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

LIN DO C #: 1552

LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

T H E I N F I N I T E P O W E R O F I N N O V A T I O N P R O D U C T I O N D A T A S H E E T

D E S C R I P T I O N

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.

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

TYPICAL APPLICATION OF LX155X USING ITS

MICROPOWER START-UP FEATURE

T A B L E 1

K E Y F E AT U R E S

■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.) p CURRENT 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

A P P L I C AT I O N S

■ECONOMY OFF-LINE FLYBACK OR FORWARD CONVERTERS

■DC-DC BUCK OR BOOST CONVERTERS

■LOW COST DC MOTOR CONTROL

	RST
AC	I ST
INPUT	VCC
	LX1552
	or
	LX1554

	Design Using		SG384x	UC384xA	LX155x
	Max. Start-up Current
			1000µA	500µA	250µA
	Specification (IST)
	Typical Start-Up
			62KΩ	124KΩ	248KΩ
	Resistor Value (RST)
	Max. Start-Up Resistor		2.26W	1.13W	0.56W
	Power Dissipation (P	)
	R

Note: Calculation is done for universal AC input speci-

fication of VACMIN= 90VRMS to VACMAX= 265VRMS using the following equation: (Resistor curr ent is selected to be

2 * IST at VACMIN.)

R =	V			, P		=	2V		2
		AC MIN							AC MAX
ST					R
	Ö2 * IST								RST

A V A I L A B L E O P T I O N S P E R P A R T #

	Part #		Start-Up		Hysteresis		Max. Duty
			Voltage				Cycle
	LX1552		16V		6V		<100%
	LX1553		8.4V		0.8V		<100%
	LX1554		16V		6V		<50%
	LX1555		8.4V		0.8V		<50%

PA C K A G E O R D E R I N F O R M AT I O N

TA (°C)

M

Plastic DIP

DM

Plastic SOIC

D

Plastic SOIC

Y

Ceramic DIP

PW

TSSOP

8-pin

8-pin

14-pin

8-pin

20-pin

0 to 70

LX155xCM

LX155xCDM

LX155xCD

—

LX155xCPW

-40 to 85

LX155xIM

LX155xIDM

LX155xID

—

—

-55 to 125

—

—

—

LX155xMY

—

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

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

Copyright © 1994	11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841	1
Rev. 1.0a 1/01

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

P R O D U C T I O N D A T A S H E E T

	ABSOLUTE MAXIMUM RATINGS	(Note 1)
	Supply Voltage (Low Impedance Source) ..................................................................	30V
	Supply Voltage (ICC < 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

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.

THERMAL DATA

M PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA	95°C/W
DM PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA	165°C/W
D PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA	120°C/W
Y PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA	130°C/W
PW PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA	144°C/W

Junction Temperature Calculation: TJ = TA + (PD x θJA).

The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow

PACKAGE PIN OUTS

COMP		1	8		VREF
VFB		2	7		VCC
ISENSE		3	6		OUTPUT
RT/CT		4	5		GND

M & Y PACKAGE

(Top View)

COMP				1	8			VREF
VFB				2	7			VCC
ISENSE				3	6			OUTPUT
RT/CT				4	5			GND

DM PACKAGE

(Top View)

COMP				1	14			VREF
N.C.				2	13			N.C.
VFB				3	12			VCC
N.C.				4	11			VC
ISENSE				5	10			OUTPUT
N.C.				6	9			GND
RT/CT				7	8			PWR GND

D PACKAGE

(Top View)

N.C.		1	20		N.C.
N.C.		2	19		N.C.
COMP		3	18		VREF
VFB		4	17		N.C.
N.C.		5	16		VCC
ISENSE		6	15		VC
N.C.		7	14		OUTPUT
RT/CT		8	13		GND
N.C.		9	12		PWR GND
N.C.		10	11		N.C.

PW PACKAGE

(Top View)

2		Copyright ©	1994
		Rev. 1.0a	1/01

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

P R O D U C T I O N D A T A S H E E T

E L E C T R I C A L C H A R A C T E R I S T I C S

(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 ≤TA ≤ 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.)

Parameter	Symbol	Test Conditions	LX155xI/155xM			LX155xC			Units
			Min. Typ. Max. Min. Typ. Max.
Reference Section
Output Voltage	VREF	TA = 25°C, IL = 1mA	4.95	5.00	5.05	4.95	5.00	5.05	V
Line Regulation		12 ≤ VIN ≤ 25V		6	20		6	20	mV
Load Regulation		1 ≤ IO ≤ 20mA		6	25		6	25	mV
Temperature Stability (Note 2 & 7)				0.2	0.4		0.2	0.4	mV/°C
Total Output Variation		Over Line, Load, and Temperature	4.9		5.1	4.9		5.1	V
Output Noise Voltage (Note 2)	VN	10Hz ≤ f ≤ 10kHz, TA = 25°C		50			50		µV
Long Term Stability (Note 2)		TA = 125°C, t = 1000hrs		5	25		5	25	mV
Output Short Circuit	ISC		-30	-100	-180	-30	-100	-180	mA
Oscillator Section
Initial Accuracy (Note 6)		TA = 25°C	48.5	50.5	52.5	48.5	50.5	52.5	kHz
		TA = 25°C, RT = 698Ω, CT = 22nF, LX1552/3 only	56	58	60	56	58	60	kHz
Voltage Stability		12 ≤ VCC ≤ 25V		0.2	1		0.2	1	%
Temperature Stability (Note 2)		TMIN ≤ TA ≤ TMAX		5			5		%
Amplitude (Note 2)		VPIN 4 peak to peak		1.7			1.7		V
Discharge Current	ID	TA = 25°C, VPIN 4 = 2V	8.0	8.3	8.6	8.0	8.3	8.6	mA
		VPIN 4 = 2V, TMIN ≤ TA ≤ TMAX	7.6		8.8	7.8		8.8	mA
Error Amp Section
Input Voltage		VPIN 1 = 2.5V	2.45	2.50	2.55	2.45	2.50	2.55	V
Input Bias Current	IB			-0.1	-1		-0.1	-0.5	µA
Open Loop Gain	AVOL	2 ≤ VO ≤ 4V	65	90		65	90		dB
Unity Gain Bandwidth (Note 2)	UGBW	TA = 25°C		0.6			0.6		MHz
Power Supply Rejection Ratio (Note 3)	PSRR	12 ≤ VCC ≤ 25V	60	70		60	70		dB
Output Sink Current	IOL	VPIN 2 = 2.7V, VPIN 1 = 1.1V	2	4		2	4		mA
Output Source Current	IOH	VPIN 2 = 2.3V, VPIN 1 = 5V	-0.5	-0.8		-0.5	-0.8		mA
Output Voltage High Level	VOH	VPIN 2 = 2.3V, RL = 15K to ground	5	6.5		5	6.5		V
Output Voltage Low Level	VOL	VPIN 2 = 2.7V, RL = 15K to VREF		0.7	1.1		0.7	1.1	V
Current Sense Section
Gain (Note 3 & 4)	AVOL		2.85	3	3.15	2.85	3	3.15	V/V
Maximum Input Signal (Note 3)		VPIN 1 = 5V	0.9	1	1.1	0.9	1	1.1	V
Power Supply Rejection Ratio (Note 3)	PSRR	12 ≤ VCC ≤ 25V		70			70		dB
Input Bias Current	IB			-2	-10		-2	-5	µA
Delay to Output (Note 2)	TPD	VPIN 3 = 0 to 2V		150	300		150	300	ns
Output Section
Output Voltage Low Level	VOL	ISINK = 20mA		0.1	0.4		0.1	0.4	V
		ISINK = 200mA		1.5	2.2		1.5	2.2	V
Output Voltage High Level	VOH	ISOURCE = 20mA	13	13.5		13	13.5		V
		ISOURCE = 200mA	12	13.5		12	13.5		V
Rise Time (Note 2)	TR	TA = 25°C, CL = 1nF		50	100		50	100	ns
Fall Time (Note 2)	TF	TA = 25°C, CL = 1nF		50	100		50	100	ns
UVLO Saturation	VSAT	VCC = 5V, ISINK = 10mA		0.7	1.2		0.7	1.2	V

(Electrical Characteristics continue next page.)

Copyright © 1994	3
Rev. 1.0a 1/01

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LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

P R O D U C T I O N D A T A S H E E T

		E L E C T R I C A L C H A R A C T E R I S T I C S		(Con't.)
	Parameter	Symbol	Test Conditions		LX155xI/155xM					LX155xC				Units
					Min. Typ. Max. Min. Typ. Max.
	Under-Voltage Lockout Section
	Start Threshold	VST	1552/1554		15		16	17	15		16		17	V
			1553/1555		7.8		8.4	9.0	7.8		8.4		9.0	V
	Min. Operation Voltage After Turn-On		1552/1554		9		10	11	9		10		11	V
			1553/1555		7.0		7.6	8.2	7.0		7.6		8.2	V
	PWM Section
	Maximum Duty Cycle		1552/1553		94		96		94		96			%
			1552/1553, RT = 698Ω, CT = 22nF				50				50			%
			1554/1555		47		48		47		48			%
	Minimum Duty Cycle							0					0	%
	Power Consumption Section
	Start-Up Current	IST					150	250			150		250	µA
	Operating Supply Current	ICC					11	17			11		17	mA
	VCC Zener Voltage	VZ	ICC = 25mA		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 VFB = 0.
4.	Gain defined as: A =	VCOMP	; 0 ≤ VISENSE ≤ 0.8V.
		VISENSE

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

Temp Stability = VREF (max.) - VREF (min.)

TA (max.) - TA (min.)

5.Adjust VCC 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.

VREF (max.) & VREF (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.

B L O C K D I A G R A M

VCC*	34V
		UVLO
		S / R	5V	VREF
			REF
GROUND**
	16V (1552/1554)	16V (1552/1554)
		8.4V (1553/1555)
	8.4V (1553/1555)
				INTERNAL
				BIAS
		VREF		VC*
		GOOD LOGIC

RT/CT	OSCILLATOR
		***	T		OUTPUT
	ERROR AMP	2R	S
		1V	R	PWM	POWER GROUND**
VFB
		R		LATCH
COMP		CURRENT SENSE
ISENSE		COMPARATOR

*- VCC 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.

4		Copyright ©	1994
		Rev. 1.0a	1/01

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

P R O D U C T I O N D A T A S H E E T

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 UNDERVOLTAGE 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

Copyright © 1994	5
Rev. 1.0a 1/01

P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7

LX1552/3/4/5

ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM

P R O D U C T I O N D A T A S H E E T

C H A R A C T E R I S T I C C U RV E S

FIGURE 1. — OSCILLATOR FREQUENCY vs. TIMING RESISTOR FIGURE 2. — MAXIMUM DUTY CYCLE vs. TIMING RESISTOR

	1000
					CT = 1nF
(kHz)-					CT = 3.3nF
	100	CT = 6.8nF			(%)
FrequencyOscillator					DutyMaximumCycle -
	10
			CT = 22nF
	1		CT = 47nF
			CT = 0.1µF
			VCC = 15V
	0.1		TA = 25°C
			1	10
	0.1				100

(RT) Timing Resistor - (k )

100
90
80
70
60
50
40
30
20
10				VCC = 15V
				TA = 25°C
0
0.1		1	10	100

(RT) Timing Resistor - (k )

FIGURE 3. — OSCILLATOR DISCHARGE CURRENT vs. TEMPERATURE

8.50

(mA)						VPIN4			= 2V
	8.40					VCC		= 15V
-
Current	8.30
Discharge	8.20
	8.10
Oscillator	8.00
	7.90
d	7.80
)
(I
	7.70
	-75 -50 -25		0	25	50	75			100 125

(TA) Ambient Temperature - (°C)

FIGURE 4. — OSCILLATOR FREQUENCY vs. TEMPERATURE

55

	54					VCC = 15V
(KHz)						RT = 10k
	53					CT = 3.3nF
	52
-
Frequency	51
	50
Oscillator	49
	48
	47
	46
	45
	-75 -50 -25		0	25	50	75 100 125

(TA) Ambient Temperature - (°C)

6		Copyright ©	1994
		Rev. 1.0a	1/01