DC1224A Analog Devices

DEMO CIRCUIT 1224 LT3593 QUICK START GUIDE LT3593 LED Driver with One Wire Control and Output Disconnect WARNING DO NOT LOOK AT OPERATING LED. This circuit produces light that can damage eyes. DESCRIPTION Demonstration circuit 1224 is a LED Driver with ately. The ILED value only changes to the com- One Wire Control and Output Disconnect featuring manding LEVEL value after the SEND/STORE the LT3593. The LT3593 is a step-up current mode button SW3 is pushed. Pushing SEND/STORE DC/DC converter designed to drive up to 10 white button also save the LEVEL value in the memory LEDs in series from a Li-Ion cell. The demo board of the micro-controller U2 as the default LED cur- has two sections. The top section showcases the rent level. small size LED drive. The maximum current is The LT3593 datasheet gives complete description 20mA. The bottom section is the control section of the part, operation and application information. that generates pulses for the CTRL pin of the LED The datasheet must be read in conjunction with driver. The number of pulses and its timing deter- this quick start guide for working on or modifying mine the current and brightness of the LEDs. the demo circuit 1224. The LCD display in the bottom section shows the Design files for this circuit board are available. status of the commanding LED current level in the Call the LTC factory. format as LEVEL=value and LED current level as , LTC and LT are registered trademarks of Linear Technology Corporation. ILED=value. The LEVEL value responses to the ThinSOT and PowerPath are trademarks of Linear Technology Corporation. UP button SW1 and DOWN button SW2 immedi- PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Input Supply Range 3 5 V IN +5V Input Supply for Control Section 4.5 5 5.5 V I Maximum Output LED Current 19 20 21 mA LED MAX V Maximum Output Voltage 40 V OUT MAX Efficiency V =5V, 8 White LEDs 81 % IN V =3.6V, 8 White LEDs 79 IN V Over voltage Protection LED Open 36 38 40 V OPEN Fs Switching Frequency 0.85 1 1.15 MHz 1 LT3593 QUICK START PROCEDURE Demonstration circuit 1224 is easy to set up to 5. Turn on the power at the input. evaluate the performance of the LT3593. Refer to NOTE. Make sure that the input voltage does not exceed 5V. Figure 1 for proper measurement equipment setup 6. Turn on the power at +5V. and follow the procedure below: 7. Check for the proper voltages and currents. 1. Place jumpers in the following positions: NOTE. By default of the demo board, the current is 20mA when JP1 PIC power is applied the very first time. 2. With power off, connect a 3V to 5V power sup- 8. Adjust the UP (SW1), DOWN (SW2), ply to V and GND. IN SEND/STORE (SW3) to the value of interest be- 3. With power off, connect 4.5V to 5.5V power tween 0 and 32, where ILED=32 gives 20mA, supply to +5V and GND. ILED=1 gives 625uA, and ILED=0 shuts down the part. 4. Connect a string of up to 10 LEDs between LED+ and LED-. The Cathode of the last LED connects to the LED-. Figure 1. Proper Measurement Equipment Setup 2