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Diamond-MM-48-AT User Manual V1.01 Page 34
10. ANALOG OUTPUT OVERVIEW
10.1 Description
Diamond-MM-48-AT uses an 8-channel 12-bit D/A converter (DAC) to provide 8 analog
voltage outputs. A 12-bit DAC can generate output voltages with the precision of a 12-bit
binary number. The maximum value of a 12-bit binary number is 2
12
- 1, or 4095, so the full
range of numerical values that you can write to the analog outputs on Diamond-MM-48-AT is
0 - 4095. The value 0 always corresponds to the lowest voltage in the output range, and the
value 4095 always corresponds to the highest voltage.
⇒ Note: In this manual, the terms analog output, D/A, and DAC are all used interchangeably
to mean the same thing.
10.2 D/A Resolution
The resolution is the smallest possible change in output voltage. For a 12-bit DAC the
resolution is 1/(2
12
), or 1/4096, of the full-scale output range. This smallest change results
from an increase or decrease of 1 in the D/A code, and so this change is referred to as 1
LSB, or 1 least significant bit. The value of this LSB is calculated based on the output range
of the circuit. On the Diamond-MM-48-AT, the output range is fixed at 0-4.096V, making the
formula simple:
1 D/A LSB = 4.096V / 4096 = 1mV
10.3 D/A Conversion Formulas and Tables
The formulas below explain how to convert between D/A codes and output voltages.
Conversion Formulas for Unipolar Output Ranges
Output voltage = D/A code x 1mV
D/A code = Desired output voltage in mV
Example: Desired output voltage = 1.234V = 1234mV; D/A code = 1234
Here is an illustration of the relationship between D/A code and output voltage for a unipolar
output range (V
REF
= Reference voltage):
D/A Code Output voltage for 0–4.096V range
0 0.000V
1 0.001V
2 0.001V
. . . . . .
4095 4.095V
10.4 D/A Output Current
The output current capability of the 4 analog outputs varies according to the output voltage.
Output current can be either sink or source, depending on the load characteristics. Normally
the output will drive a voltage to ground, in which case the output is sourcing current.
D/A voltage Sink current, max Source current, max
0-0.200V -0.5mA 4.0mA
0.201V-0.500V -1.0mA 4.0mA
0.501V-0.900V -2.0mA 4.0mA
0.901V-4.095V -4.0mA 4.0mA