qSI-8000S
Series
SI-8000S Series
Full-Mold, Separate Excitation Switching Type
sFeatures
•
•
•
•
•
•
•
•
Compact full-mold package (equivalent to TO220)
Output current: 3.0A
High efficiency: 79 to 91%
Requires only 4 external components
Phase correction and output voltage adjustment performed internally
Built-in reference oscillator (60kHz)
Built-in overcurrent and thermal protection circuits
Built-in soft start circuit (output ON/OFF control)
sApplications
• Power supplies for telecommunication equipment
• Onboard local power supplies
sLineup
Part Number
V
O
(V)
I
O
(A)
SI-8033S
3.3
SI-8050S
5.0
SI-8090S
9.0
3.0
SI-8120S
12.0
SI-8150S
15.0
sAbsolute
Maximum Ratings
Parameter
DC Input Voltage
Power Dissipation
Junction Temperature
Storage Temperature
SW Terminal Applied Reverse Voltage
Thermal Resistance(junction to case)
*SI-8033S: 35V
Symbol
V
IN
P
D1
P
D2
T
j
T
stg
V
SW
R
th(j-c)
Ratings
43
*
18(With infinite heatsink)
1.5(Without heatsink, stand-alone operation)
+125
–40 to +125
–1
5.5
Unit
V
W
W
°C
°C
V
°C/W
sRecommended
Operating Conditions
Parameter
DC Input Voltage Range
Output Current Range
Operating Junction Temperature Range
Symbol
SI-8033S
V
IN
I
O
T
jop
5.5 to 28
SI-8050S
7 to 40
Ratings
SI-8090S
12 to 40
0 to 3.0
–30 to +125
SI-8120S
15 to 40
SI-8150S
18 to 40
V
A
°C
Unit
80
qSI-8000S
Series
Caution
1. Selecting External Components
(1) Choke coil L
1
To maintain the stable operation of the regulator, choke coil L
1
should be selected appropriately.
When selecting choke coil L
1
, consider the following:
a) Suitable for a switching regulator
Do not use a coil as a noise filter because it generates excess
heat.
b) Appropriate inductance
The greater the inductance of the choke coil, the smaller the
output ripple voltage. However, the size of the coil increases
large as the inductance increases. If the inductance is low, a
greater peak current flows to the IC and loss increases. This
is not favorable for stable operation.
The standard external circuit shows reference inductance val-
ues suitable for stable operation. However, the appropriate
inductance may also be calculated as follows:
(V
IN
–V
O
)•V
O
L=
∆IL•V
IN
•f
Where, deltaIL indicates the ripple current of the choke coil
that is roughly set as follows:
• If the working output current is close to the maximum rating
(3 A) of SI-8000S
Ripple current = output current
×
0.2 to 0.3
• If the working output current is about 1.0A or less
Ripple current = output current
×
0.3 to 0.4
c) Satisfying the rated current
The rated current of a choke coil must be greater than the
maximum load current. Note that the inductance decreases
drastically and an excess current flows if the load current ex-
ceeds the rated current of the coil.
d) Good DC current superposition characteristics
The current flowing through a choke coil is a triangular wave-
form current superimposed on a DC current equal to the load
current. The coil inductance decreases as the load current
increases. In general, the coil can be used until the induc-
tance drops to 50% of the rated value. Use this as the refer-
ence value for selection.
(2) Input capacitor C
1
Input capacitor C
1
operates as a bypass capacitor in the input
circuit.
When selecting input capacitor C
1
, consider the following:
a) The breakdown voltage is higher than the maximum input volt-
age.
b) Satisfies the allowable ripple current
Exceeding the ratings of this capacitor or using it without de-
rating may reduce its service life and also cause the regulator
to malfunction. Therefore, an input capacitor with a sufficient
margin should be selected. With the SI-8000S Series, the
effective ripple current Irms flowing to the input capacitor can
be calculated approximately as follows:
V
O
×
I
O
I
rms
1.2
×
V
IN
(3) Output capacitor C
2
Output capacitor C
2
operates as a smoothing capacitor for switch-
ing output. The output ripple voltage from the regulator is deter-
mined by the product of the pulsating current part
∆IL
(=C
2
charge-
discharge current) of the choke coil current and the equivalent
series resistance ESR of the output capacitor C
2
.
V
rip
=∆IL•C2ESR
Therefore, a capacitor of low equivalent series resistance ESR
should be selected to reduce the output ripple voltage. It is rec-
ommended to select a low-impedance capacitor intended for use
with switching regulators as C
2
.
(4) Diode D
1
Use a Schottky barrier diode for D
1
. If you use a general rectifier
diode or fast recovery diode, the IC may be damaged. (Sanken
RK46 recommended)
2. Notes on Pattern Design
(1) Large current line
Since a large current flows through the bold lines in the standard
external circuit make the pattern as wide and as short as pos-
sible.
V
IN
L
1
1
SI-8000S
C
1
+
3
4
D
1
GND
GND
C
2
+
2
V
OUT
100%
Inductance
(2) Input capacitor
Place the input capacitor C
1
and output capacitor C
2
as close to
the IC as possible. Since a large current flows through the lead
wires of the input and output capacitors to charge and discharge
them quickly, minimize the lead wire length. The pattern around
the capacitors should also be minimized.
Load current
I
O
(max.)
C
1
. C
2
.
C
1
. C
2
.
+
+
50%
e) Less noise
A drum-type open magnetic core coil can affect peripheral
circuits with noise because the flux passes outside the coil.
To avoid this problem, use a toroidal, EI, or EE type open
magnetic core coil.
Example of bad pattern
Example of good pattern
84
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