SI-8025JF-T - Allegro MicroSystems, Inc.

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-8025JF 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 2.5 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.

FEATURES

■4.5 V to 40 V Input Range

■1.5 A Output Current at 2.5 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 2.5 V, 1.5 A, DC/DC Converter

Data Sheet

27469.12*

Always order by complete part number, e.g., SI-8025JF .

ABSOLUTE MAXIMUM RATINGS

Input Voltage, VI. . . . . . . . . . . . . 43 V

Output Current, IO. . . . . . . . . . . 1.5 A*

Enable Input Voltage, VOE . . . . . . . . . . . 6 V

Junction Temperature, TJ. . . . +125°C

Storage Temperature Range,

TS. . . . . . . . . . . . -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-8025

Sanken Power Devices

from Allegro MicroSystems

Switching

Regulators

SI-8025JF

Step-Down

to 2.5 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 (IO ≤ 1 A) 5.3 6.3 V

(IO ≤ 1.5 A) 6.3 40 V

DC Output Current (VI ≥ 6.3 V) 0 1.5 A

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-01952

SI-8025JF

Step-Down

to 2.5 V, 1.5 A,

DC/DC Converter

www.allegromicro.com

Switching

Regulators

ELECTRICAL CHARACTERISTICS at TA = +25°C, VI = 12 V, IO = 0.5 A (unless otherwise noted).

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Output Voltage VO2.45 2.50 2.55 V

Ref. Volt. Temp. Coeff. aVref — ±0.5 — mV/°C

Output Short-Circuit Current IOM See note 1.6 — — A

Efficiency η—74— %

Operating Frequency f — 125 — kHz

Line Regulation ∆VO(∆VI) VI = 7 V ~ 30 V, IO = 0.5 A — 25 80 mV

Load Regulation ∆VO(∆IO) VI = 12 V, IO = 0.2 A ~ 0.8 A — 10 30 mV

Quiescent Current IIQ IO = 0 A — 7.0 — m A

VCE = 0.3 V — — 200 µA

Chip Enable Voltage VCE Converter turn-off voltage — — 0.5 V

Soft-Start Current ISS VSS = 0 V — — -100 µ A

Typical values are given for circuit design information only.

Note: Output short-circuit current is at point where output voltage has decreased 5% below VO(nom).

SI-8025JF 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-8025JF

Step-Down

to 2.5 V, 1.5 A,

DC/DC Converter

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036

Switching

Regulators

TYPICAL CHARACTERISTICS

(TA = 25°C)

 Efficiency  Overcurrent Protection

 Low-Voltage Behavior  Load Regulation

 Temperature Stability

SI-8025JF

Step-Down

to 2.5 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 ApplicationSI-8025JF

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-8025JF

Step-Down

to 2.5 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 (TJ) 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 (TJ) can be determined from

either of the following equations:

TJ = (PDRθJA) + TA

or TJ = (PDRθJC) + TC

where PD = VIII – VOIO – VFIO(1 – [VO/VI])

or the adjacent graph,

VF = the Schottky diode forward voltage, and

RθJC = 6°C/W.

SI-8025JF

Step-Down

to 2.5 V, 1.5 A,

DC/DC Converter

www.allegromicro.com

Switching

Regulators

Dimensions in Millimeters

Terminal Finish: Sn–3Ag–0.5Cu, 2nd level interconnect category (e1)

Product Weight: Approx. 2.3 g

Terminal spacing is measured at lead tips.

SI-8025JF

Step-Down

to 2.5 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-8025JF

Step-Down

to 2.5 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 pr oducts described her ein, the applicability and

suitability of such pr oducts for the intended purpose shall be r eviewed at

the users responsibility .

Although Sanken undertakes to enhance the quality and r eliability of

its pr oducts, the occurr ence of failur e and defect of semiconductor

pr oducts at a certain rate is inevitable.

Users of Sanken pr oducts ar e r equested to take, at their own risk,

pr eventative measur es including safety design of the equipment or

systems against any possible injury , death, fir es or damages to society

due to device failure or malfunction.

Sanken pr oducts listed in this publication are designed and intended

for use as components in general-purpose electr onic equipment or

apparatus (home appliances, office equipment, telecommunication

equipment, measuring equipment, etc.). Their use in any application

r equiring radiation har dness assurance (e.g., aerospace equipment) is

not supported.

When considering the use of Sanken pr oducts in applications wher e

higher r eliability is r equired (transportation equipment and its contr ol

systems or equipment, fir e- or burglar-alarm systems, various safety

devices, etc.), contact a company sales r epresentative to discuss and

obtain written confirmation of your specifications.

The use of Sanken pr oducts without the written consent of Sanken in

applications wher e extremely high r eliability is requir ed (aer ospace

equipment, nuclear power-contr ol stations, life-support systems, etc.) is

strictly pr ohibited.

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