RT7275GQW

RT7275GQW RICHTEK | Alldatasheet

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UG7275GQW-00 March 2014 www.richtek.com Purpose The RT7275 is a high-performance 700kHz 3A step down regulator with an internal power switch and synchronous rectifier. This document explains the function and use of the RT7275 evaluation board (EVB) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements. Table of Contents

UG7275GQW-00 March 2014 www.richtek.com Introduction General Product Information General Description The RT7275 is a high-performance 700kHz 3A 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 RT7275 is stable with and optimized for ceramic output capacitors. With its internal 90m Ω switch and 60mΩ synchronous rectifier, the RT7275 displays excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cyc les. 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 RT7275 evaluation board uses the RT7275GQW 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 700kHz Switching Frequency at all Load Currents  3A 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

UG7275GQW-00 March 2014 www.richtek.com Key Performance Summary Table Key features Evaluation board number: PCB002_V1 Default Input voltage 12V Max Output Current 3A Default Output Voltage 1.05V Default Marking & Package Type RT7275GQW (WDFN-10L 3x3) Operation Frequency Steady 700kHz at all load currents 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

UG7275GQW-00 March 2014 www.richtek.com 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 evb_service@richtek.com.

UG7275GQW-00 March 2014 www.richtek.com 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 = 4.5V to 18V VOUT Output voltage Default output voltage = 1.05V 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 point Internal linear regulator output= 5.1V PG Power good output test point Connected to PVCC through R29, PG voltage is 5.1V when soft-start is 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 3A 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: OUT R23V = 0.765 x (1 + ) 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 RT7275 IC datasheet for more information.

UG7275GQW-00 March 2014 www.richtek.com Schematic, Bill of Materials and Board Layout EVB Schematic Diagram R29 10k TP1 PG TP2 PVCC TP3 EN TP4 SS VIN TP5 BOOT NF GND U5 WDFN-10L 3x3 EN1 FB 2 PVCC 3 SS4 VIN10 VIN9 BOOT 8 SW 7 PG 5 SW 6 GND11 TP6 SW JP1 EN

3 R30

8.2k C29 1uF C30 NF 1.4uH VOUT GND C27 0.1uF GP3 GP2 10uF 0.1uF 10uF GP4 C10 0.1uF C11 22uF C12 22uFC28 3.9nF GND CP1 Short GP5 GP1 GND C7, C9: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K C11, C12: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K L1: 1.4μH TAIYO YUDEN NR8040T1R4N, DCR=7mΩ

UG7275GQW-00 March 2014 www.richtek.com Bill of Materials Reference Qty Part number Description Package Manufacture U5 1 RT7275GQW DC/DC Converter WDFN-10L 3x3 Richtek C7,C9 2 C3216X5R1H106K160AB 10μF/±10%/50V/X5R

1206 TDK

C11,C12 2 GRM32ER61C226KE20# 22μF/±10%/16V/X5R

1210 Murata

3.9nF/±10%/50V/X7R

0603 WALSIN

C8,C10,C27 3 C1608X7R1H104K080AA 0.1μF/±10%/50V/X7R

0603 TDK

1μF/±10%/25V/X5R 1.4μH/7A/±30%, DCR=7mΩ, Inductor 8mmx8mmx4mm TAIYO YUDEN 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

UG7275GQW-00 March 2014 www.richtek.com EVB Layout Top View (1st layer) Bottom View (4th Layer)

UG7275GQW-00 March 2014 www.richtek.com Component Placement Guide—Component Side (1st layer) PCB Layout—Component Side (1st Layer)

UG7275GQW-00 March 2014 www.richtek.com PCB Layout—Inner Side (2nd Layer) PCB Layout—Inner Side (3rd Layer)

UG7275GQW-00 March 2014 www.richtek.com Component Placement Guide—Bottom Side (4th Layer) PCB Layout—Bottom Side (4th layer)

UG7275GQW-00 March 2014 www.richtek.com More Information For more information, please find the related datasheet or application notes from Rich tek 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.