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SI-8050JF
Step-Down to 5.0 V, 1.5 A, DC/DC Converter
Designed to meet high-current requirements at high efficiency in
industrial and consumer applications; embedded core, memory, or logic
supplies; TVs, VCRs, and office or telecommunications equipment, the
SI-8050JF dc/dc step-down (buck) converter offers a constant 125 kHz
switching frequency essential for low EMI noise. The npn switch is
included on the die along with the oscillator, control, and logic circuitry
requiring only four external components for a regulated 5.0 V output at
up to 1.5 A.
A wide input voltage range and integrated thermal and overcurrent
protection enhance overall system reliability. Reference accuracy and
excellent temperature characteristics are provided. An output-enable
input gives the designer complete control over power up, standby, or
power down.
This device is supplied in a fully molded TO-220-style 5-lead
flange-mounted , high power, isolated plastic package. A similar device
in a lower-power surface-mount plastic package is the SI-8050JD.
Data Sheet
27469.32*
ABSOLUTE MAXIMUM RATINGS
Input Voltage, V
I
. . . . . . . . . . . . .
43 V
FEATURES
■
7 V to 40 V Input Range
■
1.5 A Output Current at 5.0 V
■
2% Output Voltage Tolerance
■
Foldback Current Limiting
■
Constant 125 kHz Switching Frequency
■
200 µA Maximum Standby Current
■
Soft Start Prevents Supply Voltage Dip
■
Remote Voltage Sensing
■
Thermal Protection
APPLICATIONS
■
TVs, VCRs, Electronic Games
■
Embedded Core, Memory, or Logic Supplies
■
Printers and Other Office Equipment
■
Industrial Machinery
■
Telecommunications Equipment
Output Current, I
O
. . . . . . . . . . .
1.5 A*
Enable Input Voltage, V
OE . . . . . . . . . . .
6 V
Junction Temperature, T
J
. . . .
+125°C
Storage Temperature Range,
T
S
. . . . . . . . . . . .
-40°C to +125°C
* Output current rating is limited by input
voltage, duty cycle, and ambient tempera-
ture. Under any set of conditions, do not
exceed a junction temperature of +125°C.
Always order by complete part number, e.g.,
SI-8050JF
.
Sanken Power Devices
from Allegro MicroSystems
SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter
FUNCTIONAL BLOCK DIAGRAM
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Allowable Package Power Dissipation
Recommended Operating Conditions
Min
DC Input Voltage (I
O
≤
1 A)
(I
O
≤
1.5 A)
DC Output Current (V
I
≥
6.3 V)
Operating Junction Temp.
7
8
0
-30
Max
8
40
1.5
+125
Units
V
V
A
°C
For the availability of parts meeting -40°C require-
ments, contact Allegro’s Sales Representative.
This data sheet is based on Sanken data sheet SSJ-02162
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036
Copyright © 2004, 2005 Allegro MicroSystems, Inc.
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SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter
ELECTRICAL CHARACTERISTICS
at T
A
= +25°C, V
I
= 20 V, I
O
= 0.5 A (unless otherwise noted).
Limits
Characteristic
Output Voltage
Ref. Volt. Temp. Coeff.
Output Short-Circuit Current
Efficiency
Operating Frequency
Line Regulation
Load Regulation
Quiescent Current
Symbol
V
O
Test Conditions
Min.
4.90
—
See note
1.6
—
—
V
I
= 10 V ~ 30 V, I
O
= 0.5 A
V
I
= 20 V, I
O
= 0.2 A ~ 0.8 A
I
O
= 0 A
V
CE
= 0.3 V
Chip Enable Voltage
Soft-Start Current
V
CE
I
SS
Converter turn-off voltage
V
SS
= 0 V
—
—
—
—
—
—
Typ.
5.00
±0.5
—
82
125
40
10
7.0
—
—
—
Max.
5.10
—
—
—
—
100
40
—
200
0.5
-100
Units
V
mV/°C
A
%
kHz
mV
mV
mA
µA
V
µA
a
Vref
I
OM
η
f
∆V
O(∆VI)
∆V
O(∆IO)
I
IQ
Typical values are given for circuit design information only.
Note: Output short-circuit current is at point where output voltage has decreased 5% below V
O(nom)
.
Test Circuit
SI-8050JF
C1 = 220 µF/50 V
C2 = 470 µF/25 V
C3 = 0.47 µF/10 V
L1 = 100 µH
D1 = Sanken RK-16
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3
SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter
TYPICAL CHARACTERISTICS
(T
A
= 25°C)
Efficiency
Overcurrent Protection
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Low-Voltage Behavior
Load Regulation
Temperature Stability
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036
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APPLICATIONS INFORMATION
Input Capacitor
(C1). Capacitors with low impedance
for high-frequency ripple current must be used.
Output Capacitor
(C2). Capacitors with low impedance
for high-frequency ripple current must be used. Especially
when the C2 impedance is high, the switching waveform
may not be normal at low temperatures. Film or tantalum
capacitor for C2 may cause abnormal oscillations.
Catch Diode
(D1). Diode D1 must be a Schottky diode.
Other diode types will result in increased forward voltage
spikes, reverse current flow, increased IC power dissipa-
tion during the off period, and possible destruction of the
IC.
Choke Coil
(L1).
If the winding resistance of the choke
coil is too high, the circuit efficiency will decrease. As the
overcurrent protection start current is approximately 2.5 A,
attention must be paid to the heating of the coil by magnetic
saturation due to overload. To reduce the output ripple, the
inductor may be increased at the expense of excessive
board area and cost.
SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter
Soft-Start Capacitor
(C3).
Soft start for the converter
is enabled by connecting a capacitor between terminal 5
and ground. The converter may be turned off by decreasing
the terminal 5 voltage below 0.5 V with either an npn
small-signal transistor or the output of open-collector TTL.
If both a large soft-start capacitor and on/off control are
desired, collector current limiting must be used to prevent
transistor damage. No external voltage can be applied to
terminal 5.
Parallel Operation.
Parallel operation to increase load
current is not permitted.
Overcurrent Protection.
The SI-8000JF series has a
built-in fold-back type overcurrent protection circuit, which
limits the output current at a start-up mode. It thus cannot
be used in applications that require current at the start-up
mode such as:
(1) constant-current load,
(2) power supply with positive and negative outputs to
common load (a center-tap type power supply), or
(3) raising the output voltage by putting a diode or a
resistor between the device ground and system ground.
SI-8050JF
Typical Application
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