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 Output Voltage Monitor and Integrated IGBT Drive, featuring the LT3485EDD-x family of products. It demonstrates a complete photoflash application, including the photoflash capacitor, flash tube and trigger circuit. An on-board microcontroller generates the necessary signals to produce an on-demand flash, red-eye sequence, and flash capacitor refresh. The demonstration board comes in four variants. DC895A-A uses the LT3485EDD-0, while DC895A-B, DC895A-C and DC895A-D use the LT3485EDD-1, LT3485EDD-2, LT3485EDD-3, respectively. The LT3485 family of photoflash capacitor ICs is designed for use in digital camera and mobile phone applications where space is a premium. The LT3485’s patented control technique allows it to use extremely small transformers, and the improved NPN power switch requires no external Schottky diode clamp, reducing the solution size. The output voltage detection requires no external circuitry as the transformer turns ratio determines the final charger voltage. The device features a VBAT pin, which allows the use of 2 alkaline cells to charge the capacitor. The CHARGE pin gives full control of the part to the user. Driving CHARGE low shuts the part down. The LT3485 also includes a output voltage monitor, which generates an analog signal proportional to the output, and an integrated IGBT drive. WARNING! Lethal voltages are present on the DC895 circuit board. Do not operate the assembly unless you are trained to handle high voltage circuits. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. Table 1. Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE Minimum VBAT Voltage VIN = 2.8V – 4.2V 1.8VDC Maximum VBAT Voltage VIN = 2.8V – 4.2V 4.2VDC Minimum VIN Voltage VBAT = 1.8V – 4.2V 2.8VDC Maximum VIN Voltage VBAT = 1.8V – 4.2V 4.2VDC Output Voltage VIN = 2.8V – 4.2V, VBAT = 1.8V – 4.2V 320VDC, typical DC895A-D, LT3485EDD-3 750mA, typical DC895A-A, LT3485EDD-0 500mA, typical DC895A-C, LT3485EDD-2 350mA, typical DC895A-B, LT3485EDD-1 225mA, typical Average input current 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 http://www.linear.com. QUICK START PROCEDURE WARNING! Lethal voltages are present on the DC895 circuit board. Do not operate the assembly unless you are trained to handle high voltage circuits. Demonstration circuit 895 is easy to set up to evaluate the performance of the LT3485EDCB-x. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. Set the jumper at JP1 across the DAT and MCLR pins. 2. With the power supply disconnected from DC895, set the VBAT voltage between 1.8V to 4.2V. Set the VIN voltage between 2.8V and 4.2V. Turn off the power supply. 3. Connect the power supply to DC895, referring to the connection diagram given in Figure 1. 4. Turn on the power supply, verifying that the VIN and VBAT voltages are correctly set. 5. Press the ON/OFF button once. The READY/CHARGE LED should glow red as the LT3485 charges the output capacitor and then glow green. 6. To flash the xenon tube, verify that the READY/CHARGE LED is green. Avoid looking directly at the xenon flash tube and press the FLASH button once. After the tube flashes, the READY/CHARGE LED should turn red as the LT3485 replenishes the charge in the flash capacitor. 7. To generate a red-eye sequence, verify that the READY/CHARGE LED is green. Avoid looking di- rectly at the xenon flash tube and press the REDEYE button once. After the flash sequence is over, the READY/CHARGE LED should turn red as the LT3485 replenishes the charge in the flash capacitor. 8. When finished testing, press the ON/OFF switch once. This flashes the xenon tube, discharging the flash capacitor and shuts down the LT3485. The output capacitor is not completely discharged when this operation is complete. 50V or more may be left on the capacitor, so the user is cautioned to avoid physical contact with the flash tube circuitry at all times. The flash tube circuitry consists of D1, C2, R3, R10, C3, T2, FT1, and Q1. 9. Monitor the DONE, CHARGE, VOUTMONT and TRIGGER signals by using the provided test points. Do not make measurements from under the protective cover. 10. The on-board microcontroller may be disabled by removing the VIN and VBAT voltages and moving the JP1 jumper to short the GND and CLK pins. The user can charge the output capacitor and activate the flash tube by applying the appropriate signals to the CHARGE and TRIGGER test points. The timing can be validated by monitoring these and the DONE signal. Please refer to the LT3485 data sheet for detailed signal requirements. ADDITIONAL NOTES It is assumed that DC895A will be tested with power provided from an external source, such as a lab bench 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 895 PHOTOFLASH CHARGER WITH OUTPUT VOLTAGE MONITOR AND INTEGRATED IGBT DRIVE supply. Under such an operating condition, the wire length between the DC895A board and the power supply terminals can be several feet and the line loss may be excessive. For this reason, CIN has been added to the board at the input terminals to attenuate the ground shifting associated with pulling the main switch current through the wires connecting to the power supply. This capacitor would generally not be required in a battery powered portable application, where the battery would be physically located close to the LT3485 and the impedance of the connection is low. The flashtube for this reference design is a FTA160709, manufactured by Perkin-Elmer. They can be contacted at: PerkinElmer Optoelectronics Lithography and Lighting 1300 Optical Drive Azusa, CA. 91702 Figure 1. Proper Measurement Equipment Setup 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 895 PHOTOFLASH CHARGER WITH OUTPUT VOLTAGE MONITOR AND INTEGRATED IGBT DRIVE 4