8.5.1 Digital Output
As discussed previously in Overview, the digital output of the ADS79xx devices is SPI compatible. The following tables list the output codes corresponding to various analog input voltages.
Table 8. Ideal Input Voltages for 12-Bit Devices and Output Codes for 12-Bit Devices (ADS7950/51/52/53)
DESCRIPTION |
ANALOG VALUE |
DIGITAL OUTPUT |
Full scale range |
Range 1 → VREF |
Range 2 → 2×VREF |
STRAIGHT BINARY |
Least significant bit (LSB) |
VREF / 4096 |
2VREF / 4096 |
BINARY CODE |
HEX CODE |
Full scale |
VREF – 1 LSB |
2VREF – 1 LSB |
1111 1111 1111 |
FFF |
Midscale |
VREF / 2 |
VREF |
1000 0000 0000 |
800 |
Midscale – 1 LSB |
VREF / 2 – 1 LSB |
VREF – 1 LSB |
0111 1111 1111 |
7FF |
Zero |
0 V |
0 V |
0000 0000 0000 |
000 |
Table 9. Ideal Input Voltages for 10-Bit Devices and Digital Output Codes for 10-Bit Devices (ADS7954/55/56/57)
DESCRIPTION |
ANALOG VALUE |
DIGITAL OUTPUT |
Full scale range |
Range 1 → VREF |
Range 2 → 2×VREF |
STRAIGHT BINARY |
Least significant bit (LSB) |
VREF / 1024 |
2VREF / 1024 |
BINARY CODE |
HEX CODE |
Full scale |
VREF – 1 LSB |
2VREF – 1 LSB |
0011 1111 1111 |
3FF |
Midscale |
VREF / 2 |
VREF |
0010 0000 0000 |
200 |
Midscale – 1 LSB |
VREF / 2 – 1 LSB |
VREF – 1 LSB |
0001 1111 1111 |
1FF |
Zero |
0 V |
0 V |
0000 0000 0000 |
000 |
Table 10. Ideal Input Voltages for 8-Bit Devices and Digital Output Codes for 8-Bit Devices (ADS7958/59/60/61)
DESCRIPTION |
ANALOG VALUE |
DIGITAL OUTPUT |
Full scale range |
Range 1 → VREF |
Range 2 → 2×VREF |
STRAIGHT BINARY |
Least significant bit (LSB) |
VREF / 256 |
2VREF / 256 |
BINARY CODE |
HEX CODE |
Full scale |
VREF – 1 LSB |
2VREF – 1 LSB |
1111 1111 |
FF |
Midscale |
VREF / 2 |
VREF |
1000 0000 |
80 |
Midscale – 1 LSB |
VREF / 2 – 1 LSB |
VREF – 1 LSB |
0111 1111 |
7F |
Zero |
0 V |
0 V |
0000 0000 |
00 |