The RT6255A is a synchronous step-down converter with Advanced Constant On-Time (ACOT™) mode control. with the input voltage range from 4.5V to 18V and provides 5A output current. This document explains the function and use of the RT6255A evaluation board (EVB), and provides information to enable operation, modification of the evaluation board and circuit to suit individual requirements.
General Product Information
The RT6255A is a high-efficiency, monolithic synchronous step-down DC/DC converter that can deliver up to 5A output current from a 4.5V to 18V input supply.The RT6255A adopts ACOT architecture to allow the transient response to be improved and keep in constant frequency. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. Fault conditions also include output under voltage protection and thermal shutdown.
Key Performance Summary Table
Evaluation Board Number: PCB074_V1
Default Input Voltage
Max Output Current
Default Output Voltage
Default Marking & Package Type
RT6255AHGJ6F, TSOT-23-6 (FC)
Steady 500kHz at all loads
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 email@example.com.
The EVB is provided with the test points and pin names listed in the table below.
Comment (expected waveforms or voltage levels on test points)
Feedback Voltage Input
This pin is used to set the desired output voltage via an external resistive divider. The feedback reference voltage is 0.6V typically.
Power Input. Supplies the power switches of the device.
This is the power return for the IC.
Bootstrap Supply for High-Side Gate Driver. Connect a 0.1µF ceramic capacitor from LX to BOOT to power the high-side switch.
Switch node test point
Connect the output LC filter from LX to the output load.
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.
1. Apply a 12V nominal input power supply (4.5V < VIN < 18V) to the VIN and GND terminals.
2. Set the jumper at JP1 to connect terminals 2 and 3, connecting EN to VIN through resistor R30, to enable operation.
3. Verify the output voltage (approximately 5V) between VOUT and GND.
4. Connect an external load up to 5A to the VOUT and GND terminals and verify the output voltage and current.
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 x (1 + R1 / R2)
C8, C10, CB
0603 5K10 1%
0603 100K 1%
Top View (1st layer)
PCB Layout—Inner Side (2nd Layer)
PCB Layout—Inner Side (3rd Layer)
Bottom View (4th Layer)