Active Filter Design Made Easy With WEBENCH Active

Active Filter Design Made Easy With WEBENCH® Active Filter Designer Custom Active Filter Designs Including Spice Simulation 1

WEBENCH® Active Filter Designer: Active Filter Designs Within Minutes! Choose a Sensor 1. 1. Select a Filter Type & Signal Bandwidth 2. Design Frequency response 3. Analyze with SPICE 2

Accessing Filter Designer ti. com/webenchfilters Select your filter type Start Design 3

NEW Filter Designer Requirements page 4

Changes to specifications Gain units V/V Gain = 20 V/V -3 d. B = 5 k. Hz fs = 25 k. Hz 5

NEW Visualizer page Choose 0. 5 d. B Chebyshev filter 6

Filter Design Summary page Note Min Op. Amp GBWP values Note Op. Amp Bandwidth – 10 MHz 7

Filter Design adjust gain values Change Gain = 10 Update Note Min Op. Amp GBWP = 2. 104 MHz Gain = 2 Update Note Min Op. Amp GBWP = 3. 032 MHz Note Op. Amp GBWP = 4. 0 MHz 8

Electrical Simulation Click to Run Sim Select Sim Type Closed Loop Frequency Response, Sine Wave Response, Step Response 9

Everything old is new • Is live today • Big changes in Filter Type (page 1) • Bigger changes in Visualizer (page 2) • ti. com/filterdesigner 10

Hands-on Exercise Design Problem: Customer would like a bandstop filter at 1000 k. Hz with the following constraints: Type: Bandstop Center Frequency: 1 k. Hz Gain: 1 Passband Bandwith: 1 k. Hz Stopband Attenuation: -45 d. B Stopband Bandwidth: 100 Hz Goals: Generate a filter What is the output ripple of a 1 V input sine wave at 1 k. Hz? How can this be improved? Dual Supply: +/- 5 V Filter transfer function: Linear phase. 05 deg, 6 th order 11

Hands On Problems • Go to hands on problem set for Signal Chain • Work the problems from the following: • Active Filter Designer – 10 k. Hz Low Pass Filter – Optimize Low Pass Filter – Anti-aliasing filter 12

Active Filter Design Made Easy With WEBENCH® Active Filter Designer Custom Active Filter Designs Including Spice Simulation 13

Common Filter Applications Band limiting filter in a noise reduction application 14

Analog Input Common Filter Applications A. ) RAW SIGNAL Nyquist Sampling f 1 f 2 f 3 f 4 f. C B. ) AQUIRED SIGNAL Nyquist f 1 Sampling Anti-aliasing Filter f 2 15

Filter Types Lowpass, Highpass, Bandpass, and Bandstop Filters • A lowpass filter the bandwidth is equal to DC to fc • A highpass filter has a single stop-band DC to fc, and pass-band f >fc • A bandpass filter has one pass-band, between two cutoff frequencies f. L and fu>f. L, and two stop-bands 0<f<f. L and f >fu. The bandwidth = fu-f. L • A bandstop (band-reject) filter is one with a stop-band f. L<f<fu and two passbands 0<f<f. L and f >fu Adopted from: Introduction to Filter Theory – by David E. Johnson 16

Filter Types 1 -k. Hz Lowpass filter gain vs. frequency 17

Filter Types 1 -k. Hz highpass filter gain vs. frequency 18

Filter Types 1 -k. Hz bandpass filter gain vs. frequency The required level of attenuation is specified at the stop-band BW 19

Filter Types 1 -k. Hz bandstop, or band-reject filter gain vs. frequency 20

Filter Order Gain vs. frequency behavior for different lowpass filter orders Pass-band Stop-band f. C (-3 d. B) 1 k. Hz 21

Filter Order 2 nd-order lowpass, highpass and bandpass gain vs. frequency slopes 22

Why Active Filters? A comparison of a 1 k. Hz passive and active 2 nd-order, lowpass filter • Inductor size, weight and cost for low frequency filters may be prohibitive • Inductor magnetic coupling considerations • Active filter size is small and low in cost • R and C values are easily scaled in active filters 23

Popular Active Filter Topologies 2 nd-order Active filter topologies used by WEBENCH Active Filter Designer Component type for each filter topology Pass Z 1 Z 2 Z 3 Z 4 Z 5 Low R 1 R 2 C 3 C 4 na Low R 1 C 2 R 3 R 4 C 5 High C 1 C 2 R 3 R 4 na High C 1 R 2 C 3 C 4 R 5 Band R 1 R 2 C 3 C 4 R 5 24

Filter Responses Response Considerations • Amplitude vs. frequency • Phase vs. frequency • Step and impulse response characteristics 25

Filter Reponses Common active lowpass filters - amplitude vs. frequency 26

Filter Reponses Common active lowpass filters – other responses Phase vs. frequency Impulse response Group Delay 27

Specify Filter Requirements Select Filter Program Frequencies Click to Continue 28

View / Select Filter Response Performance Graphs Select Filter Approximation 29

Design Summary: Modify your Design Optimizer Dial Topology and Component Specifications Tweak Design Current Design and Design Notes Share or Copy Design 30

Electrical Simulation Click to Run Sim Select Sim Type Closed Loop Frequency Response, Sine Wave Response, Step Response 31

Hands-on Exercise Design Problem: Goals: Design a low pass filter with fast falling after the cut-off frequency. Optimize the amplifier bandwidths to be as low as possible. Filter Low pass Gain = 20 V/V -3 db = 5000 Hz Stop band frequency = 25000 Hz Stop band attenuation = - 45 d. B Chebyshev – allowable ripple <= 0. 5 d. B 32

Filter Designer Landing Page (http: //ti. com/filterdesigner ) Start Design 33

Demo 34

Optimizer Knob 35

Modify Constraints Change inputs and click “Recalculate” 36

Refine Results 37

View/Optimize Filter Response Solutions Filter Optimization Response Chart Solutions Performance Graphs 38

Optimization Graph Modify Axis Parameters 39

Charts 40

Select a Filter Response 41

Design Summary: Filter Topology Configuration Update per stage Filter Stage Schematic BOM 42

Update Gain/Topology per stage Click to update 43

Filter Stage Schematic: View Component Values 44

Filter Stage: Bill of Materials Select Alternate Part 45

Select Alternate Part 46

Design Summary: Modify your Design Optimizer Dial Topology and Component Specifications Tweak Design Current Design and Design Notes Share or Copy Design 47

Optimization Knob 48

Filter Topology Specification Cap seed and tolerances Select Alternative Amplifier Select Topology for all stages 49

Tweak Design 50

Notate and Share Design ID Share Design 51

Electrical Simulation Click to Simulate 52

Electrical Simulation Click to Run Sim Select Sim Type Closed Loop Frequency Response, Sine Wave Response, Step Response 53

Electrical Simulation Waveform List Simulation Results 54

Electrical Simulation Review Past Simulations 55

Export to External Simulator 1) Click export 3) Schematic opens in Tina or Altium (Altium requires v 14 and TI plug in) 2) Choose sim type and export format 56

Design Report View and Print PDF Report 57