RT7272BGSP Evaluation Board Purpose The RT7272B is a high-efficiency current mode synchronous step-down regulator that can deliver up to 3A output current from a wide input voltage range of 4.5V to 36V. This document explains the function and use of the RT7272B 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 ............................................................................................. 2 Bench Test Setup Conditions ......................................................................................................... 3 Headers Description and Placement .......................................................................................... 3 Test Points.................................................................................................................................. 3 Power-up & Measurement Procedure ........................................................................................ 4 Output Voltage Setting ............................................................................................................... 4 Schematic, Bill of Materials and Board Layout ............................................................................... 5 EVB Schematic Diagram ............................................................................................................ 5 Bill of Materials ........................................................................................................................... 6 EVB Layout................................................................................................................................. 7 Other Technical Information ......................................................................................................... 10 UG7272BGSP-00 April 2014 www.richtek.com RT7272BGSP Evaluation Board Introduction General Product Information General Description The RT7272B is a high efficiency, current mode synchronous step-down DC/DC converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates a 150mΩ high side and an 80mΩ low side MOSFET to achieve high conversion efficiency up to 95%. The current mode control architecture supports fast transient response and uses a simple compensation circuit. A cycle-by-cycle current limit function provides protection against a shorted output and an internal soft-start eliminates input surge current during start-up. The RT7272B provides complete protection functions such as input under voltage lockout, output under voltage protection, over current protection and thermal shutdown. The RT7272B is available in the thermal enhanced SOP-8 (Exposed Pad) package. Features 4.5V to 36V Input Voltage Range 3A Output Current Internal N-MOSFETs Current Mode Control Fixed Frequency Operation : 500kHz Adjustable Output Voltage from 0.8V to 30V High Efficiency Up to 95% Stable with Low ESR Ceramic Output Capacitors Cycle-by-Cycle Current Limit Adjustable Current Limit Key Performance Summary Table Key features Default Input Voltage Max Output Current Default Output Voltage Default Marking & Package Type Operation Frequency Other Key Features Protection UG7272BGSP-00 April 2014 Evaluation board number: PCB001_V1 12V 3A (OCP level set to 5.5A typical by RLIM = 137kΩ) 3.3V RT7272BGSP, SOP-8 (Exposed Pad) Steady 500kHz at PWM 4.5V to 36V Wide Input Voltage Range Adjustable Current Limit 2A to 6A PSM/ PWM Auto Switched. Over Current Protection & Output Under-Voltage-Protection (hiccup mode) Input Under-voltage Lock-out, Thermal Shutdown www.richtek.com 2 RT7272BGSP 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]. Test Points The EVB is provided with the test points and pin names listed in the table below. Test point/ Pin name VIN Signal Comment (expected waveforms or voltage levels on test points) Input voltage Input voltage range= 4.5V to 36V Default output voltage = 3.3V VOUT Output voltage Output voltage range= 0.8V to 30V (see ‘’ Output Voltage Setting’’ section for changing output voltage level) SW Switching node test point EN Enable test point BOOT Boot strap supply test point Floating supply voltage for the high-side N-MOSFET switch MODE RLIM test point Current limit setting point GND Ground Ground UG7272BGSP-00 April 2014 SW waveform Enable signal. EN is automatically pulled high (by R4) to enable operation. Connect EN low to disable operation. www.richtek.com 3 RT7272BGSP Evaluation Board Power-up & Measurement Procedure 1. Apply a 12V nominal input power supply (4.5V < VIN < 36V) to the VIN and GND terminals. 2. The EN voltage is pulled to logic high by R4 (100kΩ to VIN) to enable operation. Drive EN high (>2.0V) to enable operation or low (<0.4V) to disable operation. 3. Verify the output voltage (approximately 3.3V) between VOUT and GND. 4. 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 (R1, R2) between VOUT and GND with the midpoint connected to FB through RCAMP. The output is set by the following formula: VOUT = 0.8 x (1 + R1 ) R2 The installed VOUT capacitors (C4, C5) 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. This can be verified by checking the output transient response as described in the RT7272B IC datasheet. UG7272BGSP-00 April 2014 www.richtek.com 4 RT7272BGSP Evaluation Board Schematic, Bill of Materials and Board Layout EVB Schematic Diagram TP4 BOOT D2 U1 NF GP1 8 SOP-8(Exposed Pad) VIN BOOT 2 TP3 SW 0.1uF 100k C11 0.1uF TP1 EN SW R4 10uF C3 10uF C2 GND GP3 L1 1 4.7uH FB 6 0.1uF C5 C6 C12 22uF GP4 GND 2.7nF R3 TP2 MODE 24k 22uF R2 COMP 4,9 RLIM 137k RLIM NF C7 7 GND RCAMP 75k R1 0 5 R5 0 NF NF C9 NF D1 NF GND C13 R6 EN C4 VOUT 3 13k NF C8 GP2 C1 VIN C1, C2: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K C4, C5: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K L1: 4.7μH WE74437368047, DCR=15mΩ UG7272BGSP-00 April 2014 www.richtek.com 5 RT7272BGSP Evaluation Board Bill of Materials Reference Qty Part number Description Package Manufacture U1 1 RT7272BGSP DC/DC Converter PSOP-8 Richtek C1, C2 2 C3216X5R1H106K160AB 1206 TDK C4, C5 2 GRM32ER61C226KE20# 1210 Murata C7 1 0603B272K500 0603 WALSIN C3, C6, C11 3 C1608X7R1H104K080AA 0603 TDK C8,C9,C12,C13 0 L1 1 R1 1 75kΩ/±1%, Resistor 0603 R2 1 24kΩ/±1%, Resistor 0603 R3 1 13kΩ/±1%, Resistor 0603 R4 1 100kΩ/±1%, Resistor 0603 R5, D1, D2 0 Not Installed R6, RCAMP 2 0Ω, Resistor 0603 RLIM 1 137kΩ/±1%, Resistor 0603 TP 4 Test Pin GP 4 Golden Pin UG7272BGSP-00 April 2014 10μF/±10%/50V/X5R Ceramic Capacitor 22μF/±10%/16V/X5R Ceramic Capacitor 2.7nF/±10%/50V/X7R Ceramic Capacitor 0.1μF/±10%/50V/X7R Ceramic Capacitor Not Installed WE74437368047 4.7μH/19A/±20%, DCR=15mΩ, Inductor 0603 11mmx10mmx3.8mm WE www.richtek.com 6 RT7272BGSP Evaluation Board EVB Layout st Top View (1 layer) Bottom View (4th Layer) UG7272BGSP-00 April 2014 www.richtek.com 7 RT7272BGSP Evaluation Board st Component Placement Guide—Component Side (1 layer) PCB Layout—Component Side (1st Layer) UG7272BGSP-00 April 2014 www.richtek.com 8 RT7272BGSP Evaluation Board PCB Layout—Inner Side (2nd Layer) PCB Layout—Inner Side (3rd Layer) UG7272BGSP-00 April 2014 www.richtek.com 9 RT7272BGSP Evaluation Board Component Placement Guide—Bottom Side (4th Layer) PCB Layout—Bottom Side (4th layer) Other Technical Information For more information, please find the related datasheet or application notes from the Richtek website http://www.richtek.com UG7272BGSP-00 April 2014 www.richtek.com 10