1-1-2 Switching Mode Regulator ICs
SI-8000SD Series
■Features
• Surface-mount package (TO263-5)
• Output current: 3.0A
Surface Mount, Separate Excitation Step-down Switching Mode Regulator ICs
■Lineup
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
■Absolute
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
■Applications
• Power supplies for telecommunication equipment
• Onboard local power supplies
*1: 35V for SI-8033SD
*2: Limited by thermal protection circuit.
■Recommended
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.
■Electrical
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
42
ICs
SI-8000SD Series
■External
Dimensions (TO263-5)
Case temperature
measurement point
(0.40)
±0.2
(Unit : mm)
10.0
±0.2
(8.0)
4.5
3-R0.3
±0.2
1.2
(15°)
(4.4)
1.3
+0.10
–0.05
(1.75)
(6.8)
±0.2
9.2±
±0.3
15.3
(3°)
±0.1
0.10
(3°)
15.30
±0.15
±0.3
9.2
±0.2
φ
1.5 Dp:
±0.2
(3°)
(2×R0.45)
Pin Assignment
q
V
IN
w
SW
OUT
e
GND
r
V
OS
t
S.S
Plastic Mold Package Type
Flammability: 94V-0
Product Mass: Approx. 1.48g
(4.6)
2.4
(R0.3)
±0.3
±0.2
±0.2
2.0
(0.75)
4.9
0.88
±0.10
(R0.3)
2.54
0 to 6°
(0.5)
±0.1
(1.7
±0.25
)
1
2
3
9.9
±0.2
0.8
±0.25
(1.7
)
4
5
(3°)
±0.1
(1.7
±0.25
)
0.8
±0.25
(1.7
)
(3°)
2-R0.3
10.0
±0.02
■Block
Diagram
■Reference
Data
Copper Laminate Area on Glass Epoxy Board vs.
thermal resistance (junction to ambient air) (Typical Value)
1
V
IN
Internal power
supply
SW
OUT
Overcurrent
protection
2
Thermal resistance (junction to ambient air)
θ
j-a (°C/W)
55
50
With glass epoxy board of 40
×
40 mm
45
40
35
30
0
Oscillator
Reset
Latch & driver
Comparator
Thermal
protection
V
OS
Error
amplifier
4
4.9
±0.2
Reference voltage
200
400
600
800
1000
1200
1400
1600
1800
Copper Laminate Area (mm
2
)
S.S
5
3
GND
■Typical
Connection Diagram
L1
V
IN
1
V
IN
SW
OUT
2
4
+
D1
V
OUT
SI-8000SD
C
1
+
S.S
5
C
3
GND
GND
3
V
OS
C
2
C
1
: 50V/1000
µ
F
C
2
: 50V/1000
µ
F
C
3
: 0.01
µ
F
(only when soft start function is used)
L
1
: 150
µ
H
D
1
: SPB-G56 (Sanken)
GND
Diode D
1
• Be sure to use Schottky-barrier diode as D
1
.
If other diodes like fast recovery diodes are used, ICs may be destroyed because of the reverse voltage generated by the recovery voltage or ON
voltage.
Choke coil L
1
• If the winding resistance of the choke coil is too high, the efficiency may drop below the rated value.
• As the overcurrent protection starting current is about 3.5 A, take care concerning heat radiation from the choke coil caused by magnetic saturation
due to overload or short-circuited load.
Capacitors C
1
, C
2
, and C
3
• As large ripple currents flow through C
1
and C
2
, use high-frequency and low-impedance capacitors aiming for switching-mode-power-supply use.
Especially when the impedance of C
2
is high, the switching waveform may become abnormal at low temperatures.
For C
2
, do not use a capacitor with an extremely low equivalent series resistance (ESR) such as an OS capacitor or a tantalum capacitor, which may
cause an abnormal oscillation.
• C
3
is a capacitor for soft start. Leave pin 5 open if the soft start function is not used.
This pin is pulled up with a pull-up resistor inside the ICs.
To create the optimum operating conditions, place the components as close as possible to each other.
ICs
43
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