LT3485-1| Datasheet

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LT3485-0/LT3485-1/ LT3485-2/LT3485-3 Photoflash Capacitor Chargers with Output Voltage Monitor and Integrated IGBT Drive

FEATURES

DESCRIPTIO

Integrated IGBT Driver Voltage Output Monitor Uses Small Transformers: 5.8mm 5.8mm 3mm Operates from Two AA Batteries, Single Cell Li-Ion or Any Supply from 1.8V up to 10V No Output Voltage Divider Needed No External Schottky Diode Required Charges Any Size Photoflash Capacitor Available in 10-Lead (3mm 3mm) DFN
VERSION LT3485-3 LT3485-0 LT3485-2 LT3485-1 INPUT CURRENT (mA) 750 500 350 225 CHARGE TIME (sec) 2.5 3.7 5.5 4.0*

Fast Charge Time

VIN = VBAT = 3.6V 100uF capacitor, 320V. *50uF capacitor

The LT 3485 family of photoflash chargers are highly integrated ICs containing complete charger and IGBT drive functions. The patented control technique of the LT3485-x allows it to use extremely small transformers. Output voltage detection requires no external circuitry. The turns ratio of the transformer controls the final charge voltage. While charging, the output voltage on the capacitor may be monitored by a microcontroller from the monitor pin. Each device contains an on-chip high voltage NPN power switch, which can withstand negative voltages on the switch pin without an external Schottky diode. The device features a VBAT pin, which allows the use of two AA cells to charge the capacitor. The internal circuitry operates from the VIN pin. The LT3485-0 has a primary current limit of 1.4A, whereas the LT3485-3, LT3485-2, and LT3485-1 have current limits of 2A, 1A and 0.7A respectively. These different current limits result in tightly controlled input currents. The CHARGE pin gives full control of the part
to the user. Driving CHARGE low puts the part in shutdown. The DONE pin indicates when the part has completed charging. The LT3485 series of parts are housed in a leadless (3mm 3mm) DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6636021.

APPLICATIO S

Digital Camera and Cell Phone Flash Charger

TYPICAL APPLICATIO
VBAT 2 AA OR 1 TO 2 Li-Ion 1:10.2 1 4.7uF 2 VBAT DONE CHARGE GND LT3485-0 VCC 5V 0.22uF VIN IGBTPWR IGBTIN IGBTOUT VMONT SW

LT3485-0 Photoflash Charger Uses High Efficiency 3mm Tall Transformers
DANGER HIGH VOLTAGE OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY
320V 4 1M 150uF PHOTOFLASH CAPACITOR 2.2uF 600V TRIGGER T 1 2 TO MICRO 3 C
AVERAGE INPUT CURRENT 0.5A/DIV

A
VOUT 50V/DIV

FLASHLAMP

IGBT
3485 TA01

U
LT3485-0 Charging Waveform
VIN = 3.6V COUT = 100uF 1s/DIV
3485 TA02

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