RT2808AGSP Evaluation Board your power partner. 3A, 36V, 500kHz Current Mode Asynchronous Step-Down Converter Purpose The RT2808A is a current mode asynchronous step-down converter that achieves excellent load and line regulation. This document explains the function and use of the RT2808A evaluation board (EVB) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements. Table of Contents Purpose ................................................................................................................................................................. 1 Introduction............................................................................................................................................................ 2 Application ............................................................................................................................................................. 2 Key Performance Summary Table .......................................................................................................................... 2 Bench Test Setup Conditions ................................................................................................................................. 3 Schematic, Bill of Materials & Board Layout ........................................................................................................... 4 Step-Down Converter Efficiency Test ..................................................................................................................... 7 More Information.................................................................................................................................................... 8 Important Notice for Richtek Evaluation Board ....................................................................................................... 8 EVB_RT2808AGSP-00 October 2015 1 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. Introduction General Product Description The RT2808A is a current mode asynchronous step-down converter that achieves excellent load and line regulation.Over a wide input voltage range from 5.5V to 36V and supports output current up to 3A. The Current mode operation provides fast transient response and eases loop stabilization. An adjustable soft-start reduces the stress on the input source at start up. In shut down mode, the regulator draws only 25μA of supply current. The RT2808A requires a minimum number of readily available external components, providing a compact solution. The RT2808A provides protection functions inducing input under voltage lockout, cycle-by-cycle current limit, short circuit protection and thermal shutdown protection.The RT2808A is available in the SOP-8 (Exposed Pad) package. Product Features 3A Output Current Wide Operating Input Range 5.5V to 36V Adjustable Output Voltage from 1.222V to 26V High Efficiency up to 90% Internal Compensation Minimizes External Parts Count Internal Soft-Start 110mΩ Internal Power MOSFET Switch 25μA Shutdown Mode Fixed 500kHz Frequency Thermal Shutdown Cycle-by-Cycle Current Limit Available In an SOP-8 (Exposed Pad) Package RoHS Compliant and Halogen Free Application Distributive Power Systems Battery Charger DSL Modems Pre-regulator for Linear Regulators Key Performance Summary Table Key Features Evaluation Board Number : PCB011_V1 Default VIN Input Voltage 12V Max Output Current 3A Default Output Voltage 2.5V Default Marking & Package Type RT2808AGSP, SOP-8 (Exposed Pad) EVB_RT2808AGSP-00 October 2015 2 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. Bench Test Setup Conditions Headers Description and Placement Please carefully inspect the EVB IC and external components, comparing them to the following Bill of Materials, to ensure that all components are installed and undamaged. If any components are missing or damaged during transportation, please contact the distributor or send e-mail to [email protected] Test Points The EVB is provided with the test points and pin names listed in the table below. Test point/Pin name Signal Comment (expected waveforms or voltage levels on test points) VIN Input voltage Input voltage range = 5.5V to 36V VOUT Output voltage Output voltage = 2.4V SW Switch Node EN Chip Enable Operation The EN pin is externally pulled to High by adding a 100kΩ resistor (R4) from the VIN pin in this EVB setting. For another enable operation, the converter is turned on when the EN pin is higher than 1.4V and turned off when the EN pin is lower than 0.4V. GND Ground Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Power-up & Measurement Procedure 1. Connect input power (5.5V < VIN < 36V) and input ground to VIN and GND pins respectively. 2. Connect positive end and negative end of load to Vout and GND of output pins respectively. 3. The output voltage of (VOUT) can be set by R1 and R2. VOUT = VREF * (1 + R1 / R2) where VREF = 1.222V (typ.) EVB_RT2808AGSP-00 October 2015 3 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. Specification Parameter Symbol Min VIN 5.5 Input Voltage Range Output Voltage VOUT Oscillator Frequency fOSC Output Current IOUT Current Limit ILIM Typ. Max Units 36 V 2.4 400 4 500 5.25 V 600 kHz 3 A 6.5 A Schematic, Bill of Materials & Board Layout EVB Schematic Diagram Bill of Materials Reference Qty P/N Description Package Manufacture U1 1 RT2808AGSP Step-down converter SOP-8 (Exposed Pad) RICHTEK C1, C2 2 GRM32ER71H475K 4.7μF/50V/X7R C-1210 MURATA C3, C6, C11 3 C1608X7R1H104K080AA 0.1μF/±10%/50V/X7R C-0603 TDK C4, C5 2 GRM32ER61C226KE20 22μF/±10%/16V/X5R C-1210 MURATA C12 1 82pF C-0603 L1 1 NR8040T6R8N 6.8µH TAIYO YUDEN D1 1 B550C 50V/5A DIODES R1, R2, R4 3 100k C8, R5 2 NC EVB_RT2808AGSP-00 October 2015 4 R-0402 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT2808AGSP-00 October 2015 5 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT2808AGSP-00 October 2015 6 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. Step-Down Converter Efficiency Test EVB_RT2808AGSP-00 October 2015 7 http://www.richtek.com RT2808AGSP Evaluation Board your power partner. More Information For more information, please find the related datasheet or application notes from Richtek website http://www.richtek.com. Important Notice for Richtek Evaluation Board THIS DOCUMENT IS FOR REFERENCE ONLY, NOTHING CONTAINED IN THIS DOCUMENT SHALL BE CONSTRUED AS RICHTEK’S WARRANTY, EXPRESS OR IMPLIED, UNDER CONTRACT, TORT OR STATUTORY, WITH RESPECT TO THE PRESENTATION HEREIN. IN NO EVENT SHALL RICHTEK BE LIABLE TO BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL DAMAGES. EVB_RT2808AGSP-00 October 2015 8 http://www.richtek.com