MCP3421 Microchip Technology, MCP3421 Datasheet - Page 22

• Manufacturer Part Number: MCP3421
• Description: 18-Bit Analog-to-Digital Converter with I2C Interface and On-Board Reference
• Manufacturer: Microchip Technology

MCP3421
FIGURE 6-3:
Connection on I
6.2
The user can test the presence of the MCP3421 on the
I
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
(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 I
(c) A STOP or repeated START bit can then be issued
from the Master and I
FIGURE 6-4:
6.3
The MCP3421 device can be used in a broad range of
sensor and data acquisition applications.
shows an example of interfacing with a bridge sensor
for pressure measurement.
DS22003B-page 22
2
C bus line without performing an input data conver-
SDA
SCL
6-4:
Start
Device Connection Test
Bit
Application Examples
Microcontroller
(PIC16F876)
MCP3421
1
1
Device bits
2
2
1 0
C Bus.
2
C Master.
2
3
C communication can continue.
Example of Multiple Device
I
SDA SCL
Address Byte
2
C Bus Connection Test.
4
1 A2 A1 A0 1
Address bits
5
6
Temperature
7
EEPROM
(24LC01)
Sensor
(TC74)
8
R/W
9
MCP3421
Response
Figure
Start
Bit
6-5,
FIGURE 6-5:
Measurement.
In this circuit example, the sensor full scale range is
±7.5 mV with a common mode input voltage of V
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
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:
Measurement.
NPP301
Thermistor
10 kΩ
Resistor
10 kΩ
1
2
3
1
2
3
V
V
SCL
V
V
SCL
MCP3421
IN
SS
MCP3421
IN
SS
+
shows an example of temperature measure-
+
V
V
DD
DD
SDL
V
V
SDL
V
V
IN
DD
IN
DD
-
-
6
5
4
6
5
4
Example of Pressure
Example of Temperature
© 2006 Microchip Technology Inc.
0.1 µF
V
0.1 µF
V
DD
DD
10 µF
10 µF
R
R
V
V
DD
DD
(MASTER)
(MASTER)
T
T
O
O
R
R
DD
MCU
MCU
/ 2.