Linear Technology LT1172MK, LT1172MJ8, LT1172IS8, LT1172IN8, LT1172HVCT Datasheet

LT1170/LT1171/LT1172

100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators

FEATURES

■Wide Input Voltage Range: 3V to 60V

■Low Quiescent Current: 6mA

■Internal 5A Switch (2.5A for LT1171, 1.25A for LT1172)

■Very Few External Parts Required

■Self-Protected Against Overloads

■Operates in Nearly All Switching Topologies

■Shutdown Mode Draws Only 50μA Supply Current

■Flyback-Regulated Mode Has Fully Floating Outputs

■Comes in Standard 5-Pin Packages

■LT1172 Available in 8-Pin MiniDIP and Surface Mount Packages

■Can Be Externally Synchronized

APPLICATIOUS

■Logic Supply 5V at 10A

■5V Logic to ±15V Op Amp Supply

■Battery Upconverter

■Power Inverter (+ to –) or (– to +)

■Fully Floating Multiple Outputs

USER NOTE:

This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability of the LT1170/LT1171/LT1172. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1170/LT1171/LT1172 by factoring in the higher frequency. A CAD design program called SwitcherCADTM is also available.

DESCRIPTIOU

The LT®1170/LT1171/LT1172 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and “Cuk.” A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1170/LT1171/LT1172 to be built in a standard 5-pin TO-3 or TO-220 power package as well as the 8-pin packages (LT1172). This makes them extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators.

The LT1170/LT1171/LT1172 operate with supply voltages from 3V to 60V, and draw only 6mA quiescent current. They can deliver load power up to 100W with no external power devices. By utilizing current-mode switching techniques, they provide excellent AC and DC load and line regulation.

The LT1170/LT1171/LT1172 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50μA typically for standby operation.

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

SwitcherCAD is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIOU

Boost Converter (5V to 12V) Maximum Output Power*

	5V	L1**		L2	OUTPUT
		50mH		10mH	FILTER
				C3
			D1	100mF
	VIN		MBR330			12V	**
			VSW				(W)
			+		R1	1A
							POWER
+	C3*			1000mF
					1%
	LT1170			C2	10.7k
	100mF		FB
	GND	VC			R2
			R3
					1.24k
			1k		1%
			C1
			1mF
*REQUIRED IF INPUT LEADS ³ 2"			** COILTRONICS 50-2-52
			PULSE ENGINEERING 92114		1170/1/2 TA01

100

80

LT1170

BUCK-

BOOST

60

VO = 30V

BOOST

40

FLYBACK

20

BUCK-

BOOST

VO = 5V

0

0

10

20

30

40

50

INPUT VOLTAGE (V)

* ROUGH GUIDE ONLY. BUCK MODE

POUT = (5A)(VOUT)

SPECIAL TOPOLOGIES DELIVER MORE POWER.

**DIVIDE VERTICAL POWER SCALE BY TWO FOR LT1171, BY FOUR

FOR LT1172.

LT1170/1/2 TA02

1

LT1170/LT1171/LT1172

ABSOLUTE WAXIWUW	RATIUGS
Supply Voltage
LT1170/71/72HV ................................................		60V
LT1170/71/72 (See Note 1) ................................		40V
Switch Output Voltage
LT1170/71/72HV ................................................		75V
LT1170/71/72 .....................................................		65V
LT1172S8 ...........................................................		60V
Feedback Pin Voltage (Transient, 1ms)		................ ±15V
Storage Temperature Range ...............		– 65 ° C to 150°C
Lead Temperature (Soldering, 10 sec).................		300°C
Operating Junction Temperature Range		– 55 ° C to 150°C
LT1170/71/72M...............................
LT1170/71/72HVC,		0 ° C to 100°C
LT1170/71/72C (Oper.) ....................
LT1170/71/72HVC,		0 ° C to 125°C
LT1170/71/72C (Sh. Ckt.) ................
LT1170/71/72I (Oper.) ....................		– 40 ° C to 100°C
LT1170/71/72I (Sh. Ckt.).................		– 40 ° C to 125°C

Note 1: Minimum effective switch “on” time for the LT1170/71/72 (in current limit only) is ≈ 0.6μs. This limits the maximum safe input voltage during an output shorted condition. Buck mode and inverting mode input voltage during an output shorted condition is limited to:

VIN (max, output shorted) = 15V +	(R)(IL) + Vf
		(t)(f)
buck and inverting mode
R = Inductor DC resistance

IL = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172 Vf = Output catch diode forward voltage at IL

t = 0.6μs, f = 100kHz switching frequency

Maximum input voltage can be increased by increasing R or Vf. External current limiting such as that shown in AN19, Figure 39, will provide protection up to the full supply voltage rating. C1 in Figure 39 should be reduced to 200pF.

Transformer designs will tolerate much higher input voltages because leakage inductance limits rate of rise of current in the switch. These designs must be evaluated individually to assure that current limit is well controlled up to maximum input voltage.

Boost mode designs are never protected against output shorts because the external catch diode and inductor connect input to output.

PACKAGE/ORDER IUFORWATIOU

TOP VIEW

ORDER PART

GND

E2

NUMBER

1

8

VC

VSW

LT1172MJ8

2

7

FB

3

6

E1

LT1172CJ8

NC*

4

5

VIN

LT1172CN8

J8 PACKAGE

N8 PACKAGE

LT1172IN8

8-LEAD CERDIP

8-LEAD PDIP

LT1172CS8

S8 PACKAGE, 8-LEAD PLASTIC SO

* Do not connect Pin 4 of the LT1172 DIP or SO to external

LT1172IS8

circuitry. This pin may be active in future revisions.

S8 PART MARKING

TJMAX = 150°C, θJA = 100°C/W (J)

TJMAX = 100°C, θJA = 100°C/W (N)

1172

TJMAX = 100°C, θJA = 120°C/W to 150°C/W

1172I

depending on board layout (S)

BOTTOM VIEW

ORDER PART

VSW

VC

NUMBER

1

2

CASE

4

3

IS GND

LT1170MK

VIN

FB

LT1170CK

K PACKAGE, 4-LEAD TO-3 METAL CAN

LT1171MK

TJMAX

θJC

θJA

LT1171CK

LT1170MK

150°C

2°C/W

35°C/W

LT1170CK

100°C

2°C/W

35°C/W

LT1172MK

LT1171MK

150°C 4°C/W

35°C/W

LT1172CK

LT1171CK

100°C

4°C/W

35°C/W

LT1172MK

150°C

8°C/W 35°C/W

LT1172CK

150°C 8°C/W 35°C/W

Based on continuous operation.

TJMAX = 125°C for intermittent fault conditions.

FRONT VIEW

*θ will vary from

ORDER PART

approximately 25°C/W with

5

VIN

NUMBER

4

VSW

2.8 sq. in. of 1oz. copper to

3

GND

45°C/W with 0.20 sq. in. of

LT1170CQ

2

FB

1oz. copper. Somewhat

1

VC

lower values can be

LT1171CQ

Q PACKAGE, 5-LEAD DD

obtained with additional

LT1172CQ

TJMAX = 100°C, θJA = *°C/W

copper layers in multilayer

boards.

TOP VIEW

ORDER PART

NC

1

16

NC

NUMBER

NC

2

15

NC

GND

3

14

E2

LT1172CSW

VC

4

13

VSW

FB

5

12

E1

NC

6

11

VIN

NC

7

10

NC

NC

8

9

NC

SW PACKAGE, 16-LEAD PLASTIC SO WIDE

TJMAX = 100°C, θJA = 150°C/W

Based on continuous operation.

TJMAX = 125°C for intermittent fault conditions.

FRONT VIEW

ORDER PART

NUMBER

5

VIN

4

VSW

LT1170CT

3

GND

2

FB

LT1170IT

1

VC

T PACKAGE, 5-LEAD TO-220

LT1170HVCT

LT1170HVIT

TJMAX

θJC

θJA

LT1171CT

LT1170CT/LT1170HVCT

100°C

2°C/W

75°C/W

LT1171IT

LT1171CT/LT1171HVCT

°

°

°

100 C

4 C/W

75 C/W

LT1171HVCT

LT1172CT/LT1172HVCT

100°C

8°C/W

75°C/W

Based on continuous operation.

LT1172CT

TJMAX = 125°C for intermittent fault conditions.

LT1172HVCT

2

LT1170/LT1171/LT1172

ELECTRICAL CHARACTERISTICS VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.

SYMBOL	PARAMETER		CONDITIONS				MIN	TYP	MAX	UNITS
VREF	Reference Voltage		Measured at Feedback Pin				1.224	1.244	1.264	V
			VC = 0.8V			●	1.214	1.244	1.274	V
IB	Feedback Input Current		VFB = VREF					350	750	nA
						●			1100	nA
gm	Error Amplifier		DIC = ±25mA				3000	4400	6000	mmho
	Transconductance					●	2400		7000	mmho
	Error Amplifier Source or		VC = 1.5V				150	200	350	mA
	Sink Current					●	120		400	mA
	Error Amplifier Clamp		Hi Clamp, VFB = 1V				1.80		2.30	V
	Voltage		Lo Clamp, VFB = 1.5V				0.25	0.38	0.52	V
	Reference Voltage Line		3V £ VIN £ VMAX			●			0.03	%/V
	Regulation		VC = 0.8V
AV	Error Amplifier Voltage Gain		0.9V £ VC £ 1.4V				500	800		V/V
	Minimum Input Voltage (Note 3)					●		2.6	3.0	V
IQ	Supply Current		3V £ VIN £ VMAX, VC = 0.6V					6	9	mA
	Control Pin Threshold		Duty Cycle = 0				0.8	0.9	1.08	V
						●	0.6		1.25	V
	Normal/Flyback Threshold						0.4	0.45	0.54	V
	on Feedback Pin
VFB	Flyback Reference Voltage		IFB = 50mA				15.0	16.3	17.6	V
	(Note 3)					●	14.0		18.0	V
	Change in Flyback Reference		0.05 £ IFB £ 1mA				4.5	6.8	9	V
	Voltage
	Flyback Reference Voltage		IFB = 50mA					0.01	0.03	%/V
	Line Regulation (Note 3)		7V £ VIN £ VMAX
	Flyback Amplifier		DIC = ±10mA				150	300	650	mmho
	Transconductance (gm)
	Flyback Amplifier Source		VC = 0.6V		Source	●	15	32	70	mA
	and Sink Current		IFB = 50mA		Sink	●	25	40	70	mA
BV	Output Switch Breakdown		3V £ VIN £ VMAX,		LT1170/LT1171/LT1172	●	65	90		V
	Voltage		ISW = 1.5mA		LT1170HV/LT1171HV/LT1172HV	●	75	90		V
					LT1172S8	●	60	80		V
VSAT	Output Switch		LT1170			●		0.15	0.24	W
	“On” Resistance (Note 1)		LT1171			●		0.30	0.50	W
			LT1172			●		0.60	1.00	W
	Control Voltage to Switch		LT1170					8		A/V
	Current Transconductance		LT1171					4		A/V
			LT1172					2		A/V
ILIM	Switch Current Limit	(LT1170)	Duty Cycle = 50%		TJ ³ 25°C	●	5		10	A
			Duty Cycle = 50%		TJ < 25°C	●	5		11	A
			Duty Cycle = 80% (Note 2)			●	4		10	A
		(LT1171)	Duty Cycle = 50%		TJ ³ 25°C	●	2.5		5.0	A
			Duty Cycle = 50%		TJ < 25°C	●	2.5		5.5	A
			Duty Cycle = 80% (Note 2)			●	2.0		5.0	A
		(LT1172)	Duty Cycle = 50%		TJ ³ 25°C	●	1.25		3.0	A
			Duty Cycle = 50%		TJ < 25°C	●	1.25		3.5	A
			Duty Cycle = 80% (Note 2)			●	1.00		2.5	A

3

LT1170/LT1171/LT1172

ELECTRICAL CHARACTERISTICS VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.

SYMBOL		PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
IIN		Supply Current Increase				25	35	mA/A
ISW		During Switch On-Time
f		Switching Frequency			88	100	112	kHz
				●	85		115	kHz
DCMAX		Maximum Switch Duty Cycle		●	85	92	97	%
		Shutdown Mode	3V ≤ VIN ≤ VMAX			100	250	μA
		Supply Current	VC = 0.05V
		Shutdown Mode	3V ≤ VIN ≤ VMAX		100	150	250	mV
		Threshold Voltage		●	50		300	mV
		Flyback Sense Delay Time (Note 3)				1.5		μs

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

VMAX = 40V for LT1170/71/72 and 60V for LT1170/71/72HV.

Note 1: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1170, 2A for LT1171, and 1A for LT1172.

Note 2: For duty cycles (DC) between 50% and 80%, minimum

guaranteed switch current is given by ILIM = 3.33 (2 – DC) for the LT1170,

ILIM = 1.67 (2 – DC) for the LT1171, and ILIM = 0.833 (2 – DC) for the LT1172.

Note 3: Minimum input voltage for isolated flyback mode is 7V. VMAX = 55V for HV grade in fully isolated mode to avoid switch breakdown.

TYPICAL PERFORWAUCE CHARACTERISTICS

Switch Current Limit vs Duty Cycle*

	16
(A)	12
CURRENT	–55°C	25°C
	8
SWITCH	125°C
	4

*DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172.

0 0 10 20 30 40 50 60 70 80 90 100

DUTY CYCLE (%)

1170/1/2 G01

MINIMUM INPUT VOLTAGE (V)

Minimum Input Voltage

2.9

SWITCH CURRENT = IMAX

2.8

2.7

2.6

SWITCH CURRENT = 0A

2.5

2.4

2.3						100
–75 –50	–25	0	25	50	75		125	150

TEMPERATURE (°C)

1170/1/2 G02

SWITCH SATURATION VOLTAGE (V)

Switch Saturation Voltage

1.6

1.4

150°C

1.2

100°C

1.0

25°C

0.8

–55°C

0.6

0.4

0.2* DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT1172.

0

0

1

2

3

4

5

6

7

8

SWITCH CURRENT (A)*

1170/1/2 G03

Line Regulation		Feedback Bias Current vs
	Reference Voltage vs Temperature	Temperature

	5								1.250											800
REFERENCE VOLTAGE CHANGE (mV)	4								1.248											700
																			FEEDBACK BIAS CURRENT (nA)
	3				TJ = 150°C			REFERENCE VOLTAGE (V)	1.246											600
	2
	1								1.244											500
	0	TJ = –55°C				TJ = 25°C			1.242											400
	–1
									1.240											300
	–2								1.238											200
	–3
	–4								1.236											100
	–5								1.234	–50		0				100	125			0	–50		0				100	125
	0	10	20	30	40	50	60		–75		–25		25	50	75			150		–75		–25		25	50	75			150

INPUT VOLTAGE (V)		TEMPERATURE (°C)	TEMPERATURE (°C)
	1170/1/2 G04	1170/1/2 G05	1170/1/2 G06

4

LT1170/LT1171/LT1172

TYPICAL PERFORWAUCE CHARACTERISTICS

SUPPLY CURRENT (μA)

Supply Current vs Supply Voltage (Shutdown Mode)

160

TJ = 25°C

140

120

100

VC = 50mV

80

60
40
20
				VC = 0V
0
		10	20	30		40	50
0								60
			SUPPLY VOLTAGE (V)
							1170/1/2 G07

Driver Current* vs Switch Current

160

	140
(mA)	120
	100
CURRENT
	80				TJ = –55°C
DRIVER
	60
	40								TJ = ³ 25°C
	20
	0
			1	2	3			4
	0												5

SWITCH CURRENT (A)

1170/1/2 G08

*AVERAGE LT1170 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.

Supply Current vs Input Voltage*

	15
	14			TJ =	25°C
	13			NOTE THAT THIS CURRENT DOES NOT
(mA)				INCLUDE DRIVER CURRENT, WHICH IS
	12
				A FUNCTION OF LOAD CURRENT AND
CURRENT	11			DUTY CYCLE.
	10									90%		DUTY		CYCLE
SUPPLY	9									50%		DUTY		CYCLE
	8
	7									10%		DUTY		CYCLE
	6
											0% DUTY CYCLE
	5
																	60
	0			10		20		30		40			50
						INPUT VOLTAGE (V)								1170/1/2 G09

*UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH

10% OR LESS.

SUPPLY CURRENT (μA)

Shutdown Mode Supply Current

200
180
160
140
120									TJ = 150°C
100
80
60
										–55°C £ TJ £ 125°C
40
20
0
		10				30			40
0				20							50		60		70		80		90		100

VC PIN VOLTAGE (mV)

1170/1/2 G10

Error Amplifier Transconductance

	5000
	4500												gm =		DI	(VC PIN)
mho)(μ															DV (FB PIN)
	3500
TRANSCONDUCTANCE	4000
	1000
	3000
	2500
	2000
	1500
	500
	0
			–50				0								100		125
	–75				–25				25		50		75						150

TEMPERATURE (°C)

1170/1/2 G11

VC Pin Characteristics

300

200

VFB

= 1.5V

(CURRENT

INTO

VC

PIN)

A)

100

(μ

CURRENT

0

TJ = 25°C

PIN

–100

C

–200

V

–300

VFB = 0.8V (CURRENT OUT OF VC PIN)

–400

0.5

1.5

0

1.0

2.0

2.5

VC PIN VOLTAGE (V)

1170/1/2 G12

IDLE SUPPLY CURRENT (mA)

Idle Supply Current vs
Temperature
11
10			VC	= 0.6V
9
8
7
								V		SUPPLY		= 60V
6
									VSUPPLY = 3V
5
4
3
2
1
			–50					0											100		125
–75					–25						25		50				75						150

TEMPERATURE (°C)

1170/1/2 G13

FEEDBACK VOLTAGE (mV)

Feedback Pin Clamp Voltage

500

450

400

–55°C

350

300

25°C

250

150°C

200

150

100

50

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA)

1170/1/2 G14

Switch “Off” Characteristics

	1000
	900
(μA)	800
	700						VSUPPLY
CURRENT	600			VSUPPLY			= 40V
	500	VSUPPLY		= 15V
									VSUPPLY
	400	= 3V
SWITCH									= 55V
	300
	200
	100
	0	10		30	40
	0		20			50	60	70	80	90	100

SWITCH VOLTAGE (V)

1170/1/2 G15

5

LT1170/LT1171/LT1172

TYPICAL PERFORWAUCE CHARACTERISTICS

VC PIN VOLTAGE (mV)

Shutdown Thresholds

400																							–400
350
			CURRENT						(OUT		OF V		C PIN)										–350
300																							–300	V
																								C
250																							–250	PIN
200																							–200	CURRENT
150										VOLTAGE													–150
																								A)μ(
100																							–100
50						VC VOLTAGE IS REDUCED UNTIL																	–50
						REGULATOR CURRENT DROPS
0						BELOW 300μA																	0
		–50						0									100		125
–75						–25				25		50		75								150

TEMPERATURE (°C)

1170/1/2 G16

TIME (μs)

Flyback Blanking Time

2.2

2.0

1.8

1.6

1.4

1.2

1.0						100
–75 –50	–25	0	25	50	75		125	150

JUNCTION TEMPERATURE (°C)

1170/1/2 G17

FLYBACK VOLTAGE (V)

Isolated Mode Flyback Reference

Voltage

23

22
21					RFB = 500Ω
20
19
							RFB =			1k
18
17
						RFB = 10k
16
15
		–50		0										100	125
–75			–25		25				50			75				150

TEMPERATURE (°C)

1170/1/2 G18

	Transconductance of Error
	Amplifier
	7000																															–30
	6000																															0
mho)																θ
	5000																															30
(μ																																	(DEG)PHASE
TRANSCONDUCTANCE	4000																															60
																	gm
	3000																															90
	2000																															120
	1000																															150
	0																															180
–1000																																210
	1k							10k						100k										1M							10M

FREQUENCY (Hz)

1170/1/2 G19

FEEDBACK PIN VOLTAGE (mV)

Normal/Flyback Mode Threshold on Feedback Pin

500																			–24
490																			–22
480																			–20
470																			–18
460				FEEDBACK PIN VOLTAGE															–16
					(AT THRESHOLD)
450																			–14
440																			–12
430					FEEDBACK PIN CURRENT														–10
							(AT THRESHOLD)
420																			– 8
410																			– 6
400																			– 4
																125
–50		–25			0		25		50		75		100					150

TEMPERATURE (°C)

1170/1/2 G20

A)μ( CURRENT PIN FEEDBACK

6