Features and Benefits
- Charges 220µF to 320V in 3.7 Seconds from 5V (LT3420)
- Charges 100µF to 320V in 3.5 Seconds from 5V (LT3420-1)
- Charges Any Size Photoflash Capacitor
- Supports Operation from Two AA Cells or Any Supply from 1.8V to 16V
- Controlled Peak Switch Current:
- 1.4A (LT3420)
- 1.0A (LT3420-1)
- Controlled Input Current:
- 840mA (LT3420)
- 450mA (LT3420-1)
- Uses Standard Transformers
- Efficient Flyback Operation (>75% Typical)
- Adjustable Output
- Automatic Refresh
- Charge Complete Indicator
- No High Voltage Zener Diode Required
- No Output Voltage Divider Required
- Small 10-Lead MSOP Package
- Small 10-Lead (3mm × 3mm) DFN Package
The LT3420/LT3420-1 charge high voltage photoflash capacitors quickly and efficiently. Designed for use in both digital and film cameras, these devices use a flyback topology to achieve efficiencies up to four times better than competing flash modules. A unique adaptive off-time control algorithm* maintains current-limited continuous mode transformer operation throughout the entire charge cycle, eliminating the high inrush current often found in modules.
The LT3420/LT3420-1 output voltage sensing scheme* monitors the flyback voltage to indirectly regulate the output voltage, eliminating an output resistor divider or discrete zener diode. This feature allows the capacitor to be held at a fully charged state without excessive power consumption. Automatic refresh (which can be defeated) allows the capacitor to remain charged while consuming an average input current of about 2mA, at a user-defined refresh rate. A logic high on the CHARGE pin initiates charging, while the DONE pin signals that the capacitor is fully charged.
The LT3420/LT3420-1 are available in 10-Lead MSOP and (3mm × 3mm) DFN packages.
*Protected by U.S. Patents including 6518733.
- Digital Camera Flash Unit
- Film Camera Flash Unit
- High Voltage Power Supplies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (3)
DC690A: Demo Board for the LT3420 Photoflash Capacitor Chargers with Automatic Refresh.
DC646A: Demo Board for the LT3420 Photoflash Capacitor Chargers with Automatic Refresh.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
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Models for the following parts are available in LTspice:
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Sample & Buy
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.