14

LT1500/LT1501

capacitors may require the capacitor to be larger. To

ensure proper reset of the soft start capacitor, an external

resistor must be connected in parallel with the capacitor.

The resistor value should be 470k or more.

Calculating Temperature Rise

For most applications, temperature rise in the IC will be

fairly low and will not be a problem. However, if load

currents are near the maximum allowed and ambient

temperatures are also high, a calculation should be done

to ensure that the maximum junction temperature of

100

°C is not exceeded. The calculations must account for

power dissipation in the switch, the drive circuitry and the

sense resistor.

P

IR

V

V

V

V

IV

V

R

I

V

V

TOTAL

OUT

SW

OUT

OUT

IN

IN

OUT

OUT

IN

SENSE OUT

OUT

IN

)(

)

−

()

()

+

−

()

+

()

2

2

2

2

30

•

()

package and maximum ambient temperature of 85

°C

(industrial range),

P

W

()

()

+

−

()

+

()

()

=+

+

=

015

0 72 5 5 22

22

015 5 22

30

0 42 0 15 5

22

0 47

0 014

0 049

0 11

2

2

2

2

..

.

.

..

..

•

.

..

.

.

The SO package has a thermal resistance of 120

°C/W, so

maximum device temperature will be:

1

2

3

4

0.150 – 0.157**

(3.810 – 3.988)

8

7

6

5

0.189 – 0.197*

(4.801 – 5.004)

0.228 – 0.244

(5.791 – 6.197)

0.016 – 0.050

0.406 – 1.270

0.010 – 0.020

(0.254 – 0.508)

× 45°

0

°– 8° TYP

0.008 – 0.010

(0.203 – 0.254)

SO8 0695

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

*

**

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)