LSP2155
1A Ultra Low Dropout CMOS Regulator
Features General Description
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
Applications
1.2V Core Voltage for DSPs
SATA Power Supply
LCD TV/Monitor
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.
Telecom Equipment
Portable Electronics
Typical Application Circuit
VIN VOUT
LSP2155
GND
VIN OUT
C1
4.7uF
C2
2.2uF
VIN VOUT
LSP2155
GND ADJ
OUTVIN
C1
4.7uF
C2
2.2uF
R1
R2
Cff
100pF
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
Tape & Reel
Device Package Code Package Quantity Part Number
Suffix
LSP2155EXXA E SOT223-3L 2500 A
LSP2155BEXXA BE SOT223-3L 2500 A
LSP2155DXXA D TO252-3L 2500 A
LSP2155BDXXA BD TO252-3L 2500 A
LSP2155SA S SOP-8L 2500 A
Pin Assignments
(Top View)
Tab is Pin 2
3
2
1
SOT223-3L
(Top View)
Tab is Pin 2
3
2
1
TO252-3L
18
7
6
5
2
3
4
(Top View)
SOP-8L
Pin Descriptions
Pin Number
SOT223-3L
TO252-3L SOT223-3L (B)
TO252-3L (B) SOP-8L Name Description
1 3 2 VIN Voltage Input
2,TAB 1 1,4, 8 GND Ground Pin
3 2,TAB 7 VOUT Voltage Output
6 ADJ Feedback Pin
3,5 NC No Connected
LSP2155 X X X
Pa ckage :
E: SO T223-3L
Pa ckin g :
A : Tape & Reel
O utput Voltage :
Blank: ADJ
12 : 1.2V
D: TO252-3L
S: SO P-8L 25 : 2.5V
18 : 1.8V
33 : 3.3V
BE : SOT 2 2 3 -3 L
BD: TO252-3L
LSP2155
1A Ultra Low Dropout CMOS Regulator
Block Diagram
IN OUT
GND
R1
R2
AMP
Thermal
Shutdown
OverCurrent
Shutdown
Fixed version
IN OUT
GND
R1
R2
AMP
Thermal
Shutdown
OverCurrent
Shutdown
outside for ADJ
outside for ADJ
ADJ
ADJ version
Absolute Maximum Ratings
Parameter Value Unit
Input Supply Voltage -0.3 to 4 V
Maximum Output Current PD/(VIN-VOUT) A
SOT223-3L
TO252-3L
Power Dissipation
SOP-8L
Internal Limitation mW
Storage Temperature Range -65 to +150 oC
Maximum Junction Temperature 150 oC
Recommended Operating Conditions
Parameter Min Max Unit
Input Supply Voltage 1.45V (Notes1) 3.8 V
Operating Junction Temperature -20 +125 °C
Output Current 1 A
Note1 : The minimum input voltage of the LSP2155 is determined by output voltage and dropout voltage. The
minimum input voltage is defined as : VIN = VOUT + VDROP
LSP2155
1A Ultra Low Dropout CMOS Regulator
Electrical Characteristics
(VIN = VOUT+0.5V; CIN = 4.7uF, COUT = 2.2 uF, TA = 25 unless otherwise specified )℃
Parameter Symbol Test Conditions Min Typ Max Unit
Output Voltage Accuracy VO I
O= 100mA -2 +2 %
VO = 0.9V,IO=1A 550
VO =1.2V,IO=1A 250
VO =1.8V,IO=1A 160
VO =2.5V,IO=1A 140
Dropout Voltage VDROP
VO =3.3V,IO=1A 130
mV
Current Limit ILimit 2 A
Short Circuit Current ISC VO < 0.3V 0.8 A
Quiescent Current IQ V
IN = 1.7V, IO= 0mA 250 uA
Line Regulation LNR V
IN = 1.45 V to 3.8V, IO = 10mA 1 %/V
Load Regulation Error LDR I
O =10mA to 1A 2 %/V
ADJ Input Bias Current IADJ V
IN = 3.8V , VOUT = 0.9V 1 %
ADJ Reference Voltage VREF 0.882 0.9 0.918 V
Over Temperature Protection OTP 150 ℃
Over Temperature Hysteresis OTH 45
℃
Power Supply Ripple Rejection PSRR 60 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 = (VIN-VOUT) x IOUT. All integrated
circuits have a maximum allowable junction temperature (TJ max) above which normal operation is
not assured. A system designer must design the operating environment so that the operating
junction temperature (TJ) does not exceed the maximum junction temperature (TJ 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 (PD(max)) consumed by a linear regulator is computed
as:
PD(MAX) = (VIN(avg)- VOUT(avg)) x IOUT (avg) x IQ)
Where
VIN (avg) is the average input voltage.
VOUT (avg) is the average output voltage.
IOUT (avg) is the average output current.
IQ is the quiescent current.
For most LDO regulators, the quiescent current is insignificant compared to the average output
current; therefore, the term VIN (avg) x IQ can be neglected. The operating junction temperature is
computed by adding the ambient temperature (TA) 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 (RΘJC), the case to heat-sink (RΘCS), and the heat-sink to ambient (RΘSA). 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. VADJ is trimmed to 0.9V and VOUT is given by the equation:
VOUT = VADJ ( 1 + R1 / R2)
LSP2155
1A Ultra Low Dropout CMOS Regulator
ADJ
R1
R2
VOUT
Feedback resistors R1 and R2 should be high enough to keep quiescent current low, but
increasing R1 + R2 will reduce stability. In general, R1=100KΩ will produce adequate stability,
given reasonable layout precautions. To improve stability characteristics, keep parasitic on the ADJ
pin to a minimum, and lower R1 and R2 values.
LSP2155
1A Ultra Low Dropout CMOS Regulator
Typical Performance Characteristics
Line Regulation (I
OUT
=10mA)
1.18
1.19
1.20
1.21
1.22
1.4 1.8 2.2 2.6 3.0 3.4 3.8
V
IN
(V)
V
OUT
(V)
Line Regulation (I
OUT
=10mA)
1.78
1.79
1.80
1.81
1.82
2.3 2.6 2.9 3.2 3.5 3.8
V
IN
(V)
V
OUT
(V)
Load Regulation (V
OUT
=1.2V)
1.18
1.19
1.20
1.21
1.22
1.23
0.0 0.2 0.4 0.6 0.8 1.0
I
OUT
(A)
V
OUT
(V)
Load Regulation (V
OUT
=3.3V)
3.26
3.28
3.30
3.32
3.34
3.36
0.0 0.2 0.4 0.6 0.8 1.0
I
OUT
(A)
V
OUT
(V)
Quiescent Current vs. V
IN
50
75
100
125
150
175
200
1.4 1.8 2.2 2.6 3.0 3.4 3.8
V
IN
(V)
I
Q
(uA)
Ground Current vs. I
OUT
0
100
200
300
400
500
600
0.0 0.2 0.4 0.6 0.8 1.0
VO=1.2V
VO=3.3V
I
OUT
(A)
I
GND
(uA)
LSP2155
1A Ultra Low Dropout CMOS Regulator
Current Limit vs. VIN
0.4
0.8
1.2
1.6
2.0
2.4
1.4 1.8 2.2 2.6 3.0 3.4 3.8
VIN (V)
Current (A)
Dropout Voltage vs. I
OUT
0
50
100
150
200
250
300
0.0 0.2 0.4 0.6 0.8 1.0
VOUT=1.2V
VOUT=1.8V
VOUT=3.3V
I
OU
T
(A)
Dropout Voltage (mV)
I
OUT
Load Transient
(V
IN
=1.7V, Load=0.1A to 1A)
V
OUT
(AC)
20mV/div.
LSP2155
1A Ultra Low Dropout CMOS Regulator
Marking Information
SOT223-3L B type
LSP2155B-VV
YYWWXX
Part Number :
LSP 2155B-AD J : Blank
LSP 2155B-12 : 1.2V
Inte rn a l C o d e
Date Code :
WW：Nth week (01~53)
LSP 2155B-18 : 1.8V
LSP 2155B-25 : 2.5V
LSP 2155B-33 : 3.3V
YY：Year(09=2009,10=2010,11=2011,12=2012...)
TO252-3L B type
L S C
LSP2155B-VV
YYWWXX
Internal Co de
Date Code :
WW：Nth week (01~53)
Part Number :
LSP2155B-ADJ : Blank
LSP2155B-12 : 1.2V
LSP2155B-18 : 1.8V
LSP2155B-25 : 2.5V
LSP2155B-33 : 3.3V
Logo
YY：Year(09=2009,10=2010,11=2011,12=2012...)
LSP2155
1A Ultra Low Dropout CMOS Regulator
SOT223-3L
LSP2155-VV
YYWWXX
Part Number :
LSP 2155-ADJ : Blank
LSP 2155-12 : 1.2V
Inte rn a l C o d e
Date Code :
WW：Nth week (01~53)
LSP 2155-18 : 1.8V
LSP 2155-25 : 2.5V
LSP 2155-33 : 3.3V
YY：Year(09=2009,10=2010,11=2011,12=2012...)
TO252-3L
L S C
LSP2155-VV
YYWWXX
Internal Co de
Date Code :
WW：Nth week (01~53)
Part Number :
LSP2155-ADJ : Blank
LSP2155-12 : 1.2V
LSP2155-18 : 1.8V
LSP2155-25 : 2.5V
LSP2155-33 : 3.3V
Logo
YY：Year(09=2009,10=2010,11=2011,12=2012...)
SOP-8L
L S C
LSP2155-VV
YYWWXX
Logo
Date Code
Internal Code
WW：Nth week (01~53)
Part Number :
LSP2155-ADJ : Blank
LSP2155-12 : 1.2V
LSP2155-18 : 1.8V
LSP2155-25 : 2.5V
LSP2155-33 : 3.3V
YY：Year(09=2009,10=2010,11=2011,12=2012...)
LSP2155
1A Ultra Low Dropout CMOS Regulator
Package Information (All Dimensions in min)
(1) TO252-3L
Notes:
1.JEDEC Outline:TO-252 AB
Mils suggested for positive contact at mounting
Dimensions In Millimeters Dimensions In Inches
Symbol Min Nom Max Min Nom Max
A 2.18 2.29 2.39 0.086 0.090 0.094
A1 1.02 1.15 1.27 0.040 0.045 0.050
b 0.61TYP. 0.024TYP.
b2 5.20 5.35 5.50 0.205 0.211 0.217
C 0.46 0.52 0.58 0.018 0.020 0.023
C1 0.46 0.52 0.58 0.018 0.020 0.023
D 5.33 5.57 5.80 0.210 0.219 0.228
E 6.35 6.58 6.80 0.250 0.259 0.268
e 2.25BSC. 0.089BSC.
e1 4.50BSC. 0.177BSC.
H 9.00 9.70 10.40 0.354 0.382 0.409
L 0.51 0.020
L1 0.64 0.83 1.02 0.025 0.033 0.040
L2 1.52 1.78 2.03 0.060 0.070 0.080
b2
E
be
e1
DL2L1
11.0
2.0
7.2
5.6
2.25
1.2
5.6
Land Pattern Recommendation (Unit : mm)
H
L
C
A1
A
SEATING PLANE
C1
SEE NOTE2
LSP2155
1A Ultra Low Dropout CMOS Regulator
(2) SOT223-3L
Dimensions In Millimeters Dimensions In Inches
Symbol Min Nom Max Min Nom Max
A 1.50 1.65 1.80 0.059 0.065 0.071
A1 0.02 0.05 0.08 0.001 0.002 0.003
B 0.60 0.70 0.80 0.024 0.028 0.031
B1 2.90 3.15(Ref.) 0.114 0.124(Ref.)
c 0.28 0.30 0.32 0.011 0.012 0.013
D 6.30 6.50 6.70 0.248 0.256 0.264
E 3.30 3.50 3.70 0.130 0.138 0.146
e 2.3Basic 0.091Basic
e1 4.6Basic 0.181Basic
H 6.70 7.00 7.30 0.264 0.276 0.287
L 0.91 1.00 1.10 0.036 0.039 0.043
K 1.50 1.75 2.00 0.059 0.069 0.079
α 0
ο 5ο 10ο 0ο 5ο 10ο
β 13ο 13ο
e
KE
H
B1
D
e1
3.3
1.6
6.4
1.6
1.2
2.3
Land Pattern Recommendation (Unit :mm)
B
ß
ß
L
C
A
A1
Seating Plane
a
LSP2155
1A Ultra Low Dropout CMOS Regulator
(3) SOP-8L
A
D
A1
e
BB
E
E1
c
b
WITH PLATING
SECTION B-B
BASE METAL
b1
c1
b
D
A2
A3
C
θ
L1
L
0.25
Dimensions In Millimeters
Symbol Min Nom Max
A - - 1.75
A1 0.10 - 0.25
A2 1.30 1.40 1.50
A3 0.60 0.65 0.70
b 0.39 - 0.48
b1 0.38 0.41 0.43
c 0.21 - 0.26
c1 0.19 0.20 0.21
D 4.70 4.90 5.10
E 5.80 6.00 6.20
E1 3.70 3.90 4.10
e 1.27BSC
L 0.50 - 0.80
L1 1.05BSC
θ 0 - 8°
LSP2155
1A Ultra Low Dropout CMOS Regulator
Important Notice and Disclaimer
LSC reserves the right to make changes to this document and its products and specifications a
t
any time without notice. Customers should obtain and confirm the latest product information an
d
specifications before final design, purchase or use.
LSC makes no warranty, representation or guarantee regarding the suitability of its products fo
r
any particular purpose, nor does LSC assume any liability for application assistance or custome
r
p
roduct design. LSC does not warrant or accept any liability with products which are purchase
d
or used for any unintended or unauthorized application.
N
o license is granted by implication or otherwise under any intellectual property rights of LSC.
LSC products are not authorized for use as critical components in life support devices or systems
without express written approval of LSC.
