Linear Technology LT1105IN8, LT1105IN, LT1105CN8, LT1105CN, LT1103CT7 Datasheet

LT1103/LT1105

Offline Switching Regulator

OBSOLETE:

FOR INFORMATION PURPOSES ONLY

Contact Linear Technology for Potential Replacement

FEATURES

■±1% Line and Load Regulation with No Optocoupler

■Switch Frequency Up to 200kHz

■Internal 2A Switch and Current Sense (LT1103)

■Internal 1A Totem-Pole Driver (LT1105)

■Start-Up Mode Draws Only 200μA

■Fully Protected Against Overloads

■Overvoltage Lockout of Main Supply

■Protected Against Underdrive or Overdrive to FET

■Operates in Continuous or Discontinuous Mode

■Ideal for Flyback and Forward Topologies

■Isolated Flyback Mode Has Fully Floating Outputs

APPLICATIONS

U

■Up to 250W Isolated Mains Converter

■Up to 50W Isolated Telecom Converter

■Fully Isolated Multiple Outputs

■Distributed Power Conversion Networks

DESCRIPTION U

The LT®1103 Offline Switching Regulator is designed for high input voltage applications using an external FET switch whose source is driven by the open collector output of the LT1103. The LT1103 is optimized for 15W to 100W applications. For higher power applications or additional switch current flexibility, the LT1105 is available and its totem pole output drives the gate of an external FET. Unique design of the LT1103/LT1105 eliminates the need for an optocoupler while still providing ±1% load and line regulation in a magnetic flux-sensed converter. This significantly simplifies the design of offline power supplies and reduces the number of components which must cross the isolation barrier to one, the transformer.

The LT1103/LT1105 current mode switching techniques are well suited to transformer isolated flyback and forward topologies while providing ease of frequency compensation with a minimum of external components. Low external part count for a typical application combines with a

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATION U

Fully Isolated Flyback 100kHz 50W Converter with Load Regulation Compensation

OPTIONAL OUTPUT FILTER

85VAC TO 270VAC

MBR2045

10μH

5V

!

1.5KE300A

10A

5W

!

+

+

R

220k

N

E

!

+

50V

G

!

A

E

*50V

1W

AG

470μF

+

D

MUR150

220μF

T

3600μF

OL

385V

IG

V

499Ω

H

H

–

*OUTPUT CAPACITOR IS THREE 1200μF,

1N4148

1000pF

100Ω

50V CAPACITORS IN PARALLEL TO

ACHIEVE REQUIRED RIPPLE CURRENT

BRIDGE

RATING AND LOW ESR.

RECTIFIER

BAV21

WINDINGS FOR

+

LINE

BAV21

1N4148

VIN

VSW

BUK426-800A

OPTIONAL

FILTER

±12VDC OUTPUTS

13k

39μF

+

LT1103

10Ω

1%

35V

TRANSFORMER DATA:

18.7k

(V)

15V

COILTRONICS CTX110228-3

FB

+

OUT

L(PRI) = 1.6mH

GND

VC

OSC

1μF

NPRI:NSEC = 1:0.05

V

4.75k

25V

0.047μF

390pF

NBIAS:NSEC = 1:0.27

1%

330Ω

0.047μF

0.1μF

LT1103 TA13

				Load Regulation
5.25
5.20
5.15
5.10
									220VAC
5.05
5.00
4.95
								110V				85V	AC
4.90					270V	AC			AC
4.85
4.80
4.75 0
		1	2	3	4		5	6	7	8		9		10

Danger!! Lethal Voltages Present – See Text

IOUT (A)

LT1103 TA02

1

LT1103/LT1105

DESCRIPTIOU

WARUIUG!

200kHz maximum switching frequency to achieve high power density. Performance at switching frequencies above 100kHz may be degraded due to internal timing constraints associated with fully isolated flyback mode.

Included are the oscillator, control, and protection circuitry such as current limit and overvoltage lockout. Switch frequency and maximum duty cycle are adjustable. Bootstrap circuitry draws 200 A for start-up of isolated topologies. A 5V reference as well as a 15V gate bias are available to power external primary-side circuitry. No external current sense resistor is necessary with LT1103 because it is integrated with the high current switch. The LT1105 brings out the input to the current limit amplifier and requires the use of an external sense resistor.

The LT1103/LT1105 have unique features not found on other offline switching regulators. Adaptive antisat switch drive allows wide ranging load currents while maintaining high efficiency. The external FET is protected from insufficient or excessive gate drive voltage with a drive detection circuit. An externally activated shutdown mode reduces total supply current to less than 200 A, typical for standby operation. Fully isolated and regulated outputs can be generated in the optional isolated flyback mode without the need for optocouplers or other isolated feedback paths.

DANGEROUS AND LETHAL POTENTIALS ARE PRESENT IN OFFLINE CIRCUITS!

BEFORE PROCEEDING ANY FURTHER, THE READER IS WARNED THAT CAUTION MUST BE USED IN THE CONSTRUCTION, TESTING AND USE OF OFFLINE CIRCUITS. HIGH VOLTAGE, AC LINE-CONNECTED POTENTIALS ARE PRESENT IN THESE CIRCUITS. EXTREME CAUTION MUST BE USED IN WORKING WITH AND MAKING CONNECTIONS TO THESE CIRCUITS. REPEAT: OFFLINE CIRCUITS CONTAIN DANGEROUS, AC LINE-CONNECTED HIGH VOLTAGE POTENTIALS. USE CAUTION.

ALL TESTING PERFORMED ON AN OFFLINE CIRCUIT MUST BE DONE WITH AN ISOLATION TRANSFORMER CONNECTED BETWEEN THE OFFLINE CIRCUIT'S INPUT AND THE AC LINE. USERS AND CONSTRUCTORS OF OFFLINE CIRCUITS MUST OBSERVE THIS PRECAUTION WHEN CONNECTING TEST EQUIPMENT TO THE CIRCUIT TO AVOID ELECTRIC SHOCK. REPEAT: AN ISOLATION TRANSFORMER MUST BE CONNECTEDBETWEEN THECIRCUIT INPUT AND THE AC LINE IF ANY TEST EQUIPMENT IS TO BE CONNECTED.

ABSOLUTE

WAXIWUW

RATINGSU

(Note 1)

VIN ..........................................................................	30V
VSW Output Voltage (LT1103).................................	50V
VSW Output Current (200ns)(LT1105) .................	±1.5A
VC, FB, OSC, SS ........................................................	6V
ILIM (LT1105) ...........................................................	3V
0VLO Input Current ...............................................	1mA
Lead Temperature (Soldering, 10 sec.)................	300°C

Maximum Operating Ambient Temperature Range

LT1103C ..............................................	0°C to 70°C
LT1105C ..............................................	0°C to 70°C
Maximum Operating Junction Temperature Range
LT1103C .............................................	0°C to 100°C
LT1105C ............................................	0°C to 100°C
LT1105I .........................................	– 40°C to 125°C
Storage Temperature Range .................	–65°C to 150°C

2

LT1103/LT1105

PACKAGE/ORDER IUNFORWMATIOUN

TOP VIEW

PWRGND	1	14	VSW
OVLO	2	13	NC
FB	3	12	NC
VC	4	11	15V
5V	5	10	VIN
SS	6	9	OSC
GND	7	8	ILIM

N PACKAGE

14-LEAD PDIP

PINS 1 AND 7 MUST BE TIED TOGETHER

TJMAX = 100°C, θJA = 100°C/W

ORDER PART

NUMBER

LT1105CN

LT1105IN

TOP VIEW

ORDER PART

GND

NUMBER

1

8

VSW

ILIM

15V

2

7

LT1105CN8

FB

VIN

3

6

VC

OSC

LT1105IN8

4

5

N8 PACKAGE

8-LEAD PDIP

TJMAX = 100°C, θJA = 130°C/W

FRONT VIEW

ORDER PART

7

15V

NUMBER

6

VIN

5

OSC

4

GND

LT1103CT7

3

VC

2

FB

1

VSW

T7 PACKAGE

7-LEAD TO-220

CASE IS CONNECTED TO GROUND. LEADS ARE FORMED

TJMAX = 100°C, θJA = 50°C/W

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

VIN = 20V, VC = 0.85V, OVLO = 0V, VSW Open, TA = 25°C, unless otherwise noted.

SYMBOL	PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
IQ	Supply Current	8V < VIN < 30V, After Device Has Started	●	10	20	30	mA
ISTART	Start-Up Current	VIN < VIN Start Threshold	●		200	400	A
		Industrial Grade	●			450	A
	VIN Start Threshold		●	14.5	16.0	17.5	V
	VIN Shutdown Threshold	Note: Switching Stops When VSW < 10V (LT1103)	●	5.0	7.0	8.0	V
		Note: Switching Stops When VGATE < 10V (LT1105)
VREF	5V Reference Voltage		●	4.80	4.95	5.20	V
	VREF Line Regulation	10V < VIN < 30V	●		0.025	0.1	%/ V
	VREF Load Regulation	0mA < IL < 20mA	●		0.025	0.05	%/mA
	VREF Short-Circuit Current	Commercial Grade	●	25	60	110	mA
		Industrial Grade	●	20		120	mA
	15V Short-Circuit Current	Commercial Grade	●	30		130	mA
		Industrial Grade	●	25		140	mA
VGATE	15V Gate Bias Reference	17 < VIN < 30V, 0mA < IL < 30mA	●	13.8	15.0	16.2	V
	15V Dropout Voltage	VIN = 15V, IL = 30mA	●		2.0	2.5	V
	15V Short-Circuit Current		●	30	70	130	mA
SF	Oscillator Scaling Factor	FB = 4V, VC = Open, Measured at VSW, ISW = 25mA,		36	40	44	Hz • F
		OVLO = 5V, fOSC = SF/COSC, 40kHz < fOSC < 200kHz	●	32	40	48	Hz • F
	Oscillator Valley Voltage				2.0		V
	Oscillator Peak Voltage				4.5		V

3

LT1103/LT1105

ELECTRICAL CHARACTERISTICS

VIN = 20V, VC = 0.85V, OVLO = 0V, VSW Open, TA = 25°C, unless otherwise noted.

SYMBOL		PARAMETER	CONDITONS		MIN	TYP	MAX	UNIT
DC		Preset Max Switch Duty Cycle	FB = 4V, VC = Open, fOSC = 40kHz, ISW = 25mA,	●	58	65	72	%
		(LT1103)	Note: Maximum Duty Cycle Can Be Altered at OSC Pin
		Preset Max Switch Duty Cycle	FB = 4V, VC = Open, fOSC = 40kHz, ISW = 25mA,	●	56	63	70	%
		(LT1105)	Note: Maximum Duty Cycle Can Be Altered at OSC Pin
			Industrial Grade	●	55		75	%
		OVLO Threshold	Overvoltage Lockout Threshold at Which Switching is Inhibited	●	2.3	2.5	2.7	V
			Industrial Grade	●	2.2		2.8	V
		OVLO Input Bias Current	OVLO = 2V, Measured Out of Pin (Note 2)	●		1.0	3.0	µA
VFB		FB Threshold Voltage	I(VC) = 0mA		4.425	4.50	4.575	V
				●	4.400	4.50	4.600	V
		FB Input Bias Current	FB = VFB (Note 3)	●	5	10	20	µA
			Industrial Grade	●	4		22	µA
		Change in FB Input	FB = VFB, VC = 1V to 4V (Note 3)		8	11	13	µA/V
		Bias Current with Change in VC		●	7	11	14	µA/V
			Industrial Grade	●	6		15	µA/V
		FB Threshold Line Regulation	10V < VIN < 30V	●		0.025	0.10	%/V
gm		Error Amp Transconductance	I(VC) = ±50µA		9000	12000	17500	µmho
				●	6000	12000	20000	µmho
			Industrial Grade	●	5000		24000	µmho
AV		Error Amp Voltage Gain	1V < VC < 3V	●	500	1250		V/V
			Industrial Grade	●	450			V/V
		VC Switching Threshold	Switch Duty Cycle = 0%	●	0.85	1.25	1.4	V
		Shutdown Threshold Voltage		●	50	150	250	mV
			Industrial Grade	●	50		300	mV
		Error Amp Source Current		●	150	275		µA
		Error Amp Sink Current		●	1.5	3	4.5	mA
			Industrial Grade	●	0.7		4.5	mA
		Error Amp Clamp Voltage	FB = 4.75V	●	0.3	0.7	0.9	V
			FB = 4.0V	●	4.2	4.4	4.6	V
		Soft-Start Charging Current	SS = 0V	●	25	40	60	µA
			Industrial Grade	●	20		75	µA
		Soft-Start Reset Current	VIN = 6V, SS = 0.3V	●	1	2		mA
		Output Switch Leakage	VSW = 45V	●			500	µA
		(LT1103)	VSW = 15V	●			200	µA
BV		Switch Breakdown Voltage	ISW = 5mA	●	50	70		V
		(LT1103)
		VSW Current Limit (LT1103)	Duty Cycle = 25% (Note 4)	●	2.0	2.5	3.0	A
		Output Switch On Resistance		●		0.4	0.75	Ω
		(LT1103)
IIN		IQ Increase During Switch On Time	ISW = 0.5A to 1.5A	●		30	50	mA/A
ISW		(LT1103)
		Switch Output High Level	ISW = 200mA, VGATE = 15V	●	13.00	13.5		V
		(LT1105)	ISW = 750mA, VGATE = 15V	●	12.50	13.2		V
		Switch Output High Level	ISW = 200mA, VGATE = 15V	●	12.75			V
		Industrial Grade	ISW = 750mA, VGATE = 15V	●	12.25			V

4

LT1103/LT1105

ELECTRICAL CHARACTERISTICS

VIN = 20V, VC = 0.85V, OVLO = 0V, VSW Open, TA = 25°C, unless otherwise noted.

SYMBOL	PARAMETER	CONDITONS		MIN	TYP	MAX	UNIT
	Switch Output Low Level	ISW = 200mA	●		0.25	0.50	V
	(LT1105)	ISW = 750mA	●		0.75	1.50	V
	Rise Time (LT1105)	CL = 1000pF			50		ns
	Fall Time (LT1105)	CL = 1000pF			20		ns
	ILIM Threshold Voltage (LT1105)	Duty Cycle = 25% (Note 5)	●	300	375	450	mV
	Low Switch Drive Lockout	Measured at VSW (LT1103)	●	9.0	9.5	10.5	V
	Threshold	Measured at 15V Gate Bias Reference (LT1105)
	High Switch Drive Lockout	Measured at VSW (LT1103)	●	17.0	18.5	20.0	V
	Threshold	Measured at 15V Gate Bias Reference (LT1105)

The ● denotes specifications which apply over the full operating temperature range.

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.

Note 2: The OVLO pin is clamped with a 5.5V Zener and can sink a maximum input current of 1mA.

Note 3: FB input bias current changes as a function of the VC pin voltage. Rate of change of FB input bias current is 11 A/V of change on VC. By including a resistor in series with the FB pin, load regulation can be set to zero.

Note 4: Current limit on VSW is constant for DC < 35% and decreases for DC > 35% due to internal slope compensation circuity. The LT1103 switch current limit is given by ILIM = 1.76 (1.536 – DC) above 35% duty cycle.

Note 5: The current limit threshold voltage is constant for DC < 35% and decreases for DC > 35% due to internal slope compensation circuitry. The LT1105 switch current limit threshold voltage is given by VLIM = 0.225 (1.7 – DC) above 35% duty cycle.

TYPICAL PERFORWMANUCE CHARACTERISTICS

SUPPLY CURRENT (mA)

Supply Current vs Input Voltage

25

25°C

20

15

10

5

ISHUT

ISTART

0

0

5

10

15

20

25

30

INPUT VOLTAGE (V)

LT1103 G01

START-UP SUPPLY CURRENT ( A)

Start-Up Supply Current vs	Quiescent Supply Current vs
Input Voltage	Input Voltage

500
450
400
350
300
										°
					125°C					25 C
250
200
150					–55°C
100
50
0
		3	6		9			12		15
0

INPUT VOLTAGE (V)

	22
(mA)	21
	20						125°C
CURRENT
	19						25°C
	18
SUPPLY	17
	16						–55°C
QUIESCENT	15
	14
	13
	12							35
	0	5	10	15	20	25	30		40
				INPUT VOLTAGE (V)

LT1103 G02

LT1103 G03

5

LT1103/LT1105

TYPICAL PERFORWAUCE CHARACTERISTICS

		Quiescent Supply Current vs
		Temperature
	22
(mA)	21
	20									30V
CURRENT
	18
SUPPLY	19
	16
	17
													8V
QUIESCENT	15
	14
	13
	12

–75 –50 –25	0	25	50	75	100 125 150 175
	TEMPERATURE (°C)
					LT1103 G04

		VIN Start-Up Threshold vs
		Temperature
	17.5
(V)	17.0
THRESHOLD	16.5
-UP	16.0
START	15.5
IN
V	15.0

14.5 –75 –50 –25 0 25 50 75 100 125 150 175

TEMPERATURE (°C)

Shutdown Supply Current vs

Input Voltage

	500
( A)	450
	400
CURRENT
	300
SUPPLY	350
	200
	250
										VC = 75mV
SHUTDOWN	150
	100												VC = 0
	50
	0
								15			20								35
	0			5		10									25			30
						INPUT VOLTAGE (V)
																		LT1103 G05
		VIN Shutdown Threshold vs
		Temperature
(V)	8.0
	7.7
THRESHOLD
	7.4
SHUTDOWN
	7.1
IN	6.8
V
	6.5
						0		25			50		75		100 125 150 175
	–75 –50 –25

TEMPERATURE (°C)

																LT1103 G07						LT1103 G08
	Preset Switch Maximum Duty																			Switch Oscillator Frequency vs
	Cycle vs Temperature																			Capacitance
	75																		1000
DUTYSWITCHPRESETCYCLE (%)			COSC =		1000pF
	72																		FREQUENCYSWITCH(kHz)
	69
																			100
	66
	63																		10
	60
																					1000	10000
	–75 –50 –25					0		25		50		75		100 125 150 175					100
						TEMPERATURE (°C)															CAPACITANCE (pF)
																LT1103 G10						LT1103 G11

Shutdown Supply Current vs

VC Voltage

	500
	450
( A)	400
	350
CURRENT
	300
	250						125°C
SHUTDOWN						25°C
	200
	150
	100			–55°C
	50
	0	20	40	60	80	100 120 140 160 180 200
	0
					VC (mV)

LT1103 G06

Output Switch Frequency vs

Temperature

	45
(kHz)			COSC = 1000pF
	43
FREQUENCY	41
SWITCH	39
OUTPUT
	37

35 –75 –50 –25 0 25 50 75 100 125 150

TEMPERATURE (°C)

LT1103 G09

Overvoltage Lockout Threshold vs Temperature

	(V)	3.0
	THRESHOLD	2.8
	LOCKOUT	2.6
		2.4
	OVERVOLTAGE
		2.2

2.0	0	25	50	75	100 125 150 175
–75 –50 –25

TEMPERATURE (°C)

LT1103 G12

6

LT1103/LT1105

TYPICAL PERFORWMANUCE CHARACTERISTICS

OVLO Input Bias Current vs

Temperature

0

OVLO = 2V

A)

–0.5

(

CURRENT

–1.0

BIAS

–1.5

OVLOINPUT

–2.5

–2.0

–3.0

–75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C)

LT1103 G13

5V Reference Voltage vs Temperature

		5.20
		5.15
	(V)	5.10
	VOLTAGE
		5.05
	REFERENCE	5.00
		4.95
	5V	4.90
		4.85
		4.80

–75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C)

LT1103 G16

5V Reference Short-Circuit Current vs Temperature

(mA)	110
CURRENT	100
CIRCUIT-	90
	70
SHORT	80
	60
REFERENCE5V
	50
	40
	30
				–25		0	25		50		75		100 125 150 175
	–75 –50

TEMPERATURE (°C)

LT1103 G19

Soft-Start Charging Current vs

Temperature

( A)		60
		50
CURRENT
		40
CHARGING
		30
-START		20
		10
SOFT
		0
						0				50				100 125 150				175
		–75 –50 –25						25				75
						TEMPERATURE (°C)
																LT1103 G14
		5V Load Regulation vs
		Temperature
(%/mA)	0.025
	0.020
REGULATION
	0.010
5V LOAD	0.015
	0.005
		0
						0		25		50		75		100 125 150 175
		–75 –50 –25
						TEMPERATURE (°C)
																LT1103 G17
		15V Gate Bias Reference vs
		Temperature
		16.2
(V)		15.8
REFERENCE		15.4
BIAS		15.0
GATE15V		14.6
		14.2
		13.8
						0				50				100 125 150				175
		–75 –50 –25						25				75

TEMPERATURE (°C)

LT1103 G20

Soft-Start Reset Current vs

Temperature

(mA)	5
	4
CURRENTRESET
	3
-START	2
SOFT	1
	0
					0	25		50		75		100 125 150 175
	–75 –50 –25

TEMPERATURE (°C)

LT1103 G15

5V Line Regulation vs Temperature

		0.05
	(%/V)	0.04
		0.02
	REGULATION
		0.03
	5V LINE	0.01
		0

–75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C)

LT1103 G18

15V Gate Bias Dropout Voltage vs Temperature

	2.5
(V)
VOLTAGE	2.0
DROPOUT	1.5
GATE BIAS	1.0
	0.5
15V

0	0	25	50	75	100 125 150 175
–75 –50 –25

TEMPERATURE (°C)

LT1103 G21

7

LT1103/LT1105

TYPICAL PERFORWAUCE CHARACTERISTICS

	15V Gate Bias Short-Circuit												Low Switch Drive Lockout
	Current vs Temperature												Threshold vs Temperature
SHORTBIASGATE15V-CIRCUIT CURRENT (mA)	130											DRIVESWITCHLOWLOCKOUT THRESHOLD (V)	10.5
	30												9.0
	110												10.2
	90												9.9
	70												9.6
	50												9.3

–75 –50 –25	0	25	50	75	100 125 150 175	–75 –50 –25	0	25	50	75	100 125 150 175
	TEMPERATURE (°C)						TEMPERATURE (°C)
					LT1103 G22						LT1103 G23

High Switch Drive Lockout

Threshold vs Temperature

(V)	20.0
THRESHOLD	19.5
DRIVELOCKOUT	19.0
	18.0
	18.5
HIGHSWITCH	17.0
	17.5

–75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C)

LT1103 G24

Feedback Threshold vs

Temperature

	4.60
(V)	4.56
THRESHOLD	4.52
FEEDBACK	4.48
	4.44
	4.40
					0	25		50		75		100 125 150 175
	–75 –50 –25

TEMPERATURE (°C)

LT1103 G25

FB INPUT BIAS CURRENT ( A)

FB Input Bias Current vs Temperature (VC = 1V)

20

16

12

8

4

0	0	25	50	75	100 125 150 175
–75 –50 –25

TEMPERATURE (°C)

LT1103 G26

Change in FB Input Bias Current with Change in VC vs Temperature (VC = 1V to 4V)

CURRENT A/V)	14
	13
BIASINPUTFBINCHANGE VINCHANGEWITH	12
(
C
	11
	10
	9
	8
	7
							100 125 150 175
	–75 –50 –25		0	25	50	75

TEMPERATURE (°C)

LT1103 G27

ERROR AMPLIFIER TRANSCONDUCTANCE ( mho)

Error Amplifier Transconductance vs Temperature

25000

20000

15000

10000

5000	–25	0	25	50	75	100 125 150 175
–75 –50

TEMPERATURE (°C)

ERROR AMPLIFIER TRANSCONDUCTANCE (mho)

Error Amplifier Transconductance																																			Error Amplifier Voltage Gain vs
and Phase vs Frequency																																			Temperature
0.020																																200			2500
0.018								PHASE																								180		(V/V)
0.016																																160
																																		VOLTAGEAMPLIFIERGAIN
0.014									gm																							140	(DEGREES)PHASE		2000
0.012																																120
0.010																																100			1500
0.008																																80
0.006																																60			1000
0.004																																40		ERROR
																											gm
0.002																																20
																						PHASE
0																																0			500
						1			10													100
0.1																											1000								–75 –50			–25		0		25		50		75		100 125 150 175
									FREQUENCY (kHz)																															TEMPERATURE (°C)

LT1103 G28

LT1103 G29

LT1103 G30

8

LT1103/LT1105

TYPICAL PERFORWAUCE CHARACTERISTICS

Error Amplifier Source Current vs Temperature

	( A)	350
		325
	CURRENT
		300
	SOURCE	275
		250
	AMPLIFIER
		225
	ERROR	200
		175
		150

–75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C)

LT1103 G31

Error Amplifier Low Clamp Voltage vs Temperature (FB = 4.75V)

(V)	0.9
VOLTAGE	0.8
CLAMP	0.7
LOW
	0.6
AMPLIFIER
	0.5
ERROR	0.4
	0.3
						0						50				100 125 150				175
	–75 –50 –25							25						75
						TEMPERATURE (°C)
																		LT1103 G34
			LT1103 Switch Saturation Voltage
			vs Temperature
(V)	1.2
VOLTAGE	1.0
SATURATION	0.8
					ISW = 1.5A
SWITCH	0.6
	0.4
					ISW = 0.5A
LT1103	0.2

0 –75 –50 –25 0 25 50 75 100 125 150 175

TEMPERATURE (°C)

LT1103 G38

																					Error Amplifier High Clamp
	Error Amplifier Sink Current vs																				Voltage vs Temperature
	Temperature																				(FB = 4V)
(mA)CURRENTSINKAMPLIFIERERROR	4.5																			VOLTAGECLAMPHIGHAMPLIFIERERROR(V)	4.5
	4.0																				4.4
	3.5
																					4.3
	3.0
																					4.2
	2.5
																					4.1
	2.0
	1.5																				4.0
						0		25		50		75		100 125 150				175
																										0		25		50		75			100 125 150 175
	–75 –50 –25																				–75 –50 –25
						TEMPERATURE (°C)																				TEMPERATURE (°C)
																LT1103 G32																						LT1103 G33
			VC Switching Threshold Voltage																			LT1103 Output Switch Leakage
			vs Temperature																	A)		Current vs Temperature
	1.5																				200
(V)THRESHOLDSWITCHING																				(
	1.3																			CURRENTLEAKAGESWITCH	160
																												V	SW = 45V
	1.1																				120
	0.9																				80
																				OUTPUT												VSW = 15V
V	0.7																				40
C																				LT1103
	0.5																				0
						0		25		50		75		100 125 150 175												0		25		50		75			100 125 150 175
	–75 –50 –25																				–75 –50 –25
						TEMPERATURE (°C)																				TEMPERATURE (°C)
																LT1103 G35																						LT1103 G36
		LT1103 VSW Current Limit vs																				LT1103 VSW Current Limit vs
		Duty Cycle																				Temperature

	3.0		–55°C								3.0
											2.9	DC = 25%
(A)	2.5									(A)
			25°C								2.8
LIMIT										LIMIT
	2.0		125°C								2.7
CURRENT										CURRENT	2.6
	1.5										2.5
SW	1.0									SW	2.4
V										V	2.3
LT1103										LT1103
	0.5										2.2
											2.1
	0	10	20	30	40	50	60	70	80		2.0		0	25	50	75	100 125 150 175
	0										–75 –50 –25
			DUTY CYCLE (%)										TEMPERATURE (°C)
								LT1103 G39									LT1103 G40

9

LT1103/LT1105

TYPICAL PERFORWAUCE CHARACTERISTICS

LT1103 Driver Current vs

Temperature

(mA/A)	50
	40
CURRENT
	30
DRIVER
	20
LT1103
	10
	0
								0	25		50		75		100 125 150 175
	–75 –50 –25
								TEMPERATURE (°C)
																	LT1103 G41
	LT1105 Current Limit Threshold
(mV)	Voltage vs Temperature
	450
VOLTAGE				DC = 25°C
THRESHOLD	425
	375
LIMIT	400
	350
CURRENT
	325
LT1105				–50 –25				0	25		50		75		100 125 150				175
	–75
	300

TEMPERATURE (°C)

LT1103 G46

LT1105 VSW Low Saturation

Voltage vs Temperature

(V)	3.0
VOLTAGE	2.5
SATURATION	2.0
	1.5
LOW	1.0														I	SW = 750mA
SW
V	0.5
LT1105															ISW = 200mA
	0
								0				50							100 125 150								175
	–75 –50 –25								25						75
								TEMPERATURE (°C)
																						LT1103 G42
		LT1105 VSW Rise Time vs
		Temperature
	100
TIME (ns)	80
	60							CLOAD = 4700pF
RISE
SW	40
V								CLOAD = 1000pF
LT1105
	20
	0
								0	25			50			75				100 125 150 175
	–75 –50 –25

TEMPERATURE (°C)

LT1103 G44

		LT1105 VSW High Saturation
		Voltage vs Temperature
(V)	3.0
VOLTAGE	2.5
SATURATION	2.0											ISW	= 750mA
	1.5
HIGH											ISW = 200mA
	1.0
SW
V	0.5
LT1105
	0
								0							50							100 125 150							175
	–75 –50 –25											25						75
								TEMPERATURE (°C)
																										LT1103 G43
		LT1105 VSW Fall Time vs
		Temperature
	100
TIME (ns)	80
	60
FALL
														CLOAD = 4700pF
SW	40
V
LT1105	20
																			CLOAD = 1000pF
	0
								0				25			50			75				100 125 150 175
	–75 –50 –25

TEMPERATURE (°C)

LT1103 G45

10