High-Side Monitor From Analog Devices Precisely Mirrors Input Current Over The Widest Range For Optical Designs

Analog Devices ADL5315

ADL5315 has a mirror ratio of 1:1 over six decades, enabling very accurate current monitoring at very low current levels

About the ADL5315
Analog Devices is introducing a high-side monitor that provides a compact solution for the common and often challenging problem of interfacing an optical power monitoring device, such as a logarithmic amplifier, to the cathode-side of a PIN photodiode. The ADL5315 mirrors the current at the cathode at a 1:1 ratio over a six-decade range, producing an output equal to the reference current monitored. Competing optical current monitors have much higher mirror ratios over narrower ranges, rendering proportional outputs at very low input currents impossible, while discrete solutions are more complex to implement and may require significantly more board space.
ADL5315 high-side monitor
High Linearity, Wide Operating Range
The ADL5315 offers unmatched accuracy, with linearity of only 1% over a wide operating range of six decadesвЂ"from 3 nA to 3 mA. In PIN photodiode modules where only the cathode is available for connection, the high linearity allows the device to be paired with linear or logarithmic amplifiers to form a complete, precise optical power measurement system. While the ADL5315 is optimized for use with PIN photodiodes, its operating range makes it suitable for a broad array of applications that require accurate current mirroring.

Adjustable Input Current, Small Package
The ADL5315 features an adjustable input current limit to protect the photodiode from damage caused by excessive input current. Its miniature single-chip 2 mm x 3 mm package makes it well-suited for space-constrained applications, such as SFP (small form factor pluggable) optical transceiver modules. The ADL5315 is fully specified from -40 degrees C to +85 degrees C, and operates from a single 2.7 V to 8 V supply.

ADI's Optical Portfolio
The ADL5315 joins ADI's portfolio of optical power monitoring devices, including the recently announced ADL5317 bias controller and current monitor for APDs (avalanche photodiodes). The ADL5315 interfaces with ADI's AD8304, AD8305, ADL5306 and ADL5310 optical logarithmic amplifiers; and ADI's ADN2880, ADN2882 and ADN2821 high-speed TIAs (transimpedance amplifiers).

Availability and Pricing
The ADL5315 is sampling now, with volume production scheduled for October 2005. The device is priced at $1.93 per unit in 1,000-piece quantities and is packaged in a 2 mm x 3 mm, 8-lead LFCSP.

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