MIC3809 Evaluation Board Push-Pull Evaluation Board General Description Specifications The MIC3808 and MIC3809 are part of a family of complimentary gate drive Push-Pull controllers. The parts can be used to control any dual-ended switching converter topology such as Push-Pull, Half-Bridge or Full-Bridge. The MIC3808 has a 12.5V turn-on threshold while the MIC3809 has a lower turn-on threshold of 4.3V. This evaluation board provides a platform for evaluating the MIC3809 power supply controller IC in a Push-Pull converter topology. The evaluation board schematic is shown in Figure 1. Please refer to the MIC3808/9 data sheet for a detailed explanation of the control IC. Control IC..................................................... MIC3809 Power Supply Topology.............................. Push-Pull Recommended Operating Input Voltage ..36V to 72V Maximum Input Voltage ....................................... 80V Output Voltage ..................................................... 12V Maximum Output Current ...................................... 8A Output Switching Frequency.............180kHz (typical) Figure 1. MIC3809 Evaluation Board Schematic Micrel, Inc. • 2180 Fortune Drive • San Jose, Ca 95131 • USA • tel +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com January 2005 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board MOSFET is off, thereby preventing current from flowing through the other. VDS across the off MOSFET is equal to twice the input voltage. The voltage across the secondary winding is stepped down from the primary by the turns ratio of the transformer. The output inductor and capacitors filter this voltage. RC snubbers across the primary and secondary windings dampen high frequency noise spikes caused by component and circuit parasitics. Requirements The evaluation board requires a DC input power source capable of supplying at least 3.5A at 36V to obtain maximum power at the output. The output may be loaded with a resistive or active load. The active load may be set for constant current or constant resistance mode. Precautions The evaluation board does not have input reverse polarity protection. Applying a negative voltage at the +VIN terminal (with respect to the -VIN terminal) may permanently damage the components on the board. The maximum input voltage should be limited to 80 volts to prevent overvoltage stress on the components. Getting Started 1) Connect an input voltage source to the +VIN and -VIN terminals. An ammeter may be placed between the source and VIN terminals to monitor input current. 2) Connect a load to the 12V output and GND terminals. An ammeter may be used in series with the output. 3) Apply 48 volts at the input. The output voltage should be 12V. Figure 2 Startup and Bootstrap Operation At startup, Q1 and D4 regulate the initial supply voltage to the MIC3809. The voltage on the base of Q1 is regulated at one VBE drop lower than the 10V zener voltage of D4. Including the voltage drop of D5, VDD at startup is approximately 9V. A flyback winding on the output inductor provides the primary side bias voltages. Once the power supply has started up, this voltage is set higher than the 9V startup voltage and reverse bias D5 under normal operation. This improves efficiency by eliminating power loss in Q1. VDD1 is filtered to isolate the noise sensitive sections of the controller from VDD, which supplies power to the MOSFET gate drive circuit. Figure 3 Current Sense and Slope Compensation The MIC3809 uses current mode control. A current sense transformer senses the primary side current from both halves of the power transformer which improves efficiency over using a resistor for current sensing. A slope compensation ramp must be added to the current signal since the duty cycle at the output is greater than 50%. Emitter follower, Q4, Power Stage The Push-Pull transformer has split primary and secondary windings that operate out of phase with each other. Figures 2 and 3 illustrate the MOSFET drain-source voltages and drain currents. When one of the primary MOSFETs is on, driving current through one of the primary windings, the other January 2005 2 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board buffers the clock signal ramp and R9/R10 divides the signal down and mixes the ramp with the current sense resistor. The voltage across current sense resistor R3 is shown in the top waveform of Figure 4. This represents the current through the current sense transformer. The bottom waveform shows the voltage as the MIC3809's ISNS pin, which is the sum of the slope compensation signal and the voltage across the current sense resistor. For reference, Figure 5 shows the block diagram of the MIC3809. Figure 4 Figure 5 Voltage divider resistors R18/R19 and the internal Voltage Sensing and Isolation 2.5V reference set the output voltage. VOUT is The power supply provides safety isolation between calculated using the formula below: the input and output. A TL431 senses the output ⎛ R18 ⎞ voltage and compares it to an internal 2.5V ⎟ VOUT = VREF × ⎜ 1+ ⎝ R19 ⎠ reference. An opto-isolator sends the control signal, generated by the TL431 output, across the isolation Where VREF=2.5V barrier. This signal is used by the MIC3809 to control the pulse width of the gate drive signal, which regulates the output voltage. January 2005 3 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board Power Supply Performance Demo Board Efficiency VIN = 48V 12.0595 VIN = 36V IOUT = 4A 12.0590 89 87 85 12.0585 VOUT (V) VIN = 72V 83 81 12.0580 12.0575 79 77 75 0 1 2 3 4 5 6 7 8 9 10 OUTPUT CURRENT (A) 12.0570 Figure 8 The power supply transient response and bode plots are shown in figures 9 through 11. The output voltage ripple is shown in figure 12. Bode Plot 12.080 60 12.075 40 12.070 20 VIN = 36V GAIN (dB) VOUT (V) Demo Board Load Regulation 12.065 VIN = 48V 12.060 0 1 2 3 4 5 6 7 OUTPUT CURRENT (A) 8 150 Phase 100 50 0 0 Gain -20 -50 Figure 9 Figure 7 January 2005 200 VIN = 48V -100 -40 VOUT = 12V -150 IOUT = 8A -60 -200 10 100 1000 10000 100000 FREQUENCY (Hz) VIN = 72V 12.055 IOUT = 8A 12.0565 35 40 45 50 55 60 65 70 75 INPUT VOLTAGE (V) Figure 6 The line and load regulation are shown in Figures 7 and 8. 12.050 IOUT = 1A PHASE (¡) EFFICIENCY (%) 95 93 91 Demo Board Load Regulation 4 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board Figure 10 Figure 11 Figure 12 January 2005 5 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board Bill of Materials Item Part Number Manufacturer U1 MIC3809BM (1) Micrel U2 PS2703-1(M) NEC U3 TL431AIDBVR TI C1, C2, C9, C17 C3216X7R1E105K TDK or GRM21BR71E105KA99L muRata C3, C4, C5 C4532X7R2A105M TDK Description (2) (3) (4) (5) (4) Voltage Reference 1 1µF, 25V, X7R size 1206 4 1µF, 25V, X7R, 0805 4 0 (5) 1µF, 100V, X7R, 1210 0 1uF, 100V, X7R, 1210 0 220pF, 630V, X7R, 1206 2 (6) 100pF, 50V, 0805, NPO 1 (6) 220pF, 50V, 0805,NPO, 5% 1 (6) 6.8nF, 50V, X7R, 0805, 5% 1 (6) 100µF, 20V, tantalum D case. 4 4.7nF/250AC, X7R, 2220 1 open, Size 0805 3 3.3nF, 50V, X7R,0805, 5% 1 GRM32ER72A105KA01L muRata or 12101C105KAZ1A AVX (6) (5) C6, C7 GRM31BR32J221CKY01L muRata C8 VJ0805A101KXAAT Vishay Vitramon Vishay Vitramon C11 VJ0805Y682KXAAT Vishay Vitramon C13, C14, C15, C16 594D107X0020D2T Vishay Sprague C18 GA355DR7GC472K muRata (5) C12, C19, C23 (6) C20 VJ0805Y332KXAAT Vishay Vitramon C21, C22 GRM31BR32J102CKY01L muRata (5) 1nF, 250V, X7R, 1206. 2 (6) 0.1µF, 50V, X5R, 0805 1 (6) 1nF, 50V, X7R, 5%, 0805 1 200V, 1A ultrafast 1 C24 VJ0805Y104KXAAT Vishay Vitramon C25 VJ0805Y102KXAAT Vishay Vitramon D1 ES1D Diodes Inc. (7) (6) or ES1D Vishay D4 BZT52C10S Diodes Inc. 0 (7) 10V zener (6) 1 0 Vishay D5 SD103AWS Diodes Inc. or SD103AWS Vishay (7) Signal Schottky, 40V (6) 1 0 D6 1N4148W Diodes Inc. or 1N4148W Vishay January 2005 1 1µF,100V , X7R, 1206 or BZX384C10 Opto-Isolator 3 muRata or 1 1µF, 100V, X7R, 1210 GRM31CR72A105K***L VJ0805A221KXAAT MIC3809 push-pull controller (5) or C10 Qty. (7) (6) Signal diode 1 0 6 M9999-080404 (408) 955-1690 Micrel, Inc MIC3809 Evaluation Board Bill of Materials (cont.) Item Part Number Manufacturer D8, D9 30CTQ100S IR or MBRB30H100CT (8) Power Schottky, 30A, 100V 0 (10) Zetex Q2, Q3 SUD19N20-90 Vishay (6) Diodes Inc. (7) MMBTA56 T1 CTX04-16236-X2 T2 31333R L1 CTX04-16235-X1 R1, R2 CRCW080510R0FRT1 Vishay Dale R3 CRCW08054R99FRT1 Vishay dale CRCW25121002FRT1 Vishay Cooper (9) Electronics 2 PNP, MMBTA55 1 0 100:1 Current sense x-fmr 1 12µH inductor with bias winding 1 (6) 10Ω 2 (6) 4.99Ω 1% 1 (6) 10kΩ, 1/2W, 5% 1 (6) 33Ω, 1W, 5% 2 (6) 20kΩ 2 (6) 27.4kΩ 1 (6) 17.8kΩ 1 (6) 1kΩ 2 (6) 10kΩ 2 (6) 31.6kΩ 1 (6) open 3 (6) 499Ω 1 (6) 38.3kΩ 1 (6) 15Ω, 1W 2 (10) Midcom Cooper (9) Electronics Vishay dale Vishay dale R7, R22 CRCW08052002FRT1 Vishay dale R8 CRCW08052742FRT1 Vishay dale R9 CRCW08051782FRT1 Vishay dale Vishay dale R11, R19 CRCW08051002FRT1 Vishay dale R12 CRCW08053162FRT1 Vishay dale R13, R14, R16 MOSFET, Nch 200V, 90mohm 1 CRCW251233R0FRT1 CRCW08051001FRT1 1 Push-Pull Transformer R5, R6 R10, R15 FMMT493 NPN transistor (6) or R4 Vishay dale R17 CRCW08054990FRT1 Vishay dale R18 CRCW08053832FRT1 Vishay dale R20, R21 CRCW251215R0FRT1 Vishay dale Notes: Micrel Inc.: 408-944-0800 Vishay Corporation: 206-452-5664 NEC: 408-588-2247 Diodes Inc.: 805-466-4800 TDK: 847-803-6100 IR: 310-252-7105 muRata: 800-831-9172 Cooper Electronics: 888-414-2645 AVX: 843-448-9411 Midcom: 800-643-2661 January 2005 2 Vishay FMMT493 MMBTA55 Qty. (6) Q1 Q4 Description 7 M9999-080404 (408) 955-1690 Micrel, Inc MIC3809 Evaluation Board Printed Circuit Boards Top Silkscreen Overlay Bottom Silkscreen Overlay January 2005 8 M9999-080404 (408) 955-1690 Micrel, Inc MIC3809 Evaluation Board Top Layer Bottom Layer January 2005 9 M9999-080404 (408) 955-1690 Micrel MIC3809 Evaluation Board MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2005 Micrel, Incorporated. January 2005 10 M9999-080404 (408) 955-1690