Liteon Semiconductor Corporation
LSP3121
52KHZ 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%
52KHz±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
TO252-5L package
GENERAL DESCRIPTION
The LSP3121 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 LSP3121 series operates at a
switching frequency of 52 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 package is
available in a standard 5-lead TO-252 package.
APPLICATIONS
Simple High-efficiency step-down regulator
On-card switching regulators
Positive to negative converter
PIN CONFIGURATION
TO252-5L
(Top View)
5
4
3
2
1
Metal Tab GND
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
1/8
Rev1.1
Liteon Semiconductor Corporation
LSP3121
52KHZ 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
V
FB
=1.3V(Adjustable
50
I
B
Feedback bias current
40
nA
version only)
100
44
52
60
F
OSC
Oscillator frequency
KHz
38
66
I
OUT
=3A
no outside circuit
V
SAT
Saturation voltage
1.4
1.8
V
V
FB
=0V 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
no outside circuit
I
CL
Current limit
5.8
A
V
FB
=0V force driver on
no outside circuit
Output
2
mA
Output=0
V
FB
=12V force driver off
I
L
leakage
current
Output=-1
V
IN
=40V
30
mA
I
Q
Quiescent Current
V
FB
=12V force driver off
5
10
mA
Standby Quiesient
ON/OFF Pin=5V
80
200
µA
I
STBY
Current
V
IN
=40V
V
IL
V
IH
I
H
I
L
θ
JC
θ
JA
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
TO252-5L
Junction
to case
Junction
to ambient
10
30
2.4
30
µA
10
℃
/W
℃
/W
1.4
0.8
V
ELECTRICAL CHARACTERISTICS (CONTINUED)
Symbol
V
FB
η
LSP3121-3.3V
V
OUT
η
LSP3121-5V
V
OUT
η
LSP3121-12V
V
OUT
η
Parameter
Output Feedback
Efficiency
Output voltage
Efficiency
Output voltage
Efficiency
Output voltage
Efficiency
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
V
IN
=15V, I
LOAD
=3A
3/8
Typ.
1.23
72
3.3
72
5
79
12
90
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
%
Rev1.1
LSP3121-ADJ
3.168/3.135
3.432/3.465
4.8/4.75
5.2/5.25
11.52/11.4
12.48/12.6
嵌入式系统
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