lx1554 Microsemi Corporation, lx1554 Datasheet

lx1554

Manufacturer Part Number

lx1554

Description

Ultra-low Start-up Current, Current-mode Pwm

Manufacturer

Microsemi Corporation

Datasheet

1.LX1554.pdf (18 pages)

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Bonase Electronics (HK) Co., Limited

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lx1554CM

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lx1554I

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LMI

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Rev. 1.0a 1/01

H E

INPUT

-55 to 125

The LX155X family of ultra-low start-up

current (250µA max.), current mode

control IC's offer new levels of energy

efficiency for offline converter applica-

tions. They are ideally optimized for

personal computer and CRT power

supplies although they can be used in

any number of off-line applications

where energy efficiency is critical.

Coupled with the fact that the LX155X

series requires a minimal set of external

components, the series offers an

excellent value for cost conscious

consumer applications.

LX155X series demonstrates a signifi-

cant power reduction as compared with

other similar off-line controllers. Table 1

compares the SG384X, UC384XA and

the LX155X start-up resistor power

dissipation. The LX155X offers an

overall 4X reduction in power dissipa-

-40 to 85

0 to 70

Optimizing energy efficiency, the

(°C)

N F I N I T E

Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. LX1552CDMT)

Plastic DIP

8-pin

YPICAL

LX155xCM

LX155xIM

O W E R

—

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

LX1552

LX1554

ICRO

PPLICATION OF

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

O F

OWER

11861 W

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

N N O V A T I O N

TART

Plastic SOIC

8-pin

LX155xCDM

LX155xIDM

Note: Calculation is done for universal AC input speci-

fication of V

following equation: (Resistor curr ent is selected to be

2 * I

LX155X U

Max. Start-up Current

Specification (I

Typical Start-Up

Resistor Value (R

Max. Start-Up Resistor

Power Dissipation (P

tion. Additionally, the precise oscillator

discharge current gives the power

supply designer considerable flexibility

in optimizing system duty cycle

consistency.

demonstrates improved load regulation,

pulse by pulse current limiting and

inherent protection of the power supply

output switch. The LX155X includes a

bandgap reference trimmed to 1%, an

error amplifier, a current sense com-

parator internally clamped to 1V, a high

current totem pole output stage for fast

switching of power mosfet's, and an

externally programmable oscillator to

set operating frequency and maximum

duty cycle. The undervoltage lock-out

circuitry is designed to operate with as

little as 250µA of supply current

permitting very efficient bootstrap

designs.

Design Using

ESTERN

-U

The current mode architecture

—

at V

ACMIN

EATURE

ACMIN

VENUE

= 90V

)

SING

2 * I

AC MIN

)

RMS

A B L E

, G

1000µA 500µA

SG384x UC384xA LX155x

2.26W 1.13W

62K

to V

, P

ARDEN

Plastic SOIC

14-pin

ACMAX

LX155xCD

LX155xID

= 265V

124K

—

LTRA

ROVE

MAX

RMS

-L

R O D U C T I O N

using the

250µA

248K

0.56W

, CA. 92841

TART

-U

Ceramic DIP

8-pin

LX155xMY

LX1552

LX1553

LX1554

LX1555

F CURRENT SENSE DELAY TO OUTPUT

F AUTOMATIC FEED FORWARD

F PULSE-BY-PULSE CURRENT LIMITING

F ENHANCED LOAD RESPONSE

F UNDER-VOLTAGE LOCKOUT WITH

F DOUBLE PULSE SUPPRESSION

F HIGH CURRENT TOTEM POLE OUTPUT

F 500kHz OPERATION

V A I L A B L E

Part #

URRENT

—

ULTRA-LOW START-UP CURRENT

(150µA typ.)

TRIMMED OSCILLATOR DISCHARGE

CURRENT (±2% typ.)

INITIAL OSCILLATOR FREQUENCY BETTER

THAN ±4%

OUTPUT PULLDOWN DURING UVLO

PRECISION 2.5V REFERENCE (±2% max.)

(150ns typ.)

COMPENSATION

CHARACTERISTICS

HYSTERESIS

(±1Amp peak)

ECONOMY OFF-LINE FLYBACK OR

FORWARD CONVERTERS

DC-DC BUCK OR BOOST CONVERTERS

LOW COST DC MOTOR CONTROL

LX1552/3/4/5

K E Y F E A T U R E S

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

, C

Start-Up Hysteresis Max. Duty

A T A

Voltage

8.4V

16V

URRENT

P T I O N S P E R

L I N D

-M

LX155xCPW

TSSOP

20-pin

H E E T

0.8V

ODE

O C

—

PWM

# : 1552

<100%

<50%

Cycle

A R T

Related parts for lx1554

lx1554 Summary of contents

Page 1

... LOW COST DC MOTOR CONTROL Part # Start-Up Hysteresis Max. Duty 250µA Voltage LX1552 16V 6V 248K LX1553 8.4V 0.8V 0.56W LX1554 16V 6V LX1555 8.4V 0.8V using the Ceramic DIP TSSOP Y PW 8-pin 20-pin — LX155xCPW — LX155xMY , CA ...

Page 2

LX1552/3/4 ...

Page 3

(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX155xC with 0°C ...

Page 4

... Gain defined as ISENSE 5. Adjust V above the start threshold before setting at 15V Output frequency equals oscillator frequency for the LX1552 and LX1553. Output frequency is one half oscillator frequency for the LX1554 and LX1555 34V GROUND** 16V (1552/1554) 8.4V (1553/1555) OSCILLATOR ...

Page 5

GRAPH / CURVE INDEX Characteristic Curves FIGURE # 1. OSCILLATOR FREQUENCY vs. TIMING RESISTOR 2. ...

Page 6

LX1552/3/4/5 FIGURE 1. — OSCILLATOR FREQUENCY vs. TIMING RESISTOR 1000 100 C = 6.8nF T 10 ...

Page 7

FIGURE 5. — OUTPUT INITIAL ACCURACY vs. TEMPERATURE 65.0 LX1552 and LX1553 only 63.5 62.0 ...

Page 8

... 250 225 200 LX1552/LX1554 175 150 125 100 LX1553/LX1555 -75 -50 - Ambient Temperature - (°C) A 250 LX1552/LX1554 225 T = 25°C A 200 175 150 125 100 Supply Voltage - (V) CC 100 125 ...

Page 9

FIGURE 13. — DYNAMIC SUPPLY CURRENT vs. OSCILLATOR FREQUENCY 25° ...

Page 10

... FIGURE 20. — LOW LEVEL OUTPUT SATURATION VOLTAGE 1.20 LX1553 1.08 LX1555 0.96 0.84 0.72 0.60 0.48 0.36 0.24 0.12 0. 100 125 -M PWM ODE TEMPERATURE LX1552 LX1554 9.8 9.6 9.4 9.2 9.0 -75 -50 - Ambient Temperature - (°C) A DURING UNDER-VOLTAGE LOCKOUT -55° 25° 125°C A 0.1 1 Output Sink Current - (mA) ...

Page 11

FIGURE 21. — OUTPUT SATURATION VOLTAGE vs. OUTPUT CURRENT and TEMPERATURE 6 ...

Page 12

... This is especially important in off-line power supplies which are designed to operate for universal input voltages 265V AC. Figure 23 shows an efficient supply voltage using the ultra low start-up current of the LX1554 in conjunction with a bootstrap winding off of the power transformer. Circuit operation is as follows. DC BUS I > ...

Page 13

VOLTAGE REFERENCE The voltage reference is a low drift bandgap design which provides +5.0V to ...

Page 14

... Example: A flyback power supply design requires the duty cycle to be limited to less than 45%. If the output switching frequency is selected to be 100kHz, what are the values 100 a) LX1552/53, and the b) LX1554/ LX1552/53 Given 100kHz LX1554/55 ...

Page 15

... The comparator output resets the PWM latch ensuring that a single pulse appears at the output for any given oscillator cycle. The LX1554/55 series has an additional flip flop stage that limits the output to less than 50% duty cycle range as well as dividing its output frequency to half of the oscillator frequency ...

Page 16

LX1552/3/4/5 FIGURE 30. — CURRENT SENSE SPIKE SUPPRESSION LX155x ...

Page 17

...

Page 18

... This circuit uses a low-cost feedback scheme in which the 60Hz voltage developed from the primary-side control winding is 40KHz ±10% sensed by the LX1554 error amplifier. Load regulation is 25W maximum therefore dependent on the coupling between secondary and 5V +5% control windings, and on transformer leakage inductance. ...

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