1-1-3 DC/DC Converter ICs
SI-8000SD Series Surface Mount, Separate Excitation Step-down Switching Mode
■Features
■Lineup
• Surface-mount package (TO263-5)
Part Number
SI-8033SD
3.3
SI-8050SD
5.0
VO (V)
• Output current: 3.0A
IO (A)
3
• High efficiency: 79% typ. (SI-8033SD), 84%
typ. (SI-8050SD)
■Absolute Maximum Ratings
• Requires only 4 discrete external components
Parameter
Symbol
Ratings
43*1
Unit
V
Conditions
• Internally-adjusted phase correction and
output voltage
DC Input Voltage
VIN
When mounted on glass-epoxy board 40 × 40 mm
Power Dissipation*2
PD
3
W
• Built-in reference oscillator (60kHz)
(copper area: 100%)
Junction Temperature
Tj
+125
–40 to +125
3
°C
°C
• Built-in overcurrent and thermal protection
circuits
Storage Temperature
Tstg
θj-c
Thermal Resistance (Junction to Case)
°C/W
• Output ON/OFF available
Thermal Resistance
(Junction to Ambient Air)
When mounted on glass-epoxy board 40 × 40 mm
(copper area: 100%)
θj-a
33.3
°C/W
• Soft start available by S.S pin
*1: 35V for SI-8033SD
*2: Limited by thermal protection circuit.
■Applications
• Power supplies for telecommunication equipment
• Onboard local power supplies
■Recommended Operating Conditions
Ratings
Parameter
Symbol
Unit
SI-8033SD
5.5 to 28
SI-8050SD
7 to 40
DC Input Voltage Range
VIN1
IO
V
A
Output Current Range*
0 to 3.0
Operating Junction Temperature Range
Operating Temperature Range*
Tjop
Top
–30 to +125
–30 to +125
°C
°C
*: Limited by Ta-PD characteristics.
■Electrical Characteristics
(Ta=25°C)
Ratings
Parameter
Symbol
SI-8033SD
SI-8050SD
Unit
min.
3.17
typ.
max.
3.43
min.
typ.
max.
5.2
VO
3.3
4.8
5.0
Output Voltage
V
Conditions
η
VIN=15V, IO=1A
VIN=20V, IO=1A
79
VIN=15V, IO=1A
60
84
Efficiency
%
Conditions
f
VIN=20V, IO=1A
60
Oscillation Frequency
Line Regulation
kHZ
mV
Conditions
∆VOLINE
Conditions
∆VOLOAD
Conditions
∆VO/∆Ta
IS1
VIN=15V, IO=1A
25
VIN=20V, IO=1A
80
30
40
VIN=10 to 30V, IO=1A
10
100
40
VIN=8 to 28V, IO=1A
10
VIN=15V, IO=0.5 to 1.5A
±0.5
Load Regulation
mV
VIN=20V, IO=0.5 to 1.5A
Temperature Coefficient of Output Voltage
±0.5
mV/°C
Overcurrent Protection
Starting Current
3.1
20
3.1
20
A
V
Conditions
VSSL
VIN=15V
0.2
VIN=20V
0.2
Low-Level Voltage
Soft
Start Pin*
Outflow Current at
Low Voltage
ISSL
30
40
30
40
µA
Conditions
VSSL=0.2V
* Pin 5 is a soft start pin. Soft start at power on can be performed with a capacitor connected to
this pin.
SI-8000SD
SI-8000SD
SI-8000SD
The output can also be turned ON/OFF with this pin.
The output is stopped by setting the voltage of this pin to VSSL 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 C3
flows into the ON/OFF control transistor. Therefore, limit the current securely to protect the
transistor if C3 capacitance is large.
5
ON/OFF
5
ON/OFF
C3
5
ON/OFF
C3
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.
VOUT. ON/OFF
Soft start
Soft start
+VOUT. ON/OFF
ICs
20
ETC [ ETC ]
