Analog Hotspot

The Texas Instruments ADS5400 analog-to-digital converter (ADC) provides a 1-Gbit/s sample rate with a resolution of 12 bits. With its superior signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR), it’s ideal for extra-needy wireless applications like receivers for radar, electronic intelligence and jamming, and super-highspeed data acquisition. The ADS5400 offers an excellent SNR of 59 dBFS and 75-dBc SFDR in first...

Back about 1965, when I was at Philbrick, we were doing some business with Amelco Semiconductor. I had designed a good hybrid op amp (the Q85AH) and Amelco was trying to build it, but they had some test problems, and some yield problems... so I flew out to help find and solve their problems. The first morning, I put in an hour looking at their test setup. Nothing showed up right away. So we went over to their cafeteria for a cup of coffee. Several engineers ...

What is the most critical performance characteristic for clock chips used with high-performance data converters? The clock signal’s phase noise (or jitter— the time-domain representation of phase noise) is the most critical spec. But also, pay attention to the band over which the jitter has been integrated. Phase noise limits signal-to-noise ratio (SNR). For converter applications, broadband RMS additive jitter is a good...

A good general view of field-oriented control (FOC) can be found in Texas Instruments’ 1998 white paper, “Field Orientated Control of 3-Phase AC Motors”, which can be downloaded for free. For a more recent treatment, though its references go back at least as far as 1980, readers can check out “A Seamless Whole Speed Range Control of Interior PM Synchronous Machine without Position Transducer” by Filka, Balazovic, and...

Regardless of their primary field, sooner or later, most designers have to deal with motor controls. Broadly speaking, there are two methods to incorporating these components in your design. First, designers can start with one of the many choices of microcontrollers that are available and then address the challenges of making the control do what they want. Or second, designers can start at the other end and examine the interaction between motors and...

Addressing lower-cost opticalimage stabilization (OIS) as a major goal, InvenSense Inc. has unveiled the first digital dual-axis pitch and roll (X and Y) gyroscope for camera phones and digital still cameras. Its nextgeneration IDG-2000 family offers the smallest such devices on the market, housed in a 4- by 4- by 0.9-mm quad flat no-lead (QFN) package (Fig. 1). The chip is designed for OIS...

Several practical issues must be addressed when designing the clock tree for a system running synchronously at high speed. First is the signal integrity of the clock itself, i.e., maintaining low jitter and low distortion all the way to the receiver. Second is controlling clock interference with other parts of the system, as well as compliance with electromagnetic- interference (EMI) regulations. These issues are easy to understand, but hard to practice...

Synchronous detection is a measurement method where a stimulus is modulated with some frequency and the response is demodulated to bring the signal back down to base band. Performed when a dc stimulus is not acceptable, it’s widely used in medical and scientific signal conditioning and in capacitive, inductive, or complex impedance measurements. It also allows for the collection of signals in a high-noise environment. Densitydomain signal...

IT’S WELL KNOWN THAT audio power amplifiers like to get a good set of grounds, or noise around the inputs may not be rejected properly, causing hum and buzz. So when a guy called me asking how to clean up his interface from his clean audio signals to his LM3886 power amplifier, whose ground system was pretty noisy and lumpy, I thought for a second and replied that the solution was easy (Fig....

Real-world applications require real-world connections. Generally, that means an analog signal is being digitized somewhere in the system so a microprocessor, ASIC, or FPGA can gather data and make some decision. If you’re new to data converter concepts or if it’s been a long time since your last analog class, the datasheet and design specifications and considerations can seem alien or even outright confusing. So what do all of those acronyms mean, and why should you...

Tessera Technologies reports a conflict (and resolution) between the need to reduce cell-phone imager chip cost and size by producing everhigher- resolution imagers on smaller die and the consumer demand for digital-camera image quality in cell phones. The most recent solutions separate image capture from image processing—in other words, moving that processing, which can be accomplished using relatively cheap CMOS, off the more expensive imager chip. The...

V irtual pushbutton switches on handheld screens may work well, but users also want haptic feedback telling them their button-push was effective. Haptic feedback enthusiasts fondly remember the “buckling spring” technology of the IBM Model M keyboard, but time moves on. Designers who want to include haptic feedback for virtual buttons on a flat piece of glass today should look at Maxim’s MAX11810 and MAX11811 (25-MHz SPI or 400-kHz I2C). These...

HI BOB, Quite some time ago, I sent you a circuit similar to this file (see the figure). You were very kind and answered all of my questions. However, one thing you said was that the noise gain of this circuit is 1. How did you arrive at that value? (If the VOS of the op amp changes by 1 mV, the voltage across the load R will be ...

First, to those of you who have sent me e-mails about my delta-sigma series, thank you. I appreciate the kind words and notification of errors. I also received a few e-mails from some readers, mostly grad students, wanting to let me know they are way smarter than me. They included questions guaranteed to confirm their position— for example, what effect does first- through third-stage parasitic capacitance have on overall differential non-linearity performance ...

What is a chopper-stabilized operational amplifier (op amp)? Chopper-stabilized amps constantly correct low-frequency errors across the inputs of the amplifier. This makes them attractive alternatives to conventional op amps in many industrial, medical, energy, and automotive applications to simplify and accelerate the design process. When designing with chopper-stabilized op amps, you do not need to be concerned about...

When I was about 16, I went to work at Consolidated Cigar Corp. in Broad Brook, Conn. Shade-grown tobacco, under tent-cloth. I bicycled over there every morning in the summer. One of my first jobs in June 1957 was tying. All the tobacco plants had to be tied up with a string, to a wire overhead, to keep them from flopping over in bad weather. There were about 30 plants in a “bent” that was 30 feet long. We got paid about 11 cents per bent, as ...

In a conference room at Analog Devices (ADI), Howard Wisniowski holds a demo board a little bigger than a commemorative stamp about a meter above the table top. An ADI motion sensor and associated circuitry are on the board. Wisniowski drops the board into his other hand. As soon as the board starts to fall free, the motion sensor detects a change in acceleration. Before the board reaches Wisniowski’s lower hand, an LED flashes red and a tiny transducer on the...

HI BOB, I read your response to Arthur Williams in the April 23 column (“Bob’s Mailbox”). The answer as to whether or not to remove the ground plane underneath inductors is: it depends. If the inductors are cans or toroids, it does not matter as the fields are contained inside the inductor. If the inductors are air wound or chip inductors, it might be best to try...

The MCP65X 50-MHz rail-to-rail operational amplifiers from Microchip Technology include an on-chip “mCal” calibration circuit that calibrates offset voltage at powerup or on-command. An internal power on-reset detector or a signal on an external pin initiates calibration. Self-calibration provides a lower initial voltage offset than conventional op amps, along with a means to continually control drift over time and temperature, Microchip says (...

High-reliability oscillator design for satellite systems poses many challenges to the engineering community. The custom nature of the design efforts as well as the quality requirements tend to lead to large, complex specifications that drive cost, design cycle time, and overall product lead time. Materials utilized in design and construction are also limited by environmental constraints such as outgassing, radiation, the use of pure tin, and shock/vibration...