diode by the LM3595. Power dissipation must be less than

that allowed by the package. Please refer to the Absolute

Maximum Rating of the LM3595.

INPUT CAPACITOR SELECTION

The LM3595 is designed to run off of a fixed input voltage.

Depending on the stability and condition of this voltage rail, it

may be necessary to add a small input capacitor to help filter

out any noise that may be present on the line. In the event

that filtering is needed, surface-mount multi-layer ceramic

capacitors are recommended. These capacitors are small

and inexpensive. A capacitance of 1µF is typically sufficient.

THERMAL PROTECTION

The LM3595 has internal thermal protection circuitry to dis-

able the part if the junction temperature exceeds 150˚C. This

feature will protect the device from damage due to excessive

power dissipation. The device will recover and operate nor-

mally when the junction temperature falls below the maxi-

mum operating junction temperature of 105˚C. It is important

to have good thermal conduction with a proper layout to

reduce thermal resistance.

PCB LAYOUT CONSIDERATIONS

The LLP is a leadframe based Chip Scale Package (CSP)

with very good thermal properties. This package has an

exposed DAP (die attach pad) at the center of the package

measuring 2.0mm x 1.2mm. The main advantage of this

exposed DAP is to offer lower thermal resistance when it is

soldered to the thermal land on the PCB. For PCB layout,

National highly recommends a 1:1 ratio between the pack-

age and the PCB thermal land. To further enhance thermal

conductivity, the PCB thermal land may include vias to a

ground plane. For more detailed instructions on mounting

LLP packages, please refer to National Semiconductor Ap-

plication Note AN-1187.

www.national.com

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