特点
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
典型应用
典型应用
描述
The LT?3420/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.