MCP3425 datasheet(21/30 Pages) MICROCHIP

21 / 30 page

DS22072A-page 21

MCP3425

FIGURE 6-3:

Example of Multiple Device

Connection on I2C Bus.

6.2

Device Connection Test

The user can test the presence of the MCP3425 on the

I2C bus line without performing an input data conver-

sion. This test can be achieved by checking an

acknowledge response from the MCP3425 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 MCP3425 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 MCP3425 device can be used in a broad range of

sensor and data acquisition applications.

Figure 6-5 shows an example of battery voltage

measurement. The circuit uses a voltage divider if the

battery voltage is greater than the device’s internal

reference voltage (2.048V). The voltage divider circuit

is not needed if the input voltage is less than the

device’s internal reference voltage (2.048V). The user

can adjust the variable resistor (R2) to calibrate the

input voltage to be less than the device’s reference volt-

age (2.046V). The I2C pull-up resistor (Rpull-up) values

are in the range of 5 k

Ω to 10 kΩ for standard and high

speed modes (100 kHz, 400 kHz), and less than 1 k

for fast mode (3.4 MHz). Since the ADC conversion is

performed by using its internal reference voltage

(2.048V), the conversion result is not affected by the

VDD changes or Battery voltage changes within its

operating voltage range (2.7V - 5.5V).

FIGURE 6-5:

Example of Battery Voltage

Measurement.

SDA SCL

(24LC01)

Microcontroller

EEPROM

MCP3425

(TC74)

Temperature

Sensor

(PIC16F876)

SCL

SDA

1A2 A1 A0 1

Start

Bit

Address Byte

Address bits

Device bits

R/W

Start

Bit

MCP3425

Response

700 k

Resistor

MCP3425

VIN+

VIN-

VDD

VSS

SCL

SDL

10 µF

0.1 µF

Rpull-up

VDD

TO MCU

(MASTER)

4.2V

To Load

Battery

Rpull-up

Voltage

Divider

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