説明

The LT1963A series are low dropout regulators optimized for fast transient response. The devices are capable of supplying 1.5A 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 LT1963A regulators have very low output noise which makes them ideal for sensitive RF supply applications. Output voltage range is from 1.21V to 20V. The LT1963A 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 devices are 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 LT1963A regulators are available in 5-lead TO-220, DD, 3-lead SOT-223, 8-lead SO and 16-lead TSSOP packages.

 

特徴

Optimized for Fast Transient Response

Output Current: 1.5A

Dropout Voltage: 340mV

Low Noise: 40µVRMS (10Hz to 100kHz)

1mA Quiescent Current

保護ダイオード不要

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*

Stable with Ceramic Capacitors*

Reverse Battery Protection

No Reverse Current

温度制限

5-Lead TO-220, DD, 3-Lead SOT-223 and  8-Lead SO Packages

自動車用AEC-Q100認定

 

アプリケーション

3.3V to 2.5V Logic Power Supplies

Post Regulator for Switching Supplies

 

アプリケーション情報

The LT1963A series are 1.5A low dropout regulators optimized for fast transient response. The devices are capable of supplying 1.5A at a dropout voltage of 350mV. The low operating quiescent current (1mA) drops to less than 1µA in shutdown. In addition to the low quiescent current, the LT1963A 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 LT1963A-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.

Adjustable Operation

The adjustable version of the LT1963A has an output voltage range of 1.21V to 20V. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output to maintain the voltage at the  ADJ pin at 1.21V referenced to ground. The current in R1 is then equal to 1.21V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 3µA at 25°C, flows through R2 into the ADJ pin. The output voltage can be calculated using the formula in Figure 2. The value of R1 should be less than 4.17k to minimize errors in the output voltage caused by the ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero.

Aluminum Electrolytic Capacitors

Aluminum electrolytic capacitors can also be used with the LT1963A. These capacitors can also be used in conjunction with ceramic capacitors. These tend to be the cheapest and lowest performance type of capacitors. Care must be used in selecting these capacitors as some types can have ESR which can easily exceed the 3Ω maximum value.

Tantalum and Polytantalum Capacitors

There is a variety of tantalum capacitor types available, with a wide range of ESR specifications. Older types have ESR specifications in the hundreds of mΩ to several Ohms. Some newer types of polytantalum with multi-electrodes have maximum ESR specifications as low as 5mΩ. In general the lower the ESR specification, the larger the size and the higher the price. Polytantalum capacitors have better surge capability than older types and generally lower ESR. Some types such as the Sanyo TPE and TPB series have ESR specifications in the 20mΩ to 50mΩ range, which provide near optimum transient response.