MAX1452 查看數據表（PDF） - Maxim Integrated

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MAX1452

Low-Cost Precision Sensor Signal Conditioner

Maxim Integrated 

MAX1452

Low-Cost Precision Sensor

Signal Conditioner

Linear and Nonlinear

Temperature Compensation

Writing 16-bit calibration coefficients into the offset TC

and FSOTC registers compensates first-order tempera-

ture errors. The piezoresistive sensor is powered by a

current source resulting in a temperature-dependent

bridge voltage due to the sensor’s temperature resistance

coefficient (TCR). The reference inputs of the offset TC

DAC and FSOTC DAC are connected to the bridge volt-

age. The DAC output voltages track the bridge voltage as

it varies with temperature, and by varying the offset TC

and FSOTC digital code a portion of the bridge voltage,

which is temperature dependent, is used to compensate

the first-order temperature errors.

The internal feedback resistors (RISRC and RSTC) for

FSO temperature compensation are optimized to 75kΩ

for silicon piezoresistive sensors. However, since the

required feedback resistor values are sensor dependent,

external resistors may also be used. The internal resistors

selection bit in the configuration register selects between

internal and external feedback resistors.

To calculate the required offset TC and FSOTC compen-

sation coefficients, two test-temperatures are needed.

After taking at least two measurements at each tempera-

ture, calibration software (in a host computer) calculates

the correction coefficients and writes them to the internal

EEPROM.

With coefficients ranging from 0000hex to FFFFhex and a

+5V reference, each DAC has a resolution of 76μV. Two

of the DACs (offset TC and FSOTC) utilize the sensor

bridge voltage as a reference. Since the sensor bridge

voltage is approximately set to +2.5V the FSOTC and

offset TC exhibit a step size of less than 38μV.

For high-accuracy applications (errors less than 0.25%),

the first-order offset and FSO TC error should be com-

pensated with the offset TC and FSOTC DACs, and the

residual higher order terms with the lookup table. The

offset and FSO compensation DACs provide unique

compensation values for approximately 1.5°C of tem-

perature change as the temperature indexes the address

pointer through the coefficient lookup table. Changing the

offset does not effect the FSO, however changing the

FSO affects the offset due to nature of the bridge. The

temperature is measured on both the MAX1452 die and

at the bridge sensor. It is recommended to compensate

the first-order temperature errors using the bridge sensor

temperature.

Typical Ratiometric Operating Circuit

Ratiometric output configuration provides an output that is

proportional to the power supply voltage. This output can

then be applied to a ratiometric ADC to produce a digital

value independent of supply voltage. Ratiometricity is an

important consideration for battery-operated instruments

and some industrial applications.

The MAX1452 provides a high-performance ratiometric

output with a minimum number of external components

(Figure 2). These external components include the fol-

lowing:

● One supply bypass capacitor.

● One optional output EMI suppression capacitor.

● Two optional resistors, RISRC and RSTC, for special

sensor bridge types.

SENSOR

Figure 2. Basic Ratiometric Output Configuration

7

5 BDR VDD VDDF 9

6 INP

OUT 2

MAX1452

FSOTC 16

4 INM

ISRC 1

TEST VSS

83

RSTC

0.1µF 0.1µF

RISRC

+5V VDD

OUT

GND

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