DEMO CIRCUIT 1542 QUICK STARTLT3596 GUIDE LT3596 60V Step-Down 3-Channel LED Driver DESCRIPTION Demonstration circuit 1542 is a 60V Step-Down 3Channel LED Driver featuring the LT3596. The demo board is optimized for 8 LEDs, 100mA output per channel from a 48V input. When different number of LEDs is used for evaluation, it is recommended to change the resistor divider (R1 and R4) values according to the datasheet. The connections between the board and LEDs strings should be as short as feasible. pins up to VREF. The switching frequency is set to 1MHz on the demo circuit for best solution size. The LT3596 internal compensation makes it a lot easier for a designer to design different application circuits. The circuit achieves 10,000:1 PWM dimming at 100Hz PWM frequency. LED dimming can also be done by analog control of the CTRL1-3 pin. If dimming is not required, leave the PWM1-3 and CTRL1-3 terminals unconnected. The demo circuit pulls PWM1-3 and CTRL1-3 Design files for this circuit board are available. Call the LTC factory. The LT3596 datasheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1542A. LTM, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. PERFORMANCE SUMMARY Specifications are at TA = 25°C SYMBOL VIN* VOUT VOUT(MAX) IOUT DIM FSW EFE PARAMETER Input Supply Output Voltage Maximum Output Voltage Output Current PWM Dimming Ratio Switching Frequency Efficiency CONDITIONS MIN 6 8 White LEDs 98 PWM Dimming Frquency = 100Hz R3=100k VIN=48V, VOUT=29V, IOUT=100mA, BIAS=5V, No Dimming 0.9 TYP 29 38 100 10,000:1 1 90 MAX 55 32 102 1.1 UNITS V V V mA V MHz % *: Actual VIN range should be determined by the load. For 8 white LEDs per channel, use a 48V input for evaluation. QUICK START PROCEDURE Demonstration circuit 1542A is easy to set up to evaluate the performance of the LT3596. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. With power off, connect the input power supply to VIN and GND. 2. With power off, connect a 5V bias supply to BIAS and GND. Bias voltage should be less then 25V. 3. With power off, connect 3 LED strings between VOUT and LED1-, LED2-, LED3- respectively. 4. Turn on the power at the input. Be careful not to look at the LEDs directly. 1 LT3596 5. Carefully evaluate all design parameters as needed. 6. To evaluate PWM dimming, apply a PWM signal to PWM1, PWM2 and/or PWM3. To evaluate 10,000:1 PWM dimming, the PWM signal should have a frequency of 100Hz and the minimum pulse width can be as low as 1us. 7. To modify the demo board for other applications, please contact Linear Applications Group for help. Figure 1. Proper Measurement Equipment Setup 2 LT3596 3