Linear Technology LT1372HVIS8, LT1372HVIN8, LT1372HVCS8, LT1372HVCN8, LT1372CS8 Datasheet

FEATURES

■Faster Switching with Increased Efficiency

■Uses Small Inductors: 4.7μH

■All Surface Mount Components

■Only 0.5 Square Inch of Board Space

■Low Minimum Supply Voltage: 2.7V

■Quiescent Current: 4mA Typ

■Current Limited Power Switch: 1.5A

■Regulates Positive or Negative Outputs

■Shutdown Supply Current: 12μA Typ

■Easy External Synchronization

■8-Pin SO or PDIP Packages

APPLICATIOUS

■Boost Regulators

■CCFL Backlight Driver

■Laptop Computer Supplies

■Multiple Output Flyback Supplies

■Inverting Supplies

LT1372/LT1377

500kHz and 1MHz High Efficiency 1.5A Switching Regulators

DESCRIPTIOU

The LT®1372/LT1377 are monolithic high frequency switching regulators. They can be operated in all standard switching configurations including boost, buck, flyback, forward, inverting and “Cuk.” A 1.5A high efficiency switch is included on the die, along with all oscillator, control and protection circuitry. All functions of the LT1372/LT1377 are integrated into 8-pin SO/PDIP packages.

The LT1372/LT1377 typically consumes only 4mA quiescent current and has higher efficiency than previous parts. High frequency switching allows for very small inductors to be used. All surface mount components consume less than 0.5 square inch of board space.

New design techniques increase flexibility and maintain ease of use. Switching is easily synchronized to an external logic level source. A logic low on the shutdown pin reduces supply current to 12μA. Unique error amplifier circuitry can regulate positive or negative output voltage while maintaining simple frequency compensation techniques. Nonlinear error amplifier transconductance reduces output overshoot on start-up or overload recovery. Oscillator frequency shifting protects external components during overload conditions.

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

TYPICAL APPLICATIOU

5V-to-12V Boost Converter

5V

L1*

D1

4.7μH

MBRS120T3

†

VOUT

5

12V

4

V

IN

8

R1

ON

S/S

VSW

53.6k

OFF

1%

+

LT1372/LT1377

2

+

C1**

FB

C4**

22μF

GND

VC

22 F

6, 7

1

R2

C2

6.19k

1%

0.047μF

R3

C3

2k

0.0047μF

*COILCRAFT DO1608-472 (4.7 H) OR COILCRAFT DT3316-103 (10 H) OR SUMIDA CD43-4R7 (4.7 H) OR SUMIDA CD73-100KC (10 H) OR

**AVX TPSD226M025R0200

†MAX IOUT

	L1	IOUT
	4.7μH	0.25A
	10μH	0.35A

LT1372 • TA01

12V Output Efficiency

	100
			VIN = 5V
(%)	90
	80
EFFICIENCY
	70
	60
	50

0.01 0.1 1 OUTPUT CURRENT (A)

LT1372 • TA02

1

LT1372/LT1377

ABSOLUTE WAXIWUW	RATIUGS
Supply Voltage .......................................................		30V
Switch Voltage
LT1372/LT1377 ..................................................		35V
LT1372HV ..........................................................		42V
S/S Pin Voltage .......................................................		30V
Feedback Pin Voltage (Transient, 10ms)		.............. ±10V
Feedback Pin Current ...........................................		10mA
Negative Feedback Pin Voltage		±10V
(Transient, 10ms) .............................................
Operating Junction Temperature Range		0°C to 125°C*
Commercial ........................................
Industrial .........................................		– 40°C to 125°C
Short Circuit .........................................		0°C to 150°C
Storage Temperature Range ................		– 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................		300°C

PACKAGE/ORDER IUFORWATIOU

								ORDER PART NUMBER
				TOP VIEW
	VC					VSW		LT1372CN8		LT1372HVIN8
		1			8			LT1372HVCN8 LT1372IS8
	FB					GND
		2			7
								LT1372CS8		LT1372HVIS8
	NFB					GND S
		3			6
	S/S					VIN		LT1372HVCS8 LT1377CS8
		4			5
								LT1372IN8		LT1377IS8
	N8 PACKAGE			S8 PACKAGE
	8-LEAD PDIP			8-LEAD PLASTIC SO				S8 PART MARKING
	TJMAX = 125°C, θJA = 100°C/ W (N8)
								1372	1372H		1377
	TJMAX = 125°C, θJA = 120°C/ W (S8)
								1372I	1372HI		1377I

Consult factory for Military grade parts.

*Units shipped prior to Date Code 9552 are rated at 100°C maximum operating temperature.

ELECTRICAL CHARACTERISTICS

VIN = 5V, VC = 0.6V, VFB = VREF, VSW, S/S and NFB pins open, unless otherwise noted.

SYMBOL	PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
VREF	Reference Voltage	Measured at Feedback Pin		1.230	1.245	1.260	V
		VC = 0.8V	●	1.225	1.245	1.265	V
IFB	Feedback Input Current	VFB = VREF			250	550	nA
			●			900	nA
	Reference Voltage Line Regulation	2.7V ≤ VIN ≤ 25V, VC = 0.8V	●		0.01	0.03	%/V
VNFB	Negative Feedback Reference Voltage	Measured at Negative Feedback Pin		– 2.540	– 2.490	– 2.440	V
		Feedback Pin Open, VC = 0.8V	●	– 2.570	– 2.490	– 2.410	V
INFB	Negative Feedback Input Current	VNFB = VNFR	●	– 45	– 30	– 15	μA
	Negative Feedback Reference Voltage	2.7V ≤ VIN ≤ 25V, VC = 0.8V	●		0.01	0.05	%/V
	Line Regulation
gm	Error Amplifier Transconductance	IC = ±25μA		1100	1500	1900	μmho
			●	700		2300	μmho
	Error Amplifier Source Current	VFB = VREF – 150mV, VC = 1.5V	●	120	200	350	μA
	Error Amplifier Sink Current	VFB = VREF + 150mV, VC = 1.5V	●		1400	2400	μA
	Error Amplifier Clamp Voltage	High Clamp, VFB = 1V		1.70	1.95	2.30	V
		Low Clamp, VFB = 1.5V		0.25	0.40	0.52	V
AV	Error Amplifier Voltage Gain				500		V/ V
	VC Pin Threshold	Duty Cycle = 0%		0.8	1	1.25	V
f	Switching Frequency	2.7V ≤ VIN ≤ 25V
		LT1372		450	500	550	kHz
		0°C ≤ TJ ≤ 125°C	●	430	500	580	kHz
		– 40°C ≤ TJ < 0°C (I Grade)		400		580	kHz
		LT1377		0.90	1	1.10	MHz
		0°C ≤ TJ ≤ 125°C	●	0.86	1	1.16	MHz
		– 40°C ≤ TJ < 0°C (I Grade)		0.80		1.16	MHz

2

LT1372/LT1377

ELECTRICAL CHARACTERISTICS

VIN = 5V, VC = 0.6V, VFB = VREF, VSW, S/S and NFB pins open, unless otherwise noted.

SYMBOL		PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
		Maximum Switch Duty Cycle		●	90	95		%
		Switch Current Limit Blanking Time				130	260	ns
BV		Output Switch Breakdown Voltage	LT1372/LT1377	●	35	47		V
			LT1372HV
			0°C ≤ TJ ≤ 125°C	●	42	47		V
			– 40°C ≤ TJ < 0°C (I Grade)		40			V
VSAT		Output Switch “On” Resistance	ISW = 1A	●		0.5	0.8	Ω
ILIM		Switch Current Limit	Duty Cycle = 50%	●	1.5	1.9	2.7	A
			Duty Cycle = 80% (Note 1)	●	1.3	1.7	2.5	A
IIN		Supply Current Increase During Switch On-Time				15	25	mA/A
ISW
		Control Voltage to Switch Current				2		A/V
		Transconductance
		Minimum Input Voltage		●		2.4	2.7	V
IQ		Supply Current	2.7V ≤ VIN ≤ 25V	●		4	5.5	mA
		Shutdown Supply Current	2.7V ≤ VIN ≤ 25V, VS/S ≤ 0.6V
			0°C ≤ TJ ≤ 125°C	●		12	30	μA
			– 40°C ≤ TJ < 0°C (I Grade)				50	μA
		Shutdown Threshold	2.7V ≤ VIN ≤ 25V	●	0.6	1.3	2	V
		Shutdown Delay		●	5	12	25	μs
		S/S Pin Input Current	0V ≤ VS/S ≤ 5V	●	– 10		15	μA
		Synchronization Frequency Range	LT1372	●	600		800	kHz
			LT1377	●	1.2		1.6	MHz

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

Note 1: For duty cycles (DC) between 50% and 90%, minimum guaranteed switch current is given by ILIM = 0.667 (2.75 – DC).

TYPICAL PERFORWAUCE CHARACTERISTICS

		Switch Saturation Voltage																													Switch Current Limit
		vs Switch Current																													vs Duty Cycle
	1.0																													3.0
	0.9																150		°	C
(V)
													100		°C									25°C						2.5
VOLTAGE	0.8																												LIMIT(A)
	0.7																																														25°C AND
																														2.0																	125°C
SATURATIONSWITCH	0.6																												CURRENTSWITCH
																																										–55°C
	0.5																													1.5
	0.4															–55			°C
																														1.0
	0.3
	0.2																													0.5
	0.1
																														0
	0
				0.2		0.4		0.6		0.8		1.0		1.2			1.4				1.6		1.8				2.0					10		20		30		40		50		60		70			80		90		100
	0																													0
								SWITCH CURRENT (A)																													DUTY CYCLE (%)
																							LT1372 • G01																										LT1372 • G02

INPUT VOLTAGE (V)

Minimum Input Voltage vs Temperature

3.0

2.8

2.6

2.4

2.2

2.0

1.8	–25	0	25	50	75	100	125	150
–50

TEMPERATURE (°C)

LT1372 • G03

3

LT1372/LT1377

TYPICAL PERFORWAUCE CHARACTERISTICS

Shutdown Delay and Threshold	Minimum Synchronization	Error Amplifier Output Current
vs Temperature	Voltage vs Temperature	vs Feedback Pin Voltage

20								2.0		)	3.0									A)(μ	400
18								1.8		(V		fSYNC = 700kHz (LT1372)
										PP-
s)(DELAYSHUTDOWNμ									(V)THRESHOLDSHUTDOWN	VOLTAGESYNCHRONIZATIONMINIMUM	2.5	fSYNC = 1.4MHz (LT1377)								CURRENTOUTPUTAMPLIFIERERROR	300		°
16		SHUTDOWN THRESHOLD						1.6															25 C
																							–55°C
																					200
14								1.4
											2.0											125°C
12								1.2
																LT1377					100
10								1.0			1.5
8	SHUTDOWN DELAY							0.8			1.0					LT1372					0
6								0.6													–100
4								0.4			0.5										–200
2								0.2
0								0			0						75	100			–300			VREF
–50	–25	0	25	50	75	100	125	150			–50		–25	0	25	50			125 150		–0.3	–0.2	–0.1		0.1
			TEMPERATURE (°C)												TEMPERATURE (°C)							FEEDBACK PIN VOLTAGE (V)
							LT1372 • G04												LT1372 • G05						LT1372 • G06

S/S PIN INPUT CURRENT (μA)

S/S Pin Input Current vs Voltage

5

VIN = 5V

4

3

2

1

0

–1

–2

–3

–4

–5

–1	0	1	2	3	4	5	6	7	8	9
			S/S PIN VOLTAGE (V)

SWITCHING FREQUENCY (% OF TYPICAL)

Switching Frequency

vs Feedback Pin Voltage

110

100

90

80

70

60

50

40

30

20

10

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK PIN VOLTAGE (V)

TRANSCONDUCTANCE (μmho)

Error Amplifier Transconductance vs Temperature

2000
1800								gm =		I (VC)
										V (FB)
1600
1400
1200
1000
800
600
400
200
0
				25 50 75 100 125 150
–50 –25 0

TEMPERATURE (°C)

LT1372 • G07

LT1372 • G08

LT1372 • G09

VC PIN VOLTAGE (V)

VC Pin Threshold and High Clamp Voltage vs Temperature

2.4

2.2

2.0VC HIGH CLAMP

1.8

1.6

1.4

1.2

VC THRESHOLD

1.0

0.8

0.6

0.4

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

FEEDBACK INPUT CURRENT (nA)

Feedback Input Current vs Temperature

800

VFB =VREF

700

600
500
400
300
200
100
0	–25	0	25	50	75	100	125	150
–50

TEMPERATURE (°C)

NEGATIVE FEEDBACK INPUT CURRENT (μA)

Negative Feedback Input Current vs Temperature

0

VNFB =VNFR

–10

–20

–30

–40

–50

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

LT1372 • G10

LT1372 • G11

LT1372 • G12

4