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292 results found, displaying items 221 - 240
Spread-Spectrum DC-DC Converter Combats EMI
Electromagnetic radiation (called electromagnetic interference or EMI when unwanted) is emitted by almost all electronic systems, including switching regulators. The conventional approach to suppressing EMI is to block the radiation at its source...
Digitally Controlled Pots Program PWM's Features
The circuit described here is a switching 12-V, 10-A power supply whose topology is that of a conventional single-switch forward converter (Fig. 1). To derive the pulse-width modulation for its...
Low-Voltage Series Reference Draws Only 2.4 μA
For systems with miniscule power budgets, implementing a low-power voltage reference involves many compromises. One design option is the low-voltage shunt reference. Available since the birth of the bandgap cell, this device traditionally operates...
Latching Overvoltage Indicator Handles Large Overloads
This overvoltage detector can be connected to any dc power source (Fig. 1). Its purpose is to provide a visual indication of when the voltage exceeds a preset value, which may range from around 3 V...
Dual-Regulated Voltages Control STN-LCD Contrast
Generating a stable, dual-voltage, LCD-contrast supply can be difficult, particularly if the two voltage amplitudes must track each other with respect to a given reference level. In Figure 1, the ±20 V...
Micropower Circuit Offers Automatic Shutdown And Low-Battery Lockout
This micropower circuit provides shutdown, power-up, and low-battery lockout functions automatically, without the need for software or operator control (Fig. 1). Featuring 2.3-V hysteresis, the...
Differential Feedback Produces Two Regulated Outputs From One
The need often arises for a circuit with two regulated outputs from a single supply (controller). In some cases, the output won't require particularly tight regulation. Instead, only adequate regulation will be necessary for the parts to be...
Resistive Dummy Load Draws Constant Current From 1.2 To 50 V
This dummy-load circuit has been in use at Maxim for more than 10 years (see the figure). It's useful for testing power supplies and power amplifiers as well as drivers for LEDs, relays, and...
Negative-Resistance Load Canceller Helps Drive Heavy Loads
Though not difficult, driving a load from a voltage reference IC requires some attention. After determining the supply voltage and output voltage, various other design parameters need to be considered. These include the output-voltage temperature...
Flyback Power Supply Powers Subscriber Line Interface Circuit
Cable and xDSL modems are experiencing increasing popularity. For this reason, many designs are now required to interface with existing telephones at the subscriber's location. The subscriber line interface circuit (SLIC) within the modem has the...
Hot-Swap Controller Creates A Flexible Current Limiter
Current limiting is often necessary to protect a power supply from short circuits and load surges, which can pull the supply voltage low. ICs containing p-channel MOSFETs and adjustable current limits are available for this purpose. Yet most are...
Precision Current Source Design Employs Bootstrapped Integrator
The general-purpose current source in Figure 1 is accurate within 1% and insensitive to temperature (less than 50 ppm/°C). It also has a high output resistance and a wide compliance range (4.3 to 34...
Stable IQ Reduces DC-DC Losses
Inexpensive, low-power dc-dc converters can suffer power inefficiencies if the system isn't designed properly. In a low-power converter, the system efficiency is greatly affected by the controller's quiescent current. The MC34063A is...
Digital/Analog Hybrid Circuit Calculates Battery Life Expectancy
The convenience and reliability of portable electronic devices depend on efficient management of batteries and their limitations. One universal, not to mention irritating, limitation of all...
Circuit Provides High Current, Kelvin Sensing, And Automatic Shutdown
Low-noise synthesizers require quiet power supplies for their oscillators and other critical circuitry. They typically require more than 5 mA of current, however, making a voltage reference alone inadequate. Three-terminal low-dropout regulators, on...
Dual-Output SLIC Supply Shares Feedback
For some subscriber line-interface cards (SLICs), both the line and ringer voltages should be regulated under all conditions. The circuit shown in the figure meets this requirement. It accepts a 12-V...
Simple Current-Limiter And Power Switch Offer Overcurrent Protection
Many applications that use a single power supply need some type of overcurrent protection. Such a device will help prevent the entire system from shutting down in the event of a single fault or short circuit. The high-current switch Q1, driver Q3,...
Emitter-Follower Boosts Linear Regulator's Output Current
Automotive electronics often require memory for saving system information or for user inputs (the settings on a car stereo, for example). Flash memory can do the job, but flash is expensive. DRAM memory reduces the cost, but DRAM requires an...
An Almost Ideal Low-Battery Cutoff Circuit Draws Only 1.2 μA
An ideal low-battery cut-off circuit should have zero on-resistance, zero power consumption when the switch is off, and zero power consumption when the switch is on. The circuit shown in the figure meets...
Potentiometer Regulates Fast Battery Charger
Amidst the current explosion of portable electronic devices are important issues regarding battery maintenance. Learning the tricks and techniques related to the care and feeding of batteries is essential. Of particular interest are the dark secrets...
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