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| 19-1381; Rev 0; 7/98 MAX1678 Evaluation Kit General Description The MAX1678 evaluation kit (EV kit) provides a regulated 3.3V output while operating on input voltages as low as 0.7V with guaranteed start-up at 0.87V. The input source can be a 1 or 2-cell battery or a DC supply. Efficiency is typically 90% with output loads up to 100mA. The kit uses surface-mount components and is fully assembled and tested for quick evaluation. Jumpers are provided for selecting an adjustable output voltage and for shutdown control. o 0.87V to VOUT Input Range o Synchronous Rectified--No External Diode Required o 3.3V Output Voltage (or Adjustable) o 100mA Output o 90% Efficiency o 2A Shutdown Current o Small Surface-Mount Components o Inductor Damping Switch Suppresses EMI Features Evaluates: MAX1678 Component List DESIGNATION QTY C1, C2 2 DESCRIPTION 10F, 10V ceramic capacitor Taiyo Yuden LMK325BJ106MN, TDK C3225X5R1A106M 47H, 240mA power inductor Coilcraft DS1608C-473 Sumida CD43-470 Murata LQH4N470K 3-pin jumper 2-pin jumper 1M, 1% resistors Open 100k , 5% resistor MAX1678EUA Shunts MAX1678 EV kit PC board MAX1678 data sheet Ordering Information PART MAX1678EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 8 MAX L1 J1 J2 R1, R4 R2, R3 R5 U1 None None None 1 1 1 2 2 1 1 2 1 1 _________________________Quick Start The MAX1678 EV kit is shipped fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed. 1) Verify that the shunts are positioned on the jumpers as listed in Table 2 for a 3.3V output. 2) Connect a +0.87V to +3.3V supply voltage to the VIN pad. Connect ground to the GND pad. Note: once started, the input voltage may drop as low as 0.7V if the output current is less than 10mA. 3) Connect a voltmeter and the load (if any) to the VOUT pad. Component Suppliers SUPPLIER Coilcraft Coiltronics Murata Sumida Taiyo Yuden TDK PHONE 847-639-6400 561-241-7876 814-237-1431 847-956-0666 408-573-4150 847-390-4373 FAX 847-639-1469 561-241-9339 814-238-0490 847-956-0702 408-573-4159 847-390-4428 4) Turn on the power and verify that the output voltage is +3.3V. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX1678 Evaluation Kit Evaluates: MAX1678 Detailed Description Jumper Selections Two jumpers on the PC board allow selection of several configurations. Table 1 lists the jumper functions. Table 2 lists the jumper positions when setting the board for 3.3V operation. Component Selection The final circuit performance is determined by the quality of the components surrounding the MAX1678. The input and output capacitors must have low equivalent-seriesresistance (ESR) to handle the high peak currents found in switching regulators. Low ESR is especially critical in low-voltage circuits to reduce the output ripple. Ceramic capacitors are supplied on the MAX1678 EV kit because of their small size and low ESR in the value range needed for the circuit. MAX1678 OPERATION The MAX1678 is enabled. The MAX1678 is disabled. SHDN must be driven by a signal connected to the SHDN pad. VOUT is preset to 3.3V. A resistor must be installed in R3 to set the output voltage. See the MAX1678 data sheet for more information. Table 1. Jumper Functions JUMPER SHUNT POSITION J1 J1 J1 J2 J2 1&2 2&3 Open Shorted Open PIN CONNECTION SHDN connected to BATT SHDN connected to GND SHDN not controlled by the board FB pin connected to GND FB pin connected to the resistor-divider Table 2. Jumper Positions for Normal 3.3V Operation JUMPER SHUNT POSITION J1 J2 1&2 Shorted PIN CONNECTION SHDN pin connected to BATT FB pin connected to GND MAX1678 OPERATION The MAX1678 is enabled. VOUT is preset to 3.3V. L1 47H BATT J1 SHDN 1 2 3 R1 1M 1% 2 R2 OPEN 6 3 PFI 1 C1 10F 4 BATT LX 7 SHDN OUT 8 C2 10F OUT R3 OPEN U1 MAX1678 FB 5 J2 R5 100k R4 1M 1% GND GND GND PFO PFO Figure 1. MAX1678 EV Kit Schematic 2 _______________________________________________________________________________________ MAX1678 Evaluation Kit Evaluates: MAX1678 1.0" Figure 2. Component Placement Guide--Component Side 1.0" Figure 3. PC Board Layout--Component Side 1.0" Figure 4. PC Board Layout--Solder Side _______________________________________________________________________________________ 3 MAX1678 Evaluation Kit Evaluates: MAX1678 NOTES 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 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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