Diamond Power Products MM-48-AT user manual Analog Output Overview

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 212 - 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.

10.2D/A Resolution

The resolution is the smallest possible change in output voltage. For a 12-bit DAC the resolution is 1/(212), 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 (VREF = Reference voltage):

D/A Code Output voltage for 0–4.096V range

00.000V

10.001V

20.001V

. . . . . .

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
		Diamond-MM-48-AT User Manual V1.01	Page 34