Switched Capacitor Circuit, an Overview
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Run Capacitor Info-98582
Run Cap Quiz-98582_Layout 1 4/16/15 10:26 AM Page 1 ® Run Capacitor Info WHAT IS A CAPACITOR? Very simply, a capacitor is a device that stores and discharges electrons. While you may hear capacitors referred to by a variety of names (condenser, run, start, oil, etc.) all capacitors are comprised of two or more metallic plates separated by an insulating material called a dielectric. PLATE 1 PLATE 2 A very simple capacitor can be made with two plates separated by a dielectric, in this PLATE 1 PLATE 2 case air, and connected to a source of DC current, a battery. Electrons will flow away from plate 1 and collect on plate 2, leaving it with an abundance of electrons, or a “charge”. Since current from a battery only flows one way, the capacitor plate will stay BATTERY + – charged this way unless something causes current flow. If we were to short across the plates with a screwdriver, the resulting spark would indicate the electrons “jumping” from plate 2 to plate 1 in an attempt to equalize. As soon as the screwdriver is removed, plate 2 will again collect a PLATE 1 PLATE 2 charge. + BATTERY – Now let’s connect our simple capacitor to a source of AC current and in series with the windings of an electric motor. Since AC current alternates, first one PLATE 1 PLATE 2 MOTOR plate, then the other would be charged and discharged in turn. First plate 1 is charged, then as the current reverses, a rush of electrons flow from plate 1 to plate 2 through the motor windings. -
Switched-Capacitor Circuits
Switched-Capacitor Circuits David Johns and Ken Martin University of Toronto ([email protected]) ([email protected]) University of Toronto 1 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Opamps • Ideal opamps usually assumed. • Important non-idealities — dc gain: sets the accuracy of charge transfer, hence, transfer-function accuracy. — unity-gain freq, phase margin & slew-rate: sets the max clocking frequency. A general rule is that unity-gain freq should be 5 times (or more) higher than the clock-freq. — dc offset: Can create dc offset at output. Circuit techniques to combat this which also reduce 1/f noise. University of Toronto 2 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Double-Poly Capacitors metal C1 metal poly1 Cp1 thin oxide bottom plate C1 poly2 Cp2 thick oxide C p1 Cp2 (substrate - ac ground) cross-section view equivalent circuit • Substantial parasitics with large bottom plate capacitance (20 percent of C1) • Also, metal-metal capacitors are used but have even larger parasitic capacitances. University of Toronto 3 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Switches I I Symbol n-channel v1 v2 v1 v2 I transmission I I gate v1 v p-channel v 2 1 v2 I • Mosfet switches are good switches. — off-resistance near G: range — on-resistance in 100: to 5k: range (depends on transistor sizing) • However, have non-linear parasitic capacitances. University of Toronto 4 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Non-Overlapping Clocks I1 T Von I I1 Voff n – 2 n – 1 n n + 1 tTe delay 1 I fs { --- delay V 2 T on I Voff 2 n – 32e n – 12e n + 12e tTe • Non-overlapping clocks — both clocks are never on at same time • Needed to ensure charge is not inadvertently lost. -
Switched Capacitor Concepts & Circuits
Switched Capacitor Concepts & Circuits Outline • Why Switched Capacitor circuits? – Historical Perspective – Basic Building Blocks • Switched Capacitors as Resistors • Switched Capacitor Integrators – Discrete time & charge transfer concepts – Parasitic insensitive circuits • Signal Flow Graphs • Switched Capacitor Filters – Comparison to Active RC filters – Advantages of Fully Differential filters • Switched Capacitor Gain Circuits • Reducing the Effects of Charge Injection • Tradeoff between Speed and Charge Injection Why Switched Capacitor Circuits? • Historical Perspective – As MOS processes came to the forefront in the late 1970s and early 1980s, the advantages of integrating analog blocks such as active filters on the same chip with digital logic became a driving force for inovation. – Integrating active filters using resistors and capacitors to acturately set time constants has always been difficult, because of large process variations (> +/- 30%) and the fact that resistors and capacitors don’t naturally match each other. – So, analog engineers turned to the building blocks native to MOS processes to build their circuits, switches & capacitors. Since time constants can be set by the ratio of capacitors, very accurate filter responses became possible using switched capacitor techniques Æ Mixed-Signal Design was born! Switched Capacitor Building Blocks • Capacitors: poly-poly, MiM, metal sandwich & finger caps • Switches: NMOS, PMOS, T-gate • Op Amps: at first all NMOS designs, now CMOS Non-Overlapping Clocks • Non-overlapping clocks are used to insure that one set of switches turns off before the next set turns on, so that charge only flows where intended. (“break before make”) • Note the notation used to indicate time based on clock periods: ... (n-1)T, (n-½)T, nT, (n+½)T, (n+1)T .. -
Kirchhoff's Laws in Dynamic Circuits
Kirchhoff’s Laws in Dynamic Circuits Dynamic circuits are circuits that contain capacitors and inductors. Later we will learn to analyze some dynamic circuits by writing and solving differential equations. In these notes, we consider some simpler examples that can be solved using only Kirchhoff’s laws and the element equations of the capacitor and the inductor. Example 1: Consider this circuit Additionally, we are given the following representations of the voltage source voltage and one of the resistor voltages: ⎧⎧10 V fortt<< 0 2 V for 0 vvs ==⎨⎨and 1 −5t ⎩⎩20 V forte>+ 0 8 4 V fort> 0 We wish to express the capacitor current, i 2 , as a function of time, t. Plan: First, apply Kirchhoff’s voltage law (KVL) to the loop consisting of the source, resistor R1 and the capacitor to determine the capacitor voltage, v 2 , as a function of time, t. Next, use the element equation of the capacitor to determine the capacitor current as a function of time, t. Solution: Apply Kirchhoff’s voltage law (KVL) to the loop consisting of the source, resistor R1 and the capacitor to write ⎧ 8 V fort < 0 vvv12+−=ss0 ⇒ v2 =−= vv 1⎨ −5t ⎩16− 8et V for> 0 Use the element equation of the capacitor to write ⎧ 0 A fort < 0 dv22 dv ⎪ ⎧ 0 A fort < 0 iC2 ==0.025 =⎨⎨d −5t =−5t dt dt ⎪0.025() 16−> 8et for 0 ⎩1et A for> 0 ⎩ dt 1 Example 2: Consider this circuit where the resistor currents are given by ⎧⎧0.8 A fortt<< 0 0 A for 0 ii13==⎨⎨−−22ttand ⎩⎩0.8et−> 0.8 A for 0 −0.8 e A fort> 0 Express the inductor voltage, v 2 , as a function of time, t. -
Switched Capacitor Instrumentation Amplifier
LTC1043 Dual Precision Instrumentation Switched Capacitor Building Block FEATURES DESCRIPTIO U ■ Instrumentation Front End with 120dB CMRR The LTC®1043 is a monolithic, charge-balanced, dual ■ Precise, Charge-Balanced Switching switched capacitor instrumentation building block. A pair ■ Operates from 3V to 18V of switches alternately connects an external capacitor to ■ Internal or External Clock an input voltage and then connects the charged capacitor ■ Operates up to 5MHz Clock Rate across an output port. The internal switches have a ■ Low Power break-before-make action. An internal clock is provided ■ Two Independent Sections with One Clock and its frequency can be adjusted with an external capacitor. The LTC1043 can also be driven with an external APPLICATIOU S CMOS clock. The LTC1043, when used with low clock frequencies, ■ Precision Instrumentation Amplifiers provides ultra precision DC functions without requiring ■ Ultra Precision Voltage Inverters, Multipliers precise external components. Such functions are and Dividers differential voltage to single-ended conversion, voltage ■ V–F and F–V Converters inversion, voltage multiplication and division by 2, 3, 4, 5, ■ Sample-and-Hold etc. The LTC1043 can also be used for precise V–F and ■ Switched Capacitor Filters F–V circuits without trimming, and it is also a building block for switched capacitor filters, oscillators and modulators. The LTC1043 is manufactured using Linear Technology’s enhanced LTCMOSTM silicon gate process. , LTC and LT are registered trademarks of Linear Technology -
Capacitive Voltage Transformers: Transient Overreach Concerns and Solutions for Distance Relaying
Capacitive Voltage Transformers: Transient Overreach Concerns and Solutions for Distance Relaying Daqing Hou and Jeff Roberts Schweitzer Engineering Laboratories, Inc. Revised edition released October 2010 Previously presented at the 1996 Canadian Conference on Electrical and Computer Engineering, May 1996, 50th Annual Georgia Tech Protective Relaying Conference, May 1996, and 49th Annual Conference for Protective Relay Engineers, April 1996 Previous revised edition released July 2000 Originally presented at the 22nd Annual Western Protective Relay Conference, October 1995 CAPACITIVE VOLTAGE TRANSFORMERS: TRANSIENT OVERREACH CONCERNS AND SOLUTIONS FOR DISTANCE RELAYING Daqing Hou and Jeff Roberts Schweitzer Engineering Laboratories, Inc. Pullman, W A USA ABSTRACT Capacitive Voltage Transformers (CVTs) are common in high-voltage transmission line applications. These same applications require fast, yet secure protection. However, as the requirement for faster protective relays grows, so does the concern over the poor transient response of some CVTs for certain system conditions. Solid-state and microprocessor relays can respond to a CVT transient due to their high operating speed and iflCreased sensitivity .This paper discusses CVT models whose purpose is to identify which major CVT components contribute to the CVT transient. Some surprises include a recom- mendation for CVT burden and the type offerroresonant-suppression circuit that gives the least CVT transient. This paper also reviews how the System Impedance Ratio (SIR) affects the CVT transient response. The higher the SIR, the worse the CVT transient for a given CVT . Finally, this paper discusses improvements in relaying logic. The new method of detecting CVT transients is more precise than past detection methods and does not penalize distance protection speed for close-in faults. -
Switched-Capacitor Integrator
EE247 Lecture 10 • Switched-capacitor filters (continued) – Switched-capacitor integrators • DDI & LDI integrators – Effect of parasitic capacitance – Bottom-plate integrator topology – Switched-capacitor resonators – Bandpass filters – Lowpass filters – Switched-capacitor filter design considerations • Termination implementation • Transmission zero implementation • Limitations imposed by non-idealities EECS 247 Lecture 10 Switched-Capacitor Filters © 2008 H. K. Page 1 Switched-Capacitor Integrator C φ φ I φ 1 2 1 Vin - φ 2 Cs Vo + T=1/fs C C φ I φ I 1 2 Vin Vin - - C C s s Vo Vo + + φ High φ 1 2 High Æ C Charged to Vin s ÆCharge transferred from Cs to CI EECS 247 Lecture 10 Switched-Capacitor Filters © 2008 H. K. Page 2 Switched-Capacitor Integrator Output Sampled on φ1 φ φ 1 2 Vin CI φ - 1 Cs Vo Vo1 + φ φ φ φ φ Clock 1 2 1 2 1 Vin VCs Vo Vo1 EECS 247 Lecture 10 Switched-Capacitor Filters © 2008 H. K. Page 3 Switched-Capacitor Integrator ( (n-1)T n-3/2)Ts s (n-1/2)Ts nTs (n+1/2)Ts (n+1)Ts φ φ φ φ φ Clock 1 2 1 2 1 Vin Vs Vo Vo1 Φ 1 Æ Qs [(n-1)Ts]= Cs Vi [(n-1)Ts] , QI [(n-1)Ts] = QI [(n-3/2)Ts] Φ 2 Æ Qs [(n-1/2) Ts] = 0 , QI [(n-1/2) Ts] = QI [(n-1) Ts] + Qs [(n-1) Ts] Φ 1 _Æ Qs [nTs ] = Cs Vi [nTs ] , QI [nTs ] = QI[(n-1) Ts ] + Qs [(n-1) Ts] Since Vo1= - QI /CI & Vi = Qs / Cs Æ CI Vo1(nTs) = CI Vo1 [(n-1) Ts ] -Cs Vi [(n-1) Ts ] EECS 247 Lecture 10 Switched-Capacitor Filters © 2008 H. -
Practical Issues Designing Switched-Capacitor Circuit
Practical Issues Designing Switched-Capacitor Circuit ECEN 622 (ESS) Fall 2011 Practical Issues Designing Switched-Capacitor Circuit Material partially prepared by Sang Wook Park and Shouli Yan ELEN 622 Fall 2011 1 / 27 Switched-Capacitor practical issues Practical Issues Designing Switched-Capacitor Circuit MOS switch G G S Cov Cox Cov D S D Ron o Excellent Roff o Non-idea Effect Charge injection, Clock feed-through Finite and nonlinear Ron ELEN 622 Fall 2011 2 / 27 Switched-Capacitor practical issues Practical Issues Designing Switched-Capacitor Circuit Charge Injection G Qch1 Qch2 C VS o During TR. is turned on, Qch is formed at channel surface Qch = WLC OX (VGS −Vth ) When TR. is off, Qch1 is absorbed by Vs, but Qch2 is injected to C o Charge injected through overlap capacitor o Appeared as an offset voltage error on C ELEN 622 Fall 2011 3 / 27 Switched-Capacitor practical issues Practical Issues Designing Switched-Capacitor Circuit Charge Injection Effect CLK Ideal sw. Vout MOS sw. 0.1pF 1V CLK o When clock changes from high to low, Qch2 is injected to C o Compared to ideal sw., MOS sw. creates voltage error on Vout ELEN 622 Fall 2011 4 / 27 Switched-Capacitor practical issues Practical Issues Designing Switched-Capacitor Circuit Decrease Charge Injection Effect (1) CLK Vout W/L = 1/0.4 0.1pF 1V W/L = 10/0.4 o Decrease the effect of Qch o Use either bigger C or small TR. (small ratio of Cox/C) o Increased Ron ELEN 622 Fall 2011 5 / 27 Switched-Capacitor practical issues Practical Issues Designing Switched-Capacitor Circuit Decrease Charge Injection Effect (2) CLK CLKb 10/0.4 3.1/0.4 Vout With dummy sw. -
Aluminum Electrolytic Vs. Polymer – Two Technologies – Various Opportunities
Aluminum Electrolytic vs. Polymer – Two Technologies – Various Opportunities By Pierre Lohrber BU Manager Capacitors Wurth Electronics @APEC 2017 2017 WE eiCap @ APEC PSMA 1 Agenda Electrical Parameter Technology Comparison Application 2017 WE eiCap @ APEC PSMA 2 ESR – How to Calculate? ESR – Equivalent Series Resistance ESR causes heat generation within the capacitor when AC ripple is applied to the capacitor Maximum ESR is normally specified @ 120Hz or 100kHz, @20°C ESR can be calculated like below: ͕ͨ͢ 1 1 ͍̿͌ Ɣ Ɣ ͕ͨ͢ ∗ ͒ ͒ Ɣ Ɣ 2 ∗ ∗ ͚ ∗ ̽ 2 ∗ ∗ ͚ ∗ ̽ ! ∗ ̽ 2017 WE eiCap @ APEC PSMA 3 ESR – Temperature Characteristics Electrolytic Polymer Ta Polymer Al Ceramics 2017 WE eiCap @ APEC PSMA 4 Electrolytic Conductivity Aluminum Electrolytic – Caused by the liquid electrolyte the conductance response is deeply affected – Rated up to 0.04 S/cm Aluminum Polymer – Solid Polymer pushes the conductance response to much higher limits – Rated up to 4 S/cm 2017 WE eiCap @ APEC PSMA 5 Electrical Values – Who’s Best in Class? Aluminum Electrolytic ESR approx. 85m Ω Tantalum Polymer Ripple Current rating approx. ESR approx. 200m Ω 630mA Ripple Current rating approx. 1,900mA Aluminum Polymer ESR approx. 11m Ω Ripple Current rating approx. 5,500mA 2017 WE eiCap @ APEC PSMA 6 Ripple Current >> Temperature Rise Ripple current is the AC component of an applied source (SMPS) Ripple current causes heat inside the capacitor due to the dielectric losses Caused by the changing field strength and the current flow through the capacitor 2017 WE eiCap @ APEC PSMA 7 Impedance Z ͦ 1 ͔ Ɣ ͍̿͌ ͦ + (͒ −͒ )ͦ Ɣ ͍̿͌ ͦ + 2 ∗ ∗ ͚ ∗ ͍̿͆ − 2 ∗ ∗ ͚ ∗ ̽ 2017 WE eiCap @ APEC PSMA 8 Impedance Z Impedance over frequency added with ESR ratio 2017 WE eiCap @ APEC PSMA 9 Impedance @ High Frequencies Aluminum Polymer Capacitors have excellent high frequency characteristics ESR value is ultra low compared to Electrolytic’s and Tantalum’s within 100KHz~1MHz E.g. -
Measurement Error Estimation for Capacitive Voltage Transformer by Insulation Parameters
Article Measurement Error Estimation for Capacitive Voltage Transformer by Insulation Parameters Bin Chen 1, Lin Du 1,*, Kun Liu 2, Xianshun Chen 2, Fuzhou Zhang 2 and Feng Yang 1 1 State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China; [email protected] (B.C.); [email protected] (F.Y.) 2 Sichuan Electric Power Corporation Metering Center of State Grid, Chengdu 610045, China; [email protected] (K.L.); [email protected] (X.C.); [email protected] (F.Z.) * Correspondence: [email protected]; Tel.: +86-138-9606-1868 Academic Editor: K.T. Chau Received: 01 February 2017; Accepted: 08 March 2017; Published: 13 March 2017 Abstract: Measurement errors of a capacitive voltage transformer (CVT) are relevant to its equivalent parameters for which its capacitive divider contributes the most. In daily operation, dielectric aging, moisture, dielectric breakdown, etc., it will exert mixing effects on a capacitive divider’s insulation characteristics, leading to fluctuation in equivalent parameters which result in the measurement error. This paper proposes an equivalent circuit model to represent a CVT which incorporates insulation characteristics of a capacitive divider. After software simulation and laboratory experiments, the relationship between measurement errors and insulation parameters is obtained. It indicates that variation of insulation parameters in a CVT will cause a reasonable measurement error. From field tests and calculation, equivalent capacitance mainly affects magnitude error, while dielectric loss mainly affects phase error. As capacitance changes 0.2%, magnitude error can reach −0.2%. As dielectric loss factor changes 0.2%, phase error can reach 5′. -
Lecture 3 Switched-Capacitor Circuits
ECE1371 Advanced Analog Circuits Lecture 3 Switched-Capacitor Circuits Trevor Caldwell [email protected] Circuit of the Day: Schmitt Trigger Problem: Input is noisy or slowly varying How do we turn this into a clean digital output? 2 ECE1371 Lecture Plan Date Lecture (Wednesday 2-4pm) Reference Homework 2020-01-07 1 MOD1 & MOD2 PST 2, 3, A 1: Matlab MOD1&2 2020-01-14 2 MODN + Toolbox PST 4, B 2: Toolbox 2020-01-21 3 SC Circuits R 12, CCJM 14 2020-01-28 4 Comparator & Flash ADC CCJM 10 3: Comparator 2020-02-04 5 Example Design 1 PST 7, CCJM 14 2020-02-11 6 Example Design 2 CCJM 18 4: SC MOD2 2020-02-18 Reading Week / ISSCC 2020-02-25 7 Amplifier Design 1 2020-03-03 8 Amplifier Design 2 2020-03-10 9 Noise in SC Circuits 2020-03-17 10 Nyquist-Rate ADCs CCJM 15, 17 Project 2020-03-24 11 Mismatch & MM-Shaping PST 6 2020-03-31 12 Continuous-Time PST 8 2020-04-07 Exam 2020-04-21 Project Presentation (Project Report Due at start of class) 3 ECE1371 What you will learn… • Motivation for SC Circuits • Basic sampling switch and charge injection errors • Fundamental SC Circuits Sample & Hold, Gain and Integrator • Other Circuits Bootstrapping, SC CMFB 4 ECE1371 Why Switched-Capacitor? • Used in discrete-time or sampled-data circuits Alternative to continuous-time circuits • Capacitors instead of resistors Capacitors won’t reduce the gain of high output impedance OTAs No need for low output impedance buffer to drive resistors • Accurate frequency response Filter coefficients determined by capacitor ratios (rather than RC time constants and clock frequencies) Capacitor matching on the order of 0.1% - when the transfer characteristics are a function of only a capacitor ratio, it can be very accurate RC time constants vary by up to 20% 5 ECE1371 Basic Building Blocks • Opamps Ideal usually assumed Some important non-idealities to consider include: 1. -
Surface Mount Ceramic Capacitor Products
Surface Mount Ceramic Capacitor Products 082621-1 IMPORTANT INFORMATION/DISCLAIMER All product specifications, statements, information and data (collectively, the “Information”) in this datasheet or made available on the website are subject to change. The customer is responsible for checking and verifying the extent to which the Information contained in this publication is applicable to an order at the time the order is placed. All Information given herein is believed to be accurate and reliable, but it is presented without guarantee, warranty, or responsibility of any kind, expressed or implied. Statements of suitability for certain applications are based on AVX’s knowledge of typical operating conditions for such applications, but are not intended to constitute and AVX specifically disclaims any warranty concerning suitability for a specific customer application or use. ANY USE OF PRODUCT OUTSIDE OF SPECIFICATIONS OR ANY STORAGE OR INSTALLATION INCONSISTENT WITH PRODUCT GUIDANCE VOIDS ANY WARRANTY. The Information is intended for use only by customers who have the requisite experience and capability to determine the correct products for their application. Any technical advice inferred from this Information or otherwise provided by AVX with reference to the use of AVX’s products is given without regard, and AVX assumes no obligation or liability for the advice given or results obtained. Although AVX designs and manufactures its products to the most stringent quality and safety standards, given the current state of the art, isolated component failures may still occur. Accordingly, customer applications which require a high degree of reliability or safety should employ suitable designs or other safeguards (such as installation of protective circuitry or redundancies) in order to ensure that the failure of an electrical component does not result in a risk of personal injury or property damage.