LM3501_14 Datasheet, PDF (1/26 Pages) Texas Instruments – Synchronous Step-up DC/DC Converter for White LED Applications

LM3501
www.ti.com
SNVS230B – MAY 2004 – REVISED MAY 2005
LM3501 Synchronous Step-up DC/DC Converter for White LED Applications
Check for Samples: LM3501
FEATURES
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•2 Synchronous rectification, high efficiency and
no external schottky diode required
• Uses small surface mount components
• Can drive 2-5 white LEDs in series (may
function with more low V_F LEDs)
• 2.7V to 7V input range
• True shutdown isolation, no LED leakage
current
• DC voltage LED current control
• Input undervoltage lockout
• Internal output over-voltage protection (OVP)
circuitry, with no external zener diode required
LM3501-16: 15.5V OVP; LM3501-21: 20.5V OVP.
• Requires only a small 16V (LM3501-16) or 25V
(LM3501-21) ceramic capacitor at the input and
output
• Thermal Shutdown
• 0.1µA shutdown current
• Small 8-bump thin micro SMD package
APPLICATIONS
• LCD Bias Supplies
• White LED Back-Lighting
• Handheld Devices
• Digital Cameras
• Portable Applications
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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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004–2005, Texas Instruments Incorporated