UM1351_16 Datasheet, PDF (1/14 Pages) Union Semiconductor, Inc. – Hysteretic Buck High Brightness LED Driver with Internal Switch

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
 General Purpose, Constant Current
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
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