Sensors for pressure, load, temperature, acceleration andmany other physical quantities often take the form of aWheatstone bridge. These sensors can be extremely linearand stable over time and temperature. However, mostthings in nature are only linear if you don’t bend them toomuch. In the case of a load cell, Hooke’s law states that thestrain in a material is proportional to the applied stress—as long as the stress is nowhere near the material’s yieldpoint (the “point of no return” where the material ispermanently deformed).
OPTOELECTRONICS CIRCUIT COLLECTION
AVALANCHE PHOTODIODE BIAS SUPPLY 1Provides an output voltage of 0V to +80V for reverse biasingan avalanche photodiode to control its gain. This circuit canalso be reconfigured to supply a 0V to –80V output.LINEAR TEC DRIVER–1This is a bridge-tied load (BTL) linear amplifier for drivinga thermoelectric cooler (TEC). It operates on a single +5Vsupply and can drive ±2A into a common TEC.LINEAR TEC DRIVER–2This is very similar to DRIVER–1 but its power output stagewas modified to operate from a single +3.3V supply in orderto increase its efficiency. Driving this amplifier from astandard +2.5V referenced signal causes the output transistorsto have unequal power dissipation.LINEAR TEC DRIVER–3This BTL TEC driver power output stage achieves very highefficiency by swinging very close to its supply rails, ±2.5V.This driver can also drive ±2A into a common TEC. Operationis shown with the power output stage operating on±1.5V supplies. Under these conditions, this linear amplifiercan achieve very high efficiency.
Application ReportThe following collection of analog circuits may be useful in electro-optics applications such as optical networkingsystems. This page summarizes their salient characteristics.
Abstract: This document details the Lakewood (MAXREFDES7#) subsystem reference design, a 3.3V input, ±12V (±15V) output, isolated power supply. The Lakewood reference design includes a 3W primary-side transformer H-bridge driver for isolated supplies, and two wide input range and adjustable output low-dropout linear regulators (LDOs). Test results and hardware files are included.
Abstract: This document details the Riverside (MAXREFDES8#) subsystem reference design, a 3.3V input, 12V (15V) output, isolated power supply. The Riverside reference design includes a 3W primary-side transformer H-bridge driver for isolated supplies, and one wide input range and adjustable output low-dropout linear regulator (LDO). Test results and hardware files are included.
Abstract: This document details the Oceanside (MAXREFDES9#) subsystem reference design, a 3.3V to 15V input,±15V (±12V) output, isolated power supply. The Oceanside design includes a high-efficiency step-up controller, a36V H-bridge transformer driver for isolated supplies, a wide input range, and adjustable output low-dropout linearregulator (LDO). Test results and hardware files are included.
Abstract: With its small size and large load (10W) capability, the MAX13256 H-bridge transformer driver is an attractive solution forcharging supercapacitors (supercaps). However, a large capacitance on the output of the circuit can force the driver into fault modeat startup, due to the high initial charge current. This application note presents a solution that allows users to charge a largecapacitance without going into fault.
Piezoelectric motors are used in digital cameras for autofocus,zooming and optical image stabilization. Theyare relatively small, lightweight and effi cient, but theyalso require a complicated driving scheme. Traditionally,this challenge has been met with the use ofseparatecircuits, including a step-up converter and an oversizedgeneric full-bridge drive IC. The resulting high componentcount and large board space are especially problematicin the design of cameras for ever shrinking cell phones.The LT®3572 solves these problems by combining astep-up regulator and a dual full-bridge driver in a 4mm× 4mm QFN package. Figure 1 shows a typical LT3572Piezo motor drive circuit. A step-up converter is usedto generate 30V from a low voltage power source suchas a Li-Ion battery or any input power source within thepart’s wide input voltage range of 2.7V to 10V. The highoutput voltage of the step-up converter, adjustable upto 40V, is available for the drivers at the VOUT pin. Thedrivers operate in a full-bridge fashion, where the OUTAand OUTB pins are the same polarity as the PWMA andPWMB pins, respectively, and the OUTA and OUTB pinsare inverted from PWMA and PWMB, respectively. Thestep-up converter and both Piezo drivers have their ownshutdown control. Figure 2 shows a typical layout
