Tuesday, May 31, 2011

AD7879 Controller Enables Gesture Recognition on Resistive Touch Screens

Resistive touch screens conventionally fill a market niche where only a single touch is required, high resolution is paramount, a stylus facilitates specific functionality, or users must wear gloves. This article offers a new dual-touch concept using an AD7879 resistive touch-screen controller to detect the most common two-finger gestures (zoom, pinch, and rotation) using inexpensive resistive touch screens.

How to Apply DC-to-DC Step-Down (Buck) Regulators Successfully

Typical low-power systems operate with a Li-Ion battery whose output varies from 4.2 V to 3 V, while the ICs require 0.8 V, 1.8 V, 2.5 V, and 2.8 V. A simple way to reduce the voltage is to use an LDO, but power not delivered to the load is lost as heat, making LDOs inefficient when VIN is much greater than VOUT. Switching converters store energy in a magnetic field, enabling high-efficiency regulation.

Tuesday, May 03, 2011

Low-Power, Unity-Gain Difference Amplifier Implements Low-Cost Current Source

In Difference Amplifier Forms Heart of Precision Current Source, published in Analog Dialogue in September 2009, the AD8276 unity-gain difference amplifier and AD8603 micropower op amp were used to implement a precision current source. This article shows how the circuit can be simplified for use in low-cost, low-current applications—achieving ±1.5% accuracy from –40°C to +85°C.

Ask the Apps Eng 40—Switch and Multiplexer Design Considerations for Hostile Environments

This article describes the challenges that engineers face when designing switches and multiplexers into hostile environments, and suggests solutions that the circuit designer can use to protect vulnerable parts. It also introduces some new integrated switches and multiplexers that provide increased overvoltage protection, latch-up immunity, and fault protection to deal with common stress conditions.