Datasheet LTC2404, LTC2408 (Analog Devices) - 35

LTC2404/LTC2408
U U W U APPLICATIONS INFORMATION
These infrared thermocouples are self-contained: 1) they The photodiode chosen (Hammatsu S1336-5BK) pro- do not require external cold junction compensation; 2) duces an output of 500mA per watt of optical illumina- they cannot use conventional open thermocouple detec- tion. The output of the photodiode is dependent on two tion schemes; and 3) their output impedances are high, factors: active detector area (2.4mm • 2.4mm) and approximately 3kΩ. Alternatively, conventional thermo- illumination intensity. With the 5k resistor, optical inten- couples can be connected directly to the LTC2408 (not sities up to 368W/m2 at 960nM (direct sunlight is ap- shown) and cold junction compensation can be provided proximately 1000W/m2) can be measured by the LTC2408. by an external temperature sensor connected to a different With a resolution of 300pA, the optical dynamic range channel (see the thermistor circuit on CH5) or by using the covers 6 orders of magnitude. LT1025, a monolithic cold-junction compensator IC. The application circuits shown connected to the LTC2408 The components connected to CH7 are used to sense demonstrate the mix-and-match capabilities of this multi- daylight or photodiode current with a resolution of 300pA. plexed-input, high resolution ∆Σ ADC. Very low level In the figure, the photodiode is biased in photoconduc- signals and high level signals can be accommodated with tive mode; however, the LTC2408 can accommodate a minimum of additional circuitry. either photovoltaic or photoconductive configurations.
U PACKAGE DESCRIPTIO Dimensions in millimeters (inches) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640) 10.07 – 10.33* (0.397 – 0.407) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 7.65 – 7.90 (0.301 – 0.311) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 5.20 – 5.38** (0.205 – 0.212) 1.73 – 1.99 (0.068 – 0.078) 0° – 8° 0.65 0.13 – 0.22 0.55 – 0.95 (0.0256) (0.005 – 0.009) (0.022 – 0.037) BSC 0.05 – 0.21 0.25 – 0.38 (0.002 – 0.008) NOTE: DIMENSIONS ARE IN MILLIMETERS (0.010 – 0.015) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.152mm (0.006") PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.254mm (0.010") PER SIDE G28 SSOP 1098 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 35