Data Sheet

© 2009 Microchip Technology Inc. DS22226A-page 33
MCP3426/7/8
Equation 6-2 shows an example of calculating the
expected number of output code with various PGA gain
settings for Type K thermocouple output.
EQUATION 6-2: EXPECTED NUMBER OF
OUTPUT CODE FOR TYPE
K THERMOCOUPLE
FIGURE 6-7: Example of Pressure and Temperature Measurement.
log
2
50 mV
62.5μV
PGA
------------------
------------------
⎝⎠
⎜⎟
⎜⎟
⎛⎞
= 9.6 bits for PGA = 1
= 10.6 bits for PGA = 2
= 11.6 bits for PGA = 4
= 12.6 bits for PGA = 8
Expected
Number of Output Code =
Where:
1 LSB = 62.5 µV with 16 Bit configuration.
800 PGA•()ln
2()ln
-------------------------------------
⎝⎠
⎛⎞
=
5kΩ
V
DD
4
5
6
9
CH2-
V
SS
CH3+
Adr1
Adr0
3
12
CH2+
CH3-
2
13
CH1-
CH4+
1
14
CH1+
CH4-
7
8
SDA
SCL
V
DD
MCP3428
11
10
0.1 µF
10 µF
TO MCU
(MASTER)
5kΩ
V
DD
Thermistor
V
DD
Pressure Sensor
V
DD
V
DD
V
DD
R
1
R
2
Thermistor
R
2
R
1
R
1
and R
2
= Voltage Divider
V
IN
R
2
R
1
R
2
+
------------------
V
DD
×=
(NPP301)
Pressure Sensor
(NPP301)
V
IN
V
IN