MCP3421 datasheet(22/30 Pages) MICROCHIP

22 / 30 page

MCP3421

DS22003B-page 22

FIGURE 6-3:

Example of Multiple Device

Connection on I2C Bus.

6.2

Device Connection Test

The user can test the presence of the MCP3421 on the

I2C bus line without performing an input data conver-

sion. This test can be achieved by checking an

acknowledge response from the MCP3421 after send-

ing a read or write command. Here is an example using

Figure 6-4:

(a) Set the R/W bit “HIGH” in the address byte.

(b) The MCP3421 will then acknowledge by pulling

SDA bus LOW during the ACK clock and then release

the bus back to the I2C Master.

from the Master and I2C communication can continue.

FIGURE 6-4:

I2C Bus Connection Test.

6.3

Application Examples

The MCP3421 device can be used in a broad range of

sensor and data acquisition applications. Figure 6-5,

shows an example of interfacing with a bridge sensor

for pressure measurement.

FIGURE 6-5:

Example of Pressure

Measurement.

In this circuit example, the sensor full scale range is

±7.5 mV with a common mode input voltage of VDD / 2.

This configuration will provide a full 14-bit resolution

across the sensor output range. The alternative circuit

for this amount of accuracy would involve an analog

gain stage prior to a 16-bit ADC.

Figure 6-6 shows an example of temperature measure-

ment 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 6-6:

Example of Temperature

Measurement.

SDA SCL

(24LC01)

Microcontroller

EEPROM

MCP3421

(TC74)

Temperature

Sensor

(PIC16F876)

1 2 34

5 6 78

SCL

SDA

1 1 0

1A2 A1 A0 1

Start

Bit

Address Byte

Address bits

Device bits

R/W

Start

Bit

MCP3421

Response

NPP301

MCP3421

VIN+

VIN-

VDD

VSS

SCL

SDL

10 µF

0.1 µF

VDD

TO MCU

(MASTER)

VDD

10 k

Resistor

10 k

Thermistor

MCP3421

VIN+

VIN-

VDD

VSS

SCL

SDL

10 µF

0.1 µF

VDD

TO MCU

(MASTER)

VDD

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