High Efficiency Single Synchronous Buck PWM Controller


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The RT8129B is a high efficiency single phase synchronous buck controller with 5V/12V supply voltage. The RT8129B integrates a Constant-On-Time (COT) PWM controller and a MOSFET drivers with internal bootstrap diodes, which is specifically designed to improve converter efficiency at light load condition. At light load condition, it automatically operates in the diode emulation mode to reduce switching frequency and improve conversion efficiency.

Other features include power good indication, enable/disable control and internal soft-start function. The RT8129B also provide protection functions including Over-Voltage Protection (OVP), Under-Voltage Protection (UVP), current limit and thermal shutdown.

This device uses lossless low-side MOSFET RDS(ON) current sense technique for current limit with adjustable threshold set by connecting a resistor between the LGATE/OCSET and GND.

With above functions, the RT8129B provides customers a cost-effective solution for high efficiency power conversion. The RT8129B is available in the WDFN-10L 3x3 package.


  • Motherboard, Memory/Chip-set Power
  • Graphic Card, GPU/Memory Core Power
  • Low Voltage, High Current DC-DC Regulator
Key Spec.
Status Active
Vs (typ) (V) 12;5
Vin (min) (V) 2.5
Vin (max) (V) 25
Vout (min) (V) 0.8
Vout (max) (V) 3.3
Output Adj. Method Resistor
Accuracy (+/- %) 1
Freq (typ) (kHz) 150
Ext Sync No
Features Adjustable Current Limit;COT Control;Diode Emulation Mode;Enable Input;OCP;OVP;PSM;Power Good;UVP;Ultrasonic Mode Control
Package Type WDFN3x3-10
  • Wide Input Voltage Range : 2.5V to 25V
  • High Light Load Efficiency
  • Integrated High Driving Capability N-MOSFET Gate
  • Drivers and Embedded Switching Boot Diode
  • Single IC Supply Voltage : 4.5V to 13.2V
  • Power-Good Indicator
  • Enable/Disable Control
  • Internal Soft-Start
  • Programmable Current Limit Threshold
  • Under-Voltage Protection
  • Over-Voltage Protection
  • Thermal Shutdown
TitleLast UpdateShareDownload
High Efficiency Single Synchronous Buck PWM Controller2019/06/03
Technical Documents
TitleLast UpdateShareDownload
Richtek Selection Guide [Oct., 2020]2020/12/30