MAX881REVKIT

19-1372; Rev 1; 6/98 MAX881R Evaluation Kit The MAX881R IC is an inverting, charge-pump DC-DC converter with a low-noise, regulated output. Low output ripple voltage makes this device ideal for biasing the GaAsFETs commonly found in cellular telephone transmitters. The MAX881R evaluation kit (EV kit) is a fully assembled and tested surface-mount board. Provisions are made for mounting a second voltage-divider resistor, which is required for setting output voltages other than -2V. A special scope-probe socket is also mounted on the board, so output noise can be observed on an oscilloscope. Features ♦ 1mVp-p Output Voltage Ripple ♦ 2.5V to 5.5V Input Range ♦ Uses One 4.7µF and Three 1µF Ceramic Capacitors ♦ -2V Regulated Output (or Adjustable) ♦ 4mA Output Current ♦ Power OK (POK) Output ♦ Fully Assembled and Tested Surface-Mount Board Component List DESIGNATION QTY Ordering Information DESCRIPTION PART TEMP. RANGE IC PACKAGE MAX881REVKIT -40°C to +85°C 10 µMAX C1, C2, C3 3 1µF, 16V, low-ESR ceramic capacitors Taiyo Yuden EMK316BJ105KL C4 1 4.7µF, 10V, low-ESR ceramic capacitor Taiyo Yuden LMK316BJ475ML J1 1 Scope-probe connector Berg Electronics 33JR135-1 JU1 1 2-pin jumper R1 0 Not installed R2 1 100kΩ, 1% resistor R3, R4 2 1MΩ resistors Quick Start The MAX881R EV kit is fully assembled and tested. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed. U1 1 MAX881RREUB 1) Connect a 2.5V to 5.5V supply to the pad labeled VIN. Connect the ground lead to the pad labeled GND. None 1 Shunt 2) Connect a voltmeter and the load to the VOUT pad. None 1 Printed circuit board 3) Make sure there is no shunt across JU1. Component Suppliers SUPPLIER PHONE 4) Turn on the power and verify that the output is -2V. You can insert a scope probe into J1 to observe the output noise. Be sure the scope ground makes contact with the outside of the connector. FAX Berg Electronics (317) 738-2800 (317) 738-2858 Sprague (603) 224-1961 (603) 224-1430 Taiyo Yuden (408) 573-4150 (408) 573-4159 ________________________________________________________________ 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. Evaluates: MAX881R General Description Evaluates: MAX881R MAX881R Evaluation Kit Detailed Description Jumper Selection The 2-pin header, JU1, controls pin 5 (SHDN) on the IC. Table 1 outlines the shunt positions for JU1. The POK pad allows easy connection to an external system. This output pulls low when the bias voltage has reached 92.5% of its set value. Output Voltage Adjustment For output voltages other than -2V, install R1 to complete the R1/R2 output voltage divider. R2 is a 100kΩ, 1% resistor. To maintain accuracy, use a 1% resistor for R1. Use the following equations to calculate R1: Capacitor Selection Use capacitors with a low effective series resistance (ESR), such as ceramic or surface-mount chip tantalum types. Output ripple with the supplied components is typically 1mVp-p. For lower output ripple, replace C4 with a 10µF ceramic capacitor such as the Taiyo Yuden JMK316BJ106ML or a 10µF tantalum such as the Sprague 595D106X0010A2. Table 1. JU1 Shunt Position SHUNT POSITION R1 = -R2 (2 x VOUT + 1) R1 = -100kΩ (2 x VOUT + 1) Device enabled, or apply signal to the SHDN pad Open Closed 1 C1+ IN MAX881R FUNCTION Device disabled VIN 2.5V to 5.5V 10 C1 1µF 2 C1- C3 1µF 3 R3 1M POK SHDN 4 U1 N.C. MAX881R NEGOUT GND POK OUT 8 GND J1 7 R4 1M VOUT R1 OPEN 5 JU1 C2 1µF 9 SHDN FB C4 4.7µF 6 VOUT R2 100k 1% GND Figure 1. MAX881R EV Kit Schematic 2 _______________________________________________________________________________________ MAX881R Evaluation Kit Evaluates: MAX881R 1.0" Figure 2. MAX881R EV Kit Component Placement Guide— Component Side 1.0" 1.0" Figure 3. MAX881R EV Kit PC Board Layout—Component Side Figure 4. MAX881R EV Kit PC Board Layout—Solder Side _______________________________________________________________________________________ 3 Evaluates: MAX881R MAX881R 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.