0603C104K3RAC CAPACITOR, CER, KEMET 0.1µ, 25V C 15 C3216X7R2E104K CAPACITOR, CER, TDK 0.1µ, 250V C 16 C1608X7R1H104K CAPACITOR, CER, TDK 0.1µ, 50V C 17 C1210C476M8PACTU CAPACITOR, CER, TDK 47µ, 10V C 18 C1210C476M8PACTU CAPACITOR, CER, TDK 47µ, 10V C 19 C0603C221J3GAC CAPACITOR, CER, KEMET 220p, 25V C 20 OPEN C 21 C3216X7R2E104K CAPACITOR, CER, TDK 0.1µ, 250V C 22 C1608X7R1H104K CAPACITOR, CER, KEMET 0.1µ, 25V C 23 C0603C103K3RAC CAPACITOR, CER, KEMET 0.01µ, 25V C 24 C0603C473K3RAC CAPACITOR, CER, KEMET 0.047µ, 25V C 25 C0603C473K3RAC CAPACITOR, CER, KEMET 0.047µ, 25V C 26 C4532X7R3D222K CAPACITOR, CER, TDK 2200p, 2000V C 27 GRM188R61E105KA12D CAPACITOR, CER, MURATA 1.0µ, 25V C 28 C0603C224K3RAC CAPACITOR, CER, TDK 0.22µ, 25V C 29 C0603C102K3RAC CAPACITOR, CER, KEMET 1000p, 25V C 30 C0603C102K3RAC CAPACITOR, CER, KEMET 1000p, 25V C 31 C0805C471J5GAC CAPACITOR, CER, KEMET 470p, 50V C 32 C0805C471F5GAC CAPACITOR, CER, KEMET 470p, 50V C 33 C2012X7R2A332K CAPACITOR, CER, TDK 3300p, 100V C 34 OPEN C 71 C4532X7R1E156M CAPACITOR, CER, TDK 15µ, 25V C 35 C0603C102K3RAC CAPACITOR, CER, KEMET 1000p, 25V C 36 GRM188R61E105KA12D CAPACITOR, CER, MURATA 1.0u, 25V D 1 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 2 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 3 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 4 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 5 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 6 CMD2836 DIODE, DUAL SIGNAL, CENTRAL 120V, 200mA D 7 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 8 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA D 9 ZHCS350 DIODE, SIGNAL, ZETEX 40V, 500mA J 1 3104-2-00-01-00-00-08-0 PIN, BRICK, 0.040D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB 19 www.national.com AN-2067 Bill of Materials AN-2067 ITEM PART NUMBER DESCRIPTION VALUE J 2 3104-2-00-01-00-00-08-0 PIN, BRICK, 0.040D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB J 4 3104-2-00-01-00-00-08-0 PIN, BRICK, 0.040D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB J 5 3231-2-00-01-00-00-08-0 PIN, BRICK, 0.080D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB J 6 3104-2-00-01-00-00-08-0 PIN, BRICK, 0.040D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB J 8 3104-2-00-01-00-00-08-0 PIN, BRICK, 0.040D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB J 9 3231-2-00-01-00-00-08-0 PIN, BRICK, 0.080D, MILL-MAX MOUNT ON SOLDER SIDE OF PCB L 1 SRU1048-6R8Y INPUT CHOKE, Bourns 6.8uH, 4.8Arms L 2 7443556130 CHOKE, WURTH 1.2µH, 37A L 3 SDR0503-332JL CHOKE, Bourns 3.3mH, 0.045 A Q 1 SI7846DP N-FET, SILICONIX 150V, 50m Q 2 SI3475 P-FET, IR 200V, 1.6 Q 3 SI7866DP FET, SILICONIX 20V, 3m Q 4 SI7866DP FET, SILICONIX 20V, 3m Q 5 SI7866DP FET, SILICONIX 20V, 3m Q 6 SI7866DP FET, SILICONIX 20V, 3m Q 7 MMBT2907A Bipolar, PNP, 60V, 600mA Q 8 QSX6 Bipolar, NPN, 30V, 1.5A ROHM Q 9 2N7002VA FET, N_Channel, Fairchild 60V 280mA Q 10 MMBT2907A Bipolar, PNP, 60V, 600mA R 1 CRCW120610R0F RESISTOR 10 R 2 CRCW08059093F RESISTOR 90.9k R 3 CRCW06032002F RESISTOR 20k R 4 CRCW06034992F RESISTOR 49.9k R 5 CRCW06034991F RESISTOR 4.99k R 6 CRCW08059093F RESISTOR 90.9K R 7 CRCW06031001F RESISTOR 1K R 8 CRCW06036191F RESISTOR 6.19K R 9 CRCW06035R60F RESISTOR 5.6 R 10 CRCW060352302F RESISTOR 52.3K R 11 CRCW06032002F RESISTOR 20K R 12 CRCW06031001F RESISTOR 1K R 13 CRCW06035R60F RESISTOR 5.6 R 14 CRCW120649R9F RESISTOR 49.9 R 15 CRCW06036R34F RESISTOR 6.34 R 16 OPEN R 17 CRCW06032200F RESISTOR 220 R 18 CRCW06031002F RESISTOR 10k R 19 CRCW06034R70F RESISTOR 4.7 R 20 SHORT (0 Ohms) RESISTOR, 0 OHMS 0 ohms R 21 CRCW06031001F RESISTOR 1K R 22 CRCW06032000F RESISTOR 200 R 23 CRCW06031002F RESISTOR 10k R 24 CRCW06031502F RESISTOR 15k R 25 CRCW06032492F RESISTOR 24.9k R 26 CRCW060310R0F RESISTOR 10 www.national.com 20 PART NUMBER DESCRIPTION VALUE 10 R 27 CRCW060310R0F RESISTOR R 28 CRCW06031001F RESISTOR 1k R 29 CRCW06032002F RESISTOR 20.0k R 30 CRCW06031002F RESISTOR 10.0k R 31 CRCW06034990F RESISTOR 499 R 32 OPEN R 33 SHORT (0 Ohms) RESISTOR, 0 OHMS 0 ohms R 34 CRCW1218110ROFKEK RESISTOR 10, 1W R 35 CRCW1218110ROFKEK RESISTOR 10, 1W R 36 CRCW06031001F RESISTOR 1k R 37 CRCW06033011F RESISTOR 3.01k R 38 CRCW06034990F RESISTOR 499 R 39 CRCW06034702F RESISTOR 47k R 40 CRCW06034702F RESISTOR 47k R 41 CRCW06034702F RESISTOR 47k R 42 CRCW06031002F RESISTOR 10k R T1 NTCG164BH103H NTC, 10k @25°C, 1k@100°C, TDK 10k T 1 HA4000-Al POWER XFMR W/AUX, COILCRAFT 12:2 T 2 DA2319-ALB Gate Drive, Coilcraft T 3 P8208T, Pulse CURRENT XFR, PULSE ENG U 1 LM5027AMH CONTROLLER, NATIONAL SEMI U 2 PS2811-1M OPTO-COUPLER, NEC U 3 LM8261M5 OPAMP, NATIONAL SEMI U 4 LM4040CEM3-4.1 REFERENCE, NATIONAL SEMI U 5 LM4041CEM3-1.2 REFERENCE, NATIONAL SEMI Z 2 MM5Z3V6 DIODE, ZENER 3.6V 21 100:1 Fairchild www.national.com AN-2067 ITEM AN-2067 Printed Circuit Layout 30126326 Tassy 30126327 Bottom Layer www.national.com 22 AN-2067 30126328 Bottom Silk Layer 30126329 Mid 1 Layer 23 www.national.com AN-2067 30126330 Mid 2 Layer 30126331 Mid 3 Layer www.national.com 24 AN-2067 30126332 Mid 4 Layer 30126333 TASSY 25 www.national.com AN-2067 30126334 Top Layer 30126335 Top Silk Layer www.national.com 26 AN-2067 Notes 27 www.national.com LM5027A Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers 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