20

LT1941

1941f

APPLICATIO S I FOR ATIO

CHANNEL 1 OUTPUT POWER (WATTS)

0

0

1

2

3

4

6

1

23

4

1941 F09a

56

5

CHANNEL 3

OUTPUT POWER (P3)

P3 = 2W

P3 = 4W

P3 = 6W

CHANNEL 1 OUTPUT POWER (WATTS)

0

0

0.5

1.0

1.5

2.0

3.0

12

1941 F09b

3

2.5

CHANNEL 3

OUTPUT POWER (P3)

P3 = 1W

P3 = 2W

P3 = 3W

Figure 9. Power Output Capability of an Individual Channel Depends on the Output Power of the Other Channels

temperature. The output current capability of the third

channel can be calculated from the output currents and

voltages of the other channels, the switching regulator

efficiency (

resistance from junction to ambient (

P

TT

P

P

VI

V

I

I

P

V

DISS

JMAX

A

JA

DISS

=

=

=

–

–

–• –

•

θ

η

3

1

12

3

3

12

3

V3 = 12V,

25

°C/W:

P

CC

CW

W

P

W

VA

V

A

W

I

W

V

A

°°

°

=

==

==

125

75

25

2

3

2

10 8

25

2

3 3

1

17

17

12

0 141

3

–

/

–.

–.

•

– .

•

.

.

.

Note that decreasing

capability. The power output capability of the individual

channels can be calculated from the following:

Figure 9 shows power output capability if overall system

efficiency (

η) is 75% and maximum allowable power

allowable power dissipation is 2W, Channel 3 output

power is 2W and Channel 2 output power is 1W, then

Channel 1 output power can be up to 5W.

RELATED LINEAR TECHNOLOGY PUBLICATIONS

Application notes 19, 35, 44, 76 and 88 contain more

detailed descriptions and design information for buck

regulators and other switching regulators. The LT1375

data sheet has a more extensive discussion of output

ripple, loop compensation, and stability testing. Design

Notes 100 and 318 show how to generate a dual polarity

output supply using a buck regulator.