Digital to Analog Converter (Non-Clocked)

The Digital to Analog Converter models a generic DAC.

  • The DAC output continuously responds to the digital signals applied at the inputs.
  • The output voltage follows the input digital word with a propagation delay set by the Output Delay.
  • The output voltage is scaled by the Range parameter and offset by the Offset parameter.

In this topic:

Model Name: Digital to Analog Converter
Simulator: This device is compatible with the SIMPLIS simulator.
Parts Selector Menu Location: Digital Functions > A to D / D to A
Symbol Library: None - the symbol is automatically generated when placed or edited.
Model Library: None - the model is automatically generated when the simulation is run.
Subcircuit Name: SIMPLIS_DIGI1_D_D2A_CONVERTER_Y
Symbol:
 
Multiple Selections: Only one device at a time can be edited.

Editing the Digital to Analog Converter

To configure the Digital to Analog Converter, follow these steps:

  1. Double click the symbol on the schematic to open the editing dialog to the Parameters tab.
  2. Make the appropriate changes to the fields described in the table below the image.
Label Parameter Description
Output Delay Delay from when the input state changes until the output changes
Range Analog output voltage range
Offset Midpoint of analog output voltage range
Code Encoding scheme for binary inputs of the DAC
Initial Condition Initial condition of the DAC output at time=0
Number of Bits Number of input bits for this Digital to Analog Converter

To define the parameters for the interface between this digital component and each analog component connected directly to an input or output pin, follow these steps:

  1. From the Edit Digital to Analog Converter dialog box, click on the Interface tab.
  2. Make the appropriate changes to the fields described in the table below the image.
Label Parameter Description
Input Resistance Input resistance of each DAC input pin
Hysteresis, Threshold Hysteresis and Threshold of the inputs. The hysteretic-window width, HYSTWD is centered around Threshold (TH) voltage. To determine the actual threshold ( TL , THI ), substitute Threshold (TH) and Hysteresis (HYSTWD) in each of the following formulas:
Input Logic Level Actual Threshold
1 Threshold + 0.5 * Hysteresis
0 Threshold - 0.5 * Hysteresis
Output Resistance Output resistance of each DAC output pin

Examples

The test circuit used to generate the waveform examples in the next section can be downloaded here: simplis_062_dac_example.sxsch.

Waveforms

Subcircuit Parameters

Because the Digital to Analog Converter model is generated by a template script when the simulation is executed, a hand-coded model cannot be inserted into a netlist. The template script for this device is simplis_make_a2d_model.sxscr, which licensed users can download as part of a zip archive of all built-in scripts.

To download the zip archive, follow these steps:

Important: You will be prompted to log in with the user name and password you received with your license file. If you don't have the user name and password, you can email support@simplistechnologies.com with your license information to receive the login credentials. Include a screenshot of the dialog which opens when you run the Help > License Diagnostics... menu.
  1. Click http://www.simetrix.co.uk/simetrix80/scripts.zip to download the script archive.
  2. Enter the user name and password you received with your license file.

The following parameter table defines the parameters used in this model.

Parameter Name Label Data Type Range Units Parameter Description
CODE Code String
  • 'UNSIGNED'
  • 'TWOS_COMPLEMENT'
  • 'OFFSET_BINARY'
 none Encoding scheme for binary inputs of the DAC
HYSTWD,
TH		 Hysteresis,
Threshold		 Number min: 1f V Hysteresis and Threshold of the inputs. The hysteretic-window width, HYSTWD is centered around Threshold (TH) voltage. To determine the actual threshold ( TL , THI ), substitute Threshold (TH) and Hysteresis (HYSTWD) in each of the following formulas:
Input Logic Level Actual Threshold
1 Threshold + 0.5 * Hysteresis
0 Threshold - 0.5 * Hysteresis
IC Initial Condition Number
  • 0
  • 1
 none Initial condition of the DAC output at time=0
NUMBITS Number of Bits Integer   none Number of input bits for this Digital to Analog Converter
OUTPUT_OFFSET Offset Number any V Midpoint of analog output voltage range
OUTPUT_RANGE Range Number any V Analog output voltage range
OUT_DELAY Output Delay Number 1f to 1024 s Delay from when the input state changes until the output changes
RIN Input Resistance Number min: 100 Ω Input resistance of each DAC input pin
ROUT Output Resistance Number min: 1m Ω Output resistance of each DAC output pin