November 27, 2013 – Linear Technology Korea (CEO Hong Sa-kwak) announced the launch of the LT3905, a current-mode step-up DC/DC converter designed to bias APD (avalanche photodiode) functionality in optical receivers. The LT3905 provides high-side APD current monitoring with over 50 years of dynamic range and relative accuracy of less than 2% across the 3µA to 3mA range. Maximum APD current is programmed with a single resistor, and a fast current limiter with flag protection safeguards the APD during overload conditions. Adjustable output voltage provides dynamic bias control, and a programmable signal loss indicator flags low APD current. The power switch, Schottky diode, APD current monitor, current limiting, and signal loss indicator are integrated into a single IC packaged in a 3mm x 3mm QFN, delivering a compact solution footprint suitable for APD biasing applications operating at 1MHz or 2MHz switching frequencies.

The LT3905's 65V, 350mA high-efficiency integrated switch delivers high output voltages up to 60V, while the 2.7V to 12V input voltage range accommodates a wide range of input sources. Switching frequency is user-selectable at 1MHz or 2MHz, enabling designers to maximize efficiency while minimizing external component size. A constant-frequency architecture is employed to minimize output noise. Additional features include soft start, internal compensation, and programmable input undervoltage lockout.

The LT3905EUD is available in 3mm x 3mm QFN-16 and starts at $2.55 per unit in 1,000-unit quantities. The industrial-grade version, LT3905IUD, has completed testing and is guaranteed to operate at junction temperatures from -40°C to 125°C, starting at $2.81 per unit in 1,000-unit quantities. Both versions are available immediately. Detailed information is provided at www.linear.com/product/LT3905.