Small boost DC-DC converter designed to bias APD

In order to protect the APD during overload conditions, the maximum APD current is programmed with a single resistor and a fast current limiter with indicator. Dynamic bias control is available via an adjustable output voltage, while a programmable loss-of-signal indicator signals low APD current. Supplied in a 3 mm x 3 mm QFN package, the LT3905 integrates a power switch, Schottky diode, APD current monitor, current limit and loss-of-signal indicator into a single IC. A tiny footprint solution for APD biasing applications, the LT3905 operates at 1MHz or 2MHz switching frequency.

With a 2.7V to 12V input voltage range accommodating a wide range of input sources, the LT3905’s internal 65V, 350mA high efficiency switch offers output voltages as high as 60V. Switching frequency is user selectable at 1MHz or 2MHz to allow the designer to optimise efficiency and minimise the size of the external components. Other features include soft-start, internal compensation, programmable V_IN undervoltage lockout, and constant frequency architecture to minimise output noise.

Available from stock in a 3mm x 3mm QFN-16 package, the LT3905EUD is priced starting at $2.55 (USD) each in 1,000-piece quantities. With prices starting at $2.81 (USD) each in 1,000-piece quantities, an industrial grade version, the LT3905IUD, is available from stock and is also tested and guaranteed to operate from a -40°C to 125°C operating junction temperature.