OTP-538U

The OTP-538U is a thermopile sensor in classic TO-46 housing. The sensor is composed of 116
elements of thermocouple in series on a floating micro-membrane having an active diameter of 545
μm and with blacken surface to absorb the incident thermal infrared radiation, which induces a
voltage response at output terminals. The sensor chip is fabricated by a unique front-surface bulk
micromachining technology, which result in smaller size and faster to response ambient
temperature change.
The IR window is a bandpass filter having its 50% cut-on wavelength at 5 μm, and cut-down at
14μm. The sensor responses proportionally to the incident IR radiation and has a constant signal
response up to its cut-off frequency, which is limited by the sensor thermal time constant of tens
millisecond range.
The OTP-538U thermopile sensor provides nearly Johnson-noise-limited performance, which can
be calculated by its ohmic series resistance. A thermistor element, with a lead connected to
ground, is also provided inside the TO package for ambient temperature reference.