18V, 2A, ACOTTM Step-Down Converter in 8 Pin TSOT-23


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The RT6218A/B is a simple, easy-to-use, 2A synchronous step-down DC-DC converter with an input supply voltage range of 4.5V to 18V. The device integrates low RDS(ON) power MOSFETs to achieve high efficiency in a SOT23 package and build-in accurate reference voltage (0.765V by product options).

The RT6218A/B adopts Advanced Constant On-Time (ACOTTM) 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 RT6218A operates in automatic PSM that maintains high efficiency during light load operation. RT6218B operates in Forced PWM that helps meet tight voltage regulation accuracy requirements.

The RT6218A/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. The RT6218A/B series offers programmable start-up by connecting a capacitor at external SS pin. The device also includes input under-voltage lockout, output under-voltage protection, and over-temperature protection (thermal shutdown) to provide safe and smooth operation in all operating conditions. The RT6218A/B are offered in TSOT-23-8(FC) package.


  • Set-Top Boxes
  • LCD TVs
  • Home Networking Devices
  • Surveillance
  • General Purpose
Key Spec.
RT6218A RT6218B
Status Active Active
Vin (min) (V) 4.5 4.5
Vin (max) (V) 18 18
Number of Outputs 1 1
Vout (min) (V) 0.765 0.765
Vout (max) (V) 6.5 6.5
Preset Vout (V)
Output Adj. Method Resistor Resistor
Iout (max) (A) 2 2
Current Limit (typ) (A) 3.2 3.2
Freq (typ) (kHz) 650 650
Freq (min) (kHz)
Freq (max) (kHz)
Ext Sync No No
Ron_HS (typ) (mOhm) 120 120
Ron_LS (typ) (mOhm) 65 65
Iq (typ) (mA) 0.5 0.5
Features ACOT Control;Adjustable Soft-Start;Enable Input;OCP;PSM;Power Good;UVP ACOT Control;Adjustable Soft-Start;Enable Input;Force PWM;OCP;Power Good;UVP
Package Type TSOT-28(FC) TSOT-28(FC)
  • Input Supply Voltage Range : 4.5V to 18V
  • 2A Converter With Built-in 120mΩ/65mΩ Low RDS(ON) Power FETs
  • Advanced Constant On-Time (ACOTTM) Control for Ultrafast Transient Response
  • Fixed Switching Frequency : 650kHz (SOT23-8)
  • Optional for Operation Modes :
    ► Automatically Power Saving Mode (PSM) (RT6218A)
    ► Forced PWM Mode (RT6218B)
  • Optimized for Low-ESR Ceramic Output Capacitors
  • ±1.5% High-Accuracy Feedback Reference Voltage
  • Output Voltage Range : up to 6.5V
  • Externally Adjustable Soft-Start
  • Monotonic Start-Up for Pre-biased Outputs
  • Both HS/LS FETs Protection for Robust Over Current Protection
  • Input Under-Voltage Lockout (UVLO)
  • Output Under-Voltage Protection (UVP) with Hiccup Mode
  • Over-Temperature Protection (OTP) (Thermal Shutdown)
  • Enable Control
  • Power Good Indication
  • RoHS Compliant and Halogen Free
  • Available in TSOT-23-8 Package
TitleLast UpdateShareDownload
18V, 2A, ACOTTM Step-Down Converter in 8 Pin TSOT-232017/09/18
Reference Design
TitleLast UpdateShareDownload
Richtek Load Transient Tool2017/03/31
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT6218AHRGJ8FTSOT-28(FC)3000 Request Buy from Distributor
RT6218BHRGJ8FTSOT-28(FC)3000 Request Buy from Distributor