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| 19-1360; Rev 0; 7/98 MAX1676 Evaluation Kit General Description The MAX1676 is a high-efficiency, step-up DC-DC converter for portable hand-held devices. It accepts a positive input voltage between 0.7V to 5.5V and converts it to a higher output voltage. The MAX1676 includes a damping circuit (at BATT) that suppresses inductor ringing to reduce electromagnetic interference (EMI). The MAX1676 evaluation kit (EV kit) is a fully assembled and tested surface-mount printed circuit board. Three jumpers on the EV kit allow for easy access to the output voltage select, current limit, and shutdown features. The output voltage is both adjustable and pin-selectable. A movable jumper selects either a 3.3V or 5.0V output, or it can be left open and a resistor network can be used to obtain a voltage in the 2V to 5.5V range. The inductor current limit is selectable for either 0.5A or 1.0A. In shutdown mode, the MAX1676 typically draws only 0.1A. Features o Synchronous Rectification for Improved Efficiency o Operates Down to 0.7V Input Supply Voltage o No External Schottky Diode Required (for multicell applications) o Selectable Current Limit (0.5A or 1.0A) o Damping Circuit Reduces EMI o 16A Quiescent Current o 0.1A Typical Shutdown Current o Low-Battery Detector (LBI/LBO) o 10-Pin MAX Package o Surface-Mount Construction o Fully Assembled and Tested Evaluates: MAX1676 Component Suppliers Component List DESIGNATION QTY C1 C2 C3 1 1 1 DESCRIPTION 47F, 16V tantalum capacitor AVX TPSC476M016R0350 100F, 10V tantalum capacitor AVX TPSD107M010R0100 1F, Y5V ceramic capacitor Taiyo Yuden UMK212F105ZG 0.1F, X7R ceramic capacitor Taiyo Yuden UMK212BJ104KG or Murata GRM40X7R104K025AL Diode (not included; needed for 1-cell inputs) Motorola MBR0520 3-pin jumpers 22H power inductor (1.1A) Sumida CD54-220 200, 5% resistor Open MAX1676EUB SUPPLIER AVX Motorola Murata Sumida Taiyo Yuden PHONE 803-946-0690 303-675-2140 814-237-1431 847-956-0666 408-573-4150 FAX 803-626-3123 303-675-2150 814-238-0490 847-956-0702 408-573-4159 Quick Start The MAX1676 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a 1.1V to 3V supply to the pads marked +VBATT and GND. 2) Connect a voltmeter and load (if any) to the VOUT pad. 3) Place the shunt on JU3 across pins 1 and 2. 4) Place the shunt on JU1 across pins 1 and 2 for a 3.3V output voltage. 5) Place the shunt on JU2 across pins 1 and 2 for a 1A current limit. 6) Turn on the power and verify that the output voltage is 3.3V. 7) Refer to the Output Voltage Selection section to modify the board for a different output voltage. 1 C4 1 D1 JU1, JU2, JU3 L1 R1 R2-R6 U1 0 3 1 1 0 1 Ordering Information PART MAX1676EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 10 MAX ________________________________________________________________ Maxim Integrated Products 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. MAX1676 Evaluation Kit Evaluates: MAX1676 Detailed Description Input Source The input source for the MAX1676 EV kit must be greater than 1.1V for guaranteed start-up (0.7V for operation once started), and less than the output voltage. A typical input voltage range would be the 2.0V to 3.3V range of a 2-cell NiCd battery. An input voltage greater than the selected output voltage (but less than 6V) will not damage the circuit, but under these circumstances, the MAX1676's output will equal the input voltage minus the 0.7V drop of the internal diode (0.3V if D1, the Schottky diode, is in the circuit). Once started, the MAX1676 operates from the regulated output voltage. This means that the input voltage can fall below the 1.1V minimum guaranteed start-up voltage. Typically, the regulated output will be maintained even if the input voltage drops to 0.7V. Jumper Selection Three 3-pin jumpers select the output voltage, current limit, and shutdown mode. Table 1 lists the selectable jumper options. Table 1. Jumper Selection Options JUMPER JUMPER POSITION FUNCTION 3.3V fixed output 5V fixed output Adjustable output using resistor-divider R1 and R2. Inductor peak current limited to 1.0A. Inductor peak current limited to 0.5A. SHDN = High. MAX1676 enabled. SHDN = Low. MAX1676 disabled. Drive pad SHDN with an external signal. 1-2 JU1 2-3 Open JU2 1-2 2-3 1-2 JU3 2-3 Open Single-Cell Operation When using a single-cell battery, diode D1 must be installed to ensure low-voltage start-up. Use a Motorola MBR0520 or equivalent Schottky diode. +VBATT L1 22H 7 BATT LX 9 D1 OPEN R2 OPEN LBO 3 1 SHDN 6 JU3 2 3 CLSEL 5 C4 0.1F 4 1 JU2 2 3 REF GND 8 FB 1 R5 OPEN R6 OPEN 1 2 JU1 3 SHDN C3 1F C2 100F, 10V VOUT GND LBO C1 47F 16V GND R1 200 R3 OPEN 2 R4 0 (SHORT) LBI OUT 10 U1 MAX1676 Figure 1. MAX1676 EV Kit Schematic 2 _______________________________________________________________________________________ MAX1676 Evaluation Kit Using the Low-Battery Detector The MAX1676 has an additional comparator useful for monitoring the input source's voltage level. Resistors R3 and R4 are connected as a voltage-divider between the +VBATT pad and the MAX1676 LBI pin. Note that a printed circuit trace across R4 shorts the LBI pin to ground when this function is not used. Cut the trace before installing R4. Another location on the board facilitates the addition of a pull-up resistor on the LBO output. The LBO output is an open-drain output that can sink 1mA. Install resistor R2 if an external circuit is to be driven from LBO. Refer to the Low-Battery Detection section of the MAX1674/MAX1675/MAX1676 data sheet for instructions on selecting values for resistors R2, R3, and R4. Evaluates: MAX1676 Output Voltage Selection The MAX1676 is initially set to output either 3.3V or 5V, depending on the position of JU1. However, by adding external resistors, the output can be adjusted from 2.0V to 5.5V. Remove the shunt on JU1 and add the output voltage-divider resistors R5 and R6. The Selecting the Output Voltage section of the MAX1674/ MAX1675/MAX1676 data sheet gives instructions for calculating R5 and R6 values. 1.0" Figure 3. MAX1676 EV Kit PC Board Layout--Component Side 1.0" Figure 2. MAX1676 EV Kit Component Placement Guide-- Component Side 1.0" Figure 4. MAX1676 EV Kit PC Board Layout--Solder Side _______________________________________________________________________________________ 3 MAX1676 Evaluation Kit Evaluates: MAX1676 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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