Analog Devices

The LT1725 is a monolithic switching regulator controller specifically designed for the isolated flyback topology. It drives the gate of an external MOSFET and is generally powered from a third transformer winding. These features allow for an application input voltage limited only by external power path components. The third transformer winding also provides output voltage feedback information, such that an optoisolator is not required. Its gate drive capability coupled with a suitable external MOSFET can deliver load power up to tens of watts.The LT1725 has a number of features not found on most other switching regulator ICs. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An optional undervoltage lockout pin halts operation when the application input voltage is too low. An optional external capacitor implements a soft-start function. A 3V output is available at up to several mA for powering primary side application circuitry.ApplicationsTelecom Isolated ConvertersOffline Isolated Power SuppliesInstrumentation Power Supplies

The LT1737 is a monolithic switching regulator controller specifically designed for the isolated flyback topology. It drives the gate of an external MOSFET and is generally powered from a DC supply voltage. Output voltage feedback information may be supplied by a variety of methods including a third transformer winding, the primary winding or even direct DC feedback (see Applications Information). Its gate drive capability, coupled with a suitable external MOSFET and other power path components, can deliver load power up to tens of Watts.The LT1737 has a number of features not found on other isolated flyback controller ICs presently available. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An optional undervoltage lockout pin halts operation when the application input voltage is too low. An optional external capacitor implements a soft-start function.ApplicationsIsolated Flyback Switching RegulatorsMedical InstrumentsInstrumentation Power Supplies

The LT1738 is a switching regulator controller designed to lower conducted and radiated electromagnetic interference (EMI). Ultralow noise and EMI are achieved by controlling the voltage and current slew rates of an external N-channel MOSFET switch. Current and voltage slew rates can be independently set to optimize harmonic content of the switching waveforms vs efficiency. The LT1738 can reduce high frequency harmonic power by as much as 40dB with only minor losses in efficiency.The LT1738 utilizes a current mode architecture optimized for single switch topologies such as boost, flyback and Cuk. The IC includes gate drive and all necessary oscillator, control and protection circuitry. Unique error amp circuitry can regulate both positive and negative voltages. The internal oscillator may be synchronized to an external clock for more accurate placement of switching harmonics.Protection features include gate drive lockout for low VIN, soft-start, output current limit, short-circuit current limit-ing, gate drive overvoltage clamp and input supply undervoltage lockout.ApplicationsPower Supplies for Noise Sensitive Communication EquipmentEMI Compliant Offline Power SuppliesPrecision Instrumentation SystemsIsolated Supplies for Industrial AutomationMedical InstrumentsData Acquisition Systems

TheLT1739 is a 500mA minimum output current, dual op amp with outstanding distortion performance. The amplifiers are gain-of-ten stable, but can be easily compensated for lower gains. The extended output swing allows for lower supply rails to reduce system power. Supply current is set with an external resistor to optimize power dissipation. The LT1739 features balanced, high impedance inputs with low input bias current and input offset voltage. Active termination is easily implemented for further system power reduction. Short-circuit protection and thermal shutdown insure the device’s ruggedness.The outputs drive a 100Ω load to ±11.1V with ±12V supplies, and ±10.9V with a 250mA load. The LT1739 is a pin-for-pin replacement for the LT1794 in xDSL line driver applications and requires no circuit changes.The LT1739 is available in the very small, thermally enhanced, 3mm × 4mm DFN package or a 20-lead TSSOP for maximum port density in central office line driver applications. For a dual version of the LT1739, see the LT6301 data sheet.ApplicationsHigh Density ADSL Central Office Line DriversHigh Efficiency ADSL, HDSL2, G.lite, SHDSL Line DriversBuffersTest Equipment AmplifiersCable Drivers

The LT1761 series are micropower, low noise, low dropout regulators. With an external 0.01μF bypass capacitor, output noise drops to 20μVRMSover a 10Hz to 100kHz bandwidth. Designed for use in battery-powered systems, the low 20μA quiescent current makes them an ideal choice. In shutdown, quiescent current drops to less than 0.1μA. The devices are capable of operating over an input voltage from 1.8V to 20V, and can supply 100mA of output current with a dropout voltage of 300mV. Quiescent current is well controlled, not rising in dropout as it does with many other regulators.The LT1761 regulators are stable with output capacitors as low as 1μF. Small ceramic capacitors can be used without the series resistance required by other regulators.Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The device is available in fixed output voltages of 1.2V, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1761 regulators are available in the 5-lead TSOT-23 package.ApplicationsCellular PhonesPagersBattery-Powered SystemsFrequency SynthesizersWireless Modems

The LT1762 series are micropower, low noise, low dropout regulators. The devices are capable of supplying 150mA of output current with a dropout voltage of 270mV. Designed for use in battery-powered systems, the low 25µA quiescent current makes them an ideal choice. Quiescent current is well controlled; it does not rise in dropout as it does with many other regulators.A key feature of the LT1762 regulators is low output noise. With the addition of an external 0.01µF bypass capacitor, output noise drops to 20µVRMS over a 10Hz to 100kHz bandwidth. The LT1762 regulators are stable with output capacitors as low as 2.2µF. Small ceramic capacitors can be used without the series resistance required by other regulators.Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The parts come in fixed output voltages of 2.5V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1762 regulators are available in the 8-lead MSOP package.APPLICATIONSCellular PhonesBattery-Powered SystemsFrequency SynthesizersNoise-Sensitive Instrumentation Systems

The LT1763 series are micropower, low noise, low dropout regulators. The devices are capable of supplying 500mA of output current with a dropout voltage of 300mV. Designed for use in battery-powered systems, the low 30μA quiescent current makes them an ideal choice. Quiescent current is well controlled; it does not rise in dropout as it does with many other regulators.A key feature of the LT1763 regulators is low output noise. With the addition of an external 0.01μF bypass capacitor, output noise drops to 20μVRMSover a 10Hz to 100kHz bandwidth. The LT1763 regulators are stable with output capacitors as low as 3.3μF. Small ceramic capacitors can be used without the series resistance required by other regulators.Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The parts come in fixed output voltages of 1.5V, 1.8V, 2.5V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1763 regulators are available in 8-lead SO and 12-lead, low profile (4mm × 3mm × 0.75mm) DFN packages.ApplicationsCellular PhonesBattery-Powered SystemsNoise-Sensitive Instrumentation Systems

The LT1764A is a low dropout regulator optimized for fast transient response. The device is capable of supplying 3A of output current with a dropout voltage of 340mV. Operating quiescent current is 1mA, dropping to <1µA in shutdown. Quiescent current is well controlled; it does not rise in dropout as it does with many other regulators. In addition to fast transient response, the LT1764A has very low output voltage noise which makes the device ideal for sensitive RF supply applications.Output voltage range is from 1.21V to 20V. The LT1764A regulators are stable with output capacitors as low as 10µF. Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The device is available in fixed output voltages of 1.5V, 1.8V, 2.5V, 3.3V and as an adjustable device with a 1.21V reference voltage. The LT1764A regulators are available in 5-lead TO-220 and DD packages, and 16-lead FE packages.FeaturesLT1764-LT1764AStable With Ceramic Output CapacitorsApplications3.3V to 2.5V Logic Power SupplyPost Regulator for Switching Supplies

The LT1765 is a 1.25MHz monolithic buck switching regulator. A high efficiency 3A, 0.09Ω switch is included on the die together with all the control circuitry required to construct a high frequency, current mode switching regulator. Current mode control provides fast transient response and excellent loop stability.New design techniques achieve high efficiency at high switching frequencies over a wide operating voltage range. A low dropout internal regulator maintains consistent performance over a wide range of inputs from 24V systems to Li-Ion batteries. An operating supply current of 1mA improves efficiency, especially at lower output currents. Shutdown reduces quiescent current to 15µA. Maximum switch current remains constant at all duty cycles. Synchronization allows an external logic level signal to increase the internal oscillator into the range of 1.6MHz to 2MHz.Full cycle-by-cycle current control and thermal shutdown are provided. High frequency operation allows the reduction of input and output filtering components and permits the use of chip inductors.ApplicationsDSL ModemsPortable ComputersRegulated Wall AdaptersBattery-Powered SystemsDistributed Power