LSP3124 Datasheet PDF - Lite-On


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LSP3124
Lite-On

Part Number LSP3124
Description 150KHZ 3A PWM Buck DC/DC Converter
Page 9 Pages

LSP3124 datasheet pdf
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Liteon Semiconductor Corporation
LSP3124
150KHZ 3A PWM Buck DC/DC Converter
„ FEATURES
z Output voltage: 3.3V, 5.0V, 12V, and adjustable
output version
z Adjustable version output voltage range:1.23V to
18V±4%
z 150KHz±15% fixed switching frequency
z Voltage mode non-synchronous PWM control
z Thermal-shutdown and current-limit protection
z ON/OFF shutdown control input
z Operating voltage can be up to 22V
z Output load current: 3A
z Low power standby mode
z Built-in switching transistor on chip
z TO252-5L packages
„ APPLICATIONS
z Simple High-efficiency step-down regulator
z On-card switching regulators
z Positive to negative converter
„ GENERAL DESCRIPTION
The LSP3124 series are monolithic IC that design for
a step-down DC/DC converter, and own the ability of
driving a 3 A load without additio nal transistor
component. Due to reducing th e numb er o f e xternal
component, the board s pace can be saved easily.
The external shutdown function can be controlled by
logic le vel a nd then come in to s tandby mod e. T he
internal compensation mak es feedback control have
good line and load regulation without external design.
Regarding protected function, thermal shutdown is to
prevent over tempera ture operating from damag e,
and current limit is against over current operating of
the output switch. If current limit function occurred and
VFB is down to 0.5V below , the switching frequency
will be reduced. The LSP3124 series operates at a
switching frequency of 150 KHz thus allowing smaller
sized filter components than what wo uld be need ed
with lower frequency switching reg ulators. Oth er
features include a g uaranteed ±4% tolerance on
output voltage under specified input voltage and
output load conditions, and ±15% on the oscillator
frequency. The ou tput version include d fixe d 3 .3V,
5V, 12V, and an adjustable type. The package is
available in a standard 5-lead TO-252 package.
„ PIN CONFIGURATION
(Top View)
5
4
3
2
1
Metal Tab GND
SD
FB
GND
OUTPUT
VIN
Symbol Name
1 Vin
2 Output
3 Gnd
4 FB
5 SD
Descriptions
Operating Voltage Input
Switching Output
Ground
Output Voltage Feedback Control
ON/OFF Shutdown
1/9
Rev1.2
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Liteon Semiconductor Corporation
LSP3124
150KHZ 3A PWM Buck DC/DC Converter
„ ABSOLUTE MAXIMUM RATINGS
Symbol Paramrter
VCC Supply Voltage
VSD ON/OFF Pin input Voltage
VFB Feedback Pin Voltage
VOUT
Output Voltage to Ground
PD Power Dissipation
TST Storage Temperature
TOP Operating Temperature
VOP Operating Voltage
Rating
+24
-0.3 to +18
-0.3 to +18
-1
Internally Limited
-65 to +150
-40 to +125
+4.5 to +22
Unit
V
V
V
V
W
ɗ
ɗ
V
„ ELECTRICAL CHARACTERISTICS (ALL OUTPUT VOLTAGE VERSIONS)
Unless otherwise specified, VIN=12V for 3.3V,5V, adjustable version and VIN=18V for the 12V version. ILOAD=0.5A
Symbol Paramrter
IB Feedback bias current
FOSC Oscillator frequency
FCSP
Short Circuit Oscillator
Frequency
VSAT Saturation voltage
DC
Max.Duty Cycle(ON)
Min.Duty Cycle(OFF)
ICL Current limit
IL
IQ
ISTBY
Output=0
Output
leakage
Output=-1 current
Quiescent Current
Standby Quiesient
Current
VIL Low(OreNg/uOltFaForpin logic input
VIH threshold voltage
IH
ON/OFF pin logic input
current
IL
ON/OFF pin input
current
Conditions
VFB=1.3V(Adjustable
version only)
When Current Limit
Occur and
VFB0.5V, TA=25°C
IOUT=3A
no outside circuit
VFB=0V force driver on
VFB=0V force driver on
VFB=12V force driver off
Peak current
no outside circuit
VFB=0V force driver on
no outside circuit
VFB=12V force driver off
VIN=22V
VFB=12V force driver off
ON/OFF Pin=5V
VIN=22V
ON)
High(regultaor OFF)
VLOGIC=2.5V(OFF)
VLOGIC=0.5V(ON)
Min.
-10
127
110
Typ.
150
10 30 50
0
3.6
3.4
70
2.0
5
1.3
Max.
-50
-100
173
173
1.4
1.5
100
6.9
7.5
-50
-30
10
200
250
0.6
-15
-5
Unit
nA
KHz
kHz
V
%
A
μA
mA
mA
μA
V
μA
șJC Thermal Resistence
TO252-5L
Junction
to case
10
ɗ/W
Thermal Resistence
șJA
with Copper Area of
Approximately 3 in2
TO252-5L
Junction
to ambient
50
ɗ/W
Specifications with boldface type are for full operating temperature range, the other type are for TJ=25ºC.
2/9 Rev1.2



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Liteon Semiconductor Corporation
LSP3124
150KHZ 3A PWM Buck DC/DC Converter
„ ELECTRICAL CHARACTERISTICS (CONTINUED)
Sy
LSP3124-ADJ
mbol
Parameter
VFB Output Feedback
Ș Efficiency
Conditions
5V”VIN”22V
0.2A”ILOAD”3A
VOUT programmed for
3V
VIN =12V, I LOAD =3A
Typ.
1.23
75
Limit
1.193/1.18
1.267/1.28
LSP3124-3.3V
VOUT
Output voltage
5.5V”VIN”22V
0.2A”ILOAD”3A
3.3
3.168/3.135
3.432/3.465
Ș Efficiency
VIN =12V, I LOAD =3A
75
LSP3124-5.0V
VOUT
Output voltage
8V”VIN”22V
0.2A”ILOAD”3A
5
4.8/4.75
5.2/5.25
Ș Efficiency
VIN =12V, I LOAD =3A
80
LSP3124-12V
VOUT
Output voltage
15V”VIN”22V
0.2A”ILOAD”3A
12
11.52/11.4
12.48/12.6
Ș Efficiency
VIN =16V, I LOAD =3A
90
Specifications with boldface type are for full operating temperature range, the other type are for TJ=25ºC.
„ BLOCK DIAGRAM
Unit
V
VMIN
VMAX
%
V
VMIN
VMAX
%
V
VMIN
VMAX
%
V
VMIN
VMAX
%
3/9 Rev1.2



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Liteon Semiconductor Corporation
LSP3124
150KHZ 3A PWM Buck DC/DC Converter
„ FUNCTION DESCRIPTION
Pin Function
VIN
This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present
at this pin to minimiz e voltage trans ients and to supply the switching current s needed by the regulator.
Ground
Circuit ground.
Output
Interna l switch. The voltage a t th is p in switches between ( VIN – VSAT) and approxima tely – 0.5 V, with a du ty
cycle of app roxima tely V OUT / VIN. T o minimize coupling to sensitive circuitry, the PC board copper are a
connected to this pin should be kept a minimum.
Feedback
Senses the regulated output voltage to complete the feedback loop.
ON/OFF
Allows the s witching reg ulator circuit to be shutd own using lo gic leve l sig nals thus dr opping the total input
supply curre nt to approximately 1 50uA. Pulling this pin below a threshold voltage of approxima tely 1.3 V turns the
regulator on , and pu lling this pin ab ove 1.3 V (u p to a ma ximum o f 18 V) shuts the r egulator do wn. If th is
shutdown feature is not needed, the ON/O FF pin can be wired to the ground pin.
Thermal Considerations
The TO-252 surface mou nt package tab is designed to be soldered to the copper on a printed circuit b oard. Th e
copper and the board are the heat sink for this package and the other heat p roducing components, such as th e
catch diode and induc tor. The PC board copper ar ea that the package is soldered to should be at least 0.4 in2,
and ideally should have 2 or more square inches of 2 oz. Additional copper area improves the
thermal
characteristics, but with copper areas greater than approximately 6 in 2, only sma ll improve ments in hea t
dissipation are realized. If further thermal improvements a re n eeded, double sid ed, m ultilayer PC board w ith
large copper areas and/or airflow are recommended.
The LSP312 4 (TO-252 p ackage) junction te mperature rise abo ve a mbient temperature with a 3 A lo ad for
various input and output voltages. This data was taken with the circuit operatin g as a buck switching regulator
with all components mo unted on a PC board to simulate th e junction temperature u nder actual operating
conditions. T his curve ca n be used for a quick check for the a pproxima te junction temperature for various
conditions, b ut be aware tha t there a re many factors that can affect the ju nction tempe rature. When load
currents higher than 2 A are used, doub le sided or multilayer PC boards with large copper areas and/or airflow
might be needed, especially for high ambient temperatures and high output voltages.
For the best thermal per formance, wide copper tr aces and ge nerous amou nts o f prin ted circuit boa rd copper
should be us ed in the bo ard la yout. (Once exception to this is the ou tput (s witch) pin , which should not ha ve
large areas o f copper .) Large areas of copper provide the best transfer o f heat (lower ther mal resistanc e) to the
surrounding air, and moving air lowers the thermal resistance even further.
Package the rmal resistan ce and junction temperature rise nu mbers are all approximate, and there a re man y
factors that will a ffect th ese numbers. Some of th ese factors include board size, shape, th ickness, p osition,
location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper
thickness, single or double-sided, multilayer board and the amount of solder on the board. The effectiveness of
the PC board to d issipate hea t a lso depends on the size, qu antity and s pacing o f o ther compon ents on the
board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such
as the catch diode will add heat to the PC board a nd the heat can vary as the input voltage changes. For the
inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a
heat sink taking heat away from the board, or it could add heat to the board.
4/9 Rev1.2




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