PRODUCT SPECIFICATION

FAN1582

REV. 1.1.3 11/9/03

7

The current out of the adjust pin adds to the current from R1

and is typically 50µA. Its output voltage contribution is

small and only needs consideration when a very precise out-

put voltage setting is required.

Figure 2. Basic Regulator Circuit

Load Regulation

The FAN1582 family provides true remote sensing, eliminat-

ing output voltage errors due to trace resistance. To utilize

remote sensing, connect the VSENSE pin directly to the

load, rather than at the VOUT pin. If the load is more than 1"

away from the FAN1582, it may be necessary to increase the

load capacitance to ensure stability.

Thermal Considerations

The FAN1582 series protect themselves under overload con-

ditions with internal power and thermal limiting circuitry.

However, for normal continuous load conditions, do not exceed

maximum junction temperature ratings. It is important to

consider all sources of thermal resistance from junction-to-

ambient. These sources include the junction-to-case resistance,

the case-to-heat sink interface resistance, and the heat sink

resistance. Thermal resistance specifications have been

developed to more accurately reflect device temperature and

ensure safe operating temperatures. The electrical character-

istics section provides a separate thermal resistance and

maximum junction temperature for both the control circuitry

and the power transistor. Calculate the maximum junction

temperature for both sections to ensure that both thermal

limits are met.

For example, look at using an FAN1582M-1.5 to generate

3A @ 1.5V ± 2% from a 3.3V source (3.2V to 3.6V).

Assumptions:

•

thermally conductive material)

The power dissipation in this application is:

From the specification table,

= 70 + (6.39) * (5 + 3) = 121°C

The junction temperature is below the maximum rating.

Junction-to-case thermal resistance is specified from the IC

junction to the bottom of the case directly below the die. This

is the lowest resistance path for heat flow. Proper mounting

ensures the best thermal flow from this area of the package to

the heat sink. Use of a thermally conductive material at the

case-to-heat sink interface is recommended. Use a thermally

conductive spacer if the case of the device must be electri-

cally isolated and include its contribution to the total thermal

resistance.

C2

22

µF

C1

10

µF

+

+

Vcntl

Vsense

Vin

Adj Vout

FAN1582

R1

R2

50

µA

Figure 3. Application Circuit (FAN1582)

100

µF

C2

10

µF

C3

2.1V at 3A

+

10

µFC1

1

µF

C4

+

Adj

FAN1582

86.6

Ω

124

Ω

R2

R1

U1