Switching Type Regulator ICs SI-3201S
Features
Output current of 3A (Ta = 25ºC, V
IN
= 8 to 18V)
High efficiency of 82% (V
IN
= 14V, I
O
= 2A)
Requires 5 external components only
Built-in reference oscillator (60kHz)
Phase internally corrected
Output voltage internally corrected
Built-in overcurrent and thermal protection circuits
Built-in soft start circuit
External Dimensions
(unit: mm)
3.2
±0.2
0.5
10.0
±0.2
4.2
±0.2
2.8
±0.2
4.0
±0.2
7.9
±0.2
16.9
±0.3
a
(2.0)
0.95
±0.15
(4.6)
0.85
–0.1
+0.2
b
2.6
±0.1
Absolute Maximum Ratings
Parameter
Input voltage
Output voltage
SW
OUT
terminal voltage
Power Dissipation
P
D2
Junction temperature
Storage temperature
Junction to case thermal resistance
Junction to ambient-air thermal
resistance
Tj
Tstg
j
-c
j
-a
(Ta=25ºC)
Symbol
V
IN
I
O
V
SWOUT
P
D1
Ratings
35
3
–1
22
1.8
–40 to +150
–40 to +125
5.5
66.7
Unit
V
A
V
W
W
ºC
ºC
ºC/W
ºC/W
Conditions
P1.7
±0.7
•4 = 6.8
±0.7
0.45
+0.2
–0.1
3.9
±0.7
(4.3)
8.2
±0.7
With infinite heatsink
1
2
3
4
5
Stand-alone
1. V
IN
2. SW
OUT
3. GND
4. V
S
5. SS
a: Part No.
b: Lot No.
(Forming No. 1101)
Standard Circuit Diagram
V
IN
1
V
IN
c
SI-3201S
a
d
f
b
e
Recommended Operating Conditions
Parameter
Input voltage
Output current
Operating temperature
Symbol
min
V
IN
I
O
Top
8
0.5
–40
Ratings
typ
max
18
3
+85
Unit
V
A
ºC
Ta—P
D
characteristics
Conditions
SW Tr
SW
OUT
2
(8.0)
5.0
±0.6
L
1
V
O
C
1
+
5 SS
h
D
1
g
(17.9)
+
C
2
V
S
4
i
C
3
GND
GND
3
GND
Electrical Characteristics
Parameter
Output voltage
Line regulation
Load regulation
Efficiency
Symbol
min
V
O
V
O LINE
V
O LOAD
82
f
OSC
Iq
I
S
V
SSL
I
SSL
R
DIS
15
25
200
3.1
50
60
5
4.80
Ratings
typ
5.00
(V
IN
= 14V, I
OUT
= 2A, Tj = 25ºC unless otherwise specified)
C
1
: 1000µF
C
2
: 1000µF
a: Internal power supply
b: Thermal protection
c: Reference oscillator
d: Reset
e: Latch & driver
L
1
: 250µH
D
1
: RK46 (Sanken)
f : Comparator
g: Overcurrent protection
h: Error amplifier
i : Reference voltage
max
5.20
100
50
Unit
V
mV
mV
%
Conditions
V
IN
= 8 to 18V
I
O
= 0.5 to 3A
*
1
Oscillation frequency
Quiescent circuit current
Overcurrent protection starting
current
Soft
*
3
start
terminal
Low level voltage
Source current when low
Discharge resistance
70
10
kHz
mA
A
I
O
= 0A
*
2
0.2
35
V
µA
kΩ
V
SSL
= 0.2V
V
IN
= 0V
Notes:
*1. Efficiency is calculated by the following equation:
V
O
• I
O
=
• 100 (%)
V
IN
• I
IN
*2. A dropping-type overcurrent protection circuit is built in the IC.
*3. An external voltage may not be applied to the soft start terminal. As shown in the diagram to the right, use this IC in the
soft start mode with a capacitor or in the open-collector drive mode with a transistor. Leave the soft start terminal open
when not using it since it is already pulled up in the IC.
Cautions:
(1) A high-ripple current flows through
C
1
and
C
2
. Use high-ripple
type
1000µF
or higher capacitors with low internal resistance.
Refer to the respective data books for more information on
reliability and electrical characteristics of the capacitor.
(2)
C
3
is a capacitor used for soft start.
(3)
L
1
should be a choke coil with a low core loss for switching
power supplies.
(4) Use a Schottky barrier diode for
D
1
and make sure that the
reverse voltage applied to the 2nd terminal (SW
OUT
terminal) is
within the maximum ratings (–1V). If you use a fast-recovery
diode, the recovery voltage and the ON forward voltage may
cause a reversed-bias voltage exceeding the maximum ratings
to be applied to the 2nd terminal (SW
OUT
terminal). Applying a
reversed-bias voltage exceeding the maximum rating to the
2nd terminal (SW
OUT
terminal) may damage the IC.
(5) The 4th terminal (
V
S
) is an output voltage detection terminal.
Since this terminal has a high impedance, connect it to the
positive (+) terminal of
C
2
via the shortest possible route.
(6) Leave the 5th terminal (soft start terminal) open when not
using it. It is pulled up internally.
(7) To ensure optimum operating environment, connect the high-
frequency current line with minimum wiring length.
SI-3201S
5
SS
C
3
SI-3201S
5
SS
SI-3201S
5
SS
C
3
22
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