SP6127, 2A Evaluation Board Manual Easy Evaluation for the SP6127EK1 12V Input, 0 to 2A Output Non-Synchronous Buck Converter Precision 0.60V 1% High -Accuracy Reference. Small form factor Feature Rich: Single supply operation, Over- current protection with auto-restart, on/off function, Preset internal soft start, Type-II internal compensation SP6127EB SCHEMATIC VIN C1 12V Q1 4.7uF Si2343DS 2 1 Gate GND Vin L1, IHLP-2525CZ Rs=1k 3.3uH, 30mOhm, 6A VOUT LX C7 0.1uF 6 C4 SP6127 Ds RZ 22uF 1.8V 3 MBRA340T3G 2K 0-2.0A VDR R1 200k, 1% CZ 4 33pF GND VFB GND R2 5 100k, 1% D1 1N4148 SHDN High=Of f Rev 6/27/07 SP6127 Evaluation Manual Copyright 2007 Sipex Corporation USING THE EVALUATION BOARD 1) Powering Up the SP6127EB Circuit Connect the SP6127 Evaluation Board to an external +12V power supply. Connect with short leads directly to the VIN and GND posts. Connect a Load between the VOUT and GND posts, again using short leads to minimize inductance and voltage drop. 2) Measuring Output Load Characteristics Its best to GND reference scope and digital meters using the Star GND post near the output of the board. VOUT ripple can best be seen touching probe tip to the pad for COUT and scope GND collar touching Star GND post avoid a GND lead on the scope which will increase noise pickup. 3) Using the Evaluation Board with Different Output Voltages While the SP6127 Evaluation Board has been tested and delivered with the output set to 1.80V, by simply changing one resistor, R2, the SP6127 can be set to other output voltages. The relationship in the following formula is based on a voltage divider from the output to the feedback pin FB, which is set to an internal reference voltage of 0.60V. Standard 1% metal film resistors of surface mount size 0603 are recommended. R1 R2 = Vout 1 Vref Where R1 = 200k. For Vout = 0.60V setting, simply remove R2 from the board. Note that since the SP6127 Evaluation Board design was optimized for 12V down conversion to 1.80V, changes of output voltage and/or input voltage will alter performance from the data given in the Power Supply Data section. Using the SHDN (ON/OFF function) Feedback pin serves a dual role of ON/OFF control. The MOSFET driver is disabled when a voltage greater than 1V is applied at FB pin. Maximum voltage rating of this pin is 5.5V. The controlling signal should be applied through a small signal diode as shown on page 1. Note that under no-load condition an optional 10kOhm bleeding resistor across the output helps keep the output capacitor discharged. POWER SUPPLY DATA The SP6127EB is designed with an accurate 2% reference over line, load and temperature. Figure 1 data shows a typical SP6127 Evaluation Board efficiency plot, with efficiencies to 75% and output currents to 2A. SP6127 Load Regulation in Figure 2 shows very little change in output voltage from no load to 2A load. Figures 3 and 4 show the transient response of the SP6127 and overcurrent shutdown. Figures 5 and 6 show a controlled start-up with no load and 2A load when power is applied where the input current rises smoothly as the soft-start ramp increases. Figures 7 and 8 show the output ripple under no load and 2A load. 2