Datasheet

35
LTC2404/LTC2408
Dimensions in millimeters (inches) unless otherwise noted.
PACKAGE DESCRIPTIO
U
G Package
28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
G28 SSOP 1098
0.13 – 0.22
(0.005 – 0.009)
0
° – 8°
0.55 – 0.95
(0.022 – 0.037)
5.20 – 5.38**
(0.205 – 0.212)
7.65 – 7.90
(0.301 – 0.311)
1234
5
6
7
8 9 10 11 12 1413
10.07 – 10.33*
(0.397 – 0.407)
2526 22 21 20 19 18
17
16 1523242728
1.73 – 1.99
(0.068 – 0.078)
0.05 – 0.21
(0.002 – 0.008)
0.65
(0.0256)
BSC
0.25 – 0.38
(0.010 – 0.015)
NOTE: DIMENSIONS ARE IN MILLIMETERS
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
*
**
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.
These infrared thermocouples are self-contained: 1) they
do not require external cold junction compensation; 2)
they cannot use conventional open thermocouple detec-
tion schemes; and 3) their output impedances are high,
approximately 3kΩ. Alternatively, conventional thermo-
couples can be connected directly to the LTC2408 (not
shown) and cold junction compensation can be provided
by an external temperature sensor connected to a different
channel (see the thermistor circuit on CH5) or by using the
LT1025, a monolithic cold-junction compensator IC.
The components connected to CH7 are used to sense
daylight or photodiode current with a resolution of 300pA.
In the figure, the photodiode is biased in photoconduc-
tive mode; however, the LTC2408 can accommodate
either photovoltaic or photoconductive configurations.
The photodiode chosen (Hammatsu S1336-5BK) pro-
duces an output of 500mA per watt of optical illumina-
tion. The output of the photodiode is dependent on two
factors: active detector area (2.4mm • 2.4mm) and
illumination intensity. With the 5k resistor, optical inten-
sities up to 368W/m
2
at 960nM (direct sunlight is ap-
proximately 1000W/m
2
) can be measured by the LTC2408.
With a resolution of 300pA, the optical dynamic range
covers 6 orders of magnitude.
The application circuits shown connected to the LTC2408
demonstrate the mix-and-match capabilities of this multi-
plexed-input, high resolution ∆Σ ADC. Very low level
signals and high level signals can be accommodated with
a minimum of additional circuitry.
APPLICATIONS INFORMATION
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