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Union UM1351S

Hysteretic Buck High Brightness LED Driver with Internal Switch


TopologyBuck Converter
Input voltage6-35 V
Output 10.7 A


The UM1351S is a PWM step-down converter with internal power switch, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The UM1351S can drive up to 8 series connected LEDs. The device operates from an input supply between 6V and 35V and employs hysteretic control with a high side current sense resistor to set the constant output current up to 700mA. The device is well suited for applications requiring a wide input range. The high side current sensing and an integrated current sensing circuitry minimize the number of external components while delivering an accurate average output current. Depending upon supply voltage and external components, this device can provide up to 24 watts of output power.

Output current can be adjusted below the set value, by applying an external control signal to the VSET pin. The VSET pin will accept either a DC voltage or a PWM waveform. Dedicated pulse width modulation (PWM) input enables pulsed LED dimming over a wide range of brightness levels. A hysteretic control method ensures excellent input supply rejection and fast response during load transients and PWM dimming.

Applying a voltage of 0.2V or lower to the VSET pin turns the output off and switches the device into a low current standby state.

The UM1351S comes in small SOT23-5 package. It is ideal for industrial and general lighting applications.


  • Hysteretic Control with High Side Current Sensing
  • Integrated 35V 0.5Ω NDMOS
  • Up to 98% Efficiency
  • Wide Input Voltage Range: 6V to 35V
  • ±5% LED Current Accuracy
  • Adjustable Constant LED Current
  • Analog or PWM Control Signal for PWM Dimming
  • Over Temperature, Open Circuit LED Protection
  • Up to 1MHz Switching Frequency
  • Pb-Free SOT23-5 Package

Remarks:Recommended inductor values for the UM1351 are in the range 47μH to 220μH.Refer page no.10

Typical applications

  • LED Back-Side Lighting
  • General Purpose, Constant Current Source
  • Low Voltage Halogen Replacement LEDs
  • Illuminated Signs
  • Low Voltage Industrial Lighting
  • DC/DC or AC/DC LED Driver Application