Microsemi Corporation LX1554CPW, LX1554CM, LX1554CDM, LX1553IM, LX1553IDM Datasheet

Copyright © 1994

Rev. 1.0a 1/01

FOR FURTHER INFORMATION CALL [phone]

11861 WESTERN AVENUE , GARDEN GROVE, CA. 92841

1

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

PRODUCTION DATA SHEET

THE INFINITE POWER OF INNOVATION

LX1552/3/4/5

LIN DOC #:

1552

DESCRIPTION KEY FEATURES

■■

■■

■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.)

pCURRENT SENSE DELAY TO OUTPUT

(150ns typ.)

pAUTOMATIC FEED FORWARD

COMPENSATION

pPULSE-BY-PULSE CURRENT LIMITING
pENHANCED LOAD RESPONSE

CHARACTERISTICS

pUNDER-VOLTAGE LOCKOUT WITH

HYSTERESIS

pDOUBLE PULSE SUPPRESSION
pHIGH CURRENT TOTEM POLE OUTPUT

(±1Amp peak)

p500kHz OPERATION

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 applica­tions. 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.

Optimizing energy efficiency, the
LX155X series demonstrates a signifi­cant 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-

tion. Additionally, the precise oscillator
discharge current gives the power
supply designer considerable flexibility
in optimizing system duty cycle
consistency.

The current mode architecture
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 com­parator 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.

PRODUCT HIGHLIGHT

PACKAGE ORDER INFORMATION

T

A

(°C)

Plastic DIP
8-pin

0 to 70 LX155xCM LX155xCDM LX155xCD — LX155xCPW

-40 to 85 LX155xIM LX155xIDM LX155xID — —

-55 to 125 — — — LX155xMY —

M

Plastic SOIC
8-pin

DM

Plastic SOIC
14-pin

D

Ceramic DIP
8-pin

Y

TSSOP
20-pin

PW

TYPICAL APPLICATION OF LX155X USING ITS

MICROPOWER START-UP FEATURE

Max. Start-up Current
Specification (I

ST

)

Typical Start-Up
Resistor Value (R

ST

)

Max. Start-Up Resistor
Power Dissipation (PR)

Design Using

SG384xUC384xALX155x

1000µA

500µA 250µA

2.26W1.13W0.56W

62K

ΩΩ

ΩΩ

Ω 124K

ΩΩ

ΩΩ

Ω248K

ΩΩ

ΩΩ

Ω

Note:Calculation is done for universal AC input speci­fication of V

ACMIN

= 90V

RMS

to V

ACMAX

= 265V

RMS

using the

following equation: (Resistor current is selected to be

2 * I

ST

at V

ACMIN

.)

RST =, P

R

=

V

AC MIN

√2 * I

ST

2V

AC2 MAX

R

ST

TABLE 1

APPLICATIONS

■■

■■

■ECONOMY OFF-LINE FLYBACK OR

FORWARD CONVERTERS

■DC-DC BUCK OR BOOST CONVERTERS

■LOW COST DC MOTOR CONTROL

AVAILABLE OPTIONS PER PART #

Part # Start-UpHysteresisMax.Duty

Voltage Cycle

LX1552 16V 6V <100%

LX1553 8.4V 0.8V <100%

LX1554 16V 6V <50%

LX1555 8.4V 0.8V <50%

I

ST

R

ST

V

CC

AC

INPUT

LX1552

or

LX1554

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

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

LX1552/3/4/5

PRODUCT DATABOOK 1996/1997

Copyright © 1994

Rev. 1.0a 1/01

2

P

RODUCTION DATA SHEET

ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage (Low Impedance Source)..................................................................30V

Supply Voltage (I

CC

< 30mA).........................................................................Self Limiting

Output Current.............................................................................................................±1A

Output Energy (Capacitive Load)................................................................................5µJ

Analog Inputs (Pins 2, 3)...........................................................................-0.3V to +6.3V

Error Amp Output Sink Current...............................................................................10mA

Power Dissipation at TA = 25°C (DIL-8)......................................................................1W

Operating Junction Temperature

Ceramic (Y Package)............................................................................................150°C

Plastic (M, DM, D, PW Packages)........................................................................150°C

Storage Temperature Range....................................................................-65°C to +150°C

Lead Temperature (Soldering, 10 Seconds)............................................................300°C

PACKAGE PIN OUTS

V

REF

V

CC

OUTPUT
GND

COMP

V

FB

I

SENSE

RT/C

T

1 8

27

36

45

M & Y PACKAGE

(Top View)

DM PACKAGE

(Top View)

V

REF

V

CC

OUTPUT
GND

COMP

V

FB

I

SENSE

RT/C

T

1 8

27

36

45

V

REF

N.C.
V

CC

V

C

OUTPUT
GND
PWR GND

COMP

N.C.

V

FB

N.C.
I

SENSE

N.C.

RT/C

T

1 14

213

312

411

510

69

78

D PACKAGE

(Top View)

PW PACKAGE

(Top View)

1 20
219

318

417

516

615

714

813

912
10 11

N.C.
N.C.

COMP

V

FB

N.C.
I

SENSE

N.C.

RT/C

T

N.C.
N.C.

N.C.
N.C.
V

REF

N.C.
V

CC

V

C

OUTPUT
GND
PWR GND
N.C.

M PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

95°C/W

DM PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

165°C/W

D PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

120°C/W

Y PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

130°C/W

PW PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

144°C/W

Junction Temperature Calculation: T

J

= TA + (PD x θJA).

The θ

JA

numbers are guidelines for the thermal performance of the device/pc-board system.

All of the above assume no ambient airflow

THERMAL DATA

Note 1.Exceeding these ratings could cause damage to the device. All voltages are with respect

to Ground. Currents are positive into, negative out of the specified terminal. Pin
numbers refer to DIL packages only.

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

LX1552/3/4/5

PRODUCT DATABOOK 1996/1997

3

Copyright © 1994

Rev. 1.0a 1/01

PRODUCTION DATA SHEET

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX155xC with 0°C ≤ TA ≤ 70°C, LX155xI with -40°C ≤ TA ≤ 85°C, LX155xM
with -55°C ≤ T

A

≤ 125°C; VCC=15V (Note 5); RT=10K; CT=3.3nF. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the

ambient temperature.)

Reference Section

Parameter

Symbol

Test Conditions

Output Voltage V

REFTA

= 25°C, IL = 1mA

Line Regulation 12 ≤ VIN ≤ 25V
Load Regulation 1 ≤ I

O

≤ 20mA

Temperature Stability (Note 2 & 7)
Total Output Variation Over Line, Load, and Temperature
Output Noise Voltage (Note 2) V

N

10Hz ≤ f ≤ 10kHz, TA = 25°C

Long Term Stability (Note 2) TA = 125°C, t = 1000hrs
Output Short Circuit I

SC

LX155xC

Units

Min.Typ.Max.Min.Typ.Max.

LX155xI/155xM

4.955.005.054.955.005.05 V
620 620mV
625 625mV

0.2 0.4 0.2 0.4 mV/°C

4.9 5.1 4.9 5.1 V
50 50 µV

525 525mV

-30 -100-180 -30 -100-180 mA

Oscillator Section

Initial Accuracy (Note 6) TA = 25°C

TA = 25°C, RT = 698Ω, CT = 22nF, LX1552/3 only

Voltage Stability 12 ≤ V

CC

≤ 25V

Temperature Stability (Note 2) T

MIN

≤ TA ≤ T

MAX

Amplitude (Note 2) V

PIN 4

peak to peak

Discharge Current I

D

TA = 25°C, V

PIN 4

= 2V

V

PIN 4

= 2V, T

MIN

≤ TA ≤ T

MAX

48.550.552.548.550.552.5 kHz
56 58 60 56 58 60 kHz

0.2 1 0.2 1 %
55%

1.7 1.7 V

8.0 8.3 8.6 8.0 8.3 8.6 mA

7.6 8.8 7.8 8.8 mA

Output Voltage Low Level V

OLISINK

= 20mA

I

SINK

= 200mA

Output Voltage High Level V

OHISOURCE

= 20mA

I

SOURCE

= 200mA

Rise Time (Note 2) T

R

TA = 25°C, CL = 1nF
Fall Time (Note 2) TFTA = 25°C, CL = 1nF
UVLO Saturation V

SATVCC

= 5V, I

SINK

= 10mA

Error Amp Section

Current Sense Section

Gain (Note 3 & 4) A

VOL

Maximum Input Signal (Note 3) V

PIN 1

= 5V

Power Supply Rejection Ratio (Note 3) PSRR 12 ≤ VCC ≤ 25V
Input Bias Current I

B

Delay to Output (Note 2) T

PDVPIN 3

= 0 to 2V

Output Section

2.452.502.552.452.502.55 V

-0.1 -1 -0.1 -0.5 µA

65 90 65 90 dB

0.6 0.6 MHz

60 70 60 70 dB

24 24 mA

-0.5 -0.8 -0.5 -0.8 mA
5 6.5 5 6.5 V

0.7 1.1 0.7 1.1 V

2.85 3 3.152.85 3 3.15 V/V

0.9 1 1.1 0.9 1 1.1 V
70 70 dB

-2 -10 -2 -5 µA

150 300 150 300 ns

0.1 0.4 0.1 0.4 V

1.5 2.2 1.5 2.2 V
13 13.5 13 13.5 V
12 13.5 12 13.5 V

50 100 50 100 ns
50 100 50 100 ns

0.7 1.2 0.7 1.2 V

(Electrical Characteristics continue next page.)

Input Voltage V

PIN 1

= 2.5V

Input Bias Current I

B

Open Loop Gain A

VOL

2 ≤ VO ≤ 4V

Unity Gain Bandwidth (Note 2) UGBW TA = 25°C
Power Supply Rejection Ratio (Note 3) PSRR 12 ≤ V

CC

≤ 25V

Output Sink Current I

OLVPIN 2

= 2.7V, V

PIN 1

= 1.1V

Output Source Current I

OHVPIN 2

= 2.3V, V

PIN 1

= 5V

Output Voltage High Level V

OHVPIN 2

= 2.3V, RL = 15K to ground

Output Voltage Low Level V

OLVPIN 2

= 2.7V, RL = 15K to V

REF

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

LX1552/3/4/5

PRODUCT DATABOOK 1996/1997

Copyright © 1994

Rev. 1.0a 1/01

4

P

RODUCTION DATA SHEET

ELECTRICAL CHARACTERISTICS (Con't.)

Under-Voltage Lockout Section

Parameter

Symbol

Test Conditions

Start Threshold VST1552/1554

1553/1555

Min. Operation Voltage After Turn-On 1552/1554

1553/1555

LX155xC

Units

Min.Typ.Max.Min.Typ.Max.

LX155xI/155xM

15 16 17 15 16 17 V

7.8 8.4 9.0 7.8 8.4 9.0 V

9 10 11 9 10 11 V

7.0 7.6 8.2 7.0 7.6 8.2 V

PWM Section

Maximum Duty Cycle 1552/1553

1552/1553, RT = 698Ω, CT = 22nF
1554/1555

Minimum Duty Cycle

94 96 94 96 %

50 50 %

47 48 47 48 %

00%

Power Consumption Section

Start-Up Current I

ST

Operating Supply Current I

CC

VCC Zener Voltage VZICC = 25mA

150 250 150 250 µA

11 17 11 17 mA

30 35 30 35 V

Notes:2.These parameters, although guaranteed, are not 100% tested in

production.

3.Parameter measured at trip point of latch with V

FB

= 0.

4.Gain defined as:A = ; 0 ≤ V

ISENSE

≤ 0.8V.

5.Adjust V

CC

above the start threshold before setting at 15V.

6.Output frequency equals oscillator frequency for the LX1552 and
LX1553. Output frequency is one half oscillator frequency for the
LX1554 and LX1555.

7.Temperature stability, sometimes referred to as average temperature
coefficient, is described by the equation:

Temp Stability =

V

REF

(max.) & V

REF

(min.) are the maximum & minimum reference
voltage measured over the appropriate temperature range. Note that the
extremes in voltage do not necessarily occur at the extremes in
temperature.

V

REF

(max.) - V

REF

(min.)

TA (max.) - TA (min.)

∆ V

COMP

∆ V

ISENSE

BLOCK DIAGRAM

*

- V

CC

and VC are internally connected for 8 pin packages.

**

- POWER GROUND and GROUND are internally connected for 8 pin packages.

***

- Toggle flip flop used only in 1554 and 1555.

OSCILLATOR

S

R

***

V

REF

GOOD LOGIC

INTERNAL

BIAS

S / R

5V

REF

PWM
LATCH

CURRENT SENSE
COMPARATOR

1V

R

2R

ERROR AMP

16V (1552/1554)

8.4V (1553/1555)

16V (1552/1554)

8.4V (1553/1555)

UVLO

34V

GROUND**

V

CC

*

R

T/CT

V

FB

T

COMP

I

SENSE

POWER GROUND**

OUTPUT

V

C

*

V

REF

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

LX1552/3/4/5

PRODUCT DATABOOK 1996/1997

5

Copyright © 1994

Rev. 1.0a 1/01

PRODUCTION DATA SHEET

GRAPH / CURVE INDEX

Characteristic Curves

FIGURE #

1. OSCILLATOR FREQUENCY vs. TIMING RESISTOR

2. MAXIMUM DUTY CYCLE vs. TIMING RESISTOR

3. OSCILLATOR DISCHARGE CURRENT vs. TEMPERATURE

4. OSCILLATOR FREQUENCY vs. TEMPERATURE

5. OUTPUT INITIAL ACCURACY vs. TEMPERATURE

6. OUTPUT DUTY CYCLE vs. TEMPERATURE

7. REFERENCE VOLTAGE vs. TEMPERATURE

8. REFERENCE SHORT CIRCUIT CURRENT vs. TEMPERATURE

9. E.A. INPUT VOLTAGE vs. TEMPERATURE

10.START-UP CURRENT vs. TEMPERATURE

11.START-UP CURRENT vs. SUPPLY VOLTAGE

12.START-UP CURRENT vs. SUPPLY VOLTAGE

13.DYNAMIC SUPPLY CURRENT vs. OSCILLATOR FREQUENCY

14.CURRENT SENSE DELAY TO OUTPUT vs. TEMPERATURE

15.CURRENT SENSE THRESHOLD vs. ERROR AMPLIFIER OUTPUT

16.START-UP THRESHOLD vs. TEMPERATURE

17.START-UP THRESHOLD vs. TEMPERATURE

18.MINIMUM OPERATING VOLTAGE vs. TEMPERATURE

19.MINIMUM OPERATING VOLTAGE vs. TEMPERATURE

20.LOW LEVEL OUTPUT SATURATION VOLTAGE DURING UNDER-

VOLTAGE LOCKOUT

21.OUTPUT SATURATION VOLTAGE vs. OUTPUT CURRENT and
TEMPERATURE

22.OUTPUT SATURATION VOLTAGE vs. OUTPUT CURRENT and
TEMPERATURE

FIGURE INDEX

Theory of Operation Section

FIGURE #

23.TYPICAL APPLICATION OF START-UP CIRCUITRY

24.REFERENCE VOLTAGE vs. TEMPERATURE

25.SIMPLIFIED SCHEMATIC OF OSCILLATOR SECTION

26.DUTY CYCLE VARIATION vs. DISCHARGE CURRENT

27.OSCILLATOR FREQUENCY vs. TIMING RESISTOR

28.MAXIMUM DUTY CYCLE vs. TIMING RESISTOR

29.CURRENT SENSE THRESHOLD vs. ERROR AMPLIFIER OUTPUT

Typical Applications Section

FIGURE #

30.CURRENT SENSE SPIKE SUPPRESSION

31.MOSFET PARASITIC OSCILLATIONS

32.ADJUSTABLE BUFFERED REDUCTION OF CLAMP LEVEL

WITH SOFT-START

33.EXTERNAL DUTY CYCLE CLAMP AND MULTI-UNIT SYCHRONIZATION

34.SLOPE COMPENSATION

35.OPEN LOOP LABORATORY FIXTURE

36.OFF-LINE FLYBACK REGULATOR

U

LTRA-LOW START-UP CURRENT

, C

URRENT-MODE

PWM

LX1552/3/4/5

PRODUCT DATABOOK 1996/1997

Copyright © 1994

Rev. 1.0a 1/01

6

P

RODUCTION DATA SHEET

CHARACTERISTIC CURVES

FIGURE 2. — MAXIMUM DUTY CYCLE vs. TIMING RESISTOR

FIGURE 3. — OSCILLATOR DISCHARGE CURRENT vs.

TEMPERATURE

FIGURE 4. — OSCILLATOR FREQUENCY vs. TEMPERATURE

FIGURE 1. — OSCILLATOR FREQUENCY vs. TIMING RESISTOR

0.1

0

40

(RT) Timing Resistor - (k)

100

Maximum Duty Cycle - (%)

20

50

80

110100

10

60

70

90

30

VCC = 15V
T

A

= 25°C

100

0.1

0.1

1

1000

Oscillator Frequency - (kHz)

(RT) Timing Resistor - (k)

100

10

1

10

VCC = 15V
T

A

= 25°C

CT = 3.3nF

CT = 1nF

CT = 6.8nF

CT = 22nF

CT = 47nF

CT = 0.1µF

7.70

8.10

(TA) Ambient Temperature - (°C)

(I

d

) Oscillator Discharge Current - (mA)

7.90

8.20

7.80

8.30

8.40

8.00

-75

-50 -25 0 25 50 75 100 125

8.50

VCC = 15V
V

PIN4

= 2V

45

49

(TA) Ambient Temperature - (°C)

Oscillator Frequency - (KHz)

47

50

46

51

52

48

-75

-50 -25 0 25 50 75 100 125

53

VCC = 15V
R

T

= 10k

C

T

= 3.3nF

54

55