RT7235GQW Evaluation Board Purpose The RT7235 is a high-performance 650kHz 5A step down regulator with an internal power switch and synchronous rectifier. This document explains the function and use of the RT7235 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 General Product Information ........................................................................................................2 Key Performance Summary Table ...............................................................................................3 Bench Test Setup Conditions .......................................................................................................4 Headers Description and Placement ............................................................................................4 Test Points ...................................................................................................................................5 Power-up & Measurement Procedure ..........................................................................................5 Output Voltage Setting .................................................................................................................5 Schematic, Bill of Materials and Board Layout .............................................................................6 EVB Schematic Diagram ..............................................................................................................6 Bill of Materials.............................................................................................................................7 EVB Layout ..................................................................................................................................8 More Information ........................................................................................................................12 Important Notice for Richtek Evaluation Board ...........................................................................12 UG7235GQW-00 April 2014 www.richtek.com RT7235GQW Evaluation Board Introduction General Product Information General Description The RT7235 is a high-performance 650kHz 5A step down regulator with an internal power switch and synchronous rectifier. It features quick transient response using its Advanced Constant On-Time (ACOTTM) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 8V. The proprietary ACOTTM control improves upon other fast response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT7235 is stable with and optimized for ceramic output capacitors. With its internal 90mΩ switch and 60mΩ synchronous rectifier, the RT7235 displays excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-by cycle current limit, input under-voltage lock-out, externally-adjustable soft-start, output under- and overvoltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions. The RT7235 evaluation board uses the RT7235GQW IC in a WDFN-10L3x3 package with an exposed thermal pad. The IC is also available in a PTSSOP-14 package with an exposed thermal pad. Features Fast Transient Response Steady 650kHz Switching Frequency at All Load 5A Output Current Advanced Constant On-Time (ACOTTM) Control Optimized for Ceramic Output Capacitors 4.5V to 18V Input Voltage Range Internal 90mΩ Switch and 60mΩ Synchronous Rectifier 0.765V to 8V Adjustable Output Voltage Externally-adjustable, Pre-biased Compatible Soft-Start Cycle-by-Cycle Current Limit Output Over- and Under-voltage Shut-down UG7235GQW-00 April 2014 www.richtek.com 2 RT7235GQW Evaluation Board Key Performance Summary Table Key features Evaluation board number: PCB002_V1 Default Input voltage 12V Max Output Current 5A Default Output Voltage 1.05V Default Marking & Package Type RT7235GQW (WDFN-10L 3x3) Operation Frequency Steady 650kHz at all load Other Key Features Advanced constant On-time(ACOTTM) control Power Good Adjustable Soft-start (external capacitor) Protection Over current protection: Cycle-by-Cycle Current Limit Hiccup Mode Output Over- and Under-voltage Shut-down UG7235GQW-00 April 2014 www.richtek.com 3 RT7235GQW Evaluation Board 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]. UG7235GQW-00 April 2014 www.richtek.com 4 RT7235GQW Evaluation Board Test Points The EVB is provided with the test points and pin names listed in the table below. Test point/ Signal Comment (expected waveforms or voltage levels on test points) VIN Input voltage Input voltage range = 4.5V to 18V VOUT Output voltage Default output voltage = 1.05V Pin name Output voltage range = 0.765V to 8V (see ‘’ Output Voltage Setting’’ section for changing output voltage level) GND Ground Ground reference for the input voltage, output voltage and analog ground SW Switching node test point SW waveform EN Enable test point Enable signal. Drive EN or install a shorting block on Jumper JP1 to enable operation (shorting 2-3) or disable operation (shorting 1-2). JP1 Chip enable control Install jumper or drive EN directly to enable or disable operation BOOT Boot strap supply test point Floating supply voltage for the high-side N-MOSFET switch SS Soft-start control test point Soft start waveform PVCC Linear regulator output test Internal linear regulator output= 5.1V point PG Power good output test Connected to PVCC through R29, PG voltage is 5.1V when soft-start is point complete and the output voltage is in regulation Power-up & Measurement Procedure 1. Connect a jumper at JP1 terminals 1 and 2, connecting EN to GND, to disable operation. 2. Apply a 12V nominal input power supply (4.5V < VIN < 18V) to the VIN and GND terminals. 3. Set the jumper at JP1 to connect terminals 2 and 3, connecting EN to VIN through resistor R30, to enable operation. 4. Verify the output voltage (approximately 1.05V) between VOUT and GND. 5. Connect an external load up to 5A to the VOUT and GND terminals and verify the output voltage and current. Output Voltage Setting Set the output voltage with the resistive divider (R23, R28) between VOUT and GND with the midpoint at FB. The output is set by the following formula: VOUT = 0.765 x (1 + R23 ) R28 The installed VOUT capacitors (C11, C12) are 22μF, 16V X5R ceramic types. Do not exceed their operating voltage range and consider their voltage coefficient (capacitance vs. bias voltage) and ensure that the capacitance is sufficient to maintain stability and provide sufficient transient response for your application. Installing a small 5pF to 22pF capacitor at C30 (in parallel with R23) may be desirable to improve transient response for higher output voltages. See the RT7235 IC datasheet for more information. UG7235GQW-00 April 2014 www.richtek.com 5 RT7235GQW Evaluation Board Schematic, Bill of Materials and Board Layout EVB Schematic Diagram TP6 SW VIN GP4 U5 WDFN-10L 3x3 L1 9 10 C7 C9 10uF 10uF C8 0.1uF TP4 SS VIN SW VIN SW SS GND Short C27 0.1uF 8 TP5 BOOT C30 NF R23 8.2k 2 C11 22uF EN PG PVCC 5 10k R29 3 11 1 GND R30 100k GP1 GND L2 C12 22uF C10 0.1uF GP2 GND TP1 PG EN 3 2 1 BOOT FB C28 3.9nF JP1 1.4uH 7 NF 4 GP5 GND VOUT GP3 CP1 6 TP3 EN TP2 PVCC R28 22k C29 1uF C7, C9: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K C11, C12: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K L1: 1.4μH TAIYO YUDEN NR8040T1R4N, DCR=7mΩ UG7235GQW-00 April 2014 www.richtek.com 6 RT7235GQW Evaluation Board Bill of Materials Reference Qty Part number Description Package Manufacture U5 1 RT7235GQW DC/DC Converter WDFN-10L 3x3 Richtek C7,C9 2 C3216X5R1H106K160AB 1206 TDK 1210 Murata 0603 WALSIN 0603 TDK 0603 TDK 10μF/±10%/50V/X5R Ceramic Capacitor 22μF/±10%/16V/X5R C11,C12 2 GRM32ER61C226KE20# Ceramic Capacitor 3.9nF/±10%/50V/X7R C28 1 0603B392K500 Ceramic Capacitor 0.1μF/±10%/50V/X7R C8,C10,C27 3 C1608X7R1H104K080AA Ceramic Capacitor 1μF/±10%/25V/X5R C29 1 C1608X5R1E105K080AC Ceramic Capacitor C30 0 Not Installed 0603 L1 1 L2 0 Not Installed R28 1 22k/±5%, Resistor 0603 R23 1 8.2k/±5%, Resistor 0603 R29 1 10k/±5%, Resistor 0603 R30 1 100k/±5%, Resistor 0603 CP1 1 0 (Short) JP1 1 3-Pin Header TP1/2/3/4/5/6 6 Test Pin GP 5 Golden Pin 1.4μH/7A/±30%, UG7235GQW-00 NR8040T1R4N April 2014 DCR=7mΩ, Inductor 8mmx8mmx4mm TAIYO YUDEN www.richtek.com 7 RT7235GQW Evaluation Board EVB Layout Top View (1st layer) Bottom View (4th Layer) UG7235GQW-00 April 2014 www.richtek.com 8 RT7235GQW Evaluation Board Component Placement Guide—Component Side (1st layer) PCB Layout—Component Side (1st Layer) UG7235GQW-00 April 2014 www.richtek.com 9 RT7235GQW Evaluation Board PCB Layout—Inner Side (2nd Layer) PCB Layout—Inner Side (3rd Layer) UG7235GQW-00 April 2014 www.richtek.com 10 RT7235GQW Evaluation Board Component Placement Guide—Bottom Side (4th Layer) PCB Layout—Bottom Side (4th layer) UG7235GQW-00 April 2014 www.richtek.com 11 RT7235GQW Evaluation Board 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. UG7235GQW-00 April 2014 www.richtek.com 12