RT7273GQW Evaluation Board your power partner. 3-CH, 18V, Synchronous Step-Down Converter Purpose The RT7273 features three synchronous wide input range high efficiency Buck converters. The converters are designed to simplify its application while giving the designer the option to optimize their usage according to the target application. This document explains the function and use of the RT7273 evaluation board (EVB), and provides information to enable operation, modification of the evaluation board and circuit to suit individual requirements. Table of Contents Purpose ................................................................................................................................................................. 1 Introduction............................................................................................................................................................ 2 Key Performance Summary Table .......................................................................................................................... 2 Bench Test Setup Conditions ................................................................................................................................. 3 Schematic, Bill of Materials & Board Layout ........................................................................................................... 4 More Information.................................................................................................................................................... 8 Important Notice for Richtek Evaluation Board ....................................................................................................... 8 EVB_RT7273GQW-00 April 2016 1 http://www.richtek.com RT7273GQW Evaluation Board your power partner. Introduction General Product Information The RT7273 features three synchronous wide input range high efficiency Buck converters. The converters are designed to simplify its application while giving the designer the option to optimize their usage according to the target application. The converters can operate in 5V, 9V or 12V systems and have integrated power transistors. The output voltage can be set externally using a resistor divider to any value between 0.8V and the input supply minus 1V. Each converter features an enable pin that allows a delayed start-up for sequencing purposes, a soft-start pin that allows adjustable soft-start time by choosing the softstart capacitor, and a current limit pin (RLIMx) to adjust current limit by selecting an external resistor. The COMP pin allows optimizing transient versus dc accuracy response with a simple RC compensation. The switching frequency of the converters can either be set with an external resistor connected to ROSC pin or be synchronized to an external clock connected to SYNC pin if needed. The switching converters are designed to operate from 300kHz to 2.2MHz. The converters operate with 180°phase between CH 1 and CH 2, CH 3 (CH 2 and CH 3 ran in phase) to minimize the input filter requirements. The RT7273 also features a low power mode enabled by an external signal, which allows for a reduction on the input power supplied to the system when the host processor is in stand-by (low activity) mode. Product Feature Wide Input Supply Voltage Range : 4.5V to 18V Output Range : 0.8V to (VIN 1V) Fully Integrated Triple-Buck Maximum Current 3.5A/2.5A/2.5A Continuous Operation 3A/2A/2A High Efficiency Switching Frequency 300kHz to 2.2MHz Set by External Resistor External Synchronization Pin for Oscillator External Enable/Sequencing Pins Adjustable Cycle-By-Cycle Current Limit Set by External Resistor Soft-Start Current Mode Control with Simple Compensation Circuit Power Good Indicator Discontinuous Operating Mode at Light Load when LOWP = High Key Performance Summary Table Key Features Evaluation Board Number : PCB068_V1 Input Voltage Range 4.5V to 18V Max Output Current (CH1/CH2/CH3) 3.5A/2.5A/2.5A Default Output Voltage (CH1/CH2/CH3) 1.2V/1.8V/3.3V Default Marking & Package Type RT7273GQW, WQFN-40L 6x6 Operation Frequency Set by resistor connected with ROSC pin, with 383kΩ setting for 500kHz switching frequency. EVB_RT7273GQW-00 April 2016 2 http://www.richtek.com RT7273GQW 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 Power input. EN Enable test point Externally pulled high to enable and pulled low to disable this chip. It is internally pulled up to high when the pin is floating. GND Ground The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. VINR Internal Control Circuit Power Supply Voltage Input for Internal Control Circuit. PVCC 5V Internal Regulator Output Connect a capacitor 10µF between this pin and GND. VCC 4.6V Internal Regulator Output Connect a capacitor 3.3µF between this pin and GND. SS Soft-Start Control Connect an external capacitor between this pin and GND to set the soft-start time. PG Power good test point Output of power good indicator. LOWP Discontinuous Operation Mode Input Discontinuous Operating Mode at Light Load when LOWP = High (Active High). VLX Switch node test point Switch Output for CH 1/2/3. SYNC Synchronous Clock Input Connect to GND if not used. EVB_RT7273GQW-00 April 2016 3 http://www.richtek.com RT7273GQW Evaluation Board your power partner. Power-up & Measurement Procedure 1. Apply a 12V nominal input power supply (4.5< VIN < 18V) to the VIN and GND terminals. 2. Set the jumper at JP2/JP3/JP4 to connect terminals to H pin, connecting EN to enable operation. 3. Set the jumper at JP1 to short with GND, disable the frequency synchronous function. 4. Verify the output voltage (VOUT1 = 1.2V, VOUT2 = 1.8V, VOUT3 = 3.3V). Output Voltage Setting Set the output voltage with the resistive divider between VOUT and GND with the midpoint connected to FB. The output is set by the following formula : VOUT1 = 0.8 × (1 + R9 R12 VOUT2 = 0.8 × (1 + R11 VOUT3 = 0.8 × (1 + R20 R15 R13 ) ) ) Schematic, Bill of Materials & Board Layout EVB Schematic Diagram EVB_RT7273GQW-00 April 2016 4 http://www.richtek.com RT7273GQW Evaluation Board your power partner. Bill of Materials Reference Qty Part Number Description Package Manufacture U1 C1, C2, C3, C4, C5, C6, C25, C28, C29 C7, C24, C31 C9, C10, C17, C26, C30 C11, C12, C16, C18, C21, C22, C23 C13, C15, C32 1 RT7273GQW DC/DC Converter WQFN-40L 6x6 RICHTEK 9 0603B472K500 4.7nF/50V/X7R C0603 WALSIN 3 C1608X7R1H104KT000N 0.1µF/50V/X7R C0603 TDK 5 GRM31CR71E106KA12L 10µF/25V/X7R C-1206 muRata 7 GRM32ER61C226KE20L 22µF/16V/X5R C-1210 muRata 3 0603B471K200 470pF/50V/X7R C0603 WALSIN C14, C19, C20 3 NC C0603 C27 1 C2012X5R1A335KT000N 3.3µF/10V/X5R C-0805 TDK L1, L2, L3 3 NR8040T4R7N 4.7µH/4.1A 8 x 8 x 4 mm TAIYO YUDEN R1 1 51k R-0603 R3, R5, R17 3 20k R-0603 R4 1 82k R-0603 R7 1 383k R-0603 R9, R11, R20 3 40.2k R-0603 R12 1 80.8k R-0603 R13 1 12.7k R-0603 R15 1 32.4k R-0603 R16 1 75k R-0603 R18 1 100k R-0603 R1 1 51k R-0603 R3, R5, R17 3 20k R-0603 EVB_RT7273GQW-00 April 2016 5 http://www.richtek.com RT7273GQW Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT7273GQW-00 April 2016 6 http://www.richtek.com RT7273GQW Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT7273GQW-00 April 2016 7 http://www.richtek.com RT7273GQW 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 W ARRANTY, EXPRESS OR IMPLIED, UNDER CONTRACT, TORT OR STATUTORY, WITH RESPECT TO THE PRESENTATION HEREIN. IN NO EVENT SHALL RICHTEK BE LIABLE T O BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL DAMAGES. EVB_RT7273GQW-00 April 2016 8 http://www.richtek.com