top side of the board can also help. With careful layout it is

possible to reduce the

θ

shown in Figure 1

Optimizing the

θ

board exposed to lower ambient temperature allows the part

to operate with higher power dissipation. The internal power

dissipation can be calculated by summing the three main

sources of loss: output current at V

sourcing, and quiescent current at AVIN and VDDQ. During

the active state (when shutdown is not held low) the total

internal power dissipation can be calculated from the follow-

ing equations:

P

Where,

P

P

To calculate the maximum power dissipation at V

conditions at V

current. Although only one equation will add into the total,

V

P

P

The power dissipation of the LP2997 can also be calculated

during the shutdown state. During this condition the output

V

will disappear as it cannot sink or source any current (leak-

age is negligible). The only losses during shutdown will be

the reduced quiescent current at AVIN and the constant

impedance that is seen at the VDDQ pin.

P

P

P

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