1.2A, Hysteretic, High Brightness LED Driver with Internal Switch


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The RT8420 is a high-efficiency, continuous mode, inductive step-down converter, designed for driving single or multiple series-connected LED strings from a voltage source higher than the LED string voltage. It operates from an input voltage range from 7V to 50V and employs a hysteretic control loop with a high side current sense resistor to set the constant LED output current.

The RT8420 includes a low side power switch and a high side output current sensing circuit, which uses an external resistor to set the nominal average output current. The LED brightness control is achieved by analog dimming method and the maximum switching frequency is clamped when the dimming percentage is low.

The RT8420 is available in MSOP-8 (Exposed Pad) and SOP-8 (Exposed Pad) package that makes the chip more thermal efficient.


Key Spec.
Status Active
Vin (min) (V) 7
Vin (max) (V) 50
Topology Buck
Vcs (typ) (mV) 100
Dimming Control Analog;PWM
Features OCP;SCP;UVP
Package Type MSOP-8(PP);PSOP-8
  • 7V to 50V Input Voltage Range
  • Hysteretic Control with High Side Current Sensing
  • Internal N-MOSFET with 350mΩ Low RDS(ON)
  • 1.2A Output Current
  • Up to 97% Efficiency
  • Typical ±5% LED Current Accuracy
  • ADJ Pin for Analog Dimming and PWM Dimming
  • Limited Max Switching Frequency at Low Percentage Dimming
  • Input Under Voltage Lockout
  • Thermal Shutdown Protection
  • RoHS Compliant and Halogen Free