lt3010hms8e-trpbf Linear Technology Corporation, lt3010hms8e-trpbf Datasheet - Page 12

• Manufacturer Part Number: lt3010hms8e-trpbf
• Description: 50ma, 3v To 80v Low Dropout Micropower Linear Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LT3010/LT3010-5
Output Capacitance and Transient Response). Check each
passive component for absolute value and voltage ratings
over the operating temperature range.
Leakages in capacitors or from solder fl ux left after insuffi -
cient board cleaning adversely affects low quiescent current
operation. Consider junction temperature increase due to
power dissipation in both the junction and nearby compo-
nents to ensure maximum specifi cations are not violated
for the LT3010/LT3010H or external components.
Protection Features
The LT3010 incorporates several protection features which
make it ideal for use in battery-powered circuits. In ad-
dition to the normal protection features associated with
monolithic regulators, such as current limiting and thermal
limiting, the device is protected against reverse-input volt-
ages, and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal opera-
tion, the junction temperature should not exceed 125°C
(LT3010E) or 140°C (LT3010H).
The input of the device will withstand reverse voltages
of 80V. Current fl ow into the device will be limited to less
than 6mA (typically less than 100μA) and no negative
voltage will appear at the output. The device will protect
both itself and the load. This provides protection against
batteries which can be plugged in backward.
The ADJ pin of the adjustable device can be pulled above
or below ground by as much as 7V without damaging the
device. If the input is left open circuit or grounded, the
ADJ pin will act like an open circuit when pulled below
ground, and like a large resistor (typically 100k) in series
with a diode when pulled above ground. If the input is
powered by a voltage source, pulling the ADJ pin below
the reference voltage will cause the device to try and force
the current limit current out of the output. This will cause
the output to go to a unregulated high voltage. Pulling
the ADJ pin above the reference voltage will turn off all
output current.
12
In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp volt-
age if the output is pulled high, the ADJ pin input current
must be limited to less than 5mA. For example, a resistor
divider is used to provide a regulated 1.5V output from the
1.22V reference when the output is forced to 60V. The top
resistor of the resistor divider must be chosen to limit the
current into the ADJ pin to less than 5mA when the ADJ
pin is at 7V. The 53V difference between the OUT and ADJ
pins divided by the 5mA maximum current into the ADJ
pin yields a minimum top resistor value of 10.6k.
In circuits where a backup battery is required, several
different input/output conditions can occur. The output
voltage may be held up while the input is either pulled
to ground, pulled to some intermediate voltage, or is left
open circuit. Current fl ow back into the output will follow
the curve shown in Figure 5. The rise in reverse output
current above 7V occurs from the breakdown of the 7V
clamp on the ADJ pin. With a resistor divider on the
regulator output, this current will be reduced depending
on the size of the resistor divider.
When the IN pin of the LT3010 is forced below the OUT
pin or the OUT pin is pulled above the IN pin, input cur-
rent will typically drop to less than 2μA. This can happen
if the input of the LT3010 is connected to a discharged
(low voltage) battery and the output is held up by either
a backup battery or a second regulator circuit. The state
of the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.
100
90
80
70
60
50
40
30
20
10
0
0
Figure 5. Reverse Output Current
T
V
CURRENT FLOWS
INTO OUTPUT PIN
V
V
(LT3010-5)
A
IN
OUT
OUT
= 25°C
1
= 0V
= V
= V
LT3010
2
ADJ
SENSE
OUTPUT VOLTAGE (V)
3
(LT3010)
LT3010-5
4
5
6
(SEE ABOVE)
PIN CLAMP
7
ADJ
8
30105 F05
9
10
30105fc