Presentation on theme: "Applications Engineering. ON Semiconductor Page 2 Doing what we said we would do… or Why customers come to us first..."— Presentation transcript:
ON Semiconductor Page 2 Doing what we said we would do… or Why customers come to us first...
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ON Semiconductor Page 5 Stability in High Speed LDO Regulators An overview of the design relating to low drop out (LDO) regulators. Design guidelines given for the selection of components based on performance and stability requirements. Typical questions that generally need or get asked: What are my input and output requirements? Do I have transient response and magnitude requirements? Can I use a regulator or do I need a controller? What do I need for output capacitors? If my regulator is oscillating, what do I change to stop it? My regulator response is slow, so how do I speed it up without causing it to oscillate? The following slides introduce the different components and block diagrams for LDO regulators.
ON Semiconductor Page 6 Block diagram showing dual LDO controller. Startup, Over current, and Shutdown functions. Band Gap reference for setting DC output voltage. Error Amplifier for controlling external N-channel FET. Second channel FET turn on for shorting input to output. Example LDO Controller Block Diagram MC33567 Dual LDO Controller
ON Semiconductor Page 9 Simplified Block Diagram and Transfer Function A(s)B(s) C(s) + -
ON Semiconductor Page 10 Error Amplifier Detail - A(s) - dominant error amp pole - secondary error amp pole - error amp open loop gain - error amp gain bandwidth Open loop gain greater than 60dB (for less than 0.1% DC output error). Dominant pole usually set for device, although some devices allow adjusting via compensation pin. Gain bandwidth usually specified: Solve for gain bandwidth pole: Error amp designed to have secondary pole greater than gain bandwidth and usually NOT specified. If not, let: For stability analysis, assume frequency range: Error Amplifier A(s) - +
ON Semiconductor Page 11 Feedback Divider Detail - C(s) Want to design divider for DC gain of Av and AC gain of 1. Want V1 independent on reference input, Vr. Need AC gain of 1 for frequencies greater than low frequency pole of error amp. LDO controller with fixed output voltage has divider built-in and optimized. If adding to existing internal divider, follow same guidelines. Use following design guidelines to obtain these result.
ON Semiconductor Page 12 Feedback Divider Detail - C(s) - Continued Divider Design Guidelines: - output voltage (known). - reference voltage (known). - DC gain (solve for). - gain bandwidth (from error amp analysis). - error amp input capacitance (use 10pf if not specified). - first divider resistor (solve for). - second divider resistor (solve for). - divider compensation capacitor (solve for). Final solution for divider transfer function - C(s):
ON Semiconductor Page 13 Output Driver and Load Detail - B(s) Output Capacitor Load Driver Error Amp Output Transfer function for B(s) shown mainly for reference. Too complicated to deal with directly. Will develop design guidelines combining this with other functions to develop overall closed loop transfer function.
ON Semiconductor Page 14 LDO Closed Loop Transfer Function - H(s) Combining A(s), B(s), and C(s) into the expression for H(s) yields the following, which is ONLY shown for reference. The expression for H(s) contains 4 poles and one zero. It is far too complicated to work from directly. Stable response requires poles to be in left hand plane. Analyze pole locations in terms of circuit parameters to make poles be critically or over-damped (no gain peaking in closed loop response).
ON Semiconductor Page 15 LDO Closed Loop Transfer Function - H(s) - Continued LDO Regulator Stability Design Guidelines: - secondary pole for open loop (solve for). - error amp second pole (known or assumed). - driver pole frequency (if driver built in, let ). - gain bandwidth (from error amp analysis). - maximum driver transconductance gain (if driver built in, then is the output impedance of the regulator). - ESR resistance of output capacitor (solve for). - output capacitor (solve for). - overall loop response time (solve for).
ON Semiconductor Page 16 LDO Closed Loop Stability Analysis Conclusion Following design guidelines for voltage divider and stability will yield stable LDO regulator. Design can be optimized for speed with stable operation. Little or no overshoot ringing for output transient currents. Design guidelines can be used in reverse to find error amp gain bandwidth if output capacitor and ESR given. Guidelines show designer which parameters to change to improve stability and/or loop response time for design and/or actual circuits. Guidelines help designer to select proper controller/driver for application. No need to solve for poles/zeros or graphically analyze Bode plots for unity gain phase margins. All conditional guidelines must be met for stability. Guidelines do not guarantee perfect operation due to unknown parasitics and unknowns. Still need to simulate and prototype final design. Following is a design example demonstrating use of guidelines.
ON Semiconductor Page 17 Example Design using Guidelines Example LDO regulator design demonstrating design guidelines. Following graphs show closed loop response for changes in circuit. Circuit at left shows components used for examples. Design guidelines valid for other circuit configurations as well. These include PFET controllers and bipolar (NPN and PNP). Output stability necessary for steady state and transient output currents. Circuit parameters: MC MHz gain bandwidth 50 ohm output impedance Optimized internal divider MTD mhos transconductance gain 2200 pf input capacitance Load - 0.9A (2 ohms) + - Internal Divider Error Amp 1.25V Ref 1.8V Output Load Output Cap 1/2-MC33567 LDO Controller MTD3055 NFET 3.3V Gnd 12V
ON Semiconductor Page 18 Frequency Response Analysis
ON Semiconductor Page 19 Changing the ESR (Rs) of the output capacitor beyond the recommended upper and lower limits tends towards instability (gain peaking). Making the ESR larger speeds up the closed loop response but may increase the magnitude of the initial transient response due to fast changes in output current. Waveform for varying ESR of output capacitor. Rs = 30 milliohms appears optimal. (Co = 10,000uF).
ON Semiconductor Page 20 Waveform for varying output capacitance. Output capacitance less than lower limit tends towards instability (gain peaking). Output capacitance greater than lower limit yield same result (choose type and value to meet ESR requirements). Co > 100uF yields same response. (Rs = 30 milliohms)
ON Semiconductor Page 21 Waveform for changing output driver - gm and Ci. System optimized for using MTD3055. Changing output driver FET can impact loop stability (as shown for this example). If drivers need to be interchangeable, design for higher gain device (gm) and others will be stable (although loop will be slower). MTD3055: gm = 7, Ci = 2200pf MTD3302: gm = 28, Ci = 6600pf (Co = 500uF, Rs = 30mohm)
ON Semiconductor Page 22 Waveform for varying gain bandwidth of controller System optimized for gain bandwidth of MC33567 (5MHz). Making gain bandwidth higher tends towards instability (gain peaking). If designing with error amp compensation, can achieve stability by varying gain bandwidth. Designed for (Af)o = 5MHz. (MTD3055, Co=500uF, Rs=30mohm)
ON Semiconductor Page 23 Transient Response in Stable LDO regulators Transient response for changes in output currents becomes straight forward if LDO regulator closed loop response is stable. Magnitude of transient depends on rate/magnitude of change and ESR of output capacitor. Worse case is step change in output current ( ). Typical Transient Response Time for transient to return to nominal output is proportional to closed loop response time. Following is example of previous regulator design transient response for stable and “less than stable” conditions.
ON Semiconductor Page 24 (for optimized design) (from graph) Transient Response Example for Previous Design From graph, optimized design is critically damped. Over optimized designs slower but stable. Designs outside of guidelines tend to oscillate. Response time and transient amplitude agree with guidelines. MTD3055: gm = 7, Ci = 2200pf (Co = 500uF, Rs = 30mohm) (from graph)
ON Semiconductor Page 25 Specify design output voltage and current (steady state and transient). Follow design guidelines. Select controller best suited. Simulate and prototype circuit. Adjust components for optimal performance. Presentation Summary
ON Semiconductor Page 26 Reduces the total number of discrete & passive components thereby simplifying and or reducing: - System Cost- Procurement activity - Design Complexity- Overall size - Insertion cost - Component count - Performance inconsistencies- Solder reliability issues A small-package-scale integration effort that combines multiple discrete, logic and MOS devices, which may include passive devices (resistors, capacitors, inductors). MicroIntegration TM To Turn This… Into This…
ON Semiconductor Page 27 Customer benefits Improve marketplace opportunities - Performance improvement - Size reduction - Reliability improvements - Component interaction reduction Reduce overhead costs - Inventory Purchase Management - Floor and shelf space - Inspection - Component Obsolescence Lower manufacturing costs - Assembly line setup time - Capital equipment utilization - Equipment costs - Assembled wrong part ( yield) - Reduced insertion costs Lower materials costs - Component costs - Board/substrate costs - Eliminate parts (eg.: shields)
ON Semiconductor Page 28 Three types of products comprise the portfolio +Vcc I/O 1 I/O 2 Transient Protection Arrays Drive Circuits Filter circuits
ON Semiconductor Page 29 MicroIntegration TM Markets Automotive – 42/14v systems, in-car entertainment systems Computing – Power Supplies, Laptop, PC/ MTB PC, Server/ MTB Server, Work Station, Main Frame, Mid-range, Storage, Disk Drives, Peripherals, Printers, Monitors, Scanners Consumer – Power Supplies, Set-Top Boxes, Game Consoles, Smartcards, MP3s, DVDs, VCRs, Camcorders, Digital Cameras, Appliances, CD/ DVD Players, Handheld Game Boys Wireless & Portable – Power Supplies/chargers, Mobile Phones, Cordless Phones, Pagers, HH PC/PDA,Smartcards,.
Transient Voltage Suppression (TVS)
ON Semiconductor Page 31 Transient Protection Applications IC Protection IC Card I/O Input voltage Input Connector
ON Semiconductor Page 33 Low Pass Pi filter with TVS Protection
ON Semiconductor Page 34 Filter Circuits R #1#3 #6 #5 #4 R R
ON Semiconductor Page 36 Drive Circuits
ON Semiconductor Page 37 Analog Device MC33340, MC33342 Battery Fast Charge Controllers MicroIntegration TM Charge Controller Solution
ON Semiconductor Page 38 Today’s Solution For Lithium-Ion Battery Management
ON Semiconductor Page 39 Power Sequencer Application: 3.3V/1.8V Power Sequence Market Segment: Computing End Products: Mother Board
ON Semiconductor Page 40 Lithium Battery Driver Application: Lithium Battery Driver Market Segment: Wireless,Consumer IC control Battery charge End Products: Hand Helds
ON Semiconductor Page 41 Foldback Current Limiter 9V Output Enable Application: Over Current Protection Market Segment: Consumer End Products: Set Top Box- 3 per box.
ON Semiconductor Page 42 uP to FET Driver - Automotive Application: Bias Driver Circuit Market Segment: Automotive uP input 3.3v 12 V Bat FET input End Products: Engine Control Module
ON Semiconductor Page 43 MicroIntegration TM Packages MicroLeadless ™
ON Semiconductor Page 44 MicroLeadless ™ Series.040 x x x Diode Package Transistor Package 0808 Multilead Package
ON Semiconductor Page 45 MicroLeadless ™ Package Platform 80 mils Can Package 4 RC filter/ESD circuits in 1 Device
ON Semiconductor Page 46 Need library for parasitics Bump inductance Need library for parasitics Bonding inductance Ground inductance Flip chip model vs MicroLeadless TM model MicroLeadless TM Flip chip
ON Semiconductor Page 47 Bumped flip chip S21 vs frequency
ON Semiconductor Page 48 MicroLeadless TM S21 vs frequency
ON Semiconductor Page 49 Alex Lara Applications Engineer BSEE from University of Guadalajara 5 years experience in applications Motorola, ON Semiconductor Engineering Lab Manager Multiple articles and application notes
ON Semiconductor Page 50 STANDARD DESCRIPTIVE JOB TITLE FOR AN APPLICATIONS ENGINEER WITHIN THE SEMICONDUCTOR MARKET: Develop new product ideas and specifications; build hardware/software prototypes to verify new product feasibility; design and build new product evaluation and demo boards; develop SPICE macro models and perform system simulations of new products and applications; assist in evaluating and debugging new products; evaluate and build comparative matrices of Competitive products; generate product briefs, data sheets and application notes; conduct on-site design programs of new products with market leading Alpha site companies; and interface with customers and sales staff and provide technical training to Sales and FAE's. Develop new applications concepts New designs implementation Technical Reports Simulation of applications circuits Design-ins Applications Notes Development Troubleshooting Customer Application needs SPICE simulations Development Applications Engineering Key Activities
ON Semiconductor Page 51 Universal Serial Bus ON Semiconduct or ON Semiconductor Applications Engineering Activities for USB Port Applications
ON Semiconductor Page 52 Background USB, or Universal Serial Bus, is a peripheral bus connectivity standard which was conceived, developed and is supported by a group of leading companies in the computer and telecommunication industries – Compaq, DEC, IBM, Intel, Microsoft, NEC and Northern Telecom. The current standard published and implemented on most of the USB devices is version 1.1, nevertheless, the good news is, USB is getting even faster, USB 2.0 promises even higher data transfer rates, up to 480 Mbps. The higher bandwidth of USB 2.0 will allow high performance peripherals, such as monitors, video conferencing cameras, next-generation printers, and faster storage devices to be easily connected to the computer via USB. The higher data rate of USB 2.0 will also open up the possibilities of new and exciting peripherals. USB 2.0 will be a significant step towards providing additional I/O bandwidth and broadening the range of peripherals that may be attached to the PC. USB 2.0 is expected to be both forward and backward compatible with USB 1.1. Existing USB peripherals will operate with no change in a USB 2.0 system. Devices such as mice, keyboards and game pads, will not require the additional performance that USB 2.0 offers and will operate as USB 1.1 devices. All USB devices are expected to co-exist in a USB 2.0 system. The higher speed of USB 2.0 will greatly broaden the range of peripherals that may be attached to the PC. This increased performance will also allow a greater number of USB devices to share the available bus bandwidth, up to the architectural limits of USB. USB 1.1 devices operate at two different levels of speed: Low speed, 1.8Mb/s equivalent to 900KHz (ENCODE, NRZI – Non Return Zero Inverter) Full speed, 12Mb/s equivalent to 6MHz (ENCODE, NRZI – Non Return Zero Inverter) USB 2.0 devices operate are compatible to operate at three different levels of speed: Low speed, 1.8Mb/s equivalent to 900KHz (ENCODE, NRZI – Non Return Zero Inverter) Full speed, 12Mb/s equivalent to 6MHz (ENCODE, NRZI – Non Return Zero Inverter) High speed, 480Mb/s equivalent to 240MHz (ENCODE, NRZI – Non Return Zero Inverter)
ON Semiconductor Page 53 USB allows for multiple peripheral connectivity with one (1) Host 1 PC. Host PC-USB Hub Connection D. Cameras Scanners Add other HUBs Printers PDAs Cell Phones USB Connectivity
ON Semiconductor Page 54 1) ESD Protection and surge protection Devices must comply with the IEC Comply with Telcordia (formerly Bellcore) GR1089 on Surge 8x20usec waveform USB 2.0 now requires Transmission Speeds up to 480Mbits/sec (240MHz), that forces to get lower capacitances (<5pF) 3) EMI Filtering / Termination – Detection Pi Filters (RC), T Filters (LC) Pull up & Pull down resistors for speed detection (Rpu, Rpd) Impedance matching resistors (Zhsdrv) 2) Power Management 5V – 3.3V Regulators Features Power switch (pending to research) USB Device/Circuit/Component Protection USB Power Management for Host and Peripherals USB Signal Integrity USB Opportunities Areas
ON Semiconductor Page 55 Considerations for the USB ESD and TVS Protection IEC Contact and Air Discharge compliance for ESD Protection. Obtaining the lowest insertion loss in the transmission line over a specific operating bandwidth. 5pF USB 2.0 Lower capacitances (less than 5pF ) to support USB Mbits/sec (240MHz). transmission speeds up to 480Mbits/sec (240MHz). [example… ESD/TVS from connection your PDA to your computer] USB ESD Applications
ON Semiconductor Page 56 Typical USB Application Dual USB port protection Single USB port protection HOSTPC D. Cameras PDAsPrintersScannersetc. USB ESD Applications (cont’d)
ON Semiconductor Page 57 USB ESD Applications (cont’d) Compliance with IEC 61000–4–2, ESD International Standard This International Standard relates to the immunity requirements and test methods for electrical and electronic equipment subjected to static electricity discharges, from operators directly, and to adjacent objects. It additionally defines ranges of test levels which relate to different environmental and installation conditions and establishes test procedures. The object of this standard is to establish a common and reproducible basis for evaluating the performance of electrical and electronic equipment when subjected to electrostatic discharges. In addition, it includes electrostatic discharges which may occur from personnel to objects near vital equipment. IEC Test Levels This figure shows a real 8KV contact waveform taken from the ESD generator. This figure shows how the TVS clamps the ESD condition from 8KV to 8.7V, this is the way in which protection against ESD conditions is achieved by using TVS
ON Semiconductor Page 58 USB ESD Applications (cont’d) Low capacitance (less than 5pf) for High speed I/O Data lines (USB 2.0) “Low capacitance (< 5.0 pf)” is one of the most important characteristics that any device intended to be used in USB applications must have in order to minimize the signal attenuation at high speed data rate (480 Mbs, USB 2.0). This characteristic is critical, otherwise, the functionality of the USB system could be affected dramatically during high speed operation. Actually, the USB2.0 spec establishes that the capacitance between I/O data lines lines must no be higher than 5pf. Junction capacitance Model Simplified Junction capacitance Model Theoretical principle used to predict the capacitance between I/O lines for the NUP4201DR2 device C=4.52pf Real Lab measurements The total devices characterized showed an average capacitance value of around 4.45 pf between I/O lines which complies with the USB 2.0 specification (5.0 pf maximum) and reflects the results obtained from the pspice model.
ON Semiconductor Page 59 USB EMI Filtering/Termination EMI Filtering for USB 2.0 Applications. Upstream Downstream Common mode choke inductors For USB 2.0 applications, the usage of common mode choke inductors is very common for EMI filtering purposes since no extra capacitance is added between the I/O data lines.
ON Semiconductor Page 60 USB EMI Filtering/Termination EMI Filtering for USB 2.0 Applications. The equivalent PSPICE circuit for a TDK Choke model ACM P is shown below and also, its configurations for common and differential mode operation: Common Mode Differential Mode
ON Semiconductor Page 61 USB EMI Filtering/Termination EMI Filtering for USB 2.0 Applications. Common and Differential mode response of the TDK Choke model ACM P: Common Mode. In common mode operation, the Choke will have very high attenuation and will not allow the noise to go into the system. As shown in the graph (Common Mode), it starts having high attenuation (-10dB or higher) when the frequency is around 50MHz.shows a high loss characteristics. Differential Mode. In differential mode operation, the choke will not have high attenuation unless the noise signal is very high frequency (5GHz or higher). As shown in the graph, it starts having high attenuation (-10dB or higher) when the frequency is around 5GHz.
ON Semiconductor Page 62 USB EMI Filtering/Termination EMI Filtering for USB 2.0 Applications. TDK Choke Filtering response (Differential mode) V1= USB 2.0 signal applied (240MHz) V2 = Noise signal (5GHz)
ON Semiconductor Page 63 USB EMI Filtering/Termination EMI Filtering for USB 2.0 Applications. V1= USB 2.0 signal applied (240MHz) V2 = Noise signal (5GHz) LC Filter, Filtering response (Differential mode)
ON Semiconductor Page 64 CONCLUSION: Applications Engineers are key in the definition and understanding of the guide lines for New Products Development. Applications Engineers are key to increase the business of the companies because most of the time they represent an added value for the customers which allows to create a relation-ship between the company and the designers, thereby, creation of new business opportunities. Applications Engineers are key to promote the companies’ products by educating the sales department, supporting trade-shows and developing demo-kits. Applications Engineers are key to win design-ins because they can help in suggesting the most proper device for any particular application and also they can show and explain the capability of the companies’ products.