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LT1175
500mA Negative
Low Dropout Micropower
Regulator
The LT
1175 is a negative micropower low dropout regu-
lator. It features 45
μ
A quiescent current, dropping to 10
μ
A
in shutdown. A new reference amplifier topology gives
precision DC characteristics along with the ability to
maintain good loop stability with an extremely wide range
of output capacitors. Very low dropout voltage and high
efficiency are obtained with a unique power transistor anti-
saturation design. Adjustable and fixed 5V versions are
available.
Several new features make the LT1175 very user-friendly.
The Shutdown pin can interface directly to either positive
or negative logic levels. Current limit is user-selectable at
200mA, 400mA, 600mA and 800mA. The output can be
forced to reverse voltage without damage or latchup.
Unlike some earlier designs, the increase in quiescent
current during a dropout condition is actively limited.
The LT1175 has complete blowout protection with current
limiting, power limiting and thermal shutdown. Special
attention was given to the problem of high temperature
operation with micropower operating currents,
preventing
output voltage rise under no-load conditions. The LT1175
is available in 8-pin PDIP and SO packages, 3-lead SOT-
223 as well as 5-pin surface mount DD and through-hole
TO-220 packages. The 8-pin SO package is specially
constructed for low thermal resistance.
DESCRIPTIO
N
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
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Typical LT1175 Connection
OUTPUT CURRENT (A)
0
I
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.5
1175 TA02
0.1
0.3
0.6
0.7
T
J
= 25
°
C
I
LIM2
, I
LIM4
TIED TO V
IN
Minimum Input-to-Output Voltage
+
C
IN
*
*C
IS NEEDED ONLY IF REGULATOR IS MORE THAN 6" FROM
INPUT SUPPLY CAPACITOR. SEE APPLICATIONS INFORMATION
SECTION FOR DETAILS
+
C
OUT
≥
0.1
μ
F
–5V
UP TO 500mA
–V
IN
SHDN
GND
LT1175-5
SENSE
OUT
1175 TA01
I
LIM4
I
LIM2
INPUT
I
Stable with Wide Range of Output Capacitors
I
Operating Current: 45
μ
A
I
Shutdown Current: 10
μ
A
I
Adjustable Current Limit
I
Positive or Negative Shutdown Logic
I
Low Voltage Linear Dropout Characteristics
I
Fixed 5V and Adjustable Versions
I
Tolerates Reverse Output Voltage
FEATURES
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Analog Systems
I
Modems
I
Instrumentation
I
A/D and D/A Converters
I
Interface Drivers
I
Battery-Powered Systems
APPLICATIO
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