SGS Thomson Microelectronics ST735TCN, ST735TCD-TR, ST735TCD, ST735SCD-TR, ST735SCN Datasheet

300kHz, -5V/ADJ INVERTING, NEGATIVE OUTPUT

CURRENT-MODE PWM REGULATOR

■ CONVERTS +4.0V TO + 6.2V INPUT TO -5V

OUTPUT (735S) OR +3.5V TO + 9.0V TO A
NEGATIVE ADJUSTABLE OUTPUT (735T)

■ 1W GUARANTEEDOUTPUT POWER

■ 72% TYPICAL EFFICIENCY

■ 0.8mA QUIESCENT CURRENT

■ 1µA SHUTDOWN MODE

■ 300KHZ FIXED FREQUENCY OSCILLATOR

■ CURRENT MODE PWM CONVERTER

■ LOW NOISE AND JITTER

■ SOFT START

■ SIMPLE APPLICATION CIRCUIT

■ UNDERVOLTAGE LOCKOUT (735S)

DESCRIPTION

The ST735S/ST735T is a Bi-CMOS, inverting
switch mode DC-DC regulator wi th internal Power
MOSFET that generates a fixed -5V (S version) or
a negative adjustable (T version) output voltage
from a 4V (3.5V for the 735T) to 6.2V input voltage
(9V for the 735T); is gu arante ed an output current
of 200mA for inputs greater than 4.5V. The
quiescent current for this device is typically of

ST735S

ST735T

DIP-8 SO-8

0.8mA and, in shutdown mode it is reduced to
1µA.
These power-conserving features, along with high
efficiency and appli cations circuits, thaT lend itself
to minaturization, make the ST735S/ST735T
excellent in a broad range of on-card, HDD and
portable equipment applications. These device
employ a high performance c urrent mode pu lse
with modulation (PWM) control scheme to provide
tight output voltage regulation and low noise. The
fixed frequency oscillator is factory trimmed to
300KHz, a llowing for easy noise filtering. The
regulator in production is tested to guarantee an
output accuracy within ±5% over all specified
conditions.

SCHEMATIC DIAGRAM

1/11October 2002

ST735S/ST735T

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V
V

SHDN

V
V

V

OUT

I

LX

P
T

T

Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
Note 1: The input to output differential voltage is limited to VIN+|V

THERMAL DATA

DC Input Voltage (VINto GND) for ST735S

IN

DC Input Voltage (VINto GND) for ST735T (Note 1)

IN

Shutdown Voltage (SHDN to GND) -0.3 to V
Switch Voltage (Lx to VIN)

LX

Feedback Voltage (V

FB

Output Voltage (V

OUT

to GND)

OUT

to GND)
Other Input Voltage (SS, CC to GND) -0.3 to V
Peack Switch Current
Power Dissipation at Tj= 70°C DIP-8 725

tot

Storage Temperature Range

stg

Operating Junction Temperature Range

op

OUT

|<12.7V

SO-8 470

-0.3 to +7 V

-0.3 to +11 V

IN

+0.3

V

-12.5 to +0.3 V

-11to+0.3 V

-11to+0.3 V
+0.3

+

V

2A

mW

-55 to +150 °C

-40 to +125 °C

Symbol Parameter DIP-8 SO-8 Unit

R

thj-case

Thermal Resistance Junction-case

2 8 °C/W

CONNECTION DIAGRAM (top v iew)

PIN DESCRIPTION

Pin N° Symbol Name and Function

1 SHDN SHUT-DOWN Control (V
2V

REF

Reference Output Voltage

3 SS Soft Start
4 CC Compensation Input
5V

OUT

Negative Output Voltage

6 GND Ground
7 LX Switch Output
8V

IN

Positive Supply - Voltage Input

=ON GND=Shutdown

CC

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ORDERING CODES

TYPE DIP-8 SO-8 SO-8 (T&R)

ST735S ST735SCN ST735SCD ST735SCD-TR
ST735T ST735TCN ST735TCD ST735TCD-TR

TYPICAL APPLICATION CIRCUIT

ST735S/ST735T

NOTE:

1) All capacitors are X7R ceramic
can be omitted if are used higher values for the input and output capacitors (suggested C2=47µF, C1=100µF).

2) C

5

3) R

and R2must be placed is ST735T applications only. Their values are calculated by the following formula R2=(|V

1

can be chosen any value between 2kΩ and 20kΩ

APPLICATION CIRCUIT

To achieve the best performances from switching
power supply topology, p articular care to layout
drawing is needed, in order to minimize EMI and
obtain low noise. Moreover, jitter free op eration
ensures the full device fun ctionality. Layout desi gn
proposed on demoboard helps to lower the
developing time. Wire lengths must be minimized,

filter and bypass capacitors m ust be low ESR
type, placed as close as possible to the integrated
circuit. T he 4.7µF (or 6.8µF) inductor must be
chosen built on a core, taking care that saturation
current should be h igher than the peak LX switch
current. See the Peak Inductor Current vs Output
Current graph.

PRINTED DEMOBOARD (not in scale)

OUT

|/V

REF

)xR1.ForR

1

3/11

ST735S/ST735T

ELECTRICAL CHARACTERISTICS OF ST735S (Refer to test circuit,VIN=5V,CIN=4.7µF, C

all X7R ceramic, L = 4.7µH(Note1),I
value are referred at T

amb

= 25°C)

OUT

=0mA,T

= -40 to 125°C, unless otherwise specified. Typical

amb

OUT

=10µF

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

V

I

I

SUPPLY

I

STANDBY

I

PEAK

V

∆V
∆V

V
∆V
R

DSON

I

LEAK

V

f

R

Note 1: Utilize of 6.8µH permits to reach higher current capability at the same operating conditions
Note2: Guaranteed by design, but not tested in production
Note3 : Tested at I

Input Voltage 4 6.2 V

IN

Output Voltage VIN= 4.5V to 6.2V I

OUT

T

amb

V

IN

T

amb

OUT

Output Current

V
V

T
V

IN
IN

amb

IN

= -40 to 125°C

= 4.0V to 6.2V I

= -40 to 125°C

= 4.5V to 6.2V TJ= 0 to 125°C
= 4.5V to 6.2V I

= -40 to 125°C

= 4.0V V

OUT

= 0 to 200mA

OUT

= 0 to 175mA

OUT

-5.25 -5 -4.75 V

-5.25 -5 -4.75 V

200 275 mA

= 0 to 175mA

OUT

175 mA

= -5V 175 mA
Supply Current Includes Switch Current 0.8 1.6 mA
Standby Current V
Short Circuit Current VIN= 5V 0.9 A

I

SC

=0V 1 10 µA

SHDN

LX Max Peak Current (Note 2) 1.5 A
Undervoltage Lock-out 3.5 4 V

LO

Line Regulation VIN= 4.0V to 6.2V 0.1 %/V

OUT

Load Regulation I

OUT

Reference Voltage

REF

Reference Drift

REF

= 0 to 200mA 0.003 %/mA

OUT

T

=25°C (Note 3)

amb

T

= -40 to 125°C

amb

1.225 V
50 ppm/°C

LX ON Voltage 0.5 Ω
LX Leakage Current VDS= 10V 1 µA
Shutdown Pin Current 1 µA

I

SH

V

Shutdown Input Low

IL

Threshold
Shutdown Input High

IH

Threshold
Maximum Oscillator

OSC

Frequency

ν Efficency I

Compensation Pin

CC

Impedance on CC Pin

= 125µA

VREF

= 100mA 72 %

OUT

2V

300 KHz

7.5 KΩ

0.25 V

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