MCP3302-I/ST Microchip Technology, MCP3302-I/ST Datasheet - Page 19

• Manufacturer Part Number: MCP3302-I/ST
• Description: 13-Bit Differential Input, Low Power A/D Converter with SPI Serial Interface
• Manufacturer: Microchip Technology

7.0
7.1
The output code format is a binary two’s complement
scheme with a leading sign bit that indicates the sign of
the output. If the IN+ input is higher than the IN- input,
the sign bit will be a zero. If the IN- input is higher, the
sign bit will be a ‘1’.
The diagram shown in Figure 7-1 shows the output
code transfer function. In this diagram, the horizontal
axis is the analog input voltage and the vertical axis is
the output code of the ADC. It shows that when IN+ is
equal to IN-, both the sign bit and the data word is zero.
As IN+ gets larger with respect to IN-, then the sign bit
is a zero and the data word gets larger. The full scale
output code is reached at +4095 when the input [(IN+)
- (IN-)] reaches V
IN+, the two’s complement output codes will be seen
with the sign bit being a one. Some examples of analog
input levels and corresponding output codes are shown
in Table 7-1
FIGURE 7-1:
2001 Microchip Technology Inc.
Scale Output = -V
Negative Full
-V
SERIAL COMMUNICATIONS
Output Code Format
REF
Output Code Transfer Function.
REF
REF
- 1 LSB. When IN- is larger than
IN+ < IN-
0 + 1111 1111 1111 (+4095)
0 + 1111 1111 1110 (+4094)
0 + 0000 0000 0011 (+3)
0 + 0000 0000 0010 (+2)
0 + 0000 0000 0001 (+1)
0 + 0000 0000 0000 (0)
Output
Code
1 + 1111 1111 1111 (-1)
1 + 1111 1111 1110 (-2)
1 + 1111 1111 1101 (-3)
1 + 0000 0000 0001 (-4095)
1 + 0000 0000 0000 (-4096)
TABLE 7-1:
Code Examples.
Full Scale Positive
(IN+)-(IN-)=V
(IN+)-(IN-) = V
IN+ = (IN-) +2 LSB
IN+ = (IN-) +1 LSB
IN+ = IN-
IN+ = (IN-) - 1 LSB
IN+ = (IN-) - 2 LSB
(IN+)-(IN-) = V
Full Scale Negative
(IN+)-(IN-) = V
Analog Input Levels
REF
REF
REF
REF
-1 LSB
IN+ > IN-
-2 LSB
-2 LSB
-1 LSB
Binary Two’s Complement Output
Scale Output = V
MCP3302/04
Sign
Bit
0
0
0
0
0
1
1
1
1
Positive Full
1111 1111 1111
1111 1111 1110
0000 0000 0010
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 1110
0000 0000 0001
0000 0000 0000
Binary Data
V
REF
DS21697A-page 19
REF
Analog Input
-1 LSB
IN+ - IN-
Voltage
Decimal
+4095
+4094
-4095
-4096
DATA
+2
+1
-1
-2
0