RT8498GE

RT8498GE Evaluation Board your power partner. RT8498 Step-Down Converter Evaluation Board Purpose The RT8498 is specifically designed to be operated in Buck, Boost and Buck-Boost converter applications. This document explains the function and use of the RT8498 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 Bench Test Setup Conditions ........................................................................................................................................3 Schematic, Bill of Materials & Board Layout.................................................................................................................5 More Information .........................................................................................................................................................10 Important Notice for Richtek Evaluation Board...........................................................................................................10 EVB_RT8498GE-00 November 2016 1 http://www.richtek.com RT8498GE Evaluation Board your power partner. Introduction General Product Information The RT8498 is a current-mode LED driver supporting wide input voltage range from 3V to 18V and output voltage up to 18V. With internal 350kHz operating frequency, the size of the external PWM inductor and input/output capacitors can be minimized. High efficiency is achieved by a 100mV current sensing control. LED dimming control can be done from either analog or PWM signal. The RT8498 provides an internal soft-start function to avoid inrush current and thermal shutdown to prevent the device from overheat. The RT8498 is available in the SOT-23-6 package. Product Feature           High Voltage : VIN Up to 18V, VOUT Up to 18V Built-In 2A Power Switch Current-Mode PWM Control 350kHz Fixed Switching Frequency Analog, PWM Digital or PWM Converting to Analog with One External Capacitor Internal Soft-Start to Avoid Inrush Current Under-Voltage Lockout Internal Over Voltage Protection to Limit Output Voltage Cycle-by Cycle Current Limit Thermal Shutdown Key Performance Summary Table Key Features Evaluation Board Number: PCB082_V1 Default Input Voltage 4.5V to 18V Max Output Current 1A Default Output Voltage 3.0V Default Marking & Package Type RT8498GE, SOT-23-6 Operation Frequency Steady 350kHz at all loads EVB_RT8498GE-00 November 2016 2 http://www.richtek.com RT8498GE Evaluation Board your power partner. Bench Test Setup Conditions Headers Description and Placement Carefully inspect all the components used in the EVB according to the following Bill of Materials table, and then make sure all the components are undamaged and correctly installed. If there is any missing or damaged component, which may occur during transportation, please contact our distributors or e-mail us at evb_service@richtek.com. EVB_RT8498GE-00 November 2016 3 http://www.richtek.com RT8498GE Evaluation Board your power partner. 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) SW Switch node test point Switch node of the PWM converter. GND Ground Ground. DCTL DCTL Input Voltage Digital dimming control input. ACTL ACTL Input Voltage Analog dimming control input. Effective programming range is 0.65V to 1.2V. VCC Supply Voltage Input Supply voltage input. For good bypass, connect a low ESR capacitor between this pin and GND. ISN Current sense input Current sense input. Voltage threshold between VCC and ISN is 100mV. Power-up & Measurement Procedure 1. Connect input power (4.5V < VIN < 18V) and input ground to VIN and GND test pins respectively. 2. Connect positive end and negative terminals of load to VOUT2 and VOUT1 test pins respectively.. 3. Verify the output voltage/output current (approximately 3.0V/1A) between VOUT2 and VOUT1. 4. VIN = 12V, VOUT = 3V, IOUT = 1A (Buck) , LED+ = VOUT2, LED- = VOUT1, LOAD = 1LEDs or Electronic Load CV mode measure check SW pin freq = 350kHZ , ISP-ISN Threshold = 100mV LED Current Setting The LED current can be calculated by the following equation : where (VVCC VISN) is the voltage between the VCC and ISN pins (100mV typ. if ACTL dimming is not applied) and the RSENSE is the resister between the VCC and ISN pins. EVB_RT8498GE-00 November 2016 4 http://www.richtek.com RT8498GE Evaluation Board your power partner. Schematic, Bill of Materials & Board Layout EVB Schematic Diagram Bill of Materials Reference Qty Part number U1 1 RT8498GE C1, C5 2 GRM31CR71H475KA12L C2, C3 2 C3216X5R1H106K160AB C4 Package Manufacturer SOT-23-6 Richtek 4.7µF/50V/X7R/1206 C-1210 muRata 10µF/50V/X7R/1206 C-1210 TDK 1 NC C-0805 C6, C7 2 NC C-1210 C8 1 1µF/50V/X7R/0805 C-0805 TDK C9, C11 2 NC C-1210 TDK C10 1 0.47µF/16V/X7R/0603 C-0603 TDK D1 1 PMEG 4020 D-CR-73 NXP L1 1 6.8µH L-SU1028 TAIYO YUDEN R1, R4 2 Short CP-0603 R2, R3 2 NC CP-0603 R5, R6 2 SHORT CP-0805C R9 1 100mohm RC-1A R10, R11, R12, R13 4 NC R-0805 R14 1 0R/0805 R-0805 R17 1 NC R-0603 R18 1 0R/0603 R-0603 EVB_RT8498GE-00 November C2012X7R1H105KT C1608X7R1C474K000N Description NRS8040T6R8NJGJ 2512T-1-R100 RTT05000JTP WR06X000 PTL 2016 5 RALEC RALEC WALSIN http://www.richtek.com RT8498GE Evaluation Board your power partner. Efficiency: VIN (V) IIN (A) VOUT (V) IOUT (A) Eff. (%) ISP-ISN (mV) 4.5 0.834 3.405 0.974 88.369 97.9 7 0.538 3.395 0.978 88.165 98.3 10 0.379 3.382 0.974 86.915 97.9 12 0.317 3.372 0.972 86.162 97.7 15 0.257 3.369 0.97 84.771 97.6 18 0.216 3.368 0.966 83.68 97.3 Efficiency vs. VIN (L = 6.8µH / IOUT = 1A) 95 Efficiency (%) 90 85 80 75 3 6 9 12 15 18 VIN (V) Line regulation: IOUT vs. Input Voltage 1200 VIN (V) IOUT (A) 1100 I OUT (mA) 1000 900 800 700 4.5 995.2 7 986.1 10 981.8 12 981.5 15 979.1 18 976.8 600 0 3 6 9 12 15 18 Input Voltage (V) EVB_RT8498GE-00 November 2016 6 http://www.richtek.com RT8498GE Evaluation Board your power partner. Load regulation: IOUT vs. Output Voltage 1100 I OUT (mA) 1060 1020 LEDs VOUT (V) IOUT (mA) 5LED 16.21 974.8 4LED 12.88 977.5 3LED 9.38 978.1 2LED 6.46 980.5 1LED 3.38 983.8 980 940 900 0 3 6 9 12 15 18 Output Voltage (V) Waveform: Test condition:VIN = 10V, VOUT = 3V, IOUT = 1A CH1 = SW, CH2 = VOUT, CH3 = VIN, CH4 = IL EVB_RT8498GE-00 November 2016 CH1 = SW, CH2 = VOUT, CH3 = VIN, CH4 = IOUT 7 http://www.richtek.com RT8498GE Evaluation Board your power partner. Analog / PWM Dimming : ILED vs. PWM Dimming (200Hz) 1200 1000 1000 800 800 I LED (mA) I LED (mA) ILED vs. VACTL 1200 600 600 400 400 200 200 0 0 0 0.5 1 1.5 0 2 10 20 30 ILED vs. PWM Dimming (1kHz) 60 70 80 90 100 90 100 ILED vs. PWM Dimming (1kHz) 1200 1200 1000 1000 800 800 I LED (mA) I LED (mA) 50 PWM Duty (%) VACTL (V) 600 600 400 400 200 200 0 0 0 10 20 30 40 50 60 70 80 90 0 100 10 20 30 40 50 60 70 80 PWM Duty (%) PWM Duty (%) ILED vs. PWM Dimming (10kHz) ILED vs. PWM Dimming (200Hz-10kHz) 1200 1200 1000 1000 800 800 I LED (mA) I LED (mA) 40 600 600 400 400 200 200 0 0 0 10 20 30 40 50 60 70 80 90 0 100 EVB_RT8498GE-00 November 2016 10 20 30 40 50 60 70 80 90 100 PWM Duty (%) PWM Duty (%) 8 http://www.richtek.com RT8498GE Evaluation Board your power partner. PCB Layout st Top View (1 layer) Bottom View (4th Layer) EVB_RT8498GE-00 November 2016 9 http://www.richtek.com RT8498GE 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_RT8498GE-00 November 2016 10 http://www.richtek.com