MCP3424 Microchip Technology, MCP3424 Datasheet - Page 16

• Manufacturer Part Number: MCP3424
• Description: Multi-Channel Analog-to-Digital Converter
• Manufacturer: Microchip Technology

MCP3422/3/4
4.9.2
When the user gets the digital output codes from the
device as described in Section 4.9.1 “Digital output
code from device”, the next step is converting the
digital output codes to a measured input voltage.
Equation 4-4
output codes to its corresponding input voltage.
If the sign indicator bit (MSB) is ‘0’, the input voltage
is obtained by multiplying the output code with the LSB
and divided by the PGA setting.
If the sign indicator bit (MSB) is ‘1’, the output code
needs to be converted to two’s complement before
multiplied by LSB and divided by the PGA setting.
Table 4-4
output codes to input voltage.
TABLE 4-4:
DS22088C-page 16
[CHn+ - CHn-]
Input Voltage
V
REF
≤ -V
≥ V
-1 LSB
-2 LSB
- V
2 LSB
1 LSB
- 1 LSB
shows an example of converting the device
0
REF
REF
REF
CONVERTING THE DEVICE
OUTPUT CODE TO INPUT SIGNAL
VOLTAGE
shows an example of converting the
•
PGA]
EXAMPLE OF CONVERTING OUTPUT CODE TO VOLTAGE (WITH 18 BIT SETTING)
011111111111111111
011111111111111111
000000000000000010
000000000000000001
000000000000000000
111111111111111111
111111111111111110
100000000000000000
100000000000000000
Digital Output Code
MSB
0
0
0
0
0
1
1
1
1
(2
x LSB(15.625μV)/PGA = 2.048 (V) for PGA = 1
(2
x LSB(15.625μV)/PGA = 2.048 (V) for PGA = 1
(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+2
= 31.25 (μV) for PGA = 1
(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+2
= 15.625 (μV)for PGA = 1
(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0)x LSB(15.625μV)/PGA
= 0 V (V) for PGA = 1
-(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+2
= - 15.625 (μV)for PGA = 1
-(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+2
= - 31.25 (μV)for PGA = 1
-(2
LSB(15.625μV)/PGA = - 2.048 (V) for PGA = 1
-(2
LSB(15.625μV)/PGA = - 2.048 (V) for PGA = 1
16
16
17
17
+2
+2
+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0) x
+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0) x
15
15
Example of Converting Output Codes to Input Voltage
+2
+2
14
14
+2
+2
EQUATION 4-4:
Where:
If MSB = 0 (Positive Output Code):
If MSB = 1 (Negative Output Code):
13
13
2’s complement
Input Voltage
+2
+2
12
12
+2
+2
Input Voltage
11
11
+2
+2
LSB
10
10
=
+2
+2
(2
9
9
′
+2
+2
s complement of Output Code)
=
=
=
CONVERTING OUTPUT
CODES TO INPUT
VOLTAGE
8
8
+2
+2
© 2009 Microchip Technology Inc.
(Output Code)
1
7
7
+0)x LSB(15.625μV)/PGA
1
See
1’s complement + 1
+2
+2
+0)x LSB(15.625μV)/PGA
0
)x LSB(15.625μV)/PGA
0
6
6
)x LSB(15.625μV)/PGA
+2
+2
Table 4-1
5
5
+2
+2
4
4
+2
+2
•
3
3
----------- -
PGA
LSB
+2
+2
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2
2
+2
+2
1
1
•
+2
+2
----------- -
PGA
LSB
0
0
)
)