SGS Thomson Microelectronics L5973D Datasheet

2.5A SWITCH STEP DOWN SWITCHING REGULATOR

■ 2.5A INTERNAL SWITCH

■

OPERATING INPUT VOLTAGE FROM 4.4V TO 36V

■ 3.3V / (±2%) REFERENCE VOLTAGE

■ OUTPUT VOLTAGE ADJUSTABLE FROM

1.235V TO 35V

■ LOW DROPOUT OPERATION: 100% DUTY

CYCLE

■ 250KHz INTERNALLY FIXED FREQUENCY

■ VOLTAGE FEEDFO RWA R D

■ ZERO LOAD CURRENT OPERATION

■ INTERNAL CURRENT LIMITING

■ INHIBIT FOR ZERO CURRENT

CONSUMPTION

■ SYNCHRONIZATION

■ PROTECTION AGAINST FEEDBACK

DISCONNECTION

■ THERMAL SHUTDOWN

APPLICATIONS:

■ CONSUMER: STB, DVD, TV, VCR,CAR

RADIO, LCD MONITORS

■ NETWORKING: XDSL, MODEMS,DC-DC

MODULES

■ COMPUTER: PRINTERS, AUDIO/GRAPHIC

CARDS, OPTICAL STORAGE, HARD DISK
DRIVE

■ INDUSTRIAL: CHARGERS, CAR BATTERY

DC-DC CONVERTERS

L5973D

HSOP8 - EXPOSED PAD

ORDERING NUMBER: L5973D

DESCRIPTION

The L5973D is a step down monolithic power switch­ing regulator with a minimum switch current limit of

2.5A so it is able to deliver more than 2A DC current
to the load depending on the application conditions.

The output voltage can be set from 1.235V to 35V.
The high current level is also achieved thanks to an

SO8 package with exposed frame, that all ows to re­duce the R

th(j-amb)

The device uses an internal P-Channel D-MOS tran­sistor (with a typical Rdson of 250m
element to minimize the s i ze of t he ext ernal c ompo­nents.

An internal oscillator fixes the switching frequency at
250KHz.

Having a minimum input voltage of 4.4V only, it is
particularly suitable for 5V bus, availabl e in all com­puter related applications.

Pulse by pulse current limit with the internal frequen­cy modulation offers an effective constant current
short circuit protection.

down to approximately 40°C/W

Ω

) as swi tch ing

TEST APPLICATION CIRCUIT

3.3V

VIN = 4.4V to 35V

C1

10µF

35V

CERAMIC

May 2003

22nF

220pF

C4

C3

VREF

VCC

SYNC.
COMP

R3

4.7K

6

8
2

4

L5973D

3

7

GNDINH

D03IN1439

OUT

1

5

FB

L1 15µH

D1

STPS340U

R1

5.6K

R2

3.3K

VOUT=3.3V

C2

330µF

10V

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L5973D

PIN CONNECTION

OUT

SYNC

INH

COMP

1
2
3
4

8
7
6
5

D98IN955

VCC
GND
VREF
FB

PIN DESCRIP TION

N° Pin Function

1 OUT Regulator Output.
2 SYNC Master/slave synchronization.
3 INH A logical signal (active high) disables the device. If INH not used the pin must be grounded.

4 COMP E/A output for frequency compensation.
5 FB Feedback input. Connecting directly to this pin results in an output voltage of 1.23V. An external

6 VREF 3.3V V
7 GND Ground.
8 VCC Unregulated DC input voltage.

When it is open an internal pull-up disable the device.

resistive divider is required for higher output voltages.

. No cap is requested for stability.

REF

THERMAL DATA

Symbol Parameter Value Unit

R

th (j-amb)

(*) Package mounted on board

Thermal Resistance Junction to ambient Max. 40 (*) °C/W

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V
V

I

1

, V

V

4

V
V

P

tot

T

T

stg

Input Voltage 40 V

8

Output DC voltage

1

Output peak voltage at t = 0.1µs
Maximum output current int. limit.
Analog pins 4 V

5

INH -0.3V to V

3

SYNC -0.3 to 4 V

2

Power dissipation at T
Operating junction temperature range -40 to 150 °C

j

Storage temperature range -55 to 150 °C

≤ 60°C 2.25 W

amb

-1 to 40

-5 to 40

CC

V
V

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L5973D

ELECTRICAL CHARACTERISTICS

(*) Specification Referred to Tj from -40 to 125°C

(Tj = 25°C, VCC = 12V, unless otherwise specified.)

(1)

.

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

R

DSON

Operating input voltage range Vo = 1.235V; Io = 2A * 4.4 36 V

CC

Mosfet on Resistance * 0.150 0.5 Ω

I

Maximum limiting current VCC = 4.4V to 36V 2.5 3 3.5 A

l

Switching frequency * 212 250 280 KHz

f

s

225 250 275 KHz

Duty cycle 0 100 %

DYNAMIC CHARACTERISTICS (see test circuit ).

V

Voltage feedback 4.4V < VCC < 36V,

5

20mA < IO < 2A

η Efficiency V

O

= 5V, VCC = 12V 90 %

1.220 1.235 1.25 V

* 1.198 1.235 1.272 V

DC CHARACTERISTICS

I

Total Operating Quiescent

qop

*35mA

Current
Quiescent current Duty Cycle = 0; VFB = 1.5V 2.5 mA

I

q

I

qst-by

Total stand-by quiescent current V

> 2.2V * 50 100 µA

inh

V

CC

= 36V; V

> 2.2V * 80 150 µA

inh

INHIBIT

INH Threshold Voltage Device ON 0.8 V

Device OFF 2.2 V

ERROR AMPLIFIER

V

V

I

o source

I

o sink

gm Transconductance I

High level output voltage VFB = 1V 3.5 V

OH

Low level output voltage VFB = 1.5V 0.4 V

OL

Source output current V
Sink output current V
Source bias current 2.5 4 µA

I

b

DC open loop gain R

= 1.9V; VFB = 1V 200 300 µA

COMP

= 1.9V; VFB = 1.5V 1 1.5 mA

COMP

= ∞ 50 57 dB

L

= -0.1mA to 0.1mA

comp

V

= 1.9V

COMP

2.3 mS

SYNC FUNCTION

High Input Voltage V
Low Input Voltage V
Slave Sink Current V

Master Output Amplitude I
Output Pulse Width no load, V

= 4.4V to 36V 2.5 V

CC

= 4.4V to 36V 0.74 V

CC

= 0.74V

sync

V

= 2.33V

sync

= 3mA 2.75 3 V

source

= 1.65V 0.20 0.35 µs

sync

0.11

0.21

0.25

0.45mAmA

REF

REFERENCE SECTION

Reference Voltage 3.234 3.3 3.366 V

I

= 0 to 5mA

REF

* 3.2 3.3 3.399 V

VCC = 4.4V to 36V

Line Regulation I

REF

= 0mA

510mV

VCC = 4.4V to 36V

Load Regulation I

= 0 to 5mA 8 15 mV

REF

Short Circuit Current 10 8 30 mA

Notes: 1. Specification over the -40 to +125 Tj Temperature range are assu red by design, character i zation and statistical correlation.

2. Guaranteed by design.

V

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