DC1315A: 1.5A x2 @ 23V Max, 4 ~ 36V in, LED Drvr

Demonstration circuit 1315 features the LT®3475-1 dual step-down 1.5A LED driver in a 16-lead TSSOP thermally enhanced package. The demonstration circuit is designed to drive two 1.5A LED strings (one on each channel) from a high input voltage. The high switching frequency scheme permits the use of a small inductor and ceramic capacitors to save space and cost. The current mode PWM control scheme provides fast transient response and cycle-by-cycle current limiting.

DC1315 is specifically designed for high power LED applications such as automotive and avionic lighting, architectural detail lighting and display backlighting. See the LT3475-1 datasheet for more detailed information on LED brightness and dimming control using both the PWM pin function and the VADJ pin function. The PWM terminals can be used to dim the LEDs with the addition of a PWM MOSFET and the resistor short connection from LED- to GND removed.

The efficiency of DC1315A with 20V input and 4 white LEDs on each 1.5A channel is 91.5%.

NOTE: The input voltage is limited to 30V during startup. During normal (non-startup) operation, the input voltage can be as high as 36V. DC1315 allows LED string voltages up to 23V. However, some combinations of VIN, VLED, and ILED can result in the LT3475-1 getting hot.

Please consult the datasheet for thermal calculations and details. The voltages, the LED current, and the switching frequency can be adjusted for optimal thermal performance.