RT8298AGSP Evaluation Board your power partner. 6A, 24V, 600kHz Step-Down Converter with Synchronous Gate Driver Purpose The RT8298A is a current mode step-down converter with the input voltage range from 4.5V to 24V and provides 6A output current. This document explains the function and use of the RT8298A 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.................................................................................................................................................... 8 Important Notice for Richtek Evaluation Board ....................................................................................................... 8 EVB_RT8298AGSP-00 October 2015 1 http://www.richtek.com RT8298AGSP Evaluation Board your power partner. Introduction General Product Information The RT8298A is a synchronous step-down DC/DC converter with an integrated high side internal power MOSFET and a gate driver for a low side external power MOSFET. It can deliver up to 6A output current from a 4.5V to 24V input supply. The RT8298A's current mode architecture allows the transient response to be optimized over a wider input voltage and load range. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. The RT8298A is synchronizable to an external clock with frequency ranging from 300kHz to 1.5MHz. Product Feature 4.5V to 24V Input Voltage Range 6A Output Current 45mΩ Internal High Side N-MOSFET Current Mode Control 600kHz Switching Frequency Adjustable Output from 0.8V to 15V Up to 95% Efficiency Internal Compensation Stable with Ceramic Capacitors Synchronous External Clock : 300kHz to 1.5MHz Cycle-by-Cycle Current Limit Input Under Voltage Lockout Output Under Voltage Protection Power Good Indicator Thermal Shutdown Protection Force PWM Turn On RoHS Compliant and Halogen Free Key Performance Summary Table Key Features Evaluation Board Number : PCB026_V1 Default Input Voltage 12V Max Output Current 6A Default Output Voltage 3.3V Default Marking & Package Type RT8298AGSP, SOP-8 (Exposed Pad) EVB_RT8298AGSP-00 October 2015 2 http://www.richtek.com RT8298AGSP 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) Input voltage Power Input. The available input voltage range is from 4.5V to 24V. A 22µF or larger input capacitor is needed to reduce voltage spikes at the input. EN/SYNC Enable test point Enable or External Frequency Synchronization Input. A logic-high (2V < EN < 5.5V) enables the converter; a logic-low forces the IC into shutdown mode reducing the supply current to less than 3µA. For external frequency synchronization operation, the available frequency range is from 300kHz to 1.5MHz. GND Ground Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation. VCC Internal regulator output BG Driver Bias Supply. Decouple with a 1µF X5R/X7R ceramic capacitor between the VCC pin and GND. BOOT Bootstrap supply test point Bootstrap supply for high-side gate driver. Connect a 0.1µF capacitor between BOOT and SW to power the internal gate driver. SW Switch node test point Switching Node. Output of the internal high side MOSFET. Connect this pin to external low-side N-MOSFET, inductor and bootstrap capacitor. BG Internal regulator Gate Driver Output. Connect this pin to the gate of the external low-side N-MOSFET. Feedback test point Feedback Input. This pin is connected to the converter output. It is used to set the output of the converter to regulate to the desired value via an external resistive divider. The feedback reference voltage is 0.808V typically. VIN FB EVB_RT8298AGSP-00 October 2015 3 http://www.richtek.com RT8298AGSP Evaluation Board your power partner. Power-up & Measurement Procedure 1. Apply a 12V nominal input power supply (4.5V < VIN < 24V) to the VIN and GND terminals. 2. Verify the output voltage (approximately 3.3V) between VOUT and GND. 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 (R2, R3) between VOUT and GND with the midpoint connected to FB. The output is set by the following formula : VOUT = 0.808 x (1 + EVB_RT8298AGSP-00 R2 ) R3 October 2015 4 http://www.richtek.com RT8298AGSP Evaluation Board your power partner. Schematic, Bill of Materials & Board Layout TP5 BG TP4 SW 1 TP3 BS 1 EVB Schematic Diagram TP6 VOUT 1 K NC Vin J1 A VIN BS U1 C11 R5 8 SIP-2P-PW BST IN 2 L1 VOUT J4 EN GND C14 5 EN BG GND MOSFET-IRF7821 FB TP7 GND 6 C13 R2 GP1 EXT_BS R4 C6 5 6 7 8 C5 D-5 D-6 D-7 D-8 C4 G S3 S2 S1 R1 4 3 2 1 C12 4 1 EN/SY NC VCC C8 R6 3 1 GND U2 TP2 JP1 J3 GND 1 R7 7 P_SOP8 R8 1 1 2 3 1 VOUT 1 C3 C2 SW C7 GND C1 1 D2 EXT_VB EXT_VB Vin EXT_BS Bill of Materials Reference Qty Part Number Description Package Manufacture U1 1 RT8298AGSP DC/DC Converter SOP-8 (Exposed Pad) RICHTEK C1, C2 2 GRM31CR71E106KA12L 10µF/25V/X7R C-1206 MURATA C3, C7 2 C1608X7R1H104KT000N 0.1μF/50V/X7R C-0603 TDK C4, C5, C6 3 C3225X5R1E226MT 22µF/25V/X5R C-1210 TDK R4, D2, C13, R7, C8, C12 6 C14, C11 2 1µF/25V/X5R C-0603 TDK R5 1 100k R-0603 R6, R8 2 0 R-0603 R1 1 62k R-0603 R2 1 NR8040T1R4N 20k R-0603 L1 1 7443340220 2.2µF/16.5A 8.4 x 7.9 mm WE U2 1 IRF7821 30V/13.6A R-0603 FUTURE ELECTRONICS INC. EVB_RT8298AGSP-00 N/A C1608X5R1E105KT000E October 2015 5 http://www.richtek.com RT8298AGSP Evaluation Board your power partner. PCB Layout Top View (1st layer) PCB Layout—Inner Side (2nd Layer) EVB_RT8298AGSP-00 October 2015 6 http://www.richtek.com RT8298AGSP Evaluation Board your power partner. PCB Layout—Inner Side (3rd Layer) Bottom View (4th Layer) EVB_RT8298AGSP-00 October 2015 7 http://www.richtek.com RT8298AGSP 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_RT8298AGSP-00 October 2015 8 http://www.richtek.com