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UM1351

Hysteretic Buck High Brightness LED Driver with Internal Switch

UM1351Y SOT89-5

UM1351S SOT23-5

General Description

The UM1351 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 UM1351 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 UM1351 comes in small SOT89-5 and SOT23-5 packages. It is ideal for industrial and

general lighting applications.

Applications

Features



Low Voltage Halogen Replacement

LEDs



Low Voltage Industrial Lighting



LED Back-Side Lighting



Illuminated Signs



DC/DC or AC/DC LED Driver

Application



Source



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 SOT89-5 and SOT23-5 Packages