MCP3425 datasheet(28/38 Pages) MICROCHIP

28 / 38 page

MCP3425

DS22072B-page 28

FIGURE 6-7:

Example of Pressure

Measurement.

6.2.4

WHEATSTONE BRIDGE TYPE

SENSORS WITH SIGNAL

CONDITIONING

Wheatstone bridge is one of the most common

configurations in the sensor applications. Strain

gauges and pressure sensors are the common

examples. When the sensor output signal is small and

the common mode noise level is large, it needs a signal

conditioning circuit between the sensor and the

MCP3425. Figure 6-8 and Figure 6-9 show examples

of using the MCP6V01 (high precision auto-zeroed Op

Amp) for the sensor signal conditioning. Figure 6-8

shows the interface circuit with a minimum of

components between the sensor and the MCP3425,

but it is not symmetric, and therefore, the ADC input

becomes a single ended. On the other hand, the

Figure 6-9 has a symmetric and differential output, but

requires more components.

FIGURE 6-8:

Simple Signal Conditioning

Design with Asymmetric Circuit.

FIGURE 6-9:

High Performance Signal

Conditioning Design with Symmetric Circuit.

6.2.5

TEMPERATURE MEASUREMENT

Figure 6-10

shows

example

temperature

measurement using a thermistor. This example can

achieve a linear response over a 50

°C temperature

range. This can be implemented using a standard

resistor with 1% tolerance in series with the thermistor.

The value of the resistor is selected to be equal to the

thermistor value at the mid-point of the desired

temperature range.

FIGURE 6-10:

Example of Temperature

Measurement.

NPP301

MCP3425

VIN+

VIN-

VDD

VSS

SCL

SDL

10 µF

0.1 µF

VDD

TO MCU

(MASTER)

VDD

100R

MCP6V01

VDD

0.2R

MCP3425

20 k

1µF

20 k

1µF

VDD

1/2 MCP6V02

200

1µF

VDD

10 nF

200

MCP3425

200

10 k

Resistor

10 k

Thermistor

MCP3425

VIN+

VIN-

VDD

VSS

SCL

SDL

10 µF

0.1 µF

Rpull-up

VDD

TO MCU (MASTER)

VDD

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