Also see our Application Notes

• Photo-Diode Current-to-Voltage Converters - Converting the small output current of a photo-diode transducer to a fast responding voltage is often challenging. Here are some ways to use high-speed current feedback and voltage feedback op amps to do the job.

• Unlimited Capacitive Load Drive Op Amp Takes Guesswork Out Of Design - Whether or not an op amp circuit is capable of driving a capacitive load successfully, depends on several factors:
  - Op amp internal architecture (e.g. ROUT, phase margin, compensation, etc.)
  - Closed loop gain and output loading
  - Load capacitance value

• An OrCAD PSPICE Library For The VIP10 High-Speed Op Amp - Creating the op amp SPICE model from the ground-up for simulation is esoteric and often time consuming. National Semiconductor Corporation has an OrCAD Capture library (nationalhighspeed.olb) and PSPICE (nationalhighspeed.lib) model library for the industry-leading VIP10 process high-speed operational amplifiers.

85 KB

• Lower System Cost Solution for Transmitting Video - There are many types of video systems that require the source of a video signal to be located several hundred feet from a video display. A good example of this is a video surveillance system where the camera and display are located at opposite ends of a building.

44 KB

• A Multi-Band GSM/GPRS Power Amplifier Controller - Global System for Mobile Communications (GSM) is the most popular cellular phone system in the world. In a GSM cellular phone or DCS/PCS phone network, Time Division Multiple Access (TDMA) scheme is used in the same cell to provide duplex communication. The Gaussian Minimum Shift Keying (GMSK) modulation scheme is used in both forward and reverse link.

86KB

122

• Audio Amplifier Drives Thermoelectric Cooler For OC-48 Laser Module - A common problem faced by designers of laser-based fiber optic communication systems is maintaining the laser’s characteristics over temperature. As the temperature drifts, the center frequency of the laser will also drift.

• Power Supply Effects on Noise Performance - Understanding the PSRR (Power Supply Rejection Ratio) of analog circuits is an important step to improving overall mixed-signal system performance. Once you know the effects of PSRR you can compensate for them.

109 KB

• Tiny Temperature Sensors for Portable Systems - The last year has seen the introduction of silicon temperature sensors in revolutionary small packages, ideal for portable systems. This brief will discuss trade-offs in accuracy, as well as how to choose between thermistors and analog output IC temperature sensors.

• Four-Speed Fan Control Using Simple Remote Diode Temperature Sensor - The circuit shown in Figure 1 controls the speed of a 12V DC fan using an LM88 Remote Diode Temperature Sensor (RDTS) IC. The LM88 is a dual remote diode temperature sensor with 3 digital comparators and has 3 open-drain outputs (O_SP0, O_SP1 and O_CRIT) that can be used as interrupts or to signal system shutdown.

• Autonomous Fan Control For Processor Systems Using The LM85 - To lower cost, many embedded processor systems include a hardware monitor for rudimentary system diagnostics. This helps ensure that the right person is sent to fix the problem with proper replacement parts. The system diagnostics include detection of power supply over/under voltage, system fan malfunction, and system component overheating.

79 KB

• Send High-Speed ADC Data Remotely And Quietly - In the world of Analog-to-Digital conversion, it is often desired to transport the digital data downstream using a minimal group of wires. This problem is sometimes addressed by using ADCs that are serial data output capable. This solution however, has its set of challenges.

173 KB

124

• 3.3V Cable Driver and Equalizer Drive Mega-Bits @ Many Meters - Transmitting data over long distances is necessary in a wide range of applications. These include telecom and video electrical interfaces running at data rates of up to 400 Mbps over appreciable distances. Long-haul data transmission is easily accomplished with existing devices. The new CLC001 cable driver, CLC012 cable equalizer, and CLC016 data retiming PLL form a robust serial digital interface that transmits megabits of data over hundreds of meters. Figure 1 shows a typical SDI application.

• 2.5 Gbps LVDS 4 x 4 Crosspoint Switch - The unique architecture, diminutive size and flow through pinout of the DS90CP04 (Figure 1) make it an ideal building block for today’s high performance systems. This 4 x 4 crosspoint switch easily expands to build larger or uniquely shaped switch arrays. Digital control pins give the designer direct access to common building block functionality.

44 KB

• A USB-Powered Lithium-Ion Battery Charger - The Universal Serial Bus has become one of the most widespread and convenient ways to connect electronic devices to the PC. Countless modern portable products with built-in USB connectors readily use the USB data bus to transmit and receive data to and from PCs, but many of these battery-powered units still use a separate power supply for battery charging. Sometimes overshadowed by its data bus partner, each USB connection also contains a power supply bus connection.

99 KB

• Switched Capacitor Circuits Provide Efficient and Functional White-LED Drive - Since the conception of cellular phones, PDAs, and handheld computers, there has been a continuing push for more useful and dynamic displays. One of the more drastic changes in miniature display technology has emerged due to the availability of Internet content, pictures, and videos on ever shrinking personal devices. The promise of more content and functionality has caused a migration towards higher resolution color displays.

• Inductive-Based Switching Regulator Circuts Provide High-Efficiency White-LED Drives - Since the conception of cellular phones, PDAs, and handheld computers, there has been a continuing push for more useful and dynamic displays. One of the more drastic changes in miniature display technology has emerged due to the availability of Internet content, pictures, and videos on ever-shrinking personal devices. The promise of more content and functionality has caused a migration towards higher resolution color displays.

• Thermal Performance of National’s LLP Package, Highlighting the LM2750 Regulated Voltage Converter - National’s Leadless Leadframe Package (LLP) provides excellent power dissipation capability in a very small package footprint. The LLP is a chip scale package that requires minimum PCB footprint area. Unlike conventional leaded plastic packages, the LLP contains pads on the bottom of the package for PCB mounting.

• Wide-Input, High-Voltage Buck Converter - When the DC input voltage to a buck converter has a wide range, it becomes important to not only select a suitable switching regulator IC for the application, but to select the power components to handle the worst-case input voltage. For a given component, the worst case may be the maximum input voltage or the minimum input voltage, but in fact may also be somewhere in between.

• DDR-SDRAM Termination Simplified Using A Linear Regulator - With the advent of DDR-SDRAM as the industry standard for memory in desktop computers, laptops and videocards, power management has become a focal point for system designers. Active termination of bus interconnects has required the use of another regulator, increasing cost and system complexity. To specifically address this issue, National Semiconductor has just released the LP2995 DDR Termination Linear Regulator, offering a linear topology in a marketplace dominated by switchers. The implementation of this architecture has been made possible by careful examination of the system requirements. It is the intent of this article to illustrate the actual requirements of DDR-SDRAM termination and compare the two solution topologies.

• Sub-Miniature Buck Converters Tailored For Portable Power Applications - Although there are many step-down converters available in the market, they aren’t as small and precise enough to meet the demands of portable system manufacturers. National Semiconductor has recently released a family of step-down converters that accommodate the need for smaller packages with enhanced performance and features. These are the 2.8V to 5.5V and can operate from a single Li-Ion cell. They feature pin-selectable operating modes and output voltages with 1% to 2% precision as well as very low ripple (5 mV typ. in PWM mode).

• Integration Simplifies TFT Power Designs - Flat-panel video screens are becoming increasingly popular as the cost decreases and the performance increases. One major attraction of these screens is the vast amount of space saved versus the CRT displays that have been the standard for years.

• Powering Portable Devices: Alternatives To Linear Regulators In Step-Down Conversion - In portable products such as PDAs and laptop computers - powering the microprocessor from a Li-Ion battery generally means choosing a small and power-efficient step-down DC-DC converter. In terms of efficiency, a switching regulator is the best choice. However, when component height limitations rule out the use of inductors (as sometimes happens in small devices like cell phones), a converter might take the form of a low dropout (LDO) linear regulator.

56 KB

123

• High voltage, single chip DC/DC regulator optimized for flyback, boost, or forward power converter applications - Telecom and industrial applications such as local area networks (LAN), telephone interfaces (SLICs), ISDN, and xDSL terminals often require low-power multi-output, non-isolated power supplies operating from a non-regulated 12-36 V bus.  The flyback converter is often the preferred solution because of its simplicity, size, low cost, and low part count. National Semiconductor’s newest high-voltage, single-chip, DC/DC regulator is a monolithic integrated circuit specially designed and optimized for flyback, boost, or forward power converter applications.

124 KB

126

• Reworking LLP Chip Scale Package - LLP is a “Leadless Leadframe Package” – there are no leads extending beyond the package body. The contact pads are exposed and flush with the bottom of the package, providing a more compact footprint. Exposed die attach pad when soldered to the board provides a direct path for heat to transfer from the package to the PCB providing excellent thermal performance.

• Delta Sigma PLLs Raise The Standard For Performance - The high performance, low power, and low cost requirements of today’s mobile telephone handsets sometimes put designers between a rock and a hard place. System issues such as integration level, type of architecture, and critical system performance all affect key parameters such as linearity, error rates, power consumption, cost, and time-to-market.

• Partition IEEE 1149.1 SCAN Chains For Manageability! - The proliferation of IEEE 1149.1 supported devices is helping Design for Test (DfT) engineers solve complex test access problems during board test. As ICs become more complex and boards become denser, this dedicated 5-wire serial test bus provides simple, standardized access to internal test nodes unreachable with existing In-Circuit-Test (ICT) methods. Many new board designs are incorporating JTAG as a standard feature for test and programming access – in many cases there is simply no other methodology capable of achieving an acceptable level of board fault coverage, or a cost effective means of programming on-board.