6

LT3014B

3014bf

IN

LT3014B

OUT

ADJ

GND

3014 F01

R2

R1

+

R2

R1

OUTPUT RANGE = 1.22V TO 60V

1 +

()

•

Figure 1. Adjustable Operation

IN (Pin 1/Pin 8): Input. Power is supplied to the device

through the IN pin. A bypass capacitor is required on this

pin if the device is more than six inches away from the main

input filter capacitor. In general, the output impedance of

a battery rises with frequency, so it is advisable to include

a bypass capacitor in battery-powered circuits. A bypass

capacitor in the range of 0.1

µF to 10µF is sufficient. The

LT3014B is designed to withstand reverse voltages on the

IN pin with respect to ground and the OUT pin. In the case

of a reversed input, which can happen if a battery is

plugged in backwards, the LT3014B will act as if there is

a diode in series with its input. There will be no reverse

current flow into the LT3014B and no reverse voltage will

appear at the load. The device will protect both itself and

the load.

GND (Pin 2/Pins 4, 9): Ground.

ADJ (Pin 4/Pin 2): Adjust. This is the input to the error

amplifier. This pin is internally clamped to

±7V. It has a

bias current of 4nA which flows into the pin (see curve of

ADJ Pin Bias Current vs Temperature in the Typical Perfor-

mance Characteristics). The ADJ pin voltage is 1.22V

referenced to ground, and the output voltage range is

1.22V to 60V.

OUT (Pin 5/Pin 1): Output. The output supplies power to

the load. A minimum output capacitor of 0.47

µF is re-

quired to prevent oscillations. Larger output capacitors

will be required for applications with large transient loads

to limit peak voltage transients. See the Applications

Information section for more information on output ca-

pacitance and reverse output characteristics.

NC (Pin 3/Pin 3, 5, 6, 7): No Connect. No Connect pins

may be floated, tied to IN or tied to GND.

APPLICATIO S I FOR ATIO

The LT3014B is a 20mA high voltage low dropout regula-

tor with micropower quiescent current. The device is

capable of supplying 20mA at a dropout voltage of 350mV.

Operating quiescent current is only 7

µA. In addition to the

low quiescent current, the LT3014B incorporates several

protection features which make it ideal for use in battery-

powered systems. The device is 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

LT3014B acts like it has a diode in series with its output

and prevents reverse current flow.

Adjustable Operation

The LT3014B has an output voltage range of 1.22V to

60V. The output voltage is set by the ratio of two external

resistors as shown in Figure 1. The device servos the

output to maintain the voltage at the adjust pin at 1.22V

referenced to ground. The current in R1 is then equal to

1.22V/R1 and the current in R2 is the current in R1 plus

the ADJ pin bias current. The ADJ pin bias current, 4nA

at 25

°C, flows through R2 into the ADJ pin. The output

voltage can be calculated using the formula in Figure 1.

The value of R1 should be less than 1.62M to minimize

errors in the output voltage caused by the ADJ pin bias

current. The device is tested and specified with the ADJ pin

tied to the OUT pin and a 5

µA DC load (unless otherwise

specified) for an output voltage of 1.22V. Specifications

for output voltages greater than 1.22V will be proportional

1.22V). For example, load regulation for an output current

(12V/1.22V) • (–13mV) = –128mV