QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A DUAL WHITE LED DRIVER CONVERTER LT3497EDDB DESCRIPTION ming. Analog dimming is done via the WARNING SHDN/DIMMING CONTROL terminals. Please refer to the quick start procedure. The high side current sens- Do not look directly at operating LED. ing feature of the LT3497 allows one wire current This circuit produces light that can damage eyes. source, i.e. the low side of the LED string can return to ground anywhere. Demonstration circuit 1019A is a Dual White LED The LT3497 datasheet gives complete description of Driver Converter featuring the LT 3497 in a 3mm x the part, operation and application information. The 2mm DFN package. The demo circuit demonstrates datasheet must be read in conjunction with this quick small size and low component count in two inde- start guide for working on or modifying the demo cir- pendent Boost Circuits. It drives two independent cuit 1019A. LED strings at 20mA from a 3V-10V input. Other fea- tures of the LT3497, such as the internal schottky di- odes, the high switching frequency and the internal Design files for this circuit board are available. Call open circuit protection, allow the use of tiny compo- the LTC factory. nents. Different dimming controls can be imple- LTC, LT is a registered trademark of Linear Technology Corporation mented on the demo board. Optional N-MOSFET placeholders are provided to test direct PWM dim- Table 1. Performance Summary (T = 25C) A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Input Supply Range ** 3 10 V IN I Output Current 19 20 21 mA OUT V Output Voltage 19.5 V OUT h Efficiency V =3.6V 72.3 % IN V CAP pin Over voltage Protection LED Open 30 32 34 V OPEN I Quiescent Current V = 4.2V, CTRL=ON, LEDs open 15 mA Q IN I Quiescent Current in Shutdown V = 4.2V, CTRL=OFF 10 A QSHDN IN Fs Switching Frequency 1.8 2.3 2.8 MHz ** The Input Supply Range of the Demo Circuit 1019A is limited by Maximum Input Voltage of the LT3497. Always ensure that this level is not exceeded. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A DUAL WHITE LED DRIVER CONVERTER QUICK START PROCEDURE Demonstration circuit 1019A is easy to set up to 3. Turn on the power at the input. evaluate the performance of the LT3497. Refer to Fig- Note: Make sure that the input voltage does not ure 1 for proper measurement equipment setup and exceed 10V. follow the procedure below: 4. Check for the proper voltages and currents. Note: when measuring the input or output voltage Note: If the LEDs do not light up, check the jumper ripple, care must be taken to avoid a long ground lead settings. on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip 5. Once the proper operations are established, adjust directly across the Vin or Vout and GND terminals. the input within the operating range and observe See Figure 2 for proper scope probe technique. the parameters of interest. 1. Place jumpers in the following positions to test the 6. To test the filtered PWM dimming or the direct DC circuit: dimming, remove the jumper JP1 or JP2, apply the PWM or the DC signal to the SHDN/DIMMING JP1 ON CTRL1 or SHDN/DIMMING CTRL2 and observe the JP2 ON brightness of the LED output. 2. With power off, connect the input power supply to 7. To test the direct PWM dimming, follow the Direct V and GND. IN PWM Dimming section in the datasheet. Figure 1. Proper Measurement Equipment Setup 2