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.

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

Step-Down to 5.0 V, 1.5 A, DC/DC Converter

Data Sheet

27469.32*

Always order by complete part number, e.g., SI-8050JF .

ABSOLUTE MAXIMUM RATINGS

Input Voltage, V

. . . . . . . . . . . . . 43 V

Output Current, I

. . . . . . . . . . . 1.5 A*

Enable Input Voltage, V

. . . . . . . . . . .

6 V

Junction Temperature, T

. . . . +125°C

Storage Temperature Range,

. . . . . . . . . . . . -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.

SI-8050JF

Sanken Power Devices

from Allegro MicroSystems

Switching

Regulators

SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036

Switching

Regulators

FUNCTIONAL BLOCK DIAGRAM

Recommended Operating Conditions

Min

Max

Units

DC Input Voltage (I

1 A)

1.5 A)

DC Output Current (V

6.3 V)

1.5

Operating Junction Temp.

-30

+125

°C

For the availability of parts meeting -40°C require-
ments, contact Allegro's Sales Representative.

Allowable Package Power Dissipation

This data sheet is based on Sanken data sheet SSJ-02162

SI-8050JF

Step-Down

to 5.0 V, 1.5 A,

DC/DC Converter

www.allegromicro.com

Switching

Regulators

ELECTRICAL CHARACTERISTICS

at T

= +25°C, V

= 20 V, I

= 0.5 A (unless otherwise noted).

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output Voltage

4.90

5.00

5.10

Ref. Volt. Temp. Coeff.

Vref

±0.5

mV/°C

Output Short-Circuit Current

See note

1.6

Efficiency

Operating Frequency

125

kHz

Line Regulation

VI)

= 10 V ~ 30 V, I

= 0.5 A

100

Load Regulation

IO)

= 20 V, I

= 0.2 A ~ 0.8 A

Quiescent Current

= 0 A

7.0

= 0.3 V

200

µA

Chip Enable Voltage

Converter turn-off voltage

0.5

Soft-Start Current

= 0 V

-100

µA

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)

SI-8050JF

Test Circuit

C1 = 220 µF/50 V
C2 = 470 µF/25 V
C3 = 0.47 µF/10 V
L1 = 100 µH
D1 = Sanken RK-16

SI-8050JF

Step-Down

to 5.0 V, 1.5 A,

DC/DC Converter

www.allegromicro.com

Switching

Regulators

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.

Typical Application

SI-8050JF

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
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036

Switching

Regulators

Layout Guideline

APPLICATIONS INFORMATION (cont.)

Thermal Protection.

Circuitry turns off the switching

transistor when the junction temperature rises above 150°C.
It is intended only to protect the device from failures due to
excessive junction temperatures and should not imply that
output short circuits or continuous overloads are permitted.

Heat Radiation and Reliability.

The reliability of the

IC is directly related to the junction temperature (T

) in its

operation. Accordingly, careful consideration should be
given to heat dissipation. The graph on page 2 illustrates
the effect of thermal resistance on the allowable package
power dissipation.

When mounting to a heat sink, apply silicone grease (Shin-
Etsu Chemical G746, Dow Corning Toray Silicone SC102,
or Toshiba Silicone SY6260). Recommended mounting
hardware torque: 0.588 ~ 0.686 Nm or 6.0 ~ 7.0 kgf·cm
(4.34 ~ 5.06 lbf·ft).

The junction temperature (T

) can be determined from

either of the following equations:

= (P

) + T

= (P

) + T

where P

= V

(1 [V

])

or the adjacent graph,
V

= the Schottky diode forward voltage, and

= 6°C/W.

SI-8050JF
Step-Down
to 5.0 V, 1.5 A,
DC/DC Converter

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036

Switching

Regulators

Primary Packing: 50 pieces per stick

Product Thickness: 0.7 mm ±0.3 mm
Material: Hard polyvinylchloride (transparent)
Warp: Within 2 mm against L-shape dimension

Secondary Packing: Ten sticks, four layers (2000 pieces
per box). Cardboard box.

Inner Cover

Stick

Shock-Absorbing
Material (50-100 mm)

Stick

Underlay

Shipping Container Dimensions in Millimeters

SI-8050JF

Step-Down

to 5.0 V, 1.5 A,

DC/DC Converter

www.allegromicro.com

Switching

Regulators

The products described herein are manufactured in Japan by Sanken

Electric Co., Ltd. for sale by Allegro MicroSystems, Inc.

Sanken and Allegro reserve the right to make, from time to time, such

departures from the detail specifications as may be required to permit
improvements in the performance, reliability, or manufacturability of its
products. Therefore, the user is cautioned to verify that the information
in this publication is current before placing any order.

When using the products described herein, the applicability and

suitability of such products for the intended purpose shall be reviewed at
the users responsibility.

Although Sanken undertakes to enhance the quality and reliability of

its products, the occurrence of failure and defect of semiconductor
products at a certain rate is inevitable.

Users of Sanken products are requested to take, at their own risk,

preventative measures including safety design of the equipment or
systems against any possible injury, death, fires or damages to society
due to device failure or malfunction.

Sanken products listed in this publication are designed and intended

for use as components in general-purpose electronic equipment or
apparatus (home appliances, office equipment, telecommunication
equipment, measuring equipment, etc.). Their use in any application
requiring radiation hardness assurance (e.g., aerospace equipment) is
not supported.

When considering the use of Sanken products in applications where

higher reliability is required (transportation equipment and its control
systems or equipment, fire- or burglar-alarm systems, various safety
devices, etc.), contact a company sales representative to discuss and
obtain written confirmation of your specifications.

The use of Sanken products without the written consent of Sanken in

applications where extremely high reliability is required (aerospace
equipment, nuclear power-control stations, life-support systems, etc.) is
strictly prohibited.

The information included herein is believed to be accurate and

reliable. Application and operation examples described in this publica-
tion are given for reference only and Sanken and Allegro assume no
responsibility for any infringement of industrial property rights,
intellectual property rights, or any other rights of Sanken or Allegro or
any third party that may result from its use.

EI16EI

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