LM3501

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SNVS230B – MAY 2004 – REVISED MAY 2005

LM3501 Synchronous Step-up DC/DC Converter for White LED Applications

Check for Samples: LM3501

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FEATURES

(LM3501-21) ceramic capacitor at the input and

output

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Synchronous rectification, high efficiency and

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Thermal Shutdown

no external schottky diode required

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0.1µA shutdown current

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Uses small surface mount components

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Small 8-bump thin micro SMD package

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Can drive 2-5 white LEDs in series (may

APPLICATIONS

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2.7V to 7V input range

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LCD Bias Supplies

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True shutdown isolation, no LED leakage

current

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White LED Back-Lighting

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DC voltage LED current control

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Handheld Devices

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Input undervoltage lockout

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Digital Cameras

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Internal output over-voltage protection (OVP)

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Portable Applications

circuitry, with no external zener diode required

LM3501-16: 15.5V OVP; LM3501-21: 20.5V OVP.

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Requires only a small 16V (LM3501-16) or 25V

DESCRIPTION

The LM3501 is a fixed-frequency step-up DC/DC converter that is ideal for driving white LEDs for display

backlighting and other lighting functions. With fully intergrated synchronous switching (no external schottky diode

required) and a low feedback voltage (515 mV), power efficiency of the LM3501 circuit has been optimized for

lighting applications in wireless phones and other portable products (single cell Li-Ion or 3-cell NiMH battery

supplies). The LM3501 operates with a fixed 1 MHz switching frequency. When used with ceramic input and

output capacitors, the LM3501 provides a small, low-noise, low-cost solution.

Two LM3501 options are available with different output voltage capabilities. The LM3501-21 has a maximum

output voltage of 21V and is typically suited for driving 4 or 5 white LEDs in series. The LM3501-16 has a

maximum output voltage of 16V and is typically suited for driving 3 or 4 white LEDs in series (maximum number

of series LEDs dependent on LED forward voltage). If the primary white LED network should be disconnected,

the LM3501 uses internal protection circuitry on the output to prevent a destructive overvoltage event.

A single external resistor is used to set the maximum LED current in LED-drive applications. The LED current

can easily be adjusted by varying the analog control voltage on the control pin or by using a pulse width

modulated (PWM) signal on the shutdown pin. In shutdown, the LM3501 completely disconnects the input from

output, creating total isolation and preventing any leakage currents from trickling into the LEDs.

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PRODUCTION DATA information is current as of publication date.

Copyright © 2004–2005, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.