air,

chosen, and

printed circuit board, copper traces and other materials

to the surrounding air. The 8-pin SOIC package for the

MAX603/MAX604 features a special lead frame with a

lower thermal resistance and higher allowable power

dissipation. The thermal resistance of this package is

pin plastic DIP package and

ceramic DIP package.

The GND pins of the MAX603/MAX604 SOIC package

perform the dual function of providing an electrical con-

nection to ground and channeling heat away. Connect

all GND pins to ground using a large pad or ground

plane. Where this is impossible, place a copper plane

on an adjacent layer. The pad should exceed the

dimensions in Figure 4.

Figure 4 assumes the IC is an 8-pin SOIC package, is

soldered directly to the pad, has a +125°C maximum

junction temperature and a +25°C ambient air tempera-

ture, and has no other heat sources. Use larger pad

sizes for other packages, lower junction temperatures,

higher ambient temperatures, or conditions where the IC

is not soldered directly to the heat-sinking ground pad.

The MAX603/MAX604 can regulate currents up to

500mA and operate with input voltages up to 11.5V, but

not simultaneously. High output currents can only be

sustained when input-output differential voltages are

low, as shown in Figure 5. Maximum power dissipation

depends on packaging, board layout, temperature, and

air flow. The maximum output current is:

Reverse-Current Protection

The MAX603/MAX604 has a unique protection scheme

that limits reverse currents when the input voltage falls

below the output. It monitors the voltages on IN and

OUT and switches the IC’s substrate and power bus to

I

P

T

- T

V

- V

100 C

OUT max

MAX

J

A

IN

OUT

×

()

5V/3.3V or Adjustable, Low-Dropout,

8

_______________________________________________________________________________________

0

100

200

300

400

500

600

700

27

MAX604

SUPPLY VOLTAGE (V)

5

39

810

12

11

6

413

CERAMIC DIP

PLASTIC DIP

HIGH-POWER SOIC

MAXIMUM CONTINUOUS CURRENT LIMIT

OPERATING

REGION AT

0

100

200

300

400

500

600

700

7

MAX603

MAXIMUM OUTPUT CURRENT vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

59

810

12

11

6

413

CERAMIC DIP

PLASTIC DIP

HIGH-POWER

SOIC

MAXIMUM CONTINUOUS CURRENT LIMIT

OPERATING

REGION AT

Figure 5. Power Operating Regions: Maximum Output Current

vs. Differential Supply Voltage

1.0

1

0.2

10

20

6.5

1.3

65

130

POWER DISSIPATION vs.

GROUND PAD AREA

1.2

COPPER GROUND PAD AREA

1.4

1.6

1.8

1.1

1.3

1.5

1.7

8-PIN SO PACKAGE

PAPER EPOXY BOARD

SINGLE SIDED

1oz. COPPER

Figure 4. Typical Maximum Power Dissipation vs. Ground Pad

Size.