19-1400; Rev 0; 11/98 MAX1692 Evaluation Kit The MAX1692 evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board that contains a pulse-width-modulated (PWM), step-down DC-DC converter. The EV kit provides a +2.5V output voltage from a +2.7V to +5.5V input source. It delivers up to 600mA output current. The MAX1692 features internal MOSFET switches, low dropout voltage, and a 1.2%-accurate 1.25V reference. The MAX1692 EV kit provides low quiescent current and high efficiency (up to 95%) for maximum battery life. Operation at 750kHz allows the use of a tiny surface-mount inductor. Component List DESIGNATION QTY C1 C2 DESCRIPTION 1 10µF, 6.3V, X5R ceramic capacitor Taiyo Yuden JMK325BJ106MN 1 47µF, 6.3V, low ESR, electrolytic capacitor, Sanyo 6TPA47M or 47µF, 16V tantalum capacitor Sprague 594D476X0016C2T C3 1 0.1µF ceramic capacitor C4 1 0.22µF ceramic capacitor C5 1 47pF ceramic capacitor L1 1 10µH inductor Sumida CDR63B-100 (shielded) or CD43-100 (unshielded) R1 1 309kΩ, 1% resistor R2 1 301kΩ, 1% resistor R3 1 100kΩ, 5% resistor U1 1 MAX1692EUB JU1 1 3-pin header None 1 Shunt (JU1) JU2 1 2-pin header None 1 MAX1692 PC Board None 1 MAX1692 data sheet ♦ +2.7V to +5.5V Input Voltage Range ♦ +2.5V Output Voltage or Adjustable Output from 1.25V to VIN ♦ 600mA Output Current ♦ 100% Duty Cycle in Dropout ♦ 750kHz Fixed-Frequency PWM Operation ♦ Internal MOSFET Switch and Synchronous Rectifier ♦ 0.1µA IC Shutdown Current ♦ Surface-Mount Components ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE MAX1692EVKIT 0°C to +70°C IC-PACKAGE 10 µMAX Quick Start The MAX1692 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 +2.7V to +5.5V supply to the VIN pad. Connect the ground to the GND pad. 2) Connect a voltmeter to the VOUT pad. 3) Verify that the shunt is across JU1 pins 1 and 2. 4) Turn on the power supply and verify that the output is at +2.5V. Detailed Description Jumper Selection Component Suppliers SUPPLIER Features PHONE FAX Dale-Vishay 402-564-3131 402-563-6418 Sanyo 619-661-6835 619-661-1055 Sprague 603-224-1961 603-224-1430 Sumida 708-956-0666 708-956-0702 Taiyo Yuden 408-573-4150 Shutdown Mode The MAX1692 EV kit features a shutdown mode that reduces the MAX1692 IC’s quiescent current to 0.1µA, preserving battery life. The 3-pin header, JU1, selects the shutdown mode (Table 1). Table 1. Jumper JU1 Functions SHUNT LOCATION SHDN PIN 408-573-4159 1&2 Connected to VIN Note: Please indicate that you are using the MAX1692 when contacting these component suppliers. 2&3 MAX1692 OUTPUT MAX1692 enabled, VOUT = 2.5 Connected to GND Shutdown mode, VOUT = 0 ________________________________________________________________ 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 1-800-835-8769. Evaluates: MAX1692 General Description Evaluates: MAX1692 MAX1692 Evaluation Kit Table 2. Jumper JU2 Functions Table 3. R1/R2 for Other Output Voltages SHUNT LOCATION SYNC/PWM PIN OPERATING MODE VOUT (V) R1 (1%) R2 (1%) 1.50 66.5k 301k On Connected to VIN MAX1692 operates in PWM low-noise mode. 1.80 140k 301k 2.50 309k 301k Pulled to GND via 100k MAX1692 operates in PWM/PFM mode. 2.70 357k 301k 3.32 511k 301k Driven from external clock SYNC/PWM pin is driven by an external clock between 500kHz and 1000kHz. Off (not installed) Changing Current Limit The inductor current limit can be set to 0.6A or 1.2A. The EV kit is factory-configured for a 1.2A limit. To set the limit to 0.6A, cut the PC trace shorting JU3 pins 1 & 2, and then short JU3 pins 2 & 3. This allows for use of the smallest possible inductor for low-current applications. Operating Mode The MAX1692 operates in one of three modes to optimize performance. A fixed-frequency (PWM) mode switches at a fixed frequency for easy post-filtering. A synchronizable PWM mode uses an external clock to control harmonics. A PWM/PFM mode extends battery life by operating in PWM mode under heavy loads and in PFM mode under light loads for reduced power consumption. The EV kit operates at a 750kHz switching frequency and allows the use of a small-value inductor. The switching frequency can also be synchronized to an external clock ranging from 500kHz to 1000kHz. The 2pin header JU2 selects the operating mode (Table 2). 1 VIN 2.7V TO 5.5V C1 10µF 6.3V 2 C3 0.1µF JU1 SHDN 1 2 8 IN Evaluating Other Output Voltages The EV kit’s output is set to +2.50V by connecting FB to resistor-divider R1/R2. However, the output voltage can also be adjusted between +1.232V and VIN by changing R1 and R2 values. Select feedback resistor R2 in the 5kΩ to 500kΩ range. R1 is then given by: R1 = R2 [(VOUT / VFB) - 1] where VFB = 1.232V and VOUT = output voltage. The unloaded output voltage is typically 1% above the nominal output voltage. Table 3 lists values for R1 for different output voltages. LX BP U1 PGND MAX1692 SHDN FB L1 10µH 10 VIN 5 VIN JU2 7 SYNC/PWM LIM SYNC/PWM R2 301k 1% 1 REF C4 0.22µF GND 6 3 C2 47µF 6.3V R1 309k 1% 3 4 2 JU3 3 R3 100k Figure 1. MAX1692 EV Kit Schematic 2 VOUT 2.5V 9 _______________________________________________________________________________________ C5 47pF MAX1692 Evaluation Kit Evaluates: MAX1692 1.0" 1.0" Figure 2. MAX1692 EV Kit Component Placement Guide— Component Side Figure 3. MAX1692 EV Kit PC Board Layout—Component Side 1.0" Figure 4. MAX1692 EV Kit PC Board Layout—Solder Side _______________________________________________________________________________________ 3 Evaluates: MAX1692 MAX1692 Evaluation Kit 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 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.