RT6251BHGQW Evaluation Board your power partner. 3A, 18V, Synchronous Step-Down Converter Purpose The RT6251BH 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 RT6251BH 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_RT6251BHGQW-00 December 2015 1 http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. Introduction General Product Information The RT6251BH is a high efficiency, monolithic synchronous step-down DC/DC converter that can deliver up to 3A output current from a 4.5V to 18V input supply. The RT6251BH current-mode architecture with external compensation allows the transient response to be optimized over a wide range of loads and output capacitors. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. Fault condition protections include output under-voltage protection, output over-voltage protection, and over-temperature protection. The low current shutdown mode provides output disconnection, enabling easy power management in battery-powered systems. Product Feature Low RDS(ON) Power MOSFET Switches 46mΩ/36mΩ Input Voltage Range : 4.5V to 18V Adjustable Switching Frequency : 200kHz to 1.2MHz Current-Mode Control Synchronous to External Clock : 200kHz to 1.2MHz Accurate Voltage Reference 0.8V±1% Monotonic Start-Up into Pre-biased Outputs Adjustable Soft-Start Power Good Indicator Under-Voltage and Over-Voltage Protection Input Under-Voltage Lockout Key Performance Summary Table Key Features Evaluation Board Number : PCB058_V1 Default Input Voltage 12V Max Output Current 3A Default Output Voltage 3.3V Default Marking & Package Type RT6251BHGQW, WQFN-14AL 3.5x3.5 Operation Frequency Steady 200kHz to 1.2MHz EVB_RT6251BHGQW-00 December 2015 2 http://www.richtek.com RT6251BHGQW 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) Oscillator Resistor and External Frequency Synchronization Input Oscillator Resistor and External Frequency Synchronization Input. Connecting a resistor from this pin to GND sets the switching frequency or connecting an external clock to this pin changes the switching frequency. GND System Ground System Ground. Provide the ground return path for the control circuitry and low-side power MOSFET. The exposed pad must be soldered to a large PCB and connected to GND for minimum power dissipation. PVIN Power Input Power Input. Supplies the power switches of the device. VIN Supply Voltage Input Supply Voltage Input. Supplies the control circuitry and internal reference of the device. FB Feedback Voltage Input Feedback Voltage Input. This pin is used to set the desired output voltage via an external resistive divider. The feedback reference voltage is 0.8V typically. COMP Compensation Node Compensation Node. The current comparator threshold increases with this control voltage. Connect external compensation elements to this pin to stabilize the control loop.capacitor between the BOOT and LX pins. SS/TR Soft-Start and Tracking Control Input Soft-Start and Tracking Control Input. Connect a capacitor from SS to GND to set the soft-start period. The soft-start period can be used to track and sequence when the external voltage on this pin overrides the internal reference. RT/SYNC EVB_RT6251BHGQW-00 December 2015 3 http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. Test point/ Pin name Signal Comment (expected waveforms or voltage levels on test points) EN Enable Control Input Enable Control Input. Floating this pin or connecting this pin to logic high can enable the device and connecting this pin to GND can disable the device. LX Switch node test point Switch Node. LX is the switching node that supplies power to the output and connect the output LC filter from LX to the output load. BOOT Bootstrap Supply for High-Side Gate Driver Bootstrap Supply for High-Side Gate Driver. Connect a 100nF or greater capacitor from LX to BOOT to power the high-side switch. Power Good Indicator Output Power Good Indicator Output. This pin is an open-drain logic output that is pulled to ground when the output voltage is lower or higher than its specified threshold under the conditions of OVP, OTP, dropout, EN shutdown, or during slow start. PGOOD Power-up & Measurement Procedure 1. Apply a 12V nominal input power supply (4.5V < VIN < 18V) to the VIN and GND terminals. 2. Set the jumper at J9 to connect terminals 1 and 2, connecting EN to VIN through resistor REN1, to enable 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. The output is set by the following formula : VOUT = VFB × (1 + R1 ) R2 EVB_RT6251BHGQW-00 December 2015 4 http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. Schematic, Bill of Materials & Board Layout EVB Schematic Diagram Bill of Materials Reference Qty Part Number Description Package Manufacture C3, C7, CBOOT 3 C1608X7R1H104KT000N 0.1µF/50V/X7R/0603 C-0603 TDK RTR1, RTR2, RPG2, REN2, C2F, CFF, CEN 7 CSS 1 0603B103K500 10nF/50V/X7R/0603 C-0603 WALSIN Ccomp1 1 0603B153K500CT 15nF/50V/X7R/0603 C-0603 WALSIN Ccomp2 1 0603B181K500 180pF/50V/X7R/0603 C-0603 C1, C2 2 UMK325BJ106MM-T 10µF/50V/X5R/1210 C-1210 C4 1 GRM31CR71H475KA12L 4.7µF/50V/X7R/1206 C-1210 WALSIN TAIYO YUDEN muRata C5, C6 2 C3225X5R1E226MT 22µF/25V/X5R/1210 C-1210 TDK D1 1 NC GP1 1 SS SIP-1P-GP GP2 1 EN SIP-1P-GP GP3 1 BS SIP-1P-GP GP4 1 LX SIP-1P-GP GP5 1 VIN_EXT SIP-1P-GP GP6 1 PG SIP-1P-GP EVB_RT6251BHGQW-00 NC December 2015 5 http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. Reference Qty Part Number Description Package Manufacture GP7 1 VCC_EXT SIP-1P-GP GP8 1 SYNC SIP-1P-GP GP9 1 TRACK SIP-1P-GP JP1 1 SIP-2P SIP-2P JP2,J9 2 SIP-3P SIP-2P J1 1 PVIN\GND SIP-2P-PWR_1 J3 1 VOUT sip-4p_pw_l J4 1 GND sip-4p_pw_l L1 1 4.7µH L-GSTB135 3 100k/0603 R0603 1 3.48k/0603 R0603 R1 1 75k/0603 R0603 R2 1 24k/0603 R0603 U1 1 DC/DC Converter WQFN-14AL 3.5 x 3.5 Z1, Z2, Z3, Z4 4 SIP-1P-M PAD6 Z5, Z6 2 SIP-1P-TP FK_1 RPG1, REN1, RT Rcomp1 EVB_RT6251BHGQW-00 RT6251BHGQW December 2015 6 TAIYO YUDEN RICHTEK http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT6251BHGQW-00 December 2015 7 http://www.richtek.com RT6251BHGQW Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT6251BHGQW-00 December 2015 8 http://www.richtek.com RT6251BHGQW 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 T O BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL DAMAGES. EVB_RT6251BHGQW-00 December 2015 9 http://www.richtek.com