LT3013B データシートの表示（PDF） - Linear Technology

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LT3013B

250mA, 4V to 80V Low Dropout Micropower Linear Regulator with PWRGD

Linear Technology 

LT3013B

APPLICATIONS INFORMATION

The LT3013B is a 250mA high voltage low dropout regulator

with micropower quiescent current. The device is capable

of supplying 250mA at a dropout voltage of 400mV. Op-

erating quiescent current is only 65μA. In addition to the

low quiescent current, the LT3013B incorporates several

protection features which make it ideal for use in bat-

tery-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

LT3013B acts like it has a diode in series with its output

and prevents reverse current flow.

Adjustable Operation

The LT3013B has an output voltage range of 1.24V to 60V.

The output voltage is set by the ratio of two external resis-

tors as shown in Figure 1. The device servos the output to

maintain the voltage at the adjust pin at 1.24V referenced

to ground. The current in R1 is then equal to 1.24V/R1 and

the current in R2 is the current in R1 plus the ADJ pin bias

current. The ADJ pin bias current, 30nA 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 250k to minimize errors in the output

voltage caused by the ADJ pin bias current.

The adjustable device is tested and specified with the ADJ

pin tied to the OUT pin and a 5μA DC load (unless otherwise

specified) for an output voltage of 1.24V. Specifications for

output voltages greater than 1.24V will be proportional to

the ratio of the desired output voltage to 1.24V; (VOUT/

1.24V). For example, load regulation for an output current

change of 1mA to 250mA is –7mV typical at VOUT = 1.24V.

At VOUT = 12V, load regulation is:

(12V/1.24V) • (–7mV) = –68mV

Output Capacitance and Transient Response

The LT3013B is 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 LT3013B 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 LT3013B, will increase the

effective output capacitor value.

Extra consideration must be given to the use of ceramic

capacitors. Ceramic capacitors are manufactured with a

variety of dielectrics, each with different behavior across

temperature and applied voltage. The most common

dielectrics used are specified with EIA temperature char-

acteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and

Y5V dielectrics are good for providing high capacitances

in a small package, but they tend to have strong voltage

IN OUT

LT3013B

VIN

ADJ

GND

R2 +

VOUT

R1

3013 F01

 VOUT = 1.24V

1+

R2

R1

+ (IADJ)(R2)

VADJ = 1.24V

IADJ = 30nA AT 25°C

OUTPUT RANGE = 1.24V TO 60V

Figure 1. Adjustable Operation

3013bfb

8

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