DESCRIPTION

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 20µVRMS over 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

 

CARACTÉRISTIQUES

-Low Noise: 20µVRMS (10Hz to 100kHz)
-Output Current: 500mA
-Low Quiescent Current: 30µA
-Wide Input Voltage Range: 1.8V to 20V
-Low Dropout Voltage: 300mV
-Very Low Shutdown Current: < 1µA
-No Protection Diodes Needed
-Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3V, 3.3V, 5V
-Adjustable Output from 1.22V to 20V
-Stable with 3.3µF Output Capacitor
-Stable with Aluminum, Tantalum or Ceramic Capacitors
-Reverse Battery Protection
-No Reverse Current
-Overcurrent and Overtemperature Protected
-8-Lead SO and 12-Lead (4mm × 3mm) DFN Packages

 

CANDIDATURES

-Cellular Phones
-Battery-Powered Systems
-Noise-Sensitive Instrumentation Systems

 

INFORMATIONS SUR LES APPLICATIONS

The LT1763 series are 500mA low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 500mA at a dropout voltage of 300mV. Output voltage noise can be lowered to 20µVRMS over a 10Hz to 100kHz bandwidth with the addition of a 0.01µF reference bypass capacitor. Additionally, the reference bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. The low operating quiescent current (30µA) drops to less than 1µA in shutdown. In addition to the low quiescent current, the LT1763 regulators incorporate several protection features which make them ideal for use in battery-powered systems. The devices are protected against both reverse input and reverse output voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1763-X acts like it has a diode in series with its output and prevents reverse current flow. Additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20V and still allow the device to start and operate.

Output Capacitance and Transient Response

The LT1763 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 3.3µF with an ESR of 3Ω, or less, is recommended to prevent oscillations. The LT1763-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1763-X, will increase the effective output capacitor value. With larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance, 4.7µF of output capacitor is recommended. With a 1000pF bypass capacitor or larger, a 6.8µF output capacitor is recommended.

Protection Features

The LT1763 regulators incorporate several protection features which make them ideal for use in battery-powered circuits. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the devices are protected against reverse input voltages, reverse output voltages and reverse voltages from output to input.