QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 895 PHOTOFLASH CHARGER WITH OUTPUT VOLTAGE MONITOR AND INTEGRATED IGBT DRIVE LT3485EDD-0/-1/-2/-3 DESCRIPTION Demonstration circuit 895 is a Photoflash Charger with external circuitry as the transformer turns ratio deter- Output Voltage Monitor and Integrated IGBT Drive, fea- mines the final charger voltage. turing the LT3485EDD-x family of products. It demon- strates a complete photoflash application, including the The device features a V pin, which allows the use of 2 photoflash capacitor, flash tube and trigger circuit. An BAT alkaline cells to charge the capacitor. The CHARGE pin on-board microcontroller generates the necessary sig- gives full control of the part to the user. Driving nals to produce an on-demand flash, red-eye sequence, CHARGE low shuts the part down. The LT3485 also in- and flash capacitor refresh. cludes a output voltage monitor, which generates an analog signal proportional to the output, and an inte- The demonstration board comes in four variants. grated IGBT drive. DC895A-A uses the LT3485EDD-0, while DC895A-B, DC895A-C and DC895A-D use the LT3485EDD-1, WARNING Lethal voltages are present on the DC895 LT3485EDD-2, LT3485EDD-3, respectively. circuit board. Do not operate the assembly unless you are trained to handle high voltage circuits. The LT3485 family of photoflash capacitor ICs is de- signed for use in digital camera and mobile phone appli- Design files for this circuit board are available. Call cations where space is a premium. The LT3485s pat- the LTC factory. ented control technique allows it to use extremely small transformers, and the improved NPN power switch re- , LTC and LT are registered trademarks of Linear Technology Corporation. quires no external Schottky diode clamp, reducing the solution size. The output voltage detection requires no Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum V Voltage V = 2.8V 4.2V 1.8VDC BAT IN Maximum V Voltage V = 2.8V 4.2V 4.2VDC BAT IN Minimum V Voltage V = 1.8V 4.2V 2.8VDC IN BAT Maximum V Voltage V = 1.8V 4.2V 4.2VDC IN BAT Output Voltage V = 2.8V 4.2V, V = 1.8V 4.2V 320VDC, typical IN BAT DC895A-D, LT3485EDD-3 750mA, typical Average input current DC895A-A, LT3485EDD-0 500mA, typical DC895A-C, LT3485EDD-2 350mA, typical DC895A-B, LT3485EDD-1 225mA, typical 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 895 PHOTOFLASH CHARGER WITH OUTPUT VOLTAGE MONITOR AND INTEGRATED IGBT DRIVE OPERATING PRINCIPLES The theory of operation of the LT3485 and xenon flash tube illumination has been discussed at length in the LT3485 data sheet and the Linear Technology Application Note AN95, respectively. The reader is referred to these documents, available online at