Passives What Are Passives? What Do They Do? What’s Out There To Choose From? Which One Is Right For Me? Starting Slide

What Are Passives? Passives are components that can function without a separate power supply The most common are: - Resistors - Capacitors - Inductors There are also diodes, but they won’t be discussed here.

What Do They Do? Basics Common Uses in APA Applications Resistors Capacitors Inductors Common Uses in APA Applications

What Do They Do? Basics Resistors Capacitors Inductors Resists Electrical Potential Resistivity is constant across the frequency band No energy is stored, only dissipated Capacitors Stores energy in the electric field Inductors Store energy in the magnetic field Inductors are discussed on next page

What Do They Do? Common Uses in APA Applications Resistors Voltage Dividers Gain Setting Current Limiting Filtering RC filter may be used to filter the output of a class-D Voltage dividers can be used to set the bias voltage Gain setting is used in such parts as the TPA6120A2, TPA6211A1, TPA0211

What Do They Do? Common Uses in APA Applications Capacitors DC Blocking Power Supply Decoupling Filtering RC Filter may be used to filter the output of a class-D Always use power supply decoupling DC blocking caps are used in almost all of our amplifiers.

What Do They Do? Common Uses in APA Applications Inductors Output Filtering EMI Blocking Power Supply Filtering LC Filter may be used to filter the output of a class-D Sometimes Inductors are used to Filter the Power Supply. Be careful that the inductor has the proper current rating so that it won’t be destroyed, current limit the device, or saturate. Won’t be discussing EMI here

What’s Out There to Choose From? Mounting Methods Resistors Capacitors Inductors

What’s Out There to Choose From? Mounting Methods Thru-Hole Applies to Resistors, Capacitors, and Inductors Component has metal leads that go through holes on the board Surface Mount Component has no leads. It is soldered directly down to pads on the board Surface Mount is the best way to go. Leaded parts can act like antennas.

What’s Out There to Choose From? Resistors Thin Film Low Distortion Excellent TCR (typical between +/-5 and +/-50 PPM/oC) Excellent Tolerance (typical between 0.01 to 0.5%) Low Power Ratings are Common (<1W, often much less) Subject to long lead times Thin Film is best for Hi-Fi AP is not equipped to detect the noise/distortion difference between thin film and thick film or even carbon.

What’s Out There to Choose From? Resistors Thick Film Higher Distortion than Thin Film Good TCR (typical between +/-100 and +/-300, but can go up to +/-1000 PPM/oC) Good Tolerance (typical between 1 and 5%) Low Power Ratings are Common (<1W, often much less) Thick Film is basically a shielded ceramic.

What’s Out There to Choose From? Resistors Ceramic High Distortion TCR is poor (typical > 1000 PPM/oC) Tolerance (typical between 5 to 10%) Generally thru-hole only

What’s Out There to Choose From? Resistors Carbon Film Highest Distortion TCR can vary greatly (typical between +/-300 and greater than -1500 PPM/oC) Tolerance (typical >5%) Generally thru-hole only

What’s Out There to Choose From? Capacitors Film (PPS – Polyphenylene Sulfide, Polypropylene, Polystyrene, Polyester) Can have low ESR Values up to 1uF (typically much lower) TCR < 1% DC/oC Tolerance from +/-2% to +/-10% No Piezoelectric Effect No Shock Noise No audible noise High Stability 0.1395uF/mm3 (ECPU1E105J/K105, 25Vdc) See app note on page http://www.panasonic.com/industrial/components/pdf/031111%20Sample-board.pdf PPS is the best because it has best performance temp and frequency, as well as distortion and dielectric effect. Only goes up to .22uF ECPU(A) is second best for values above .22uF (in panasonic line). See Panasonic’s line of specialty polymers for large value (up to 400+uF) caps that have low esr, low distortion, very good temp coefficients http://www.panasonic.com/industrial/components/specialty_polymer.htm

What’s Out There to Choose From? Capacitors MLCC (Multilayer Ceramic Chip) Can have low ESR Values up to and greater than 100uF Different types have different ratings B TCR= +/10%, Tol = +/-10%, +/-20% X7R TCR= +/-15%, Tol = +/-10%, +/-20% X5R TCR= +/-15%, Tol = +/-10%, +/-20% F TCR= +30, -80% Tol = +80, -20% Y5V TCR= +22, -82%, Tol = +80, -20% Noisier than Film 10 to 20dB more distortion than Film 0.32uF/mm3 (ECJ2FF1E105Z) Film is best, but ceramics have a wider range of values to play with.

What’s Out There to Choose From? Capacitors Tantalum Can have low ESR High capacitance values available Can operate over a broad voltage range TCR typically +/-10% DC/oC Tolerance from +/-5% to +/-20% Price and availability fluctuate. 0.1221uF/mm3 (Kemet T491A105M025AS) 0.0014uF/mm3 (AVX TAJD107K020R) Kemet is 1uF, 25V device AVX is 100uF, 20V device.

What’s Out There to Choose From? Capacitors Electrolytic Can have low ESR Extremely High capacitance values available Can operate over a broad voltage range Tolerance typically +/-20% Very noisy High Distortion Large Footprint 0.0032uF/mm3 (EEUFM1E101) Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

What’s Out There to Choose From? Capacitors ESR ESR is Equivalent Series Resistance Will cause a voltage drop, even when the cap looks like a “short” ESL ESL is Equivalent Series Inductance After a certain frequency, the capacitor begins to “look” like an inductor. The impedance goes up as the frequency goes up. Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

What’s Out There to Choose From? Capacitors Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

What’s Out There to Choose From? Inductors Wound Coil A length of wire wrapped around a core. Can be an air core. Must be shielded. Torroid Core A donut shaped piece of magnetic material around which a wire is wrapped. High Q, small size, compact, good at high frequencies, self shielding. Ferrite Bead Inductive material that maintains a low impedance throughout the low frequency range, but a high impedance at high frequencies. Common Mode Choke Typically made of a Torroid Core, Common Mode Chokes are used to reduce noise across long lengths of line. List goes on…

Which One Is Right For Me? What’s the Application? Other Factors Guidelines

Which One Is Right For Me? What’s the Application? Is component noise an issue? No – System could be noisy to begin with Yes – Quiet system, such as Hi-Fi Is the component in the signal path? No – A pullup resistor, a power supply decoupling cap, inductor in the power supply path. Yes – Gain setting resistors, dc blocking caps, inductors used for filtering the output. Is this a proof of concept prototype or a final product?

Which One Is Right For Me? Other Factors Cost Lead time Is what I want even manufactured?

Which One Is Right For Me? Guidelines Resistors Signal path of quiet system Thin Film Signal path of noisy system Thick Film Out of signal path Thick Film, Ceramic, Carbon Film Lead Times Unacceptable Proof of Concept All will work

Which One Is Right For Me? Guidelines Capacitors Signal path of quiet system PPS, Polypropylene, other film Low ESR! Signal path of noisy system MLCC, Tantalum Power supply decoupling MLCC, Electrolytic, Tantalum Output Filtering Film, MLCC Electrolytic may be better than Tantalum for power supply decoupling because of the large bulk sizes and the relative market stability. Electrolytics tend to have low ESR Look at Panasonic’s SPCaps for output coupling.

Which One Is Right For Me? Guidelines Inductors Proper choice for use (ferrite bead, common mode choke, etc.) Correct Value! Correct Current Rating Correct Frequency Rating Low DCR! Proper choice for use has mostly to do with EMI. This will deal with filters.

Which One Is Right For Me? Guidelines Inductors Correct Value Correct Value is Critical Failure to get correct value can cause: Shift in cutoff frequency Peaking High current draw Inductor saturation Always err on the side of caution! Best to make the inductor too big rather than too small! Proper choice for use has mostly to do with EMI. This will deal with filters.

Which One Is Right For Me? F = cutoff frequency Lp = Ln. C1=C2=10% of 2Cf

Which One Is Right For Me? Inductor Choices RL = 8W Peak will cause problems. Inductor value was too low. The capacitance had to be changed to get the same cutoff frequency. Would have been better to have a higher inductance value and a lower capacitance value.

Which One Is Right For Me? Guidelines Inductors Correct Current Rating Check ISAT of inductor. Ensure it is greater than maximum current draw Look at curves in inductor datasheet. Inductance vs. Current curves will indicate how the inductance drops with current. May be of more value than just ISAT. Correct Frequency Rating Check manufacturer curves to determine at what frequencies the inductance starts to roll off. Low DCR! The lower the better! Proper choice for use has mostly to do with EMI. This will deal with filters.

Which One Is Right For Me? Inductance vs. Current