Evaluates: MAX8815A 19-4216 Rev 0 7/08 MAX8815A Evaluation Kit General Description Features The MAX8815A evaluation kit (EV kit) is a fully assem- Up to 97% Efficiency with Internal Synchronous Rectifier bled and tested printed-circuit board (PCB) for evaluat- ing the MAX8815A step-up converter. The MAX8815A Low 35A (Switching) Quiescent Current is a 1A (maximum load), 97% efficient, 35A quiescent Guaranteed 1A Output Current at 5V from 2.5V Input current step-up converter with True Shutdown and is Guaranteed 500mA Output Current at 5V from 1.8V ideal for use in DSC, DVC, and other handheld appli- Input cations. The MAX8815A EV kit is designed for a 5V Low-Noise Constant Frequency Operation (FPWM output and also provides a jumper for evaluation of Mode) fixed-frequency pulse-width-modulation mode (FPWM) or normal mode. 2MHz PWM Switching Frequency Preset (5V) or Adjustable Output (3.3V to 5V) Controlled Current in Soft-Start Limits Inrush Current True Shutdown is a trademark of Maxim Integrated Products, Inc. True Shutdown Internal Compensation Overload/Short-Circuit Protection 0.1A Shutdown Current Component Suppliers Lead-Free and RoHS Compliant SUPPLIER PHONE WEBSITE Fully Assembled and Tested NEC TOKIN 408-324-179 0 www .nec-tok inameric a.com America, Inc. Ordering Information Sullins Electroni cs Corp . 760-744-012 5 www .s ulli n selectronic s.com Taiyo Yuden 408-573-4 150 www.t-yuden.com PART TYPE TOKO 847-297-0 070 www.toko.com MAX8815AEVKIT+ EV Kit Note: Indicate that you are using the MAX8815A when contact- +Denotes lead-free and RoHS compliant. ing these component suppliers. Component List DESIGNATION QTY DESCRIPTION DESIGNATION QTY DESCRIPTION 1.2H inductor C1A 0 Not installed, capacitor L1 1 TOKO A1124BS-1R2 (DE4512CK 10F 10%, 6.3V X5R ceramic Series) capacitor (0805) C1B 1 R1 0 PCB short, resistor (0402) Taiyo Yuden JMK212BJ106KG, or equivalent R2 0 Not installed, resistor (0402) C2A 0 Not installed, capacitor R3 1 100 1% resistor (0402) 22F/10V, 70m ESR tantalum MAX8815AETB+ (10 TDFN-EP, U1 1 C2B 1 capacitor 3mm x 3mm) NEC Tokin PSLB31A226M 1 PCB: MAX8815A Evaluation Kit+ 0.1F 20%, 10V X5R ceramic C3 1 capacitor (0402) Taiyo Yuden LMK105BJ104MV 3-pin headers 1 x 36-pin headers, 0.1in centers JU1, JU2 2 ( com es in 1 x 36-p i n stri p s, cut to fit) Sullins PEC36SAAN Digi-Key S1012E-36-ND Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.MAX8815A Evaluation Kit Normal Mode Quick Start Drive SKIPB low to select the normal mode of opera- Recommended Equipment tion. In this mode, the device operates in PWM only A 1.2V to 5.5V power supply capable of delivering when driving medium to heavy loads. As the load cur- 2.5A rent decreases and crosses the low-power idle-mode threshold, the PWM comparator and oscillator are dis- One voltmeter (DMM) abled. In this low-power mode, switching occurs only Load capable of sinking 1A as needed to service the output. This improves the effi- Ammeter (optional) ciency for light loads, and the device consumes only 35A under no-load conditions. The threshold for enter- Procedure ing skip mode is approximately 90mA load with a 3.6V The MAX8815A EV kit is fully assembled and tested. input and 5V output. When switching in normal mode, Follow the steps below to verify board operation. the inductor current terminates at zero for each switch- 1) Preset the power supply to 3.6V. ing cycle. 2) Turn off the power supply. Do not turn on the FPWM Mode power supply until all connections are completed. Drive SKIPB high to select the FPWM mode of opera- 3) Verify that the shunt on JU1 is connected to OFF tion. The IC switches at a constant frequency (2MHz) (pins 2 and 3). Verify that the shunt on JU2 is con- and modulates the MOSFET switch pulse width nected to NORM (pins 2 and 3). to control the power transferred per cycle to regulate the output voltage. Switching harmonics gene- 4) Connect the positive power-supply terminal to the rated by fixed-frequency operation are consistent pad on the EV kit labeled IN. Connect the power- and easily filtered. This is important in noise-sensitive supply ground terminal to the pad on the EV kit applications. labeled GND. The MAX8815A does not allow for dynamic switching 5) Connect a voltmeter across the OUT pad on the EV between normal and FPWM modes. kit and the GND pad on the EV kit. 6) Connect the 1A load between OUT and GND with Shutdown Mode the load set to minimum. Connect ON to GND or connect a shunt to pins 2 and 3 of JU1 to place the MAX8815A in shutdown mode and 7) Turn on the power supply. reduce supply current to 0.1A. In shutdown, the 8) Verify that the voltmeter is reading 0V and input control circuitry, internal switching MOSFET, and current is less than 1A. synchronous rectifier turn off and LX becomes high 9) Remove the shunt from the OFF position (pins 2 impedance. Connect ON to IN or connect a shunt to and 3) of JU1 and place it on the ON position (pins pins 1 and 2 of JU1 for normal operation. 1 and 2) of JU1. Evaluating Other Output Voltages 10) Verify the voltmeter is measuring between 4.95V The MAX8815A EV kit is designed for the preset output and 5.05V. voltage of 5V. To set other output voltages, use external 11) Slowly increase the load up to 1A and verify the feedback resistors. output voltage. To set the output voltage between 3.3V and 5V, cut the PCB short on resistor R1, and connect FB to the center Detailed Description of an external resistor voltage-divider between OUT Normal and FPWM Mode and GND, as shown in Figure 2. Select the value of R2 The MAX8815A operates in two modes, normal mode no more than 500k, and then calculate the value for and FPWM mode, depending on the voltage at SKIPB. R1 as follows: SKIPB is assigned to pin 2 on jumper JU2. Connecting R1 = R2 (V /V - 1) OUT FB a shunt to pins 2 and 3 of JU2 sets the IC to normal where V is the FB regulation voltage, 1.265V (typ). FB operation. Connecting a shunt to pins 1 and 2 sets the IC to FPWM mode only. 2 Evaluates: MAX8815A