Supertex SR087 Datasheet

Supertex inc.

Inductorless Switching Regulator

SR087

Adjustable Off-Line

Features

► Efcient operation without magnetics

► No high voltage capacitors

► Adjustable main output voltage (9.0 to 50V)

► Additional 5.0V internal regulator

► Up to 100mA combined output current

► Single BOM for 120VAC/230VAC

► Built-in soft start

► Less than 200mW standby power

Applications

► White goods

► Household appliances

► Lighting controls

► Circuit breakers

► Keep-alive supplies

General Description

The Supertex SR087 is an inductorless switching regulator designed
to operate directly from a rectied AC line. The operating principle is
to turn on a pass transistor when the rectied AC is below the output
voltage, and to turn it off when the output voltage reaches a specic
level. A linear regulator supplied by V

5.0V output. Efciencies of around 55% may be realized for loads
up to 1.0W in 120VAC applications, with around 50% efciencies for
loads up to 800mW in 230VAC applications.

A logic-level enable input allows the SR087 to be disabled – useful
when it is employed as a keep-alive power supply.

WARNING! Galvanic isolation is not provided. Dangerous
voltages are present when connected to the AC line. It is the
responsibility of the designer employing the SR087 to ensure
adequate safeguards are in place to protect the end user from
electrical shock.

The circuits shown in this datasheet are not guaranteed to meet
surge and conducted EMI requirements. The effectiveness of these
circuits may vary with a particular application. The designer should
conduct tests to ascertain compliance with applicable standards and
regulations.

provides an additional xed

OUT

Typical Application Circuit

1.25A

90 -

270VAC

50/60Hz

Doc.# DSFP-SR087
D080613

275V

50A

1.0kV

1.0A

390kΩ 1.1MΩ

Enable

STGD5NB120SZ

GATE

VIN

VGD

SR087

EN

GND

100nF

VOUT

FB

VREG

1.0µF

5.0V
@60mA

470µF

100nF

V

OUT

9.0 - 50VDC
@ 100mA - I

R

= R

1

2

R

2

12.4kΩ

V

1.25V

OUT

REG

- 1

Supertex inc.

www.supertex.com

SR087

Ordering Information

Part Number Package Option Packing

SR087SG-G

-G indicates package is RoHS compliant (‘Green’)

8-Lead SOIC
Narrow Body w/ Heat Slug

2500/Reel

Absolute Maximum Ratings

Parameter Value

Output voltage (V

) -0.3V to 56V

OUT

Feedback voltage (VFB) -0.3V to 6.5V

Enable voltage (VEN) -0.3V to 6.5V

Operating junction temperature -40oC to +125oC

Absolute Maximum Ratings are those values beyond which damage to the device may
occur. Functional operation under these conditions is not implied. Continuous operation
of the device at the absolute rating level may affect device reliability. All voltages are
referenced to device ground.

Typical Thermal Resistance

Package θ

8-Lead SOIC 84OC/W*

ja

Pin Conguration

1

VIN

2

EN

3

GND

VREG

4

Heat Slug

8-Lead SOIC

(top view)
Backside on the SOIC package is at ground potential and may be
connected to ground or left unconnected.

8

7

6

5

GATE

VGD

VOUT

VFB

Product Marking

YYWW

SR087

LLLL

Package may or may not include the following marks: Si or

YY = Year Sealed
WW = Week Sealed
L = Lot Number
= “Green” Packaging

8-Lead SOIC

Recommended Operating Conditions

Sym Parameter Min Typ Max Units Conditions

V

OUT

I

OUT

V

HR

Specications (Unless otherwise noted, T

Sym Parameter Min Typ Max Units Conditions

I

GD

I

OUT(int)

V

GD

V

Gate(hi)

V

Gate(lo)

V

FB(off)

V

FB(hys)

I

FB

V

TRIP(on)

Note:

1. Referenced to V

Output voltage 9.0 - 50 V ---

Load on V
on V

REG

Headroom for internal linear regulator (V

Current consumption at V

Current consumption of the lower circuitry - - 400 µA V

Gate drive supply voltage

Gate output high voltage

Gate output low voltage

, including feedback divider and load

OUT

OUT

= -40°C to +85°C, Voltages referenced to GND pin)

A

GD

1

1

1

100 - - µA ---

- V

) 4.0 - - V ---

REG

- - 60 µA ---

11 13 15 V ---

11 - 15 V ---

- - 0.5 V ---

= 9.0 - 50V

OUT

Feedback voltage (gate off) 1.18 1.25 1.31 V ---

Feedback voltage hysteresis - 50 - mV ---

FB input current - - 500 nA ---

VIN trip voltage (gate on)

OUT.

1

0 - 3.0 V ---

Doc.# DSFP-SR087
D080613

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Specications (cont.)

1.25A

Sym Parameter Min Typ Max Units Conditions

V

TRIP(off)

V

V

t

DIG(on)

t

DIG(off)

t

DFG(off)

V

EN(on)

EN(off)

REG

VIN trip voltage, Gate off

Enable voltage, on 0.2 - - V ---

Enable voltage, off - - 0.75 V

VIN – Gate turn-on delay 0 - 1.0 µs C

VIN – Gate turn-off delay - - 600 ns C

FB – Gate turn-off delay - - 450 ns C

Regulated output voltage 4.750 5.000 5.250 V I

1

9.0 - 15 V ---

---

REG

Gate

Gate

Gate

LOAD

0mA < I

ΔIV

REG

V

D

Note:

1. Referenced to V

V

load regulation -50 - +50 mV

REG

V

OUT

Gate – VGD diode drop - - 1.0 V I = 20mA

OUT.

Block Diagram

SR087

= 1.0nF

= 1.0nF

= 1.0nF VFB = 1.5V

= 1.0mA, V

< 60mA,

LOAD

= 9.0V, T

OUT

= 25°C

Amb

= 9.0V

90 to
270VAC
50/60Hz

275V

50A

1.0kV

1.0A

R

390kΩ

EN

PD

R

GD

1.1MΩ

VIN

13V

Upper circuitry
powered by V

Lower circuitry
powered by V

SR087

STGD5NB120SZ

- V

GD

OUT

- GND

OUT

GATE

Level
Translator

VGD

R
Q
S

1.25V

C

GD

100nF

GND

REG

C

OUT

1.0µF

VOUT

1

FB

VREG

9.0 - 50VDC

C

OUT

470µF

5.0V

C

REG

100nF

R

FB(HI)

R

FB(LO)

12.4kΩ

= R

FB(LO)

V

OUT

1.25V

- 1

Doc.# DSFP-SR087
D080613

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3

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SR087 Timing

RF

V

FB(OFF)

1+

RF

B(HI)

B(LO)

V

V

OUT

SR087

Pass Transistor on

IN

not to scale

Pass Transistor is turned

V

OUT

falls below:

IN

+ V

TRIP(ON)

on when V

Pass Transistor is on but
not conducting since the

Data Sheet Application Section:

Typical Application Circuit

F

V

90 to 270VAC

50/60Hz

IN

1

1.0A

Z

1

275V

50A

* Two resistors used in

series for reasons of

high voltage creepage

and resistor voltage rating.

Enable

100kΩ

input voltage is lower

than the output voltage

D

1

1.0kV

1.0A

200kΩ

200kΩ

R

7

*R

*R

1

2

2

STGD5NB120SZ

*R
510kΩ

*R

510kΩ

VIN

EN

3

4

Pass Transistor is on

and conducting

Q

1

C

1

100nF

8 1

GATE

7

VGD VOUT

SR087

GND

3

Pass Transistor is

turned off once V

reaches the trip point

C

2

1.0µF

6

5

FB

VREG

4

V

REG

5.0VDC

C
100nF

C

3

470µF

4

OUT

V

OUT

12.6VDC

R

5

113kΩ

R

6

12.4kΩ

Doc.# DSFP-SR087
D080613

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SR087

V

Output Voltage*

V

may be adjusted in the range of 9V to 50V*‚ by changing

OUT

feedback resistor R5 according to the following equation.

R5 = R6 [(V

/ 1.25V) - 1]

OUT

Leave R6 at 12.4kΩ or less - it assures a minimum 100µA
load required for the proper operation of the SR087. Change
R3 and R4 according to the R3+R4 equation below. Select
C2 and C3 with appropriate voltage ratings. For C3, use a
low ESR capacitor with an adequate ripple current rating
(800mA

Since V
mum current available from V

). Use ceramic for C2.

RMS

is a linear regulator supplied from V

REG

is reduced as V

REG

, the maxi-

OUT

OUT

is in-

creased due to power considerations.

I

REG(max)

= 1.5W / (V

- 5.0V), or 60mA, whichever is less.

OUT

Input Voltage

To reduce standby power for 230VAC-only applications,
or for supply voltages less than 90Vrms, R3 and R4 should
be changed according to the R3+R4 equation below. R1+R2
should remain at 400kΩ or less. Two resistors in series
are employed to ensure adequate creepage distances for
230VAC operation. For 120VAC-only applications, single re­sistors may be employed.

mH’s) interferes with the normal operation of the SR087 and
should not be used. This is not a concern with the normal
inductance of the AC line or for AC line lters.

AC Line

SR087

Circuitry

The SR087 draws current from the AC line in short, high
current pulses. The transformer’s high inductance tends to
limit the current pulse. Furthermore, inductive kickback on
the falling edge of the current pulse can create high voltage
spikes which must be absorbed by the transient protector.

EMI Capacitor

The use of a small-value capacitor from circuit common to
earth ground prevents the SR087 from operating and should
not be employed.

AC Line

earth

ground

SR087 &
Circuitry

circuit

common

Output Ripple*

Storage capacitor C3 was sized to provide about 2V
at 100mA load (I

OUT

+ I

). For lighter loads, C3 may be re-

REG

duced. Conversely, C3 may be increased for lower ripple.
Use a low ESR capacitor with an adequate ripple current
rating (800mA

for 100mA loads). Efciency and output

RMS

current capability may drop with increased capacitance be­cause of a smaller conduction angle associated with lower
ripple. Due to feedback hysteresis, ripple cannot be reduced
below 4%.

V

*V

REG

must not fall below 9.0V.

RIPPLE(P-P)

requires at least 4.0V of headroom. Therefore, V

≈ (I

OUT

+ I

REG

) / 2fINC

3

, including ripple,

OUT

ripple

P-P

Line Transformer

During initial testing it is tempting to use an isolation
transformer or a variable transformer on the AC line. However,
the high inductance of the transformer (frequently in the

R3 + R4 Equation:

2

√ 2V

- V

IN

(R3 + R4) <

2

- VXcos

X

π • 25µ

-1

√2 • V

X

IN

where VX = V

EMI

The SR087 circuit as depicted on Page 1, (Typical Application
Circuit), meets FCC Class B and CISPR 14-1 (household
appliances) requirements for conducted emissions, for
combined loads of less than 20mA (I

OUT

+ I

REG

).

Fuse

Although the average current drawn from the AC line is
low, the RMS current is fairly high due to the current being
drawn in short, high-current pulses. Since a fuse is basically
a resistor with a power dissipation given by I

2

R, the fuse

RMS

must be sized for the RMS current, not the average current.
For a 1.0W load and 120VAC the RMS current is 700mA
and for a 0.5W load at 230VAC it is 360mA

RMS

.

RMS

Load

Total load on the SR087 is the total load current drawn from
V

(I

) and, since the linear regulator is supplied from

OUT

, it also includes the current drawn from V

Use the minimum anticipated RMS value for VIN.
Take resistor tolerance into account, selecting the

+ 15V

next lower standard value. Choosing a lower value
has no effect other than higher standby power.

REG

(I

REG

). Total

V

OUT

OUT

OUT

,

Doc.# DSFP-SR087
D080613

5

Supertex inc.

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SR087

load is calculated as follows:

I

P

LOAD

LOAD

= I

= V

OUT

+ I

OUT

(I

REG

OUT

+ I

REG

)

UPS

The SR087 will not operate from uninterruptable power
supplies having a square wave output. This type of output is
usually referred to as ‘modied sine wave’.

Transient Protection

The transient protector must be located before the bridge
rectier. The reason for this is to minimize capacitance to
allow the rectied AC to fall below V

OUT

.

Additional Transient Protection

10Ω, 3.0W

1.0A

Wire Wound

90 to
270VAC
50/60Hz

1.0µF
240VAC
X2

275V

50A

1.0kV

1.0A

200kΩ

200kΩ

Enable

STGD5NB120SZ

510kΩ

510kΩ

Since there is no capacitor to absorb AC line transients,
complete transient protection must be provided by the TVS
or MOV device. Since the recommended IGBT is rated at

1.2kV and the SR087 never sees the full input voltage, the
bridge rectier becomes the limiting element when selecting
an MOV. If using a 1.0kV bridge, an MOV having a clamping
voltage of < 1.0kV is recommended.

An RC network on the AC line, as shown in the circuit below,
affords additional protection from line transients, as well as
reducing conducted EMI. It does, however, reduce power
supply efciency.

V

OUT

9.0 - 50VDC
@ 100mA - I

100nF

470µF

R

= R

1

R

2

10.0kΩ

2

V

OUT

1.25V

GATE

VIN

EN

100nF

VGD

SR087

GND

VOUT

VREG

FB

1.0µF

5.0V
@60mA

REG

- 1

Pin Description

Name Pin Description

VIN 1 Rectied AC input voltage

EN 2 Active low enable input

GND 3

VREG 4 Regulated output voltage, xed 5.0V

FB 5 Feedback input

VOUT 6 Output voltage (9.0 - 50V adj.)

VGD 7 Gate drive supply (referenced to V

GATE 8 Drives external IGBT pass transistor

Doc.# DSFP-SR087
D080613

Circuit ground

Note: circuit ground will be at the AC line potential

)

OUT

Supertex inc.

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SR087

8-Lead SOIC (Narrow Body w/Heat Slug) Package Outline (SG)

4.90x3.90mm body, 1.70mm height (max), 1.27mm pitch

D

8

Note 1
(Index Area
D/2 x E1/2)

1

EE1

Top View

A

A2

A

A1

e

Side View

Seating

Plane

b

A

Note 1

Thermal Pad Zone

Bottom View

h

D1

Exposed

h

View A-A

8

E2

1

θ1

View B

Gauge

L2

Plane

L

L1

Seating

θ

Plane

View B

Notes:

1. If optional chamfer feature is not present, a Pin 1 identier must be located in the index area indicated. The Pin 1 identier can be: a molded mark/
identier; an embedded metal marker; or a printed indicator.

Symbol A A1 A2 b D D1 E E1 E2 e h L L1 L2 θ θ1

Dimension

(mm)

NOM - - - - 4.90 - 6.00 3.90 - - - - -

MAX 1.70 0.15 1.55* 0.51 5.00*

JEDEC Registration MS-012, Variation BA, Issue E, Sept. 2005.

* This dimension is not specied in the JEDEC drawing.

† This dimension differs from the JEDEC drawing.

Drawings not to scale.
Supertex Doc. #: DSPD-8SOSG, Version D041009.

MIN 1.25* 0.00 1.25 0.31 4.80*

3.30

3.81

†

5.80* 3.80*

†

6.20* 4.00*

2.29

2.79

†

†

0.25 0.40

1.27
BSC

1.04
REF

0.50 1.27 8O15

0.25
BSC

O5O

0

(The package drawing(s) in this data sheet may not reect the most current specications. For the latest package outline

information go to http://www.supertex.com/packaging.html.)

Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives

an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability
to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and
specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com)

©2013 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.

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D080613

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1235 Bordeaux Drive, Sunnyvale, CA 94089

Tel: [phone]

www.supertex.com

O