lt3060 Linear Technology Corporation, lt3060 Datasheet - Page 11

• Manufacturer Part Number: lt3060
• Description: 45v Vin, Micropower, Low Noise, 100ma Low Dropout, Linear Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
The LT3060 is a micropower, low noise, low dropout voltage,
100mA linear regulator with micropower shutdown. The
device supplies up to 100mA at a typical dropout voltage
of 300mV and operates over a 1.6V to 45V input range.
A single external capacitor can provide programmable
low noise reference performance and output soft-start
functionality. For example, connecting a 10nF capacitor
from the REF/BYP pin to GND lowers output noise to
30μV
also soft-starts the reference and prevents output voltage
overshoot at turn-on.
The LT3060’s quiescent current is merely 40μA but provides
fast transient response with a minimum low ESR 2.2μF
ceramic output capacitor. In shutdown, quiescent current
is less than 1μA and the reference soft-start capacitor is
reset.
The LT3060 optimizes stability and transient response
with low ESR, ceramic output capacitors. The regulator
does not require the addition of ESR as is common with
other regulators. The LT3060 typically provides 0.1% line
regulation and 0.03% load regulation.
Internal protection circuitry includes reverse-battery
protection, reverse-output protection, reverse-current
protection, current limit with foldback and thermal
shutdown.
This “bullet-proof” protection set makes it ideal for use in
battery-powered systems. In battery backup applications
where the output is held up by a backup battery and the
input is pulled to ground, the LT3060 acts like it has a
diode in series with its output and prevents reverse current
fl ow. Additionally, 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 45V and the
device still starts normally and operates.
Adjustable Operation
The LT3060 has an output voltage range of 0.6V to 44.5V. 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 ADJ pin voltage at 0.6V referenced to ground.
The current in R1 is then equal to 0.6V/R1, and the current
in R2 is the current in R1 minus the ADJ pin bias current.
RMS
over a 10Hz to 100kHz bandwidth. This capacitor
The ADJ pin bias current, 15nA at 25˚C, fl ows from the
ADJ pin through R1 to GND. Calculate the output voltage
using the formula in Figure 1. The value of R1 should be no
greater than 124k to provide a minimum 5μA load current
so that errors in the output voltage, caused by the ADJ
pin bias current, are minimized. 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.
The LT3060 is tested and specifi ed with the ADJ pin tied
to the OUT pin, yielding V
output voltages greater than 0.6V are proportional to the
ratio of the desired output voltage to 0.6V: V
example, load regulation for an output current change
of 1mA to 100mA is 0.2mV (typical) at V
V
Table 1 shows 1% resistor divider values for some common
output voltages with a resistor divider current of 5μA.
Table 1. Output Voltage Resistor Divider Values
OUT
0 6
12
.
V
= 12V, load regulation is:
IN
V
V
V
1.2
1.5
1.8
2.5
3.3
(V)
OUT
3
5
•
( .
SHDN
IN
0 2
GND REF/BYP
LT3060
Figure 1. Adjustable Operation
mV
OUT
ADJ
)
=
4
3060 F01
mV
R2
R1
(k Ω)
OUT
118
121
124
115
124
124
115
R1
= 0.6V. Specifi cations for
I
V
V
OUTPUT RANGE
V
AD
OUT
ADJ
OUT
J J
=
=
=
15
0 6
0 6
.
.
nA at
V
V
⎛
⎜
⎝
1
25
OUT
+
LT3060
=
OUT
º
R
R
C
0 6
2
1
(k Ω)
.
118
182
249
365
499
562
845
⎞
⎟
⎠
R2
V to
= 0.6V. At
/0.6V. For
–
(
I
11
ADJ
44 5
.
•
V
R
3060f
2
)