Features for the LM3553SDEV
- Accurate and Programmable LED Current up to 1.2A in 128 Steps
- Total solution Size <30mm2
- 90% Peak Efficiency
- Drives 2 LEDs in Series with 1.2A from 5V input
- Drives 2 LEDs in Series with 600mA from 3.0V Input
- Drives 1 LED with 1.2A from 3.0V Input
- Adjustable Over-Voltage Protection Allows for Single or Series LED Operation
- Four Operating Modes: Torch, Flash, Indicator, and Voltage Mode (4.98V)
- Programmable Flash Pulse Safety Timer in 16 Steps
- TX Input Ensures Synchronization with RF Power Amplifier Pulse or Prevents LED from Overheating
- LED Disconnect During Shutdown
- Flash/Imager Synchronization via FEN Pin
- Active Low Hardware Reset
- Multi-Function Pin (RESET and GPIO)
- Low Profile 12-pin LLP Package (SDF12A: 3mm x 3mm x 0.8mm, 0.4mm pitch)
Applications:
- Camera Phone LED Flash
- Smartphone and PDA Flash
- LED Backlight
Description for the LM3553SDEV
The LM3553 is a fixed frequency, current mode step-up DC/DC converter with two regulated current sinks. The device is capable of driving loads up to 1.2A from a single-cell Li-Ion battery.
One or more high current flash LEDs can be driven in series either in a high power Flash mode or a lower power Torch mode controlled by either an internal register or the FEN pin. Additionally a low current (20mA) indicator mode and a fixed output voltage mode are also available.
The LM3553 has 128 current levels and 176 flash safety timer durations that are user adjustable via an I2 C compatible interface. Internal soft-start eliminates large inrush currents at start-up. Over-voltage protection circuitry and 1.2MHz switching frequency allow for the use of small, low-cost output capacitors with lower voltage ratings.
The LM3553 is an asynchronous step-up DC/DC converter with an I2C compatible control interface designed for white LED Flash applications. The evaluation board is setup to drive two white flash LEDs with a series flash current of 500mA. Flash duration and current can both be configured by adjusting values stored in the internal control registers. The LM3553 is available in a 3 mm by 3mm LLP package.