Description
The LT3478/LT3478-1 are 4.5A step-up DC/DC converters designed to drive LEDs with a constant current over a wide programmable range. Series connection of the LEDs provides identical LED currents for uniform brightness without the need for ballast resistors and expensive factory calibration.
The LT3478-1 reduces external component count and cost by integrating the LED current sense resistor. The LT3478 uses an external sense resistor to extend the maximum programmable LED current beyond 1A and also to achieve greater accuracy when programming low LED currents. Operating frequency can be set with an external resistor from 200kHz up to 2.25MHz. Unique circuitry allows a PWM dimming range up to 3000:1 while maintaining constant LED color. The LT3478/LT3478-1 are ideal for high power LED driver applications such as automotive TFT LCD backlights, courtesy lighting and heads-up displays. One of two CTRL pins can be used to program maximum LED current. The other CTRL pin can be used to program a reduction in maximum LED current vs temperature to maximize LED usage and improve reliability.
Additional features include inrush current protection, programmable open LED protection and programmable soft-start. Each part is available in a 16-pin thermally enhanced TSSOP Package.
Features
- True Color PWM™ Dimming Delivers Constant LED Color with Up to 3000:1 Range
- Wide Input Voltage Range: 2.8V to 36V
- 4.5A, 60mΩ, 42V Internal Switch
- Drives LEDs in Boost, Buck-Boost or Buck Modes
- Integrated Resistors for Inductor and LED Current Sensing
- Program LED Current:
100mA to 1050mA (LT3478-1)
(10mV to 105mV)/RSENSE (LT3478) - Program LED Current De-Rating vs Temperature
- Separate Inductor Supply Input
- Inrush Current Protection
- Programmable Soft-Start
- Fixed Frequency Operation from 200kHz to 2.25MHz
- Open LED Protection (Programmable OVP)
- Accurate Shutdown/UVLO Threshold with Programmable Hysteresis
- 16-Pin Thermally Enhanced TSSOP Package
Packeging
TSSOP-16
