lt3014bes5 Linear Technology Corporation, lt3014bes5 Datasheet - Page 6

• Manufacturer Part Number: lt3014bes5
• Description: 20ma, 3v To 80v Low Dropout Micropower Linear Regulator
• Manufacturer: Linear Technology Corporation

LT3014B
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 7µA. 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.
PI FU CTIO S
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 0.1µF 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.
6
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(SOT-23 Package/DD Package)
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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 5µA DC load (unless otherwise
specified) for an output voltage of 1.22V. Specifications
for output voltages greater than 1.22V will be proportional
to the ratio of the desired output voltage to 1.22V (V
1.22V). For example, load regulation for an output current
change of 1mA to 20mA is –13mV typical at V
At V
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 0.47µF 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.
(12V/1.22V) • (–13mV) = –128mV
OUT
= 12V, load regulation is:
V
Figure 1. Adjustable Operation
IN
V
V
I
OUTPUT RANGE = 1.22V TO 60V
ADJ
OUT
ADJ
IN
LT3014B
= 4nA AT 25°C
= 1.22V
= 1.22V
GND
OUT
ADJ
•
( )
1 +
R2
R1
R2
R1
+ (I
ADJ
+
)(R2)
3014 F01
V
OUT
OUT
= 1.22V.
OUT
3014bf
/