19-0034; Rev 0; 5/92 MAX731 Evaluation Kit ____________________________Features ♦ Load Currents Guaranteed to 200mA with No External MOSFET ♦ Step-Up from a 2.0V Input ♦ 170kHz High-Frequency Current-Mode PWM ♦ 82% to 87% Typical Efficiencies at Full Load ♦ Overcurrent and Soft-Start Protection ♦ Shutdown Capability ______________Ordering Information PART TEMP. RANGE MAX731EVKIT-DIP 0°C to +70°C BOARD TYPE Through Hole ______________________________EV Kit ____________________Component List DESIGNATION IC1 None C1, C7 QTY DESCRIPTION SOURCE 1 1 2 MAX731CPA Printed circuit board 0.1µF ceramic capacitors 150µF, 25V electrolytic capacitors MAXC001 4.7µF capacitor 0.15µF ceramic capacitors Schottky diode 1N5817 1/4W, 5% 10kΩ resistor Jumper Maxim Maxim C2, C8 2 C3 1 C4, C5, C6 3 D1 R1 J2 1 1 1 L1 1 Sumida USA 22µH inductor (708) 956-0666 Maxim Motorola Sumida RCH-110-220M Coilcraft PCH-27-223 Wilco ITS220 FAX (708) 956-0702 Sumida Japan 03-3607-5111 FAX 03-3607-5428 Coilcraft USA (708) 639-6400 FAX (708) 639-1469 Coilcraft Taiwan 8862-268-2146 FAX 8862-268-2092 Wilco (317) 293-9300 FAX (317) 293-9462 _______________Terminal Description TERMINAL NAME FUNCTION VIN Positive Input. Connect to positive teminal of voltage power supply. SHDN SHUTDOWN – active low. Ground to power down; ties to VIN for normal operation. Output power FET is held off when SHDN is low. GND Circuit Ground. Connect to negative terminal of input voltage supply. This is also the output voltage negative terminal. VOUT Positive Output. Connect to load. ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX731 EV Kit _______________General Description The MAX731 evaluation kit (EV kit) facilitates assembly and evaluation of Maxim’s MAX731 +5V step-up currentmode DC-DC converter. The EV kit includes all needed components (unassembled) and a printed circuit board. When completed, the EV kit is a working DC-DC step-up converter with +5V output voltage at 200mA. Typical full-load efficiencies are 82% to 87%. The MAX731 uses current-mode pulse-width modulation (PWM) to provide precise output regulation and low subharmonic noise. Typical no-load supply current is 2mA. The MAX731 features cycle-by-cycle current limiting, overcurrent limiting, external shutdown, and programmable soft-start protection. The EV kit components are suitable for through-hole mounting to make construction and evaluation easy. Refer to the MAX731 data sheet for detailed electrical and operating specifications. MAX731 EV Kit MAX731 Evaluation Kit ________________Operating Principle This switch-mode regulator uses a current-mode pulsewidth modulation (PWM) controller as a simple boost regulator to convert an unregulated 2.0V DC voltage to a higher output. The current-mode PWM architecture provides cycle-by-cycle current limiting and excellent load-transient response. For detailed description, see the MAX731/MAX752 data sheet. _____________Assembly Instructions CAUTION: Observe the following safety measures. 1. Do not apply power until all components are installed. 2. Do not solder or work on circuit while power is applied. 3 Never apply more than the maximum supply voltage to VIN. The EV kit is shipped unassembled. You will need the following tools for assembly: 1. Long-nose pliers 2. Wire cutters 3. 30W soldering iron and rosin-core solder 4. Hook-up wire (#18-22AWG) for the input and output connections CAUTION: Using a high-wattage soldering iron or acid-core solder may damage the board and components. Install the components as shown in Figure 1 and solder them in place. Observe polarity on the capacitors, diode, and IC. Keep all leads short. Inspect the completed board for cleanliness, shorts, and solder splashes. A socket may be added for IC1, but it may degrade performance with high load currents. In general, sockets are not recommended. The printed circuit board accommodates a variety of 2 inductors. When installing the inductors, make sure one end is connected on the trace leading to VIN. The other inductor terminal connects to the same trace as diode D1. Only one of the jumpers must be installed; install J2 for the MAX731. Examine the board for parts incorrectly inserted before applying power. Verify that the electrolytic capacitors’ positive terminal aligns with the plus (+) sign on the printed circuit board. The cathode ban on D1 must be as indicated on the board legend. _____________________________Testing When testing, use an adjustable bench power supply as a source (VIN). Start with no load, then add a resistive load before connecting to the actual circuit. This procedure minimizes the chances of damaging the device and ensures that accurate data is collected in an orderly manner. The bench power supply should have a 3A to 6A capability, and its current limiting should be set to prevent interaction with the EV kit’s peak currents. The input voltage range is 2.0V to 5.0V. The maximum load current is 200mA. Shutdown The DC-DC converter operates only if SHDN is connected to VIN. Even with SHDN grounded, however, there is a DC path from VIN to VOUT, and VOUT will be one diode drop lower than VIN. This is due to the basic topography of step-up converters, and would be the case even with IC1 removed from the circuit. Some current (VIN/10kΩ) also flows from VIN to SHDN, due to R1. Internal Reference The +1.23V bandgap reference supplies up to 100µA at VREF. A 4.7µF reference bypass capacitor is recommended for the MAX731. _______________________________________________________________________________________ MAX 731 Evaluation Kit C2 150µF MAX731 EV Kit VIN INSTALL J2 FOR THE MAX731. J1 R1 10k L1 C1 0.1µF IC1 1 SHDN 2 3 C3 SHDN V+ 8 VREF VOUT 7 MAX731 SS LX CC GND C4 4 4.7µF J2 D1 1N5817 C8 C7 0.1µF 150µF VOUT 6 5 Figure 1c. DIP PC Layout, Component Side (1X scale) 0.15µF C5 0.15µF C6 0.15µF Figure 1a. EV Kit Schematic Figure 1d. DIP PC Layout, Solder Side (1X scale) Figure 1b. DIP PC Layout, Through-Hole Placement (1X scale) _______________________________________________________________________________________ 3 MAX731 EV Kit MAX731 Evaluation Kit 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. 4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1992 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.