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| 19-3442; Rev 0; 10/04 MAX5074 Evaluation Kit General Description The MAX5074 evaluation kit (EV kit) is a fully assembled and tested circuit board that contains a high-efficiency, 14W, forward DC-DC converter in the industry-standard 1/8th-brick footprint. The circuit is configured for a 12V output voltage and provides up to 1.2A of current. Power for the circuit can be provided from a 36V to 72V DC source as well as sources used in the telecom/datacom markets, industrial environments, and in automotive 42V power systems. The EV kit uses the MAX5074 IC that includes internal power MOSFETs. High efficiency up to 85% at 1.2A is achieved using an internally clamped two-transistor topology. Part of the efficiency improvement is due to the recovery of stored leakage and magnetizing inductance energy at the primary side. The MAX5074 is programmed to switch at 250kHz. The undervoltage lockout (UVLO) threshold is programmed to 30V and the integrated fault protection provides effective fault management. Output galvanic isolation is achieved by an optocoupler and the surface-mount power transformer. Warning: The MAX5074 EV kit is designed to operate with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or power the sources connected to it must be careful to follow safety procedures appropriate to working with high-voltage electrical equipment. Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this kit with care to avoid possible personal injury. The EV kit user should not probe the circuit with an oscilloscope probe and ground clip unless they have experience with high voltages. 36V to 72V Input Range 12V Output Provides Up to 1.2A 85% Efficiency at 48V and 1.2A 1/8th-Brick Module Footprint Cycle-by-Cycle Current-Limit Protection Programmable Integrating Fault Protection Programmed for 250kHz Switching Frequency Internal Thermal Shutdown Basic Primary to Secondary Isolation Soft-Start Fully Assembled and Tested Features Isolated 14W Forward DC-DC Converter Evaluates: MAX5074 Ordering Information PART MAX5074EVKIT TEMP RANGE 0C to +50C IC PACKAGE 20 TSSOP-EP* *EP = Exposed pad. Component List DESIGNATION QTY C1 1 DESCRIPTION 4.7F 10%, 16V X7R ceramic capacitor (1206) TDK C3216X7R1C475K 100pF 5%, 50V C0G ceramic capacitor (0603) TDK C1608C0G1H101K 0.1F 10%, 50V X7R ceramic capacitors (0603) TDK C1608X7R1H104K DESIGNATION QTY C4, C6 2 DESCRIPTION 220pF 10%, 50V X7R ceramic capacitors (0603) TDK C1608X7R1H221K 1.0F 10%, 50V X7R ceramic capacitor (1206) TDK C3216X7R1H105K 1.0F 20%, 100V X7R ceramic capacitor (1210) TDK C3225X7R2A105M C2 1 C8 1 C3, C5, C7, C17 4 C9 1 ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. MAX5074 Evaluation Kit Evaluates: MAX5074 Component List (continued) DESIGNATION QTY C10, C11 2 DESCRIPTION 0.01F 10%, 100V X7R ceramic capacitors (0805) TDK C2012X7RZA103K or Murata GRM21BR72A103K 0.15F 10%, 25V X7R ceramic capacitor (0603) TDK C1608X7R1E154K 0.047F 10%, 16V X7R ceramic capacitor (0603) Murata GRM188R71E473K 0.33F 10%, 16V X7R ceramic capacitor (0603) TDK C1608X7R1C334K 47F 20%, 16V POSCAP capacitors (D2) Sanyo 16TQC47M 0.0047F 10%, 250VAC X7R ceramic capacitor (2220) Murata GA355DR7GC472KY 120V, 200mA fast-switching diodes (SOD-323) Diodes Incorporated BAV19WS 80V, 2A Schottky diodes (SMB) Diodes Incorporated B280 DESIGNATION QTY L1 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 T1 U1 U2 D3, D4 2 None C18 1 C15, C16 2 C14 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 DESCRIPTION 68H, 2.1A inductor Coilcraft MSS1278-683MX 143k 1% resistor (0603) 16.2k 1% resistor (0603) 562 1% resistor (0805) 0.1, 0.5W 1% resistor (1206) IRC LRC-LR1206-01-R100-F 316k 1% resistor (0603) 14.7k 1% resistor (0603) 1.78k 1% resistor (0603) Not installed, resistor (0603) 24.9k 1% resistor (0603) 1M 5% resistor (0603) 200k 1% resistor (0603) 100 1% resistor (0603) 604 1% resistor (0603) 15 5% resistor (0603) 18W Transformer Coilcraft C0984-C MAX5074AUP (20-pin TSSOP-EP) 30V, 100% to 200% CTR optically isolated error amplifier (8-pin SO) Fairchild Semiconductor FOD2712 MAX5074 PC board C12 1 C13 1 D1, D2, D5 3 Component Suppliers SUPPLIER Coilcraft Diodes Inc Fairchild Semiconductor IRC Murata Sanyo Electronic Device TDK PHONE 847-639-6400 805-446-4800 888-522-5372 361-992-7900 770-436-1300 619-661-6322 847-803-6100 FAX 847-639-1469 805-446-4850 -- 361-992-3377 770-436-3030 619-661-1055 847-390-4405 WEBSITE www.coilcraft.com www.diodes.com www.fairchildsemi.com www.irctt.com www.murata.com www.sanyodevice.com www.component.tdk.com Note: Indicate that you are using the MAX5074 when contacting these component suppliers. 2 _______________________________________________________________________________________ MAX5074 Evaluation Kit Quick Start Required Equipment * 30V to 80V, 2A power supply * Voltmeter The MAX5074 EV kit is fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed: 1) Connect a 33F, 100V bulk capacitor at the VIN and PGND terminals. 2) Connect the 30V to 80V power supply to the VIN pinhole. Connect the power supply's ground to the PGND pinhole. Do not exceed 80V input voltage. 3) Connect a voltmeter to the VOUT and SGND pinholes. 4) Turn on the power supply and set the voltage above 48V. 5) Verify that VOUT measures 12V at the voltmeter. the primary side from biasing resistor R7 and compensation resistor/capacitor network R13/C14. The MAX5074 IC switches at a preconfigured 250kHz frequency set by resistor R9 and capacitor C2. The 4-layer PC board layout and component placement has been designed for the industry-standard 1/8thbrick footprint and pinout. The PC board top and bottom layers are designed with 2oz copper for improved performance. Evaluates: MAX5074 Undervoltage Lockout (UVLO) The MAX5074 EV kit requires a 36V to 72V, 2A DC source connected across the VIN and PGND pin-holes for normal operation. The MAX5074 EV kit UVLO is programmed to 30V by resistors R5 and R6. Use the following equation to calculate new resistor values for R5 and R6 to reconfigure the UVLO threshold. VINSTARTUP R5 = - 1 x R6 1.25V where VINSTARTUP is the new undervoltage threshold and resistor R6 is typically 14.7k. The turns ratio of transformer T1 may have to change to accommodate the desired operating range. Detailed Description The MAX5074 EV kit is an isolated 14W forward DC-DC converter that provides 12V at up to 1.2A at the output. The circuit can be powered from a 36V to 72V DC source that provides at least 2A. The 14W forward converter achieves high efficiency by using a clamped two-transistor power topology with both power transistors integrated on the MAX5074 IC. Current-sense resistor R4 senses the current through the primary of transformer T1 and then turns off both internal transistors when the trip level of 156mV is reached. For a continuous short circuit at the output, the fault-integration feature provides hiccup fault protection, thus greatly minimizing destructive temperature rise. Fault integration times can be adjusted with resistor R10 and capacitor C3. The surface-mount transformer features a bias winding, which, along with diode D5, resistor R14, and capacitor C8, powers the MAX5074 IC after the undervoltage lockout threshold is exceeded. No reset windings are required with a clamped two-transistor power topology. Diodes D1 and D2 recover the magnetic energy stored in the transformer and feed it back to the input. The transformer provides primary-to-secondary galvanic isolation. On the transformer's secondary side, optically isolated error amplifier (U2) along with feedback resistors R1 and R2 provide voltage feedback to the primary side. The MAX5074 receives the voltage feedback signal on Output Voltage (VOUT) The MAX5074 EV kit's output (VOUT) is set to 12V by feedback resistors R1 and R2. To generate output voltages other than 12V, in the range of 8V to 13V, select different values for voltage-divider resistors R1 and R2. Use the following equation to select new resistor values. V R1 = OUT - 1 x R2 1.24 V where R2 is typically 16.2k and VOUT is the desired output voltage. Inductor L1 and transformer T1 may require replacement after reconfiguring the output voltage setting. The minimum output voltage is limited by resistor R3 and optocoupler U2. _______________________________________________________________________________________ 3 MAX5074 Evaluation Kit Evaluates: MAX5074 Switching Frequency The MAX5074 EV kit switching frequency is programmed to 250kHz with resistor R9 and capacitor C2. The switching frequency can be reprogrammed by replacing these components. Refer to the Oscillator section in the MAX5074 data sheet for details on selecting new values. Integrating Fault Protection The MAX5074 IC integrates a fault protection feature that ignores transient overcurrent conditions for a programmable amount of time. The initial ignore time is programmed to 3.2ms with capacitor C3. Use the following equation to reconfigure the initial overcurrent ignore time: C3 80A x t SH 2.7 Current Limiting The EV kit features primary-side cycle-by-cycle current limit. The MAX5074 IC turns off both internal switching transistors when the voltage at the CS pin of the MAX5074 reaches 156mV. Current-sense resistor R4 limits the peak primary current to approximately 1.56A (156mV / 0.1 = 1.56A). This limits short-circuit current on the secondary output (VOUT) to approximately 2A. To evaluate different current limits, current-sense resistor R4 must be replaced with a different value surface-mount resistor (1206 size) as determined by the following equation: R4 = 156mV ILIM where tSH is the desired ignore time. Once the ignore time is exceeded, the MAX5074 IC stops switching and resistor R10 discharges capacitor C3 towards the internal restart threshold of 1.9V during the recovery time interval of 35ms. Use the following equation to select a new value for resistor R10 to adjust the recovery time: R10 t RT 2.7 C 3 x In 1.9 where ILIM is the desired maximum peak primary-side current limit. where tRT is the new recovery time. Select a recovery time that is at least 10 times longer than the ignore time tSH. Refer to the Integrating Fault Protection section in the MAX5074 data sheet for additional information. 4 _______________________________________________________________________________________ MAX5074 Evaluation Kit Evaluates: MAX5074 VIN VIN PGND C9 1.0F R11 200k R5 316k C4 220pF XFRMRH 18 R6 14.7k 3 R10 1M 5% C3 0.1F FLTINT UVLO 4 5 RCFF RAMP 15 VIN 13 C10 D1 0.01F R14 15 5% 25T 3 11 22T D3 D5 5 C8 1.0F DRVIN REGOUT RTCT 2 R9 24.9k C2 100pF C5 0.1F CSS 7 OPTO GND PGND CS 6 9 11 10 R12 100 C6 220pF SRC 12 VOUT 11T 6 T1 8 C18 0.0047F D4 L1 68H C15 47F 16V C16 47F 16V VOUT VOUT C17 0.1F SGND 19 HVIN 16 DRNH TP1 8 PPWM BST 17 C7 D2 0.1F C11 0.01F 1 U1 MAX5074 XFRMRL INBIAS 20 14 1 C1 4.7F R4 0.100 8 2 LED C E C12 0.15F R3 562 R1 143k R7 1.78k FB 7 R8 OPEN R13 604 C14 0.33F 3 6 U2 COMP FOD2712 5 N.C. 1 N.C. 4 GND C13 0.047F R2 16.2k NOTE: ALL RESISTORS ARE 1% UNLESS OTHERWISE SPECIFIED. Figure 1. MAX5074 EV Kit Schematic _______________________________________________________________________________________ 5 MAX5074 Evaluation Kit Evaluates: MAX5074 Figure 2. MAX5074 EV Kit Component Placement Guide-- Component Side Figure 3. MAX5074 EV Kit PC Board Layout--Layer 1, Component Side Figure 4. MAX5074 EV Kit PC Board Layout--Layer 2, Ground Planes Figure 5. MAX5074 EV Kit PC Board Layout--Layer 3, Power and Ground Planes 6 _______________________________________________________________________________________ MAX5074 Evaluation Kit Evaluates: MAX5074 Figure 6. MAX5074 EV Kit PC Board Layout--Layer 4, Solder Side Figure 7. MAX5074 EV Kit Component Placement Guide-- Solder Side Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 7 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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