LT3905

PRODUCTION

Boost DC/DC Converter with APD Current Monitor

Part Models: 4
1ku List Price: Starting From $3.07

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Overview

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 V_IN Undervoltage Lockout
High Efficiency Step-Up Converter
Selectable 1MHz/2MHz Switching Frequency
Internally Compensated
Internal Soft-Start
2.7V to 12V V_IN 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.

Applications

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

Part Models: 4
1ku List Price: Starting From $3.07

Documentation

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 Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LT3905EUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3905EUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3905IUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3905IUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Apr 11, 2019 - 19_0067 Notification of Wafer Fab Location Change for 0.35 BCD Process
		PCN19_0067_Form Material_Report Delta Qualification Matrix Qualification Results Summary Detailed Parts List Other
LT3905EUD#PBF	PRODUCTION
LT3905EUD#TRPBF	PRODUCTION
LT3905IUD#PBF	PRODUCTION
LT3905IUD#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

Parts	Product Life Cycle	Description
Protection Switches & Controllers 1
LTC4224-1 LTC4224-2		Compact Dual Low Voltage Hot Swap Controller

Tools & Simulations

LTspice 1

LT3905 Demo Circuit - Adjustable APD Bias Supply (2.7-12V to 54V @ 1mA)

Models for the following parts are available in LTspice:

LT3905

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.

Evaluation Kits

LT3905 Demo Board | Boost with APD Current Monitor, 2.7V ≤ VIN ≤ 12V, VOUT = 50V @ 2mA

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Product Details

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.