A PIC32 bootloader that supports about every update channel possible: UART, USB-HID, USB-MSD, Ethernet, or SD cards. This application note describes how to use bootloader to upgrade firmware on PIC32 devices without the need for an external programmer or debugger. The source code consists of following implementations of bootloader, 1) UART 2) USB device based […]
Category Archives: app notes
App Note: Adjustable power supply using a digital potentiometer
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. […]
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: Analog sensor signal conditioning circuits
An analog sensor outputs a voltage relative to whatever it measures, as opposed to digital sensors that provide the reading as a number. These voltages sometimes need to be conditioned to be useful. Microchip describes various analog sensor conditioning circuits: Analog sensors produce a change in an electrical property to indicate a change in its […]
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: Mixed signal circuit board layout considerations
Hli located an interesting app note from Cypress called “Mixed Signal Circuit Board Layout Considerations”. “It discusses how to layout a board to have good analog performance, even if you have digital stuff on the same board. Some parts are specific for the Cypress PSoCs, but much of the advice is applicable generally. The PSoCs […]
App note: Driving analog inputs of SAR analog to digital converters
Here is an app note from Microchip describing how to drive analog inputs of Successive Approximation Register analog to digital converters. Driving any A/D Converter (ADC) can be challenging if all issues and trade-offs are not well understood from the beginning. With Successive Approximation Register (SAR) ADCs, the sampling speed and source impedance should be […]
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: Powering portable media players
Here is an app note from Texas Instruments on how to power various systems required for portable media players. These devices require several different voltages, multiple power sources, as well as integrated battery charging. The article describes each individual section in detail.
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.