LT1072CS8#TRPBF Datasheet LT1072CSW#PBF, LT1072CT#06PBF, LT1072IT#PBF | P10-P12

10

LT1072

1072fc

Flyback Converter

Negative to Positive Buck-Boost Converter External Current Limit

R1

1k

V

IN

NOTE THAT THE LT1072 GND PIN

IS NO LONGER COMMON TO V

IN

(–)

LT1072 • TA06

C1

1000pF

C2

R

S

R2

+

–

V

IN

V

SW

FB

V

C

GND

LT1072

Q1

C3

0.47µF

V

OUT

5V

1.5A

D2

D1

OPTIONAL

FILTER

1

3

N*

N* =

C2

0.15µF

C4

25µF*

V

IN

20 TO 30V

R3

1.5k

REQUIRED IF INPUT LEADS ≥ 2"

OPTIONAL TO REPLACE R4 AND C3

*

**

C1

500µF

R4

1k

**

R1

3.74k

R2

1.24k

V

IN

V

SW

FB

V

C

GND

LT1072

L2

10µH

C4

200µF

V

SNUB

V

OUT

+ V

f

I

PRI

I

PRI

I

PRI

(I

PRI

) (L

L

)

V

SNUB

I

PRI

N

∆I

V

IN

0V

0

CLAMP TURN-ON

SPIKE

PRIMARY FLYBACK VOLTAGE =

LT1072 SWITCH VOLTAGE

AREA “a” = AREA “b” TO MAINTAIN

ZERO DC VOLTS ACROSS PRIMARY

SECONDARY VOLTAGE

AREA “c” = AREA “d” TO MAINTAIN

ZERO DC VOLTS ACROSS SECONDARY

PRIMARY CURRENT

SECONDARY CURRENT

LT1070 SWITCH CURRENT

SNUBBER DIODE CURRENT

V

OUT

+ V

f

N

N • V

IN

t =

a

b

c

d

LT1072 • TA04

+

V

IN

V

SW

FB

V

C

GND

LT1072

C2

1000µF

C1

0.22µF

C4

25µF*

R2

1.24k

R3

2.2k

R1

11.3k

V

OUT

12V, 0.5A

V

IN

–12V

D1

L1**

220µH

Q1

*

**

REQUIRED IF INPUT LEADS ≥ 2"

PULSE ENGINEERING 52626

OPTIONAL

INPUT

FILTER

L3

OPTIONAL

OUTPUT

FILTER

L2

C3

LT1072 • TA05

+

TYPICAL APPLICATIO S

U

11

LT1072

1072fc

Positive to Negative Buck-Boost Converter

External Current Limit

LT1072 • TA08

D1

R1

500Ω

R2

≈ 2V

V

X

V

C

GND

LT1072

Voltage Boosted Boost Converter

LT1072 • TA09

D2

D1

TOTAL INDUCTANCE = 8mH

INTERLEAVE PRIMARY AND

SECONDARY FOR LOW LEAKAGE

INDUCTANCE

1

L1

N = 5

+

C2

0.047µF

R3

10k

V

IN

15V

C1

200µF

R4

1.5k

1/2W

C3

0.68

R1

98k

V

OUT

100V AT 75mA

R2

1.24k

V

IN

V

SW

FB

V

C

GND

LT1072

+

C

C5

100µF*

V

IN

10 TO 30V

*REQUIRED IF INPUT LEADS ≥ 2"

**PULSE ENGINEERING 92113

†

TO AVOID START-UP PROBLEMS

FOR INPUT VOLTAGES BELOW 10V,

CONNECT ANODE OF D3 TO V

IN

,

AND REMOVE R5. C1 MAY BE

REDUCED FOR LOWER OUTPUT

CURRENTS. C1 ≈ (500µF)(I

OUT

).

FOR 5V OUTPUTS, REDUCE R3

TO 1.5k, INCREASE C2 TO 0.3µF,

AND REDUCE R6 TO 100Ω

LT1072 • TA07

R4

47Ω

D1

D2

1N914

C1

†

1000µF

C

C3

2µF

R5

†

470Ω, 1W

C

C2

0.1µF

D3

†

1N4001

C4

5µF

R6

470Ω

R2

1.24k

L1**

200µH

R3

5k

V

OUT

–12V AT 2A

R1

10.7k

V

IN

V

SW

FB

V

C

GND

LT1072

+

TYPICAL APPLICATIO S

U

12

LT1072

1072fc

Negative Buck Converter

LT1072 • TA11

R3

C3

25µF*

V

IN

–20V

R2

1.24k

Q1

2N3906

R1

4.64k

C2

500µF

D1

L1**

220µH

C1

V

IN

V

SW

FB

V

C

GND

LT1072

LOAD

–5.2V AT 1A

OPTIONAL

OUTPUT

FILTER

L2

4µH

C4

200µF

OPTIONAL

INPUT

FILTER

L3

REQUIRED IF INPUT LEADS ≥ 2"

PULSE ENGINEERING 52626

*

**

+

Positive Buck Converter

Driving High Voltage FET

(for Offline Applications, See AN-25)

LT1072 • TA10

+

10 TO 20V

V

IN

V

SW

GND

LT1072

D1

GD

Q1

LT1072 • TA12

C1

1µF

R3

470Ω

OPTIONAL

OUTPUT

FILTER

REQUIRED IF INPUT LEADS ≥ 2"

PULSE ENGINEERING 52626

*

**

D1

r

D2

L2

4µH

1N914

V

IN

V

SW

FB

V

C

GND

LT1072

R2

1.24k

R4

10Ω

100mA

MINIMUM

5V, 1A

C3

2.2µF

C2

1µF

D3

V

IN

R1

3.74k

L1**

220µH

C4

500µF

C5*

25µF

C5

200µF

+

TYPICAL APPLICATIO S

U

LT1072CS8#TRPBF

LT1072CS8#TRPBF

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