RT2875BQGCP Evaluation Board your power partner. RT2875B Synchronous Step-Down Converter Evaluation Board Purpose The RT2875B is a high efficiency, current-mode synchronous DC/DC step-down converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. his document explains the function and use of the RT2875B 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 .......................................................................................................................... 3 Bench Test Setup Conditions ................................................................................................................................. 3 Schematic, Bill of Materials & Board Layout ........................................................................................................... 5 Step-Down Converter Efficiency Test ..................................................................................................................... 8 More Information.................................................................................................................................................... 9 Important Notice for Richtek Evaluation Board ....................................................................................................... 9 EVB_RT2875BQGCP-00 November 2015 1 http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. Introduction General Product Description The RT2875B is a high efficiency, current-mode synchronous DC/DC step-down converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates 95mΩ high-side and 70mΩ low-side MOSFETs to achieve high conversion efficiency. The current-mode control architecture supports fast transient response and simple external compensation. A cycle-by-cycle current limit function provides protection. against shorted output and an external soft-start eliminates input current surge during start-up. The RT2875B provides complete protection functions such as input under-voltage lockout, output under-voltage protection, over-current protection and thermal shutdown.The RT2875B is available in the thermal enhanced TSSOP-14 (Exposed Pad) package. The RT2875B provides Hiccup Mode Under Voltage Protection (UVP). When the VFB voltage drops below 0.3V, the UVP function will be triggered to shut down switching operation. If the UVP condition remains for a period, the RT2875B will retry automatically. When the UVP condition is removed, the converter will resume operation. The UVP is disabled during soft-start period. Product Features 3A Output Current Internal N-MOSFETs Current Mode Control Adjustable Switching Frequency : 300kHz to 2.1MHz Adjustable Current Limit : 1.5A to 6A Synchronous to External Clock : 300kHz to 2.1MHz Adjustable Output Voltage from 0.6V to 24V High Efficiency Up to 95% Stable with Low ESR Ceramic Output Capacitors Cycle-by-Cycle Current Limit Input Under-Voltage Lockout Output Under-Voltage Protection Thermal Shutdown RoHS Compliant and Halogen Free Application Point of Load Regulator in Distributed Power Systems Digital Set Top Boxes Broadband Communications EVB_RT2875BQGCP-00 November 2015 2 http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. Key Performance Summary Table Key Features Evaluation Board Number : PCB013_V1 Default Input Voltage 12V Max Output Current 3A Default Output Voltage 3.3V Default Marking & Package Type RT2875BQGCP, TSSOP-14 (Exposed Pad) Operation Frequency 300kHz to 2.1MHz (Adjusted by RT Value, Defult RT = 100k, Frequency = 500kHz) 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] EVB_RT2875BQGCP-00 November 2015 3 http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. 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) SW Switch Node Connect to external L-C filter. PGND Power Ground Ground. The exposed pad must be soldered to a large PCB and connected to PGND for maximum power dissipation. RT/SYNC Oscillator Resistor Oscillator Resistor and External Frequency Synchronization Input. Must connect a resistor from this pin to GND to set the switching frequency. If SYNC clock is requested, connect an external clock to change the switching frequency. AGND Analog Ground Ground. RLIM Current Limit Setting Connect a resistor from this pin to GND to set the current limit value. FB Feedback Voltage Input The pin is used to set the output voltage of the converter to regulate to the desired via a resistive divider. Feedback reference = 0.6V. COMP Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND. In some cases, an additional capacitor from COMP to GND is required. SS Soft-Start Time Setting. Connect a capacitor from SS to GND to set the soft-start period. EN Enable Enable Control Input. High = Enable. PGOOD Power Good Output. Power Good Indicator Output. VIN Input Voltage Input voltage range = 4.5V to 36V. BOOT Boot Bootstrap Supply for High-Side Gate Driver. Connect a 0.1µF ceramic capacitor between the BOOT and SW pins. Power-up & Measurement Procedure 1. Connect input power (4.5V< 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 = 0.6V (typ.) Specification Parameter Symbol Min Input Voltage Range VIN Oscillator Frequency fOSC Output Current IOUT EN Input Voltage VEN EVB_RT2875BQGCP-00 November 2015 Typ. Max Units 4.5 36 V 300 2100 kHz 3 1.4 4 1.5 A 1.6 V http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. Schematic, Bill of Materials & Board Layout EVB Schematic Diagram Bill of Materials Reference Q'ty Part Number Description Package Manufacture U2 1 RT2875BQGCP Step-down Converter PTSSOP-14 RICHTEK Css, C3, C6, C11 4 C1608X7R1H104KT000N 0.1μF/50V/X7R C-0603 TDK C1, C2 2 GRM32ER71H106KA12 10μF/50V/X7R C-1210 Murata C4, C5 2 GRM32ER61C226KE20L 22μF/16V/X5R C-1210 MURATA C7 1 0603B333K500 3.3nF/50V/X7R C-0603 WALSIN R5, C8, C9, C12, C13 5 NC C/R-0603 D1 0 NC D2 0 NC L1 1 RT, R4, RPG 3 100K R-0603 RLIM 1 33k R-0603 R1 1 115K R-0603 R2 1 25.5K R-0603 R3 1 10K R-0603 EVB_RT2875BQGCP-00 4.7μH/7A 744 771 404 7 November 2015 5 WE http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT2875BQGCP-00 November 2015 6 http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT2875BQGCP-00 November 2015 7 http://www.richtek.com RT2875BQGCP Evaluation Board your power partner. Step-Down Converter Efficiency Test EVB_RT2875BQGCP-00 November 2015 8 http://www.richtek.com RT2875BQGCP 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_RT2875BQGCP-00 November 2015 9 http://www.richtek.com