SILAN SC431 Datasheet

Silan
Semiconductors

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PFM CONTROLLED SET UP DC/DC
CONVERTERS

DESCRIPTION

The SC431XX series is a group of PFM (frequency)
controlled set-up DC/DC converters. The SC431XX Series
employs CMOS process and laser trimming technologies to
attain low power and high accuracy.

A common problem among pagers is one of noise, but with
the SC431XX, high frequency noise that occurs during switching
is reduced .

Output voltage is programmable in 0.1V steps between

2.0V-7.0V and maximum frequency is 100KHz (typ).

With a built-in switching transistor, a step-up circuit can be
configured using a coil, diode and capacitor connected
externally.

Also available is a CE (chip enable) function that reduces
power consumption during shutdown mode, and an independent
V

pin function (separated power supply and voltage detect

DD

pins) for fly-back circuit.

FEATURES

* Low noise
* Operating voltage range: 0.9V-10V
* Output voltage range: 2.0V-7.0V
* Output voltage accuracy :2.5%
* Maximum oscillator frequency: 100KHz()

SC431XX

SOT-89

* Built-in switching transistor
* CE function and/or separated V

types
* Selectable with 5 pin packages
* Small package: SOT-89 mini-power mold (3

pin)

APPLICATIONS

* Pagers
* Palmtops
* Cameras, video cameras
* Various portable products

DD/VOUR

PIN ASSIGNMENT

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

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SOT-89

123

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1

Rev: 1.0 2001.02.02

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Silan
Semiconductors

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BLOCK DIAGRAM

LX



V

VLXlimiter V

Buffer

ref

DD

SC431XX

V

OUT

V

SS

PFM controll



100kHz

OSC

Chip enable

CE




ABSOLUTE MAXIMUM RATING

Characteristic Symbol Value Unit

V

pin voltage V

OUT

LX pin voltage V
LX pin current I
CE pin voltage V
VDDpin voltage V
Continuous total power dissipation P
Storage temperature T
Operating Temperature T

(Tamb=25°C)

OUT

LX

LX

CE

DD

D
STG
OPR

12 V
12 V

400 Ma

VSS-0.3~V

-30 ~ +80 °C

-40~+125 °C

+0.3 V

OUT

12 V

500 mW

ELECTRICAL CHARACTERISTICS

SC431XX-01

Parameter Symbol Test conditions Min Typ Max Unit

Output voltage V
Maximum input voltage V
Operation start-up voltage V
Operation hold voltage V
No –load input current I

Supply current 1 I

External components connected 2.94 3.00 3.06 V

OUT

IN

External component connected. I

ST

External component connected. I

HID

VIN=output voltage x 0.6, I

IN

No external components. Apply output voltage

DD1

x0.95toV

(Tamb=25°C, fosc=32768Hz,unless otherwise specified)

10 V

=1mA 0.80 0.90 V

OUT

=1mA 0.70 V

OUT

=0mA (note1). 4.6 9.3 µA

OUT

OUT.

19.7 39.4 µA

(To be continued)

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

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2

Rev: 1.0 2001.02.02

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Silan
Semiconductors

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(Continued)

Parameter Symbol Test conditions Min Typ Max Unit

Supply current 2 I

Lx switch-on resistance R

Lx leakage current I

No external components. Apply output voltage

DD2

x0.95toV
No external components. Apply output voltage

SWON

x0.95toV
No external components. V

LXL

OUT.

OUTVLX

=0.4V.

=10V 1.0

OUT=VLX

No external components. Apply output voltage

Duty ratio DTY

x0.95toV

LX: 300Ω pull-up to 5V.

OUT

Measuring of LX waveform.

Maximum oscillation
frequency

MAX F

No external components. Apply output voltage

OSC

x0.95toV

LX: 300Ω pull-up to 5V. Duty

OUT

ratio 75%. Measuring of LX waveform.
No external components. Apply output voltage

Lx limit voltage V

LXLMT

x0.95toV

. Apply voltage to LX. Voltage

OUT

required to produce FOSC x 2.

Efficiency (note3) E

External component connected. 80 %

FFI

SC431XX-02

Parameter Symbol Test conditions Min Typ Max Unit

Output voltage V
Maximum input voltage V

Operation start-up voltage V

Operation hold voltage V

No –load input current I

Supply current 1 I

Supply current 2 I

Lx switch-on resistance R

DD1

DD2

SWON

External component connected. 2.94 3.00 3.06 V

OUT

IN

External component connected.

ST

I

=1Ma.

OUT

External component connected.

HID

I

=1mA.

OUT

VIN=output voltage x 0.6,

IN

I

=0mA (note1)

OUT

No external components.
Apply output voltage x 0.95 to V

OUT.

No external components.
Apply output voltage x 0.95 to V

OUT.

No external components.
Apply output voltage x 0.95 to V

OUT

VLX=0.4V.

SC431XX

2.1 4.2

5.2 7.9

70 75 80 %

85 100 115 KHz

0.7 1.1 V

10 V

0.80 0.90 V

0.70 V

4.6 9.3

19.7 39.4

2.1 4.2

5.2 7.9

(To be continued)

µA

Ω

µA

µA

µA

µA

Ω

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

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3

Rev: 1.0 2001.02.02

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