LM3500MT-16

• Synchronous rectification is required with high efficiency and no external Schottky diode
• Use small surface mount components
• Can drive 2-5 white LED series
  (Possible features with lower cost.)_targetV F light-emitting diode)
• Input voltage range of 2.7V to 7V
• Internal output overvoltage protection (OVP) circuitry requires any external Zener diodes
  LM3500 - 16：15.5V OVP; LM3500 - 21: 20.5V OVP.
• True off-isolation
• Input undervoltage lockout
• Only small ceramic capacitors are required for input and output
• Thermal shutdown
• 0.1μA shutdown current
• Small 8-ball low profile micro SMD package

illustrate

The LM3500 is a fixed frequency step-up DC/DC converter ideal for driving white LED display backlighting and other lighting functions. Fully integrated with synchronous switching (no external Schottky diode required) and low feedback voltage (500mV), the LM3500 circuit is optimized for power efficiency in wireless handsets and other portable products (single-cell Li-ion battery or 3-cell lighting applications powered by NiMH batteries). The LM3500 operates a fixed switching frequency of 1MHz. When ceramic input and output capacitors are used together, the LM3500 provides a small, low-noise, low-cost solution.

Two LM3500 options are available with different output voltage capabilities. The LM3500-21 has a maximum output voltage of 21V and is usually suitable for driving 4 or 5 white LEDs in series. The LM3500-16 has a maximum output voltage of 16V and is usually suitable for driving 3 or 4 white LEDs in series (the maximum number of LEDs in series depends on the forward voltage of the LED). If the main white LED network should be disconnected, the LM3500 uses an internal protection circuit output to prevent damaging overvoltage events.

A single external resistor is used to set the maximum LED current for LED drive applications. The LED current can be easily adjusted using the pulse-width modulation (PWM) signal using the shutdown pin. In shutdown, the LM3500 completely disconnects the output input, creating complete isolation and preventing any trickle of leakage current from the LED.

apply

• LCD bias power supply
• White LED backlight
• Handheld devices
• Digital cameras
• Portable applications