LT3420 - Photoflash Capacitor Chargers with Automatic Refresh

Features

  • 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

Typical Application

LT3420 Typical Application
LT3420 Typical Application

Description

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.

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing
RoHS
LT3420EDD-1#PBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3420EDD-1#TRPBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3420EDD#PBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3420EDD#TRPBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3420EMS-1#PBF MS-10 MS E 05-08-1661 Yes
LT3420EMS-1#TRPBF MS-10 MS E 05-08-1661 Yes
LT3420EMS#PBF MS-10 MS E 05-08-1661 Yes
LT3420EMS#TRPBF MS-10 MS E 05-08-1661 Yes


LT3420 Package Drawing
LT3420 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LT3420EDD-1#PBF 3x3 DFN-10 E $3.57 $2.50 Yes
LT3420EDD-1#TRPBF 3x3 DFN-10 E $2.60 Yes
LT3420EDD#PBF 3x3 DFN-10 E $3.57 $2.50 Yes
LT3420EDD#TRPBF 3x3 DFN-10 E $2.60 Yes
LT3420EMS-1#PBF MS-10 E $3.57 $2.50 Yes
LT3420EMS-1#TRPBF MS-10 E $2.56 Yes
LT3420EMS#PBF MS-10 E $3.57 $2.50 Yes
LT3420EMS#TRPBF MS-10 E $2.56 Yes
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC460A LT3420EMS | Strobe Capacitor Charger, High Voltage Supply, 1.8V to 10V Input, 320Vout $150.00
DC646A LT3420EMS | Strobe Capacitor Charger, High Voltage Supply, Input = 1.8V to 16V, Vout = 300V $150.00
DC690A LT3420EMS-1 | Strobe Capacitor Charger, High Voltage Supply, Vbatt = 1.8V - 6V, Vcc = 2.3V - 6V, Strobe Cap = 320V $125.00
Buy Now
Click here to view our complete list of demo boards

Applications

  • Digital Camera Flash Unit
  • Film Camera Flash Unit
  • High Voltage Power Supplies

Product Notifications

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Design Tools

LTspice

LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

To launch a ready to run LTspice demonstration circuit for this part:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice does not automatically open after clicking the link above, you can instead run the simulation by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTspice and open the demonstration circuit by selecting 'Open' from the 'File' menu

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice:
LT3420
LT3420-1

Technical Support