Liteon Semiconductor Corporation
LSP3122
150KHZ 3A PWM Buck DC/DC Converter
FEATURES
Output voltage: 3.3V, 5.0V, 12V, and adjustable
output version
Adjustable version output voltage range:1.23V to
37V±4%
150KHz±15% fixed switching frequency
Voltage mode non-synchronous PWM control
Thermal-shutdown and current-limit protection
ON/OFF shutdown control input
Operating voltage can be up to 40V
Output load current: 3A
Low power standby mode
Built-in switching transistor on chip
TO220-5L，TO252-5L and TO263-5L packages
GENERAL DESCRIPTION
The LSP3122 series are monolithic IC that design for
a step-down DC/DC converter, and own the ability of
driving a 3A load without additional transistor
component. Due to reducing the number of external
component, the board space can be saved easily.
The external shutdown function can be controlled by
logic level and then come into standby mode. The
internal compensation makes feedback control have
good line and load regulation without external design.
Regarding protected function, thermal shutdown is to
prevent over temperature operating from damage,
and current limit is against over current operating of
the output switch. The LSP3122 series operates at a
switching frequency of 150 KHz thus allowing smaller
sized filter components than what would be needed
with lower frequency switching regulators. Other
features include a guaranteed ±4% tolerance on
output voltage under specified input voltage and
output load conditions, and ±15% on the oscillator
frequency. The output version included fixed 3.3V,
5V, 12V, and an adjustable type. The packages are
available in a standard 5-lead TO-220 package，
5-lead TO252 package
and a 5-lead TO-263
package.
(2) TO252-5L
(Top View)
5 SD
4 FB
3 GND
2 OUTPUT
1 VIN
5
4
3
2
1
Metal Tab GND
SD
FB
GND
OUTPUT
VIN
APPLICATIONS
Simple High-efficiency step-down regulator
On-card switching regulators
Positive to negative converter
PIN CONFIGURATION
(1) TO220-5L
(Top View)
Metal Tab Gnd
(3) TO263-5L
(Top View)
5
4
3
2
1
SD
FB
GND
OUTPUT
VIN
Symbol
1
2
3
4
5
Name
Vin
Output
Gnd
FB
SD
Descriptions
Operating Voltage Input
Switching Output
Ground
Output Voltage Feedback Control
ON/OFF Shutdown
Metal Tab Gnd
1/12
Rev1.5
Liteon Semiconductor Corporation
LSP3122
150KHZ 3A PWM Buck DC/DC Converter
BLOCK DIAGRAM
SD
5
1 VIN
220mV
Current
Source
bias
1.235V
Reference
2.5V
Regulator
Start up
Comp
-
+
200mV
Comp
+
FB 4
Amp
-
Frequency
compensation
-
+
Comp
Pre-driver
150KHz
OSC.
Thermal
Limit
ABSOLUTE MAXIMUM RATINGS
Symbol
V
CC
V
SD
V
FB
V
OUT
P
D
T
ST
T
OP
V
OP
Paramrter
Supply Voltage
ON/OFF Pin input Voltage
Feedback Pin Voltage
Output Voltage to Ground
Power Dissipation
Storage Temperature
Operating Temperature
Operating Voltage
Rating
+45
-0.3 to +25
-0.3 to +25
-1
Internally Limited
-65 to +150
-40 to +125
+4.5 to +40
Unit
V
V
V
V
W
℃
℃
V
2/12
-
+
3A
Switch
2
3
OUTPUT
GND
Rev1.5
Liteon Semiconductor Corporation
LSP3122
150KHZ 3A PWM Buck DC/DC Converter
ELECTRICAL CHARACTERISTICS (ALL OUTPUT VOLTAGE VERSIONS)
Unless otherwise specified, V
IN
=12V for 3.3V,5V, adjustable version and V
IN
=24V for the 12V version. I
LOAD
=0.5A
Symbol
Paramrter
Conditions
Min.
Typ.
Max.
Unit
50
V
FB
=1.3V(Adjustable
40
nA
I
B
Feedback bias current
version only)
100
127
150
173
KHz
F
OSC
Oscillator frequency
110
173
I
OUT
=3A
no outside circuit V
FB
=0V
V
SAT
Saturation voltage
1.16
1.4
V
force driver on
Max.Duty Cycle(ON)
V
FB
=0V force driver on
100
%
DC
0
Min.Duty Cycle(OFF)
V
FB
=12V force driver off
Peak current
3.6
6.9
A
I
CL
Current limit
no outside circuit
V
FB
=0V force driver on
no outside circuit V
FB
=12V
Output
50
µA
Output=0
I
L
leakage
force driver off
current
Output=-1
V
IN
=40V
5
30
mA
I
Q
Quiescent Current
V
FB
=12V force driver off
7.8
10
mA
Standby Quiesient
ON/OFF Pin=5V V
IN
=12V
85
200
µA
I
STBY
Current
V
IL
V
IH
I
H
I
L
θ
JC
ON/OFF pin logic input
threshold voltage
ON/OFF pin logic input
current
ON/OFF pin input
current
Thermal Resistence
Thermal Resistence
With copper area of
approximately 3 in
2
Low(regultaor ON)
High(regultaor OFF)
V
LOGIC
=2.5V(OFF)
V
LOGIC
=0.5V(ON)
TO252-5L
TO220-5L
TO263-5L
TO252-5L
TO220-5L
TO263-5L
Junction to
case
Junction to
ambient
2.0
6
0.02
10
2.5
3.5
30
28
30
15
µA
5
℃
/W
1.4
0.6
V
θ
JA
℃
/W
3/12
Rev1.5
Liteon Semiconductor Corporation
LSP3122
150KHZ 3A PWM Buck DC/DC Converter
ELECTRICAL CHARACTERISTICS (CONTINUED)
Symbol
LSP3122-ADJ
V
FB
η
LSP3122-3.3V
V
OUT
η
LSP3122-5V
V
OUT
η
LSP3122-12V
V
OUT
Parameter
Output Feedback
Efficiency
Output voltage
Efficiency
Output voltage
Efficiency
Output voltage
Conditions
4.5V≤V
IN
≤40V
0.2A≤I
LOAD
≤3A
V
OUT
programmed for
3V
V
IN
=12V, I
LOAD
=3A
5V≤V
IN
≤40V
0.2A≤I
LOAD
≤3A
V
IN
=12V,
I
LOAD
=3A
7V≤V
IN
≤40V
0.2A≤I
LOAD
≤3A
V
IN
=12V,
I
LOAD
=3A
15V≤V
IN
≤40V
0.2A≤I
LOAD
≤3A
Typ.
1.23
72
3.3
72
5
79
12
11.52/11.4
12.48/12.6
4.8/4.75
5.2/5.25
3.168/3.135
3.432/3.465
Limit
1.193/1.18
1.267/1.28
Unit
V
V
MIN
V
MAX
%
V
V
MIN
V
MAX
%
V
V
MIN
V
MAX
%
V
V
MIN
V
MAX
%
η
Efficiency
V
IN
=15V, I
LOAD
=3A
90
Specifications with
boldface type
are for full operating temperature range, the other type are for TJ=25
º
C.
4/12
Rev1.5
Liteon Semiconductor Corporation
LSP3122
150KHZ 3A PWM Buck DC/DC Converter
TYPICAL PERFORMANCE CHARACTERISTICS
Normalized Output Voltage
Switch Saturation Voltage
SATURATION VOLTAGE(V)
1.60
1.40
1.20
1.00
1
0.80
0.60
2
3
0.5
1
2
3
SWITCH CURRENT(A)
Switching Frequency
160
155
FREQUENCY (KHz)
150
145
140
135
130
1.5
OUTPUT VOLTAGE CHANGE(%)
V
IN
=20V
1.0
0.5
0
-0.5
-1.0
-1.5
0 25 50 75 100 125
-50 -25
JUNCTION TEMPERATURE(℃)
Dropout Voltage
INPUT-OUTPUT DIFFERENTIAL (V)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0 25 50 75 100 125
-50 -25
JUNCTION TEMPERATURE(℃)
ON/OFF Threshold Voltage
THRESHOLD VOLTAGE(V)
2.5
2.0
1.5
1.0
0.5
0.0
ON
OFF
I
LOAD
=3A
Normalixed at T
J
=25℃
1:-40℃
2:25℃
3:125℃
V
IN
=12V
L=33µH R
IND
=0.04O
V
OUT
=V
REG
-50mV
I
LOAD
=3A
I
LOAD
=1A
-50 -25
0
25
50 75 100 125
JUNCTION TEMPERATURE(℃)
Switch Current Limit
SWITCH CURRENT LIMIT(A)
5.50
5.00
4.50
4.00
3.50
V
IN
=12V
Vout=5V
-50 -25 0 25 50 75 100 125
JUNCTION TEMPERATURE(℃)
5/12
-50 -25 0 25
Rev1.5
50 75 100 125
JUNCTION TEMPERATURE(℃)
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