LT1963 datasheet(9/16 Pages) LINER

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LT3020/LT3020-1.2/

LT3020-1.5/LT3020-1.8

3020fc

APPLICATIO S I FOR ATIO

The LT3020 is a very low dropout linear regulator capable

of 0.9V input supply operation. Devices supply 100mA of

output current and dropout voltage is typically 150mV.

Quiescent current is typically 120

µA and drops to 3µA in

shutdown. The LT3020 incorporates several protection

features, making it ideal for use in battery-powered sys-

tems. The device protects itself against reverse-input and

reverse-output voltages. In battery backup applications

where the output is held up by a backup battery when the

input is pulled to ground, the LT3020 acts as if a diode is

in series with its output which prevents reverse current

flow. 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 10V without affecting start-

up or normal operation.

Adjustable Operation

The LT3020’s output voltage range is 0.2V to 9.5V. Figure

1 shows that the output voltage is set by the ratio of two

external resistors. The device regulates the output to

maintain the ADJ pin voltage at 200mV referenced to

ground. The current in R1 equals 200mV/R1 and the

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

current. The ADJ pin bias current of 20nA flows out of the

pin. Use the formula in Figure 1 to calculate output voltage.

An R1 value of 20k sets the resistor divider current to

µA. Note that in shutdown the output is turned off and

the divider current is zero. Curves of ADJ Pin Voltage vs

Temperature and ADJ Pin Bias Current vs Temperature

appear in the Typical Performance Characteristics section.

Specifications for output voltages greater than 200mV are

proportional to the ratio of desired output voltage to

200mV; (VOUT/200mV). For example, load regulation for

BLOCK DIAGRA

SHUTDOWN

–

CURRENT

GAIN

THERMAL

SHUTDOWN

3020 BD

ERROR AMP

NO-LOAD

RECOVERY

(7, 8)

OUT

(1, 2)

OUT SENSE

(3)

NOTE:

FOR LT3020 ADJUST PIN 3 IS CONNECTED TO

THE ADJUST PIN, R1 AND R2 ARE EXTERNAL.

FOR LT3020-1.X PIN 3 IS CONNECTED TO THE

OUTPUT SENSE PIN, R1 AND R2 ARE INTERNAL.

GND

(4,9)

ADJ

(3)

25k

SHDN

(5)

200mV

212mV

BIAS CURRENT

AND

REFERENCE

GENERATOR

FIXED

VOUT

1.2V

1.5V

1.8V

20k

100k

130k

160k

SHDN

3020 F01

OUT

VIN

ADJ

GND

LT3020-ADJ

VOUT

VOUT = 200mV

VADJ = 200mV

IADJ = 20nA AT 25°C

OUTPUT RANGE = 0.2V TO 9.5V

1 +

– IADJ (R2)

()

Figure 1. Adjustable Operation

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