1-1-2 Switching Mode Regulator ICs
SI-8000SD Series
sFeatures
• Surface-mount package (TO263-5)
• Output current: 3.0A
Surface Mount, Separate Excitation Step-down Switching Mode Regulator ICs
sLineup
Part Number
V
O
(V)
I
O
(A)
SI-8033SD
3.3
3
SI-8050SD
5.0
• High efficiency: 79% typ. (SI-8033SD), 84%
typ. (SI-8050SD)
• Requires only 4 discrete external components
• Internally-adjusted phase correction and
output voltage
• Built-in reference oscillator (60kHz)
• Built-in overcurrent and thermal protection
circuits
• Output ON/OFF available
• Soft start available by S.S pin
sAbsolute
Maximum Ratings
Parameter
DC Input Voltage
Power Dissipation*
2
Junction Temperature
Storage Temperature
Thermal Resistance (Junction to Case)
Thermal Resistance
(Junction to Ambient Air)
Symbol
V
IN
P
D
T
j
T
stg
Ratings
43*
1
3
+125
–40 to +125
3
33.3
Unit
V
W
°C
°C
°C/W
°C/W
When mounted on glass-epoxy board 40
×
40 mm
(copper area: 100%)
When mounted on glass-epoxy board 40
×
40 mm
(copper area: 100%)
Conditions
θ
j-c
θ
j-a
sApplications
• Power supplies for telecommunication equipment
• Onboard local power supplies
*1: 35V for SI-8033SD
*2: Limited by thermal protection circuit.
sRecommended
Operating Conditions
Ratings
Parameter
DC Input Voltage Range
Output Current Range*
Operating Junction Temperature Range
Operating Temperature Range*
Symbol
V
IN1
I
O
T
jop
T
op
SI-8033SD
5.5 to 28
0 to 3.0
–30 to +125
–30 to +125
SI-8050SD
7 to 40
Unit
V
A
°C
°C
*: Limited by Ta-P
D
characteristics.
sElectrical
Characteristics
Ratings
Parameter
Symbol
min.
Output Voltage
Efficiency
Oscillation Frequency
Line Regulation
Load Regulation
Temperature Coefficient of Output Voltage
Overcurrent Protection
Starting Current
Soft
Start Pin
*
Low-Level Voltage
Outflow Current at
Low Voltage
V
O
Conditions
3.17
SI-8033SD
typ.
3.3
V
IN
=15V, I
O
=1A
79
V
IN
=15V, I
O
=1A
60
V
IN
=15V, I
O
=1A
25
V
IN
=8 to 28V, I
O
=1A
10
V
IN
=15V, I
O
=0.5 to 1.5A
±0.5
3.1
V
IN
=15V
0.2
20
30
40
V
SSL
=0.2V
20
3.1
V
IN
=20V
0.2
30
40
30
80
max.
3.43
min.
4.8
SI-8050SD
typ.
5.0
V
IN
=20V, I
O
=1A
84
V
IN
=20V, I
O
=1A
60
V
IN
=20V, I
O
=1A
40
V
IN
=10 to 30V, I
O
=1A
10
V
IN
=20V, I
O
=0.5 to 1.5A
±0.5
40
100
max.
5.2
(T
a
=25°C)
Unit
V
%
kH
Z
mV
mV
mV/°C
A
V
η
Conditions
f
Conditions
∆V
OLINE
Conditions
∆V
OLOAD
Conditions
∆V
O
/∆T
a
I
S1
Conditions
V
SSL
I
SSL
Conditions
µ
A
* Pin 5 is a soft start pin. Soft start at power on can be performed with a capacitor connected to
this pin.
The output can also be turned ON/OFF with this pin.
The output is stopped by setting the voltage of this pin to V
SSL
or lower.
Soft-start pin voltage can be changed with an open-collector drive circuit of a transistor.
When using both the soft-start and ON/OFF functions together, the discharge current from C
3
flows into the ON/OFF control transistor. Therefore, limit the current securely to protect the
transistor if C
3
capacitance is large.
The ON/OFF pin is pulled up to the power supply in the IC, so applying the external voltage is
prohibited.
If this pin is not used, leave it open.
SI-8000SD
SI-8000SD
SI-8000SD
5 ON/OFF
5 ON/OFF
C3
5 ON/OFF
C3
V
OUT.
ON/OFF
Soft start
Soft start
+V
OUT.
ON/OFF
54
ICs
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