Filter Designer has always been a good, solid member of the WEBENCH® family of design software. Now it is not just good; its improvements make it easier than ever to use.
You first start on the WEBENCH Filter Designer landing page. Figure 1 shows the first Filter Designer view: the Filter Designer Requirements page.
Figure 1: Enter your filter design parameters on the Filter Designer Requirements page
The Filter Designer Requirements page has a new small and compact view for selecting the filter type. Initially, you will select your basic filter response along the top: lowpass, highpass, bandpass or bandstop. As you select your filter response, you will notice that the graph changes based on your selection. Figure 1 shows a lowpass filter example.
The next step is to enter your required filter parameters. If you want to take the fast lane, enter your filter’s gain, -3dB frequency, passband ripple, stopband frequency and stopband attenuation. The graph describes these variables. Finally, enter your filter’s power-supply voltages at the bottom of the page. This will help the WEBENCH Filter Designer tool select the correct amplifiers for your filter.
Now click the Start Filter Design button. This takes you to the Filter Designer Visualizer page; see Figure 2.
Figure 2: Pick the signal response or your final filter on the Filter Designer Visualizer page
At the top of Figure 2, you can see that the four graphs contain theoretical responses of the Solutions table filters (bottom of Figure 2). These graphs hold the gain, phase, group-delay and step-response plots. If your hover your mouse over these plots, you will see the filter approximation type, order and coordinates.
The bottom of the page shows a list of all filter approximation types that meet your filter design parameters (Figure 1). The possible approximation types include:
Bessel.
Butterworth.
Linear phase 0.05°.
Linear phase 0.5°.
Transitional Gaussian 6dB.
Transitional Gaussian 12dB.
A variety of Chebyshev filters.
Choose your approximation type by clicking Select. This sends you to the Filter Designer Design Summary page (Figure 3).
Figure 3: Your fully designed filter appears on the Filter Designer Design Summary page
This final circuit diagram includes the recommended amplifier, resistors and capacitors. If you scroll down, you will find the bill of materials (BOM) for each stage.
At this point you are done. If you are curious about your circuit’s response over frequency or time, however, it may be worth it to go to the simulation page by clicking the Sim button at the top of the page (Figure 4).
Figure 4: Initiate SPICE simulations on the optional Filter Designer Simulation page
On the Filter Designer Simulation page, you can execute TI SPICE simulations to graphically acquire simulation data. The simulations possible with this tool are:
Closed-loop frequency response.
Sine wave.
Step response.
In the Filter Designer SPICE environment, you can view the output of the entire circuit as well as the intermediate outputs. You can also adjust the input signals to match your application requirements.
Compared to the first release of Filter Designer, you will find that this tool now offers clarity and simplicity. Go experiment; you will find that you can create your filters faster than ever before.