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
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 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)
Demonstration circuit 1956A features the LT3905, a boost DC/DC Converter with APD current monitor that comes in a 3mm × 3mm QFN package. This demo board is designed to convert a 2.7V to 12V input to a 50V output at 2mA. The LT3905 is equipped with indicators for monitoring APD current, overload, and loss-of-signal (LOS) conditions, which can easily be changed with their respective resistors. In addition, the output voltage can be adjusted via the CTRL pin. DC1956A is designed for 1MHz operation but can also be programmed for 2MHz by moving jumper JP2.
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:
LT3905 Companion Parts
Recommended Related Parts
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.
Sample & Buy
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 Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.