lt3014bes5-trpbf Linear Technology Corporation, lt3014bes5-trpbf Datasheet - Page 7

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

APPLICATIO S I FOR ATIO
PI FU CTIO S
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.
The LT3014 is a 20mA high voltage low dropout regulator
with micropower quiescent current and shutdown. The
device is capable of supplying 20mA at a dropout voltage
of 350mV. The low operating quiescent current (7µA)
drops to 1µA in shutdown. In addition to the low quiescent
current, the LT3014 incorporates several protection fea-
tures 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 LT3014 acts
like it has a diode in series with its output and prevents
reverse current flow.
Adjustable Operation
The LT3014 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 2. 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. Note that in shutdown the output is turned off
and the divider current will be zero. 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
U
U
U
U
U
(SOT-23 Package/DD Package)
W
U
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.
than 1.22V will be proportional to the ratio of the desired
output voltage to 1.22V (V
regulation for an output current change of 1mA to 20mA
is –13mV typical at V
regulation is:
Output Capacitance and Transient Response
The LT3014 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 0.47µF with an ESR of 3Ω or less is
recommended to prevent oscillations. The LT3014 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 LT3014, will increase the
effective output capacitor value.
(12V/1.22V) • (–13mV) = –128mV
V
Figure 1. Adjustable Operation
IN
V
V
I
OUTPUT RANGE = 1.22V TO 60V
ADJ
OUT
ADJ
IN
= 4nA AT 25°C
LT3014
= 1.22V
= 1.22V
GND
OUT
OUT
ADJ
OUT
= 1.22V. At V
•
( )
1 +
/1.22V). For example, load
R2
R1
R2
R1
+ (I
ADJ
+
)(R2)
3014 F01
OUT
V
OUT
LT3014
= 12V, load
3014fb
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