RT7249GQW Evaluation Board your power partner. 3A, 18V Synchronous Step-Down Converter with Adjustable Current Limited Power Switch Purpose The RT7249 is a current mode step-down converter with the input voltage range from 4.5V to 18V and provides 3A outputcurrent. This document explains the function and use of the RT7249 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 ........................................................................................................... 5 More Information.................................................................................................................................................... 9 Important Notice for Richtek Evaluation Board ....................................................................................................... 9 EVB_RT7249GQW-00 April 2016 1 http://www.richtek.com RT7249GQW Evaluation Board your power partner. Introduction General Product Information The RT7249 is a high efficiency, monolithic synchronous step-down DC/DC converter with a power switch.The buck converter can deliver up to 3A output current from 4.5V to 18V input supply. The RT7249’s current-mode architecture and external compensation allow the transient response to be optimized over a wide input range and loads. Cycle-by-cycle current limit provides protection against shorted output and soft-start eliminates input current surge during start-up. The RT7249 also provides under-voltage protection and thermal shutdown. PWM frequency is adjustable by the ROSC pin and Power Switch current limit can also be adjusted by the RLIM pin. The low current (<3µA) in shutdown mode provides output disconnection, enabling easy power management in bettery-powered systems. The RT7249 is available in the WQFN-16L 4x4 package. Product Feature Buck Regulator 4.5V to 18V Input Voltage Range 3A Output Current Internal N-Chanel MOSFETs Current Mode Control Adjustable PWM Frequency Adjustable Output from 0.8V to 15V Adjustable Soft-Start Time Stable with Ceramin Output Capactiors Cycle-by-Cycle Current Limit Input Under-Voltage Lockout Output Under-Voltage Protection Thermal Shutdown Power Switch ±15% Current-Limit Accuracy at 1.2A Adjustable Current Limit : 75mA to 2580mA Meet USB Current-Limiting Requirements Reverse Input-Output Voltage Protection Built Soft-Start 120mΩ High-Side MOSFET Operating Range : 2.5V to 5.5V Key Performance Summary Table Key Features Evaluation Board Number : PCB067_V1 Default Input Voltage 12V Max Output Current 3A Default Output Voltage 5V Default Marking & Package Type RT7249GQW, WQFN-16L 4x4 Operation Frequency 500kHz Switching Frequency EVB_RT7249GQW-00 April 2016 2 http://www.richtek.com RT7249GQW 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. Supply voltage range is from 4.5V to 18V. Must bypass with a suitable large ceramic capacitor. PGND Ground Power Ground. The exposed pad must be soldered to a large PCB and connected to PGND for maximum thermal dissipation. AGND Ground Analog Ground. SS Soft-Start Soft-Start Time Setting. SS controls the soft-start period. Connect a capacitor from SS to GND to set the soft-start period. An internal current source (6μA) charges 0.1μF capacitor and sets the soft-start period to 13.5ms. If SS is floating, the SS charge current will decrease to 1/128μA and charge 30pF capacitor to set the soft-start period to 4ms. COMP Compensation Node 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. ROSC Frequency Setting Switching Frequency Setting. RLIM Current Limit Setting Current Limit Setting. Switch current limit threshold can be set by an external resistor. Current limit value is from 75mA to 2580mA. The value of 10kΩ ≤ RILIM ≤ 210kΩ is recommended. EVB_RT7249GQW-00 April 2016 3 http://www.richtek.com RT7249GQW Evaluation Board your power partner. Test point/ Pin name Signal Comment (expected waveforms or voltage levels on test points) EN_SW Enable Power Switch test pin Enable Control Input for Power Switch. FAULT FAULT test point Active-Low Open-Drain Output. Asserted during over current, over temperature, or reverse voltage conditions. SW_OUT Power Switch Output Power Switch Output. SW_IN Power Switch Input Power Switch Input. Supply voltage range is from 2.5V to 5.5V. FB Feedback Voltage Feedback Voltage Input. This pin is connected to the converter output. It is used to set the output of the converter to regulate the desired value via an resistive divider. LX Switch Node test pin Switch Node. Output of the internal high-side MOSFET. Connect this pin to external low-side N-MOSFET, inductor and bootstrap capacitor. BOOT BOOT Node test pin Bootstrap Supply for High-Side Gate Driver. Connect a 1μF ceramic capacitor between the BOOT and LX pins. V5V V5V test pin BG Driver Bias Supply. Decouple with a 1μF X5R/X7R ceramic capacitor between the V5V and GND pins. EN Enable test pin Enable Control Input for Buck Converter. A logic-high enables the converter; a logic-low forces the device into shutdown mode. Power-up & Measurement Procedure 1. Set the jumper at JP1 to connect terminals 1 and 2, connecting Vout to SW_IN 2. Apply a 12V nominal input power supply to the VIN and GND terminals. 3. Connect an external load up to 6A 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 External Input and GND with the midpoint connected to VREFIN. The output is set by the following formula : VOUT = VFB R2 (R1 + R2) EVB_RT7249GQW-00 April 2016 4 http://www.richtek.com RT7249GQW Evaluation Board your power partner. Schematic, Bill of Materials & Board Layout EVB Schematic Diagram Bill of Materials Reference Qty Part Number Description Package Manufacture C1, C2, C10 3 UMK325BJ106MM 10µF/X5R/50V/1206 C-1206 TAIYO YUDEN C3, C7, C9 3 C1608X7R1H104KT000N 0.1µF/X7R/50V/0603 C-0603 TDK C4, C5, C8 3 C3225X5R1E226MT 22µF/X5R/25V/1210 C-1210 TDK C6 1 C11, C16 2 C-0603 WALSIN C12, C19 2 C14, C15 2 C-0603 TDK C17 1 C18, C20 2 C-0603 TDK C3_1 1 NC GP1 1 EN GP3, GP4, GP8 3 GND GP5 1 Vin EVB_RT7249GQW-00 April NC/1210 0603B472K500 4.7nF/X7R/50V/0603 NC/0603 C1608X5R1E105KT000E 1µF/X5R/25V/0603 NC C1608X7R1H104KT000N 2016 0.1µF/X7R/50V/0603 5 http://www.richtek.com RT7249GQW Evaluation Board your power partner. Reference Qty Part Number Description Package Manufacture GP6 1 Vout GP7 1 SW_OUT GP9 1 SW_IN_S GP10 1 SS GP14 1 SW GP15 1 V5V GP16 1 nFAULT GP17 1 BOOT GP11 1 RSOC GP12 1 RLIM GP13 1 ENSW JP1 1 SW_IN J1 1 Vin, GND L2 1 NR8040T4R7N 4.7µH R1 1 0603 40K2 1% 40.2k/0603 R-0603 R2 1 7.68k/0603 R-0603 R3 1 20k/0603 R-0603 R4 1 53.6k/0603 R-0603 R5 1 10k/0603 R-0603 R6, R7, R8 3 100k/0603 R-0603 U1 1 DC/DC Converter WQFN-16L 4x4 Z1, Z2, Z3, Z4 4 SIP-1P-M Z11, Z12, Z13, Z14 4 FK_1 EVB_RT7249GQW-00 April RT7249GQW 2016 6 TAIYO YUDEN RICHTEK http://www.richtek.com RT7249GQW Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT7249GQW-00 April 2016 7 http://www.richtek.com RT7249GQW Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT7249GQW-00 April 2016 8 http://www.richtek.com RT7249GQW 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_RT7249GQW-00 April 2016 9 http://www.richtek.com