DC646A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 646 STROBE CAPACITOR CHARGER, HIGH VOLTAGE SUPPLY LT3420 DESCRIPTION Demonstration circuit 646 is a DC-DC flyback This demonstration circuit is particularly useful for converter using the LT 3420EMS to rapidly charge an applications such as digital cameras and high voltage output capacitor to 300V for photoflash applications. supplies that require high efficiency and small size. It demonstrates a simple application circuit operating Design files for this circuit board are available. Call the in high efficiency and shows appropriate layout LTC factory. techniques for the LT3420EMS. The circuit uses LT is a trademark of Linear Technology Corporation. small surface mount components and has very small board space compared to conventional solutions. QUICK START PROCEDURE Demonstration circuit 646 is easy to set up to evaluate the 2. Set JP1 to DISCONNECT position for separate input performance of the LT3420EMS. Refer to Figure 1 for proper power operation. Connect input power source Vcc to the measurement equipment setup and follow the procedure Vcc and GND terminals, and limit the input voltage from below: 2.3V to 6V. NOTE: When measuring the input or output voltage ripple, 3. Connect load (a 220uF, 350V photoflash capacitor) care must be taken to avoid a long ground lead on the between the +Strobe Cap and Strobe Cap terminals. oscilloscope probe. Measure the input or output voltage 4. Set JP2 to ON position to enable Charge operation. ripple by touching the probe tip directly across the V or IN V and GND terminals. See Figure 2 for proper scope OUT 5. Slowly turn on power source Vbatt and Vcc. Check for the probe technique. proper output voltages. V = 300V. OUT NOTE: For safe operation, always shield the circuit NOTE: If there is no output, temporarily disconnect the when power is on, and always discharge the high load and make sure that JP2 is set to ON position. voltage output capacitor after power is off. 6. For single source operation, set the input source selector Warning: Operate by high voltage trained personnel only Jumper JP1 to CONNECT position. Remove the connection of power source Vcc. Limit the input voltage 1. With power off, connect input power source Vbatt to the from 2.3V to 6V. Vcc will be powered from Vbatt. Vbatt and GND terminals. Input voltage is limited to between 1.8V to 6V. 7. To shut down the circuit, connect the JP2 to OFF position. The output capacitor charging is disabled. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 646 STROBE CAPACITOR CHARGER, HIGH VOLTAGE SUPPLY Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2