LSP2155
1A Ultra Low Dropout CMOS Regulator
Features
Low-Dropout Regulator Supports Input
Voltages Down to 1.45V
Output Voltage Available in fixed 1.2V,
1.8V, 2.5V, 3.3V and ADJ version
Stable with 2.2uF or higher Ceramic Output
Capacitor
Low Dropout Voltage: 250mV at 1A
Low Quiescent Current
Over Temperature Protection
Over Current Protection
Short Circuit Protection
Package：SOT223-3L, TO252-3L,
SOP-8L
General Description
The LSP2155 is a 1A CMOS LDO regulator
that features a low quiescent current, ultra
low input, output and dropout voltages, as
well as over temperature shutdown. It is
available in SOT223-3L, TO252-3L, SOP-8L
package. The fixed output voltage of the
LSP2155 is set at the factory and trimmed to
±2%. The LSP2155 is stable with a ceramic
output capacitor of 2.2uF or higher. This
family of regulators can provide either a
stand-alone power supply solution or act as
a post regulator for switch mode power
supplies. They are particularly well suited for
applications requiring low input and output
voltage.
Applications
1.2V Core Voltage for DSPs
SATA Power Supply
LCD TV/Monitor
Telecom Equipment
Portable Electronics
Typical Application Circuit
VIN
VIN
VOUT
OUT
VIN
VIN
VOUT
R1
Cff
100pF
OUT
LSP2155
C1
4.7uF
GND
C2
2.2uF
C1
4.7uF
LSP2155
GND
ADJ
C2
R2
2.2uF
Please be aware that an
Important Notice
concerning availability, disclaimers, and use in critical
applications of LSC products is at the end of this document.
LSP2155
1A Ultra Low Dropout CMOS Regulator
Ordering Information
L S P 2 15 5 X X X
Package :
B E : S O T 2 2 3 -3 L
B D : T O 2 5 2 -3 L
E : S O T 2 2 3 -3 L
D : T O 2 5 2 -3 L
S : S O P -8 L
O u tp u t V o lta g e :
B la n k : A D J
1 2 : 1 .2 V
1 8 : 1 .8 V
2 5 : 2 .5 V
3 3 : 3 .3 V
P a c k in g :
A : Tape & R eel
Device
LSP2155EXXA
LSP2155BEXXA
LSP2155DXXA
LSP2155BDXXA
LSP2155SA
Package Code
E
BE
D
BD
S
Package
SOT223-3L
SOT223-3L
TO252-3L
TO252-3L
SOP-8L
Tape & Reel
Part Number
Quantity
Suffix
2500
A
2500
A
2500
A
2500
A
2500
A
Pin Assignments
SOT223-3L
(Top View)
TO252-3L
(Top View)
SOP-8L
(Top View)
3
2
1
Tab is Pin 2
3
2
1
Tab is Pin 2
1
2
3
4
8
7
6
5
Pin Descriptions
SOT223-3L
TO252-3L
1
2,TAB
3
Pin Number
SOT223-3L (B)
TO252-3L (B)
3
1
2,TAB
Name
VIN
GND
VOUT
ADJ
NC
Description
Voltage Input
Ground Pin
Voltage Output
Feedback Pin
No Connected
SOP-8L
2
1,4, 8
7
6
3,5
LSP2155
1A Ultra Low Dropout CMOS Regulator
Block Diagram
IN
Fixed version
OUT
IN
OverCurrent
Shutdown
Thermal
Shutdown
ADJ version
OUT
OverCurrent
Shutdown
Thermal
Shutdown
R1
AMP
AMP
R1
outside for ADJ
ADJ
R2
GND
R2
outside for ADJ
GND
Absolute Maximum Ratings
Parameter
Input Supply Voltage
Maximum Output Current
Power Dissipation
Storage Temperature Range
Maximum Junction Temperature
SOT223-3L
TO252-3L
SOP-8L
Value
-0.3 to 4
PD/(V
IN
-V
OUT
)
Internal Limitation
-65 to +150
150
Unit
V
A
mW
o
o
C
C
Recommended Operating Conditions
Parameter
Input Supply Voltage
Operating Junction Temperature
Output Current
Min
1.45V
(Notes1)
-20
Max
3.8
+125
1
Unit
V
°C
A
Note1 : The minimum input voltage of the LSP2155 is determined by output voltage and dropout voltage. The
minimum input voltage is defined as : V
IN
= V
OUT
+ V
DROP
LSP2155
1A Ultra Low Dropout CMOS Regulator
Electrical Characteristics
(V
IN
= V
OUT
+0.5V; C
IN
= 4.7uF, C
OUT
= 2.2 uF, T
A
= 25
℃
unless otherwise specified )
Parameter
Output Voltage Accuracy
Symbol
V
O
Test Conditions
I
O
= 100mA
V
O
= 0.9V,I
O
=1A
V
O
=1.2V,I
O
=1A
V
O
=1.8V,I
O
=1A
V
O
=2.5V,I
O
=1A
V
O
=3.3V,I
O
=1A
V
O
<
0.3V
V
IN
= 1.7V, I
O
= 0mA
V
IN
= 1.45 V to 3.8V, I
O
= 10mA
I
O
=10mA to 1A
V
IN
= 3.8V , V
OUT
= 0.9V
Min Typ Max Unit
-2
550
250
160
140
130
2
0.8
250
1
2
0.882
1
0.9
150
45
60
0.918
+2
%
Dropout Voltage
V
DROP
mV
Current Limit
Short Circuit Current
Quiescent Current
Line Regulation
Load Regulation Error
ADJ Input Bias Current
ADJ Reference Voltage
Over Temperature Protection
Over Temperature Hysteresis
Power Supply Ripple Rejection
I
Limit
I
SC
I
Q
L
NR
L
DR
I
ADJ
V
REF
O
TP
O
TH
PSRR
A
A
uA
%/V
%/V
%
V
℃
℃
dB
Application Description
The LSP2155 family of low-dropout regulators have several features that allow them to apply to a
wide range of applications. The family operates with very low input voltage (1.45V) and low dropout
voltage (see Electrical Characteristics Table), making it an efficient stand-alone power supply or
post regulator for battery or switch mode power supplies. The 1A output current make the
LSP2155 family suitable for powering many microprocessors and FPGA supplies. The LSP2155
family also has low output noise (typically 40uVRMS with 2.2uF output capacitor), making it ideal
for use in telecom equipment.
External Capacitor Requirement
A 2.2uF or larger ceramic input bypass capacitor, connected between VIN and GND and located
close to the LSP2155, is required for stability. A 1.0uF minimum value capacitor from VOUT to
GND is also required. To improve transient response, noise rejection, and ripple rejection, an
additional 10uF or larger, low ESR capacitor is recommended at the output. A higher-value, low
ESR output capacitor may be necessary if large, fast-rise-time load transients are anticipated and
the device is located several inches from the power source, especially if the minimum input voltage
of 1.45 V is used.
Regulator Protection
The LSP2155 features internal current limiting, thermal protection and short circuit protection.
During normal operation, the LSP2155 limits output current to about 2A. When current limiting
LSP2155
1A Ultra Low Dropout CMOS Regulator
engages, the output voltage scales back linearly until the over current condition ends. While
current limiting is designed to prevent gross device failure, care should be taken not to exceed the
power dissipation ratings of the package. If the temperature of the device exceeds 160°C, thermal-
protection circuitry will shut down. Once the device has cooled down to approximately 45°C below
the high temp trip point, regulator operation resumes. The short circuit current of the LSP2155 is
about 1A when its output pin is shorted to ground.
Thermal Information
The amount of heat that an LDO linear regulator generates is: D = (V
IN
-V
OUT
) x I
OUT
. All integrated
circuits have a maximum allowable junction temperature (T
J
max) above which normal operation is
not assured. A system designer must design the operating environment so that the operating
junction temperature (T
J
) does not exceed the maximum junction temperature (T
J
max). The two
main environmental variables that a designer can use to improve thermal performance are air flow
and external heat-sink. The purpose of this information is to aid the designer in determining the
proper operating environment for a linear regulator that is operating at a specific power level.
In general, the maximum expected power (P
D
(max)) consumed by a linear regulator is computed
as:
P
D
(MAX) = (V
IN
(avg)- V
OUT
(avg)) x I
OUT
(avg) x I
Q
)
Where
V
IN
(avg) is the average input voltage.
V
OUT
(avg) is the average output voltage.
I
OUT
(avg) is the average output current.
I
Q
is the quiescent current.
For most LDO regulators, the quiescent current is insignificant compared to the average output
current; therefore, the term V
IN
(avg) x I
Q
can be neglected. The operating junction temperature is
computed by adding the ambient temperature (T
A
) and the increase in temperature due to the
regulator's power dissipation. The temperature rise is computed by multiplying the maximum
expected power dissipation by the sum of the thermal resistances between the junction and the
case (R
ΘJC
), the case to heat-sink (R
ΘCS
), and the heat-sink to ambient (R
ΘSA
). Thermal resistances
are measures of how effectively an object dissipates heat. Typically, the larger the device, the
more surface area available for power dissipation, so that the object's thermal resistance will be
lower.
ADJ VERSION
The adjustable version uses external feedback resistors to generate an output voltage anywhere
from 1.45V to 5.0V. V
ADJ
is trimmed to 0.9V and VOUT is given by the equation:
V
OUT
= V
ADJ
( 1 + R1 / R2)
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