App note: Solid-State Relays


Solid-state relays introduction from Vishay, Link here (PDF)

MOSFET SSRs feature an optocoupler construction, but have a pair of MOSFETs on the output instead of a phototransistor. A pair of source-coupled MOSFETs emulate an electromechanical relay by providing bidirectional switch capability and a linear contact. No output power supply is required.

App note: Flow sensing in tankless water heaters


Contactless reed switches from Littelfuse provides flow and water presence monitoring. Link here (PDF)

Reed switches and sensors are highly effective solutions for flow sensing applications that can be used for detecting the presence of fluid flow in a system or even measure the rate of fluid flow.

Tankless water heaters are becoming a widely popular solution for water heating needs. The availability of hot water on demand and the perceived limitless supply of hot water make these types of water heaters much more attractive than traditional tank water heaters. These water heaters also provide long-term energy savings since energy is used only when there is a demand for hot water. In order to effectively heat the water when there is a demand, a sensor is needed to detect the flow of water.

App note: Creating a custom flash-based bootstrap loader (BSL)


An application note (PDF!) from TI on creating a custom flash-based bootstrap loader (BSL):

MSP430F5xx and MSP430F6xx devices have the ability to locate their bootstrap loader (BSL) in a protected location of flash memory. Although all devices ship with a standard TI BSL, this can be erased,and a custom made BSL can be programmed in its place. This allows for the creation of using custom communication interfaces, startup sequences, and other possibilities. It is the goal of this document to describe the basics of the BSL memory, as well as describe the TI standard BSL software so it may be reused in custom projects.
This application report also includes a small demonstration BSL that can be used on MSP430G2xx devices. An entry sequence starts the code update and allows the new user code to be sent and stored in flash. A one-byte feedback is provided to indicate status. TA0-based UART communication is used for entry sequence, data, and feedback.

App note: Parallel configuration of H-bridges featuring the MC33932 and MC34932 ICs


Old application note from ON Semiconductors on getting increased power capability by paralleling H-bridges and overcoming current limit imbalance between the two drivers by properly designing the board layout. Link here (PDF)

Two or more H-bridges can be operated in parallel to increase the current handling capacity of the circuit. In this application note, paralleling of H-bridges has been exemplified using a dual H-bridge model MC33932/MC34932. However, paralleling of H-bridges is not an easy task, as any offset or mismatch between the two MOSFETs can cause one of them to hit the over current/temperature limit before the other, forcing very high-current through one of the H-bridges in parallel configuration, which may initiate device shutdown.

The objective of this application note is to present a method to obtain twice the current from a dual H-bridge by paralleling the dual H-bridges located on the same die. This document also presents the various methods to calculate the junction temperature, to ensure the device operates within the thermal limits specified in the data sheet.

App note: Duty cycle and power optimization


Power saving specially on battery operated devices need to be kept, in this application note from ON Semiconductors discussed how to keep duty cycle in which a wireless RF device is operated at a minimum time. Link here (PDF)

Consider a battery powered device (target), which should receive data from a second device (initiator) from time to time. To reduce power consumption, the target switches its receiver on for only a short while, checking if there is any RF activity, and returns to sleep if there is no data to receive.

The ratio of the time ton during which the target is powered on, to the time toff during which the target is powered off is called duty cycle. If for example the target is powered off for 1 second, powered on for 1 millisecond, powered off for 1 second and so on, its duty cycle is 1:1000.

App note: Rectifiers for Power Factor Correction


Another Vishay’s app note about power factor correction this time about the component used and their effects. Link here (PDF)

PFC devices are generally selected base on the speed of their reverse recovery time (trr). Currently for CCM (Continuous-Conduction-Mode) and CRM (Critical Conduction-Mode) PFC devices in market, rectifiers up to 600 V with trr smaller or equal to 35 ns are generally used as CCM PFC; rectifiers up to 600 V with reverse recovery time between 35 ns to 60 ns are used as CRM PFC.

It should be noted there is a tradeoff between forward voltage drops and switching speed; when the reverse recovery time of Ultrafast rectifiers are less than 35 ns, their forward voltage drops would increase significantly, in turn the devices’ forward surge current abilities would be diminished, therefore cautious attention should be taken when selecting the appropriate CCM or CRM PFC devices for various switch mode power supply applications, such that expected performance could be achieved and better reliability would still be ensured.

App note: Power factor correction with ultrafast diodes


Vishay’s app note in keeping the power supplies’ power factor in check with their ultrafast diodes. Link here (PDF)

More and more switched mode power supplies (SMPS) are being designed with an active power factor correction (PFC) input stage. This is mainly due to the introduction of regulations aimed at restricting the harmonic content of the load current drawn from power lines. However, both the user and the power company benefit from PFC, so it just makes good sense.

App note: Stepper motor control using the PIC16F684


Stepper motor control using the PIC16F684 application note (PDF!) from Microchip:

This application note describes how to drive a bipolar stepping motor with the PIC16F684. The Enhanced Capture Compare PWM (ECCP) module is used to implement a microstepping technique known as hightorque microstepping. The microcontroller’s 8 MHz internal oscillator allows the signals generated by the ECCP module to achieve frequencies above the audible range.

App note: Limiting inrush current


Aimtec’s app note on inrush current on power converters and their solution. Link here

Inrush currents can be problematic in circuits that utilize overload protection devices such as fuses and circuit breakers. The selection of overcurrent protection devices is made more complicated when high inrush currents are present. False overload conditions can trigger unwanted protection events.