Norwood, MA -
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.
High Linearity, Wide Operating Range The ADL5315 offers unmatched accuracy, with linearity of
only 1% over a wide operating range of six decades—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 × 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 × 3 mm, 8-lead LFCSP
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