4A, 18V, 500kHz, ACOT® Step-Down Converter


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The RT6254A/B is a high-performance, synchronous step-down DC-DC converter that can deliver up to 4A output current from a 4.5V to 18V input supply. The device integrates low RDS(ON) power MOSFETs, accurate 0.6V reference and an integrated diode of bootstrap circuit to offer a very compact solution.

The RT6254A/B adopts Advanced Constant On-Time (ACOT®) control architecture that provides ultrafast transient response and further reduces the external-component count. In steady states, the ACOT® operates in nearly constant switching frequency over line, load and output voltage ranges and makes the EMI filter design easier.

The device offers Independent enable control input pin and power good indicator (TSOT-23-8 only) for easily sequence control. To control the inrush current during the startup, the device provides a fixed 1.5ms soft-start up. Fully protection features are also integrated in the device including the cycle-by-cycle current limit control, UVP, input UVLO and OTP.

The RT6254A/B is available in the TSOT-23-6 (FC) and TSOT-23-8 (FC) package.


  • Set Top Box
  • Portable TV
  • Access Point Router
  • DSL Modem
  • LCD TV
Key Spec.
RT6254A RT6254B
Status Active Active
Vin (min) (V) 4.5 4.5
Vin (max) (V) 18 18
Number of Outputs 1 1
Vout (min) (V) 0.6 0.6
Vout (max) (V) 5 5
Output Adj. Method Resistor Resistor
Iout (max) (A) 4 4
Current Limit (typ) (A) 6.2 6.2
Freq (typ) (kHz) 500 500
Ext Sync No No
Ron_HS (typ) (mOhm) 48 48
Ron_LS (typ) (mOhm) 25 25
Iq (typ) (mA) 0.115 0.115
Features ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;OTP;PSM;Power Good;SCP;Stable with Ceramic Capacitor;UVP ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;OTP;PSM;Power Good;SCP;Stable with Ceramic Capacitor;UVP
Package Type TSOT-26(FC);TSOT-28(FC) TSOT-26(FC);TSOT-28(FC)
  • 4.5V to 18V Input Voltage Range
  • 4A Output Current
  • Constant-on-Time Mode to Enables Fast Transient Response
  • Low Output Ripple and Allows Ceramic Output Capacitor
  • 500kHz Switching Frequency
  • High Efficient Internal Power MOSFET Switch Optimized for Lower Duty Cycle Applications
  • Integrated 48mΩ/25mΩ MOSFETs
  • Adjustable Output Voltage from 0.6V to 5V
  • Internal Soft-Start (1.5ms typ.)
  • Built-In UVP/OTP
  • Power Good Indicator (90%)
  • Input Under Voltage Lockout
  • TSOT-23-6 (FC) and TSOT-23-8 (FC) Packages
TitleLast UpdateShareDownload
4A, 18V, 500kHz, ACOT® Step-Down Converter2016/08/17
Technical Documents
TitleLast UpdateShareDownload
Richtek Selection Guide [Oct., 2021]2022/09/03
TitleLast UpdateShareViews
How to estimate control loop bandwidth from the transient response time?2017/03/30 1571
Evaluation Boards
TitleLast UpdateShareDownload
4A, 18V, 500kHz, Step-Down Converter Evaluation Board2021/01/21
Reference Design
TitleLast UpdateShareDownload
Richtek Load Transient Tool2022/07/25
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT6254AHGJ6FTSOT-26(FC)3000 Not available Not available
RT6254AHGJ8FTSOT-28(FC)3000 Request Not available
RT6254AHGJ8FTSOT-28(FC)3000 Request Buy from Distributor
RT6254BHGJ6FTSOT-26(FC)3000 Request Not available
RT6254BHGJ6FTSOT-26(FC)3000 Request Buy from Distributor
RT6254BHGJ8FTSOT-28(FC)3000 Request Not available
RT6254BHGJ8FTSOT-28(FC)3000 Request Buy from Distributor