DESCRIPTION

The LT1764 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 LT1764 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 LT1764 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 LT1764 regulators are available in 5-lead TO-220, DD and Exposed Pad 16-lead TSSOP packages.

 

CARACTÉRISTIQUES

Optimized for Fast Transient Response

Output Current: 3A

Dropout Voltage: 340mV at 3A

Low Noise: 40µVRMS (10Hz to 100kHz)

1mA Quiescent Current

Wide Input Voltage Range: 2.7V to 20V

Aucune diode de protection n'est nécessaire

Controlled Quiescent Current in Dropout

Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V

Adjustable Output from 1.21V to 20V

<1µA Quiescent Current in Shutdown

Stable with 10µF Output Capacitor

Reverse Battery Protection

No Reverse Current

Limitation thermique

Available in 5-Lead TO-220, DD and 16-Lead TSSOP Packages

 

CANDIDATURES

3.3V to 2.5V Logic Power Supply

Post Regulator for Switching Supplies

 

APPLICATIONS  INFORMATION

The LT1764 series are 3A low dropout regulators optimized for fast transient response. The devices are capable of supplying 3A at a dropout voltage of 340mV. The low operating quiescent current (1mA) drops to less than 1µA in shutdown. In addition to the low quiescent current, the LT1764 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 LT1764-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 LT1764 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 10µF with an ESR in the range of 50mΩ to 3Ω is recommended to prevent oscillations. Larger values of output capacitance can decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1764-X, will increase the effective output capacitor value.

Overload Recovery

Like many IC power regulators, the LT1764-X has safe operating area protection. The safe area protection decreases the current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage.

The protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown.

When power is first turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. During the start-up, as the input voltage is rising, the input-to-output voltage differential is small, allowing the regulator to supply large output currents. With a high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. Other regulators, such as the LT1085, also exhibit this phenomenon, so it is not unique to the LT1764 series.