Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsData collecting ICsData acquisition IC - DAC 16 Bit SSOP 20

MAX1407/MAX1408/MAX1409/MAX1414

Low-Power, 16-Bit Multichannel DAS with

Internal Reference,10-Bit DACs, and RTC

44 ______________________________________________________________________________________

maintain the reference electrode bias voltage by virtue of

the feedback path through the sensor.

Optical Reflectometry

Figure 26 illustrates the MAX1407/MAX1414 in an optical

reflectometry application. The first DAC is used with an

external transistor to set the bias current through the LED

and the second DAC is used to properly bias and convert

the photodiode current to a voltage measured by the

ADC. The low input bias current into the DAC feedback

pin (FB2) allows the measurement of very small currents.

The DACs provide the flexibility in setting an accurate

and stable LED current and adjusting the bias across the

photodiode. Set the LED bias current externally if the

MAX1409 is used in this application.

Thermistor Measurement

A thermistor connected in a half-bridge configuration

as shown in Figure 27 is used to measure temperatures

very accurately with the MAX1407/MAX1408/

MAX1409/MAX1414. The internal reference drives the

thermistor as well as the ADC, so the reference varia-

tion is cancelled out when calculating the temperature.

The only significant errors are from the R

resistor and

the thermistor itself. The ADC performs a unipolar con-

version with the PGA set to a gain of 1V/V.

Figure 27. Thermistor Application Circuit

MAX1407

MAX1408

MAX1409

MAX1414

REF

DRDY NOT AVAILABLE ON THE MAX1409

BAND

GAP

WAKE-UP

INTERRUPT

GENERATOR

REF

DRDY

INT

AGND

4.7µF

BUF

8:1

MUX

16b ADC

CMP

REF

IN0

8:1

MUX

Figure 28. Thermocouple Application Circuit