How to use a digital potentiometer to calibrate and control an adjustable power supply. A resistive feedback network is often used to set the output voltage of a power supply, since fixed resistors are simple to use and low cost. However, because a fixed network is not adjustable, the output voltage cannot be accurately set. […]
Tag Archives: app note
App note: Switching regulators for poets
The basics of SMPS design, written by the late analog guru Jim Williams: A problem is that while everyone agrees that working switching regulators are a good thing, everyone also agrees that they are difficult to get working. Switching regulators, with their high efficiency and small size, are increasingly desirable as overall package sizes shrink. […]
App note: Voltage translation circuits
Here is an app note from Texas Instruments describing how to implement basic voltage translation circuits in your design. Today’s complex electronic systems involve a multitude of power planes. In order for these mixed-mode systems to operate properly, some type of voltage translation or clamping is necessary. This allows the different input/outputs (I/O) to communicate […]
App note: Low-cost, low-distortion square to sinewave signal converter
Convert square wave clock signals to low distortion sinewaves: This circuit derives a pure sinewave from a crystal-controlled clock source by using a ring counter to remove the highest-amplitude unwanted harmonics, and filtering the result with an 8th-order lowpass, switched-capacitor elliptic filter
App note: The FET-OR connection for power supplies
Here is a reference design from Maxim how to built a circuit that would seamlessly switch to the secondary power supply if the primary fails. This power-supply sequencer senses a loss of the main supply voltage and, by controlling the two FETs, automatically switches the load to the secondary (backup) supply.
App note: ATtiny40 Qtouch reference design
Here is a reference design from Atmel designed to demonstrate the Qtouch capabilities of the ATtiny40 microcontroller. Only one pin, and a PCB pad is needed to make a capacitive touch button. The reference design is to demonstrate the capabilities of the Atmel ATtiny40, which supports QTouch, the latest capacitive touch technology. The technology requires […]
App note: Collection of Jim Williams’ app notes
In June 2011 the electronics world lost a great man, Jim Williams. He was a analog circuit guru, and a scientist at Linear Technology. Here is a collection of some of the app notes he wrote. Via the Amp hour.
App note: PCB layout for analog to digital converters
NXP provides some PCB layout design guidelines for the ADC modules in their LPC1100 and LPC1300 microcontrollers. These ADC modules, like many microcontrollers, use the power supply voltage as a reference so special care has to be taken to eliminate noise: The microcontrollers in the LPC1100 and LPC1300 families are all equipped with a single […]
App note: Calibration of touch-screens
Here is an app note from Maxim describing how to implement touch screen calibration. It provides the reader with the necessary mathematical tools needed to address issues with mechanical misalignment and scaling due to imperfections in the touch screen: Mechanical misalignment and scaling factors can lead to a mismatch between the values from a touch-panel […]
App note: USB keyboard using MSP430 microcontrollers
This reference design from Texas Instruments shows how to build a USB keyboard design using a MSP430 microcontroller. The article contains the full design: the keyboard matrix, schematic, and the firmware needed to get it going. This application report describes the implementation of a USB keyboard with the following characteristics: • 101 keys, 2 LEDs: […]
App note: Adding a USB printer to your USB host PIC project
Here is an app note from Microchip explaining how to implement the USB printer class on PICs that have USB host capability. This will allow you to connect your project to a printer. The USB Printer Class, used on one of Microchip’s microcontrollers with the USB OTG peripheral, allows an embedded application to utilize a […]
App note: Exposed pads on some IC packages
Some IC packages have a large exposed pad on the bottom. It’s usually connected to the chips ground, and helps cool the chip by transferring heat to the PCB. This app note from Maxim describes the functionality of exposed pads, as well as their proper use.
App note: External current limiting circuit
Learn how to implement fixed current limiting in power-supply designs: In every power supply application there exists the possibility to short the output to ground causing excessive current to be drawn from the power supply. In order to limit the output current from becoming excessive the following examples of current limiting circuits are suggested.
App note: Isolating analog and digital power supplies
Texas Instruments’ advice for isolating digital and analog power supplies in mixed signal circuits. This application note recommends power supply and ground noise-reduction techniques through the use of bypass capacitors and ferrite beads in TI’s PLL-based clock distribution circuits (CDC) devices. This application note also includes a numeric example, calculating the value of bypass and […]
App note: The effect of power supply noise on oscillator phase noise
TI on limiting phase noise from oscillators [PDF!]: This report provides the description of local oscillator (LO) phase noise degradation due to supply noise. Brief theoretical information supported by experiments carried out to demonstrate this degradation is discussed. The importance of selecting appropriate low-noise LDO (low-dropout) linear regulators is discussed.
App note: Theory of operation of linear regulators
Here is an app note from Texas Instruments describing the theory of operation of linear regulators. It goes on to explain and compare various topologies used in integrated linear voltage regulators. The explosive proliferation of battery powered equipment in the past decade has created unique requirements for a voltage regulator that cannot be met by […]
App note: USB Keyboard Demonstration
Here is an USB keyboard demonstration from Atmel. The document describes how to start, and design USB HID class keyboard applications on the STK525 starter kit.
App note: Add high voltage capability to current sense monitors
Here is an app note from Maxim describing how to add high voltage capability up to 300V for the MAX47X (which have been replaced by MAX407X) bidirectional current sense monitors. Since the MAX47X draw low current, a simple floating power supply can be used to power the device even at 300V. The circuit of Figure […]
App note: Using UART Auto-Baud detection on dsPIC30 digital signal processors
Here is a app note from Microchip describing how to implement the Auto-Baud detection for UART operation on dsPIC30 digital signal processors. This function is useful when the oscillator of the dsPIC is unknown and/or the baud rate is unknown. All current dsPIC30F devices have a UART peripheral with Auto Baud capability. The signal on […]
App note: Automatic current-limiting in hot-swap applications
Maxim describes how current limiting functions on their MAX5976 Hot-Swap IC. This chip is useful for hot-swap applications, it allows the safe insertion and removal of circuits while the power is applied. Because the MAX5976 and similar devices use a single resistor to set soft-start and overcurrent protection levels, simple changes to the basic application […]