LT1074/LT1076

13

Tapped-Inductor Buck Converter

Positive-to-Negative Converter with 5V Output

TYPICAL APPLICATIO S

+

+

GND

FB

LT1074HV

R1

2.8k

R2

2.21k

D2

35V

5W

C3

200

50V

R3

1k

C2

0.2

L1*

LT1074 •TA02

D1**

D3

1N5819

31

C1

4400

(2 EA

2200

16V)

L2

5

C4

390

16V

0.01

+

PULSE ENGINEERING #PE

±65282

*

**

†

MOTOROLA MBR2030CTL

IF INPUT VOLTAGE IS BELOW 20V,

MAXIMUM OUTPUT CURRENT WILL BE REDUCED. SEE AN44

20V

5V, 10A

†

R3*

2.74k

V

GND

R4

1.82k*

C2

1000

10V

L1

25

5A

††

+

+

D1

†

MBR745

R1**

5.1k

C3

0.1

C4**

0.01

+

R2**

10k

C1

220

50V

* = 1% FILM RESISTORS

D1 = MOTOROLA-MBR745

C1 = NICHICON-UPL1C221MRH6

C2 = NICHICON-UPL1A102MRH6

L1 = COILTRONICS-CTX25-5-52

V

4.5V to

40V

IN

–5V,1A***

+

200

10V

–

OPTIONAL FILTER

5

LOWER REVERSE VOLTAGE RATING MAY BE USED FOR LOWER INPUT VOLTAGES.

LOWER CURRENT RATING IS ALLOWED FOR LOWER OUTPUT CURRENT. SEE AN44.

R1, R2, AND C4 ARE USED FOR LOOP FREQUENCY COMPENSATION WITH LOW INPUT VOLTAGE,

BUT R1 AND R2 MUST BE INCLUDED IN THE CALCULATION FOR OUTPUT VOLTAGE DIVIDER VALUES.

LOWER CURRENT RATING MAY BE USED FOR LOWER OUTPUT CURRENT. SEE AN44.

R3 =

–2.37 (K

Ω)

R1 = (R3) (1.86)

R2 = (R3) (3.65)

MAXIMUM OUTPUT CURRENT OF 1A IS DETERMINED BY MINIMUM INPUT

VOLTAGE OF 4.5V. HIGHER MINIMUM INPUT VOLTAGE WILL ALLOW MUCH HIGHER

OUTPUT CURRENTS. SEE AN44.

LT1074 • TA03

LT1074

FB

FOR HIGHER OUTPUT VOLTAGES, INCREASE R1, R2, AND R3 PROPORTIONATELY.

FOR INPUT VOLTAGE > 10V, R1, R2, AND C4 CAN BE ELIMINATED, AND COMPENSATION IS

DONE TOTALLY ON THE V PIN.

C

†

††

**

**