The ADL5317 is high-voltage, wide dynamic range biasing and current monitoring device optimized for use with avalanche photodiodes. With the provision of a stable high-voltage supply up to 80V, the bias voltage at the VAPD pin can be varied from 6V to 75V using the 3V compatible VSET pin. The current sourced from VAPD pin, over a range of 5nA to 5mA, is accurately mirrored with an attenuation of 5 and sourced from the IPDM monitor output. In a typical application, the monitor output drives current-input logarithmic amplifier to produce an output representing the optical power incident upon the photodiode. The photodiode anode may be connected to high-speed transimpedance amplifier for the extraction of the data stream.

Signal applied at VSET pin of 0.2V to 2.5V with respect to COMM is amplified by fixed gain of 30 to produce the 6V to 75V bias at pin VAPD. The accuracy of the ADL5317's bias control interface allows for straightforward calibration to maintain constant avalanche multiplication factor of the photodiode over temperature. The current monitor output, IPDM, maintains its high linearity versus photodiode current over the full range of APD bias voltage. The current ratio of 5:1 remains constant as VSET and VPHV are varied.

The ADL5317 is built for exceptional performance and low noise design for all APD modules and systems in next generation optical networks.