Mixed signal system: DAC

Hi,

I have rarely used simulink before today. I understand that you can design analog filters using simulink, but can you incorporate a digital block in your system?

I am working on a PWM based DAC, here I am modeling PWM(Digital) using VHDL and output from PWM needs to be passed to a LPF. Is it possible to simulate the whole system in simulink?

Thanks in advance.

Answer 1

[Pragati]

Yes, absolutely. Simulink is well suited for modeling systems that contain both digital and analog components, which makes it a good fit for a PWM-based DAC.

For a system-level study, you do not necessarily need to start with VHDL. You can model the PWM generator behaviorally in Simulink, generate the PWM bitstream, and then feed it into an analog low-pass filter to reconstruct the desired analog signal. This allows you to evaluate key design tradeoffs such as PWM frequency, duty-cycle resolution, filter cutoff frequency, output ripple, settling time, and spectral performance.

A typical model would look like:

Input Signal

|

v

PWM Generator

|

v

PWM Output

|

v

Low-Pass Filter

|

v

Analog Output

Using Mixed-Signal Blockset, you can extend the model beyond the ideal case by including mixed-signal effects such as clock jitter, timing delays, quantization effects, noise sources, and DAC nonidealities. This enables architecture exploration and performance verification before moving to RTL or hardware implementation.

Once you have validated the architecture at the system level, you can replace the behavioral PWM model with your VHDL implementation through HDL co-simulation if RTL verification is required.

For early design and filter optimization, however, a pure Simulink/Mixed-Signal Blockset model is typically the fastest and most productive approach. Based on your description, simulating the complete PWM-DAC-plus-LPF system in Simulink is a very natural workflow and is fully supported.