1. Products
  2. Power Management
  3. Switching Regulators
  4. Step-Up (Boost) Regulators
  5. Internal Power Switch Boost Regulators
  6. LT3905


Features and Benefits

  • 65V, 350mA Internal DMOS Switch
  • Integrated Schottky Diode
  • 2% Accurate APD Current Monitoring Over the 3μA to 3mA Range
  • Single Resistor Programs Maximum APD Current
  • Fast APD Current Limiter with Indicator
  • Programmable Loss-of-Signal Indicator
  • CTRL Pin Adjusts Output Voltage
  • Programmable VIN Undervoltage Lockout
  • High Efficiency Step-Up Converter
  • Selectable 1MHz/2MHz Switching Frequency
  • Internally Compensated
  • Internal Soft-Start
  • 2.7V to 12V VIN Range
  • Low Shutdown Current: <1μA

Product Details

The LT3905 is a fixed frequency current-mode step-up converter designed to bias avalanche photodiodes (APD) in optical receivers. The LT3905 features high side APD current monitoring over four decades of dynamic range with better than 2% relative accuracy over the 3μA to 3mA range.

The maximum APD current is programmed with a single resistor, and a fast current limiter with indicator protects the APD during overload conditions. Adjustable output voltage provides dynamic bias control, and an adjustable loss-of-signal indicator flags low APD current.

Coupled with the integrated DMOS power switch and Schottky rectifier, the LT3905 provides a compact total solution with few external components and low solution cost. Constant switching frequency results in predictable output noise that is easy to filter.

The LT3905 is available in the tiny footprint (3mm × 3mm) 16-Lead QFN Package.


  • APD Bias
  • PIN Diode Bias
  • Optical Receivers and Modules
  • Fiber Optic Network Equipment

Product Lifecycle icon-recommended 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 (1)

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.

To launch ready-to-run LTspice demonstration circuits for this part:

Step 1: Download and install LTspice on your computer.

Step 2: Click on the link in the section below to download a demonstration circuit.

Step 3: If LTspice does not automatically open after clicking the link below, 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.


Models for the following parts are available in LTspice:


Product Recommendations

LT3905 Companion Parts

Recommended Related Parts

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.

Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
LT3905EUD#PBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
LT3905EUD#TRPBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
LT3905IUD#PBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
LT3905IUD#TRPBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
Wafer Fabrication Data R570 Reliability Data

PCN-PDN Information

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Sample & Buy

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Buy Now Pricing

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Evaluation Boards

Pricing displayed is based on 1-piece.

Up to two boards can be purchased through Analog.com. To order more than two, please purchase through one of our listed distributors.

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.