DEMO CIRCUIT 988 LT3585EDDB-0/-1/-2/-3 QUICK START GUIDE LT3585EDDB -0/-1/-2/-3 Photoflash Charger with Ad- justable Input Current and IGBT Driver DESCRIPTION DC988-C and DC988-D use the LT3585EDD-1, WARNING LT3585EDD-2, LT3585EDD-3, respectively. Do not look directly at flash. The LT3585-x are highly integrated devices de- This circuit produces light that can damage eyes. signed to charge photoflash capacitors in digital WARNING and film cameras. Its unique control technique al- Lethal voltages are present on the circuit lows for the use of extremely small transformers. board. Each part contains an on-chip high voltage NPN Do not operate the assembly unless you are power switch. Output voltage detection is com- trained to handle high voltage circuits pletely contained within the part, eliminating the need for any discrete zener diodes or resistors for high voltage output sensing. The output can be Demonstration circuit 988 is a Photoflash Charger adjusted by simply changing the turns ratio of the with Adjustable Input Current and IGBT Driver fea- transformer. turing the LT3585EDDB-x family of products. It demonstrates a complete xenon photoflash solu- The CHRG/IADJ pin gives full control of the part to tion, including the photoflash capacitor, flash tube the user. Driving CHRG/IADJ lows puts the part in and trigger circuit, along with an input current ad- shutdown. The CHRG/IADJ pin can also be used just capability. An on-board microcontroller gener- to reduce the current of the charger, useful in ex- ates the necessary signals to produce an on- tending battery life. The DONE pin indicates when demand flash, red-eye sequence, and flash ca- the part has completed charging. pacitor refresh. Design files for this circuit board are available. The demonstration board comes in four variants. Call the LTC factory. DC988-A uses the LT3585EDD-0, while DC988-B, , LTC, and LT are registered trademarks of Linear Technology Corporation. PERFORMANCE SUMMARY Specifications are at TA = 25C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VBAT VBAT Voltage Range VIN = 2.8V 4.2V 1.8 4.2 V VIN VIN Voltage Range VBAT = 1.8V 4.2V 2.8 4.2 V VOUT Output Voltage VIN = 2.8V 4.2V, VBAT = 1.8V 4.2V 320 V Charge Time LT3585-3, VBAT = 3.6V, CHRG/IADJ high 468 mS TCHARGE LT3585-0, VBAT = 3.6V, CHRG/IADJ high 600 LT3585-1, VBAT = 3.6V, CHRG/IADJ high 1180 LT3585-2, VBAT = 3.6V, CHRG/IADJ high 779 Charge time (Reduced current) LT3585-3, VBAT = 3.6V, CHRG/IADJ hi-Z 890 mS TCHAREG(R) LT3585-0, VBAT = 3.6V, CHRG/IADJ hi-Z 1237 LT3585-1, VBAT = 3.6V, CHRG/IADJ hi-Z 2547 1 L T3585EDDB-0/-1/-2/-3 PERFORMANCE SUMMARY Specifications are at TA = 25C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS LT3585-2, VBAT = 3.6V, CHRG/IADJ hi-Z 1550 QUICK START PROCEDURE 7. To flash the xenon tube, verify that the WARNING READY/CHARGE LED is green. Avoid look- ing directly at the xenon flash tube and press Do not look directly at flash. the FLASH button once. After the tube This circuit produces light that can damage eyes. flashes, the READY/CHARGE LED should WARNING turn red as the LT3585 replenishes the charge Lethal voltages are present on the circuit in the flash capacitor. board. 8. To generate a red-eye sequence, verify that Do not operate the assembly unless you are the READY/CHARGE LED is green. Avoid trained to handle high voltage circuits looking directly at the xenon flash tube and press the REDEYE button once. After the flash sequence is over, the READY/CHARGE Demonstration circuit 988 is easy to set up to LED should turn red as the LT3585 replen- evaluate the performance of the LT3585EDDB-x. ishes the charge in the flash capacitor. For proper measurement equipment setup and 9. When finished testing, press the ON/OFF test, refer to figure 1 and follow the procedure be- switch once. This flashes the xenon tube, dis- low: charging the flash capacitor and shuts down the LT3585. The output capacitor is not com- 1. Set the jumper at JP1 across the DAT and pletely discharged when this operation is MCLR pins. complete. 50V or more may be left on the ca- 2. Set the jumper at JP2 to the HIGH CURRENT pacitor, so the user is cautioned to avoid position. physical contact with the flash tube circuitry at 3. With the power supply disconnected from all times. The flash tube circuitry consists of DC988, set the VBAT voltage between 1.8V to the secondary of T1, D1, C2, R3, R10, C3, T2, 4.2V. Set the VIN voltage between 2.8V and FT1, and Q1. 4.2V. Turn off the power supply. 10. If low current charging is desired, move the 4. Connect the power supply to DC988, referring jumper at JP2 to the LOW CURRENT position to the connection diagram given in figure 1. and repeat steps 4-9 as necessary. 5. Turn on the power supply, verifying that the 11. Monitor the DONE, CHARGE, and TRIGGER VIN and VBAT voltages are correctly set. signals by using the provided test points. Do not make measurements from under the pro- 6. Press the ON/OFF button once. The tective cover. READY/CHARGE LED should glow red as the LT3585 charges the output capacitor and then glow green when it is done. 2