The RT5761A/B is a simple, easy-to-use, 1A synchronous step-down DC-DC converter with an input supply voltage range from 2.5V to 6V. The device build-in an accurate 0.6V reference voltage and integrates low RDS(ON) power MOSFETs to achieve high efficiency in a UDFN-6L 1.4x1 package.

The RT5761A/B adopts Advanced Constant On-Time (ACOT®) control architecture to provide an ultrafast transient response with few external components and to operate in nearly constant switching frequency over the line, load, and output voltage range. The RT5761A operate in automatic PSM that maintain high efficiency during light load operation. The RT5761B operate in Forced PWM that help to meet tight voltage regulation accuracy requirements.

The RT5761A/B senses both FETs current for a robust over-current protection. The device features cycle-by-cycle current limit protection and prevent the device from the catastrophic damage in output short circuit, over current or inductor saturation. A built-in soft-start function prevents inrush current during start-up. The device also includes input under-voltage lockout, output under-voltage protection, and over-temperature protection to provide safe and smooth operation in all operating conditions.


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Key Spec.
RT5761A RT5761B
Status Active Active
Vin (min) (V) 2.5 2.5
Vin (max) (V) 6 6
Number of Outputs 1 1
Vout (min) (V) 0.6 0.6
Vout (max) (V) 6 6
Output Adj. Method Resistor Resistor
Iout (max) (A) 1 1
Current Limit (typ) (A) 2.65 2.65
Freq (typ) (kHz) 2200 2200
Ext Sync No No
Ron_HS (typ) (mOhm) 120 120
Ron_LS (typ) (mOhm) 80 80
Iq (typ) (mA) 0.025 0.3
Features 100% Duty Cycle;ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Internal Compensation;OCP;OTP;PSM;Power Good;Stable with Ceramic Capacitor;UVP 100% Duty Cycle;ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Force PWM;Internal Compensation;OCP;OTP;Power Good;Stable with Ceramic Capacitor;UVP
Package Type UDFN1.4x1-6(FC) UDFN1.4x1-6(FC)
  • Input Voltage Range from 2.5V to 6V
  • Integrated 120mΩ and 80mΩ FETs
  • 1A Output Current, up to 95% Efficiency
  • 100% Duty Cycle for Lowest Dropout
  • 1% Internal Reference Voltage
  • 2.2MHz Typical Switching Frequency
  • Power Saving Mode for Light Loads (RT5761A)
  • Low Quiescent Current: 25μA (Typ.)
  • Fast Advanced Constant On-Time (ACOT®) Control
  • Internal Soft Startup (0.6ms)
  • Enable Control Input
  • Power Good Indicator
  • Both FETs Over-Current Protection
  • Negative Over-Current Protection (RT5761B)
  • Input Under-Voltage Lockout Protection
  • Hiccup-Mode Output Under-Voltage Protection
  • Over-Temperature Protection
  • RoHS Compliant and Halogen Free
TitleLast UpdateDownload
6V 1A, ACOT® Buck Converter in Thin UDFN-6L 1.4x1 Package2020/12/14
Reference Design
TitleLast UpdateDownload
Richtek Load Transient Tool2022/07/25