LX1571 Microsemi Corporation, LX1571 Datasheet

LX1571

Manufacturer Part Number

LX1571

Description

PHASE MODULATED AC SYNCHRONOUS SECONDARY-SIDE CONTROLLER

Manufacturer

Microsemi Corporation

Datasheet

1.LX1571.pdf (12 pages)

Available stocks

Company

Part Number

Manufacturer

Quantity

Price

Company:

Meier Automation Equipment Co., Limited

Part Number:

LX1571CM

Manufacturer:

LINFINITY

Quantity:

20 000

Current page: 1 of 12
Download datasheet (258Kb)

Rev. 0.9.3

H E

The LX1570/71 series of controller ICs are

designed to provide all control functions in

a secondary-side regulator for isolated auxil-

iary or secondary power supplies. Auxiliary

or secondary-side controllers are used in a

variety of applications including multiple

output off-line power supplies, commonly

found in desktop computers, as well as tele-

communications applications. Although they

can be used in all secondary output applica-

tions requiring precision regulation, they are

mainly optimized for outputs delivering more

than 3A current where standard three-termi-

nal regulators lack the desired efficiency. For

these applications, the Mag Amp regulators

have traditionally been used. However, Mag

Amps have several disadvantages. First, be-

cause they have to withstand the maximum

input voltage during a short-circuit condition,

they are "over designed", typically by 2 times,

increasing the cost and size of the power

supply. Second, Mag Amps are inherently

leading edge modulators, so they can only

1/97

N F I N I T E

O W E R

-55 to 125

-40 to 85

P R O D U C T H I G H L I G H T

0 to 70

LX1571

OUT

DRV

GND

(°C)

F O R F U R T H E R I N F O R M A T I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1

D E S C R I P T I O N

COMP

O F

S.S.

C.S.

11861 W

Note: All surface-mount packages are available in Tape & Reel.

P A C K A G E O R D E R I N F O R M A T I O N

Append the letter "T" to part number. (i.e. LX157xCDMT)

N N O V A T I O N

Plastic DIP

8-pin

LX157xCM

LX157xIM

approach a certain maximum duty cycle, lim-

ited by the minimum delay and the mag-

netic BH loop characteristic of the Mag Amp

core. This forces an increase in the size of

the main transformer as well as the output

inductor, resulting in higher overall system

cost. The LX1570/71 eliminates all the

disadvantages of the Mag Amp approach

as well as improving system perfor-

mance and reducing overall system cost.

ler IC that controls the duty cycle of a switch

in series with the secondary AC output of

the power transformer in buck-derived ap-

plications, such as forward or bridge topolo-

gies. It offers features such as 100% duty

cycle operation for maximum energy trans-

fer, pulse-by-pulse and hiccup current limit-

ing with long off-time between the cycles

for reduced power dissipation, high-fre-

quency operation for smaller magnetics, soft-

start, and current mode control for excel-

lent dynamic response.

ESTERN

The LX1570/71 is a current mode control-

—

VENUE

, G

Aux Output

12V/8A

ARDEN

Plastic SOIC

8-pin

LX157xCDM

LX157xIDM

A T E N T

HASE

—

ROVE

ODULATED

R E L I M I N A R Y

, CA. 92841

AC S

E N D I N G

Ceramic DIP

8-pin

YNCHRONOUS

LX157xMY

LX1570

LX1571

p REPLACES COSTLY MAG-AMP CORES WITH

p LOOK-AHEAD SWITCHING

p LOWER OVERALL SYSTEM COST

p LOWER PEAK CURRENT STRESS ON THE

p ALLOWS HIGHER OPERATING FREQUENCY

p EASY SHORT-CIRCUIT PROTECTION

p CURRENT MODE APPROACH ACHIEVES

Part #

VA I L A B L E

—

A LOW ON-RESISTANCE MOSFET

SWITCH TURN ON BEFORE THE AC INPUT

TO ACHIEVE 100% ENERGY TRANSFER

PRIMARY SWITCH

AND SMALLER OUTPUT INDUCTOR

EXCELLENT DYNAMIC RESPONSE

SECONDARY-SIDE REGULATOR IN OFF-LINE

POWER SUPPLIES

COMPUTER POWER SUPPLIES, 3.3V OUTPUT

FOR NEW LOW-VOLTAGE PROCESSORS

AND MEMORIES

TELECOMMUNICATION AND MILITARY

DC/DC CONVERTERS

LX1570/1571

K E Y F E A T U R E S

A P P L I C A T I O N S

Threshold

-0.2V

C.L.

A T A

ECONDARY

P T I O N S P E R

Transformer Currents

LIN D

Resistive

Sensing

Current

Option

-S

C.S.

H E E T

IDE

O C

ONTROLLER

ENSURES

Application

#: 1570

Currents

Output

< 4A

> 4A

A R T

Related parts for LX1571

LX1571 Summary of contents

Page 1

... FOR NEW LOW-VOLTAGE PROCESSORS AND MEMORIES TELECOMMUNICATION AND MILITARY DC/DC CONVERTERS C.L. C.S. Part # Threshold Option Resistive LX1570 -0.2V Sensing Current LX1571 1V Transformer Currents Sensing Ceramic DIP Y 8-pin — — LX157xMY , CA. 92841 #: 1570 ONTROLLER ENSURES Application ...

Page 2

LX1570/1571 P HASE ...

Page 3

... SS I SS-DIS LX1570 V CSI LX1571 LX1570 I CSB LX1571 LX1570 A CS LX1571 LX1570 V CSMIN LX1571 10% Overdrive LX1570 V CLP LX1571 LX1570 V CLH LX1571 V HCCP LX1570/1571 -S C IDE ONTROLLER -40 to 85ºC for the A = 25ºC value.) A LX1570/1571 Min. Typ. Max. 2.475 2 ...

Page 4

... The output drive is terminated and latched off when this voltage amplified by the internal gain (see option table) exceeds the voltage set by the E.A output voltage. The maximum allowable voltage at this pin during normal operation is -0.8V typ for LX1570 and 6V typ for LX1571. GND 5 This pin is combined control circuitry and power GND ...

Page 5

HASE AC(+) 100kHz - 150kHz 20-30V, 100-150kHz 20V-30V Secondary Transformer AC(-) V (17 to 20V) ...

Page 6

... LX1570/1571 P HASE (+) Q1 Secondary Transformer Voltage (-) FIGURE 2 — THE LX1571 IN A TYPICAL SECONDARY-SIDE POWER SUPPLY APPLICATION ODULATED YNCHRONOUS ECONDARY 1/2 D1 ...

Page 7

... The output drive turns the external power MOSFET on and current ramps up in the inductor. Inductor current is sensed with an external resistor (or in the case of LX1571 with a current transformer) and is compared to the threshold at the inverting input of the current sense (C.S.) comparator. This threshold is set by the voltage feedback loop, which is controlled by the error amplifier ...

Page 8

... ODULATED YNCHRONOUS ECONDARY Transformer Voltage LX157x OUT DRV LX1571 C.S. Signal C Voltage T FIGURE 4B — STEADY-STATE OPERATION TIMING DIAGRAM where C Start- Example RAMP ...

Page 9

HASE 16V V Cap START OUT DRV FIGURE 5 — ...

Page 10

... COMP by where: COMP inductor peak current resistor divider gain, (-15 for LX1570, 3 for LX1571 diode forward voltage BE (0.65V typ ODULATED YNCHRONOUS ECONDARY ...

Page 11

... S FIGURE 8 — THE LX1571 IN A 12V/8A SECONDARY-SIDE POWER SUPPLY APPLICATION Unless otherwise noted all resistors are 1/4W, 5%. Note 1: For further information on PE64978 contact Pulse Engineering at 619-674-8100. Note 2: A high value resistor must be coupled back to "COMP" pin to insure proper operation under light load conditions. ...

Page 12

... S FIGURE 9 — THE LX1571 IN A 3.3V/10A SECONDARY-SIDE POWER SUPPLY APPLICATION Unless otherwise noted all resistors are 1/4W, 5%. Note 1: For further information on PE53700 and PE64978 contact Pulse Engineering at 619-674-8100. Note 2: A high value resistor must be coupled back to "COMP" pin to insure proper operation under light load conditions. ...

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