L5970AD Datasheet L5970AD, L5970ADTR | P1-P3

1/11

L5970AD

March 2005

1 General Features

■ 1.5A 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

■ 500KHz INTERNALLY FIXED FREQUENCY

■ VOLTAGE FEEDFORWARD

■ ZERO LOAD CURRENT OPERATION

■ INTERNAL CURRENT LIMITING

■ INHIBIT FOR ZERO CURRENT

CONSUMPTION

■ SYNCHRONIZATION

■ PROTECTION AGAINST FEEDBACK

DISCONNECTION

■ THERMAL SHUTDOWN

1.1 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

2 Description

The L5970AD is a step down monolithic power

switching regulator with a switch current limit of 1.5A

so it is able to deliver more than 1A DC current to the

load depending on the application conditions.

The output voltage can be set from 1.235V to 35V.

The device uses an internal P-Channel D-MOS tran-

sistor (with a typical R

DSON

of 200m

Ω

) as switching

element to avoid the use of bootstrap capacitor and

guarantee high efficiency.

An internal oscillator fixes the switching frequency at

500KHz to minimize the size of external components.

Having a minimum input voltage of 4.4V only, it is

particularly suitable for 5V bus, available in all com-

puter related applications.

Pulse by pulse current limit with the internal frequen-

cy modulation offers an effective constant current

short circuit protection.

1.5A SWITCH STEP DOWN SWITCHING REGULATOR

Figure 2. Test and Application Circuit

D05IN1530

L5970AD

10µF

35V

CERAMIC

330µF

10V

VOUT=3.3V

VIN = 4.4V to 35V

5.6K

3.3K

4.7K

22nF

220pF

L1 15µH

STPS2L25U

COMP

VCC

OUT

GNDINH

3.3V

SYNC.

VREF

gure 1.

age

Table 1. Order Codes

Part Number Package

L5970AD SO-8

L5970ADTR SO-8 in Tape & Reel

SO-8

Rev. 1

L5970AD

2/11

Table 2. Thermal Data

(*) Package mounted on board

Figure 3. Pin Connection (top view)

Table 3. Pin Description

Table 4. Absolute Maximum Ratings

Symbol Parameter Value Unit

th (j-amb)

Thermal Resistance Junction to ambient Max. 120 (*) °C/W

N. Name Description

1 OUT Regulator Output.

2 SYNC Master/Slave Synchronization. When it is open, a signal synchronous with the turn-off of the inter-

nal power is present at the pin. When connected to an external signal at a frequency higher than

the internal one, then the device is synchronized by the external signal.

Connecting together the SYNC pin of two devices, the one with the higher frequency works as

master and the other one, works as slave.

3INH

A logical signal (active high) disables the device. With IHN higher than 2.2V the device is OFF and with

INH lower than 0.8V, the device is ON.

If INH is not used the pin must be grounded. When it is open, an internal pull-up disables the device.

4 COMP E/A output to be used for frequency compensation.

5 FB Stepdown feedback input. Connecting the output voltage directly to this pin results in an output

voltage of 1.235V. An external resistor divider is required for higher output voltages (the typical

value for the resistor connected between this pin and ground is 4.7K).

REF

Reference voltage of 3.3V. No filter capacitor is needed to stability.

7 GND Ground.

Unregulated DC input voltage.

Symbol Parameter Value Unit

Input Voltage 40 V

Output DC voltage

Output peak voltage at t = 0.1µs

-1 to 40

-5 to 40

Maximum output current int. limit.

, V

Analog pins 4 V

INH -0.3V to V

SYNC -0.3 to 4 V

tot

Power dissipation at T

amb

≤ 60°C 0.75 W

Operating junction temperature range -40 to 150 °C

stg

Storage temperature range -55 to 150 °C

OUT

SYNC

INH

COMP

VCC

VREF

GND

D98IN955

3/11

L5970AD

Table 5. Electrical Characteristics (T

= 25°C, V

= 12V, unless otherwise specified.)

Note: 1. Guaranteed by design

Symbol Parameter Test Condition Min. Typ. Max. Unit

Operating input voltage range 4.4 36 V

DSON

Mosfet on Resistance 0.250 0.5 Ω

Maximum limiting current V

= 4.4V to 36V 1.8 A

Switching frequency 500 KHz

Duty cycle 0 100 %

DYNAMIC CHARACTERISTICS

Voltage feedback 4.4V < V

< 36V 1.220 1.235 1.25 V

η Efficiency V

= 5V, V

= 12V 90 %

DC CHARACTERISTICS

qop

Total Operating Quiescent Current 5 7 mA

Quiescent current Duty Cycle = 0; V

= 1.5V 2.7 mA

qst-by

Total stand-by quiescent current V

inh

> 2.2V 50 100 µA

INHIBIT

INH Threshold Voltage Device ON 0.8 V

Device OFF 2.2 V

ERROR AMPLIFIER

High level output voltage VFB = 1V 3.5 V

Low level output voltage VFB = 1.5V 0.4 V

o source

Source output current V

COMP

= 1.9V; V

= 1V 200 300 µA

o sink

Sink output current V

COMP

= 1.9V; V

= 1.5V 1 1.5 mA

Source bias current 2.5 4 µA

DC open loop gain R

= ∞ 50 57 dB

gm Transconductance I

comp

= -0.1mA to 0.1mA

COMP

= 1.9V

2.3 mS

SYNC FUNCTION

High Input Voltage V

= 4.4V to 36V 2.5 V

REF

Low Input Voltage V

= 4.4V to 36V 0.74 V

Slave Sink Current

sync

= 0.74V

(1)

sync

= 2.33V

0.11

0.21

0.25

0.45

Master Output Amplitude I

source

= 3mA 2.75 3 V

Output Pulse Width no load, V

sync

= 1.65V 0.20 0.35 µs

REFERENCE SECTION

Reference Voltage 3.234 3.3 3.366 V

REF

= 0 to 5mA

= 4.4V to 36V

3.2 3.3 3.399 V

Line Regulation I

REF

= 0mA

= 4.4V to 36V

510mV

Load Regulation I

REF

= 0 to 5mA 8 15 mV

Short Circuit Current 10 18 30 mA

P1-P3 P4-P6 P7-P9 P10-P11

L5970AD

Mfr. #:

Buy L5970AD

Manufacturer:

STMicroelectronics

Description:

Switching Voltage Regulators 4.4-36V 1A Step-Down

Lifecycle:

New from this manufacturer.

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L5970AD

L5970AD

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