LTC2424 datasheet(27/28 Pages) LINER

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LTC2424/LTC2428

APPLICATIONS INFORMATION

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 3k

Ω. Alternatively, conventional thermo-

couples can be connected directly to the LTC2428 (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 LTC2428 can accommodate

either photovoltaic or photoconductive configurations.

The photodiode chosen (Hammatsu S1336-5BK) pro-

duces an output of 500mA per watt of optical illumination.

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 intensities up to

368W/m2 at 960nM (direct sunlight is approximately

1000W/m2) can be measured by the LTC2428. With a

resolution of 1nA, the optical dynamic range covers 5

orders of magnitude.

The application circuits shown connected to the LTC2428

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.

Dimensions in millimeters (inches) unless otherwise noted.

PACKAGE DESCRIPTIO

G Package

28-Lead Plastic SSOP (0.209)

(LTC DWG # 05-08-1640)

G28 SSOP 1098

0.13 – 0.22

(0.005 – 0.009)

° – 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)

12 3

6 7 8

9 10 11 12

10.07 – 10.33*

(0.397 – 0.407)

22 21 20 19 18 17 16 15

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

LTC2424 Datasheet(PDF) 27 Page - Linear Technology

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