The LA5756 is a separately-excited step-down switching regulator (variable type).
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Features
•
Output smoothing condenser can use a Low ESR condenser for the reliability improvement
•
High efficiency
•
Four external parts
•
Time-base generator (80kHz) incorporated
•
Current limiter incorporated
•
Thermal shutdown circuit incorporated
•
Soft start circuit incorporated
Specifications
Maximum Ratings
at Ta = 25°C
Parameter
Input voltage
Output current
SW pin application reverse
Allowable power dissipation
Symbol
VIN max
IO max
VSW
Pd max1
Pd max2
Operating temperature
Storage temperature
Topr
Tstg
Infinite heat sink.
No heat sink.
Conditions
Ratings
34
3.5
-1
7.5
1.75
-30 to +125
-40 to +150
Unit
V
A
V
W
W
°C
°C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating
Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.
Recommended Operating Conditions
at Ta = 25°C
Parameter
Input voltage range
Symbol
VIN
Conditions
Ratings
4.5 to 32
Unit
V
Semiconductor Components Industries, LLC, 2013
August, 2013
62409 SY 20090611-S00001 / 41509 MS / 40809 MS 20090326-S00003 No.A1438-1/4
LA5756
Electrical Characteristics
at Ta
=
25°C, VO = 3.3V
Parameter
Reference voltage
Efficiency
Switching frequency
Line regulation
Load regulation
Output voltage temperature coefficient
Ripple attenuation factor
Current limiter operating voltage
Thermal shutdown operating temperature
Thermal shutdown hysteresis width
Symbol
VOS
η
f
ΔV
OLINE
ΔV
OLOAD
ΔV
O/ΔTa
RREJ
IS
TSD
ΔTSD
VIN = 15V, IO = 1.0A
VIN= 8 to 20V, IO=1.0A
VIN = 15V, IO = 0.5 to 1.5A
Designed target value*
f = 100 to 120Hz
VIN = 15V
Designed target value*
Designed target value*
4.2
165
15
60
Conditions
min
1.235
Ratings
typ
1.26
78
80
40
10
±0.5
45
100
100
30
max
1.285
V
%
kHz
mV
mV
mV/°C
dB
A
°C
°C
Unit
* Designed target value: No measurement made.
Package Dimensions
unit : mm (typ)
3376
10.0
Pd max -- Ta
3.6
2.7
10.4 MAX
10.0
4.5
1.3
Allowable power dissipation, Pd max -- W
8.0
7.5
100×100×1.5mm
3
Infinite heat sink
θjc=5°C
15.0
6.0
5.6
50×50×1.5mm
3
Al heat
sink
mounting
torque
39N⋅cm
silicone
grease
applied
40
60
80
100
120
140
160
MSG07021
(8.8)
15.5
21.3
4.0
3.3
2.0
1.75
30×30×1.5mm
3
No heat sink
0.9
1 2
(1.6)
5
0.8
1.7
0.4
3.15
7.05
0
-30 -20
0
20
Ambient temperature, Ta --
°C
SANYO : 220-5HMDB
Pin Assignment
(1)VIN (2)SWOUT (3)GND (4)VOS (5)SS
No.A1438-2/4
LA5756
Block Diagram
VIN 1
Constnt
Current
Circuit
Reg.
OCP
2 SWOUT
OSC
RESET
DRIVE
Comp.
TSD
4 VOS
Amp.
ON/OFF Comp.
0.4V
VREF
5
SS
3
GND
Application Circuit Example
L1
VIN
SWOUT
LA5756
C1
D1
C2
VOS
SS
C3
GND
R2
R1
Notes: C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft function is not necessary.
Description of Functional Settings
1. Calculation equation to set the output voltage
This IC controls the switching output so that the VOS pin voltage becomes 1.26V (typ).
The equation to set the output voltage is as follows:
R2
VO = 1+
× 1.26V(typ)
R1
The VOS pin has the inrush current of 1μA (typ). Therefore, the error becomes larger when R1 and R2 resistance
values are large.
No.A1438-3/4
LA5756
2. Start delay function
The SS pin has the internally-connected 10μA (typ) constant-current supply. When the voltage of SS pin exceeds
the threshold voltage, the regulator starts operation. As the threshold is 0.62V(typ), the start delay time can be
calculated as follows:
ex. For setting at 1μF
Td =
C
×
V 1μ
×
0.4
=
=
40 msec
10μ
i
Timing Chart
VIN
SWOUT
VOUT
Td
Tss
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