CMPWR101

Rev. 3 | Page 9 of 12 | www.onsemi.com

Performance Information (cont’d)

CMPWR101 Typical Thermal Characteristics

The overall junction to ambient thermal resistance (

θ

of two paths in series. The first path is the junction to the case (

θ

and the second path is case to ambient (

θ

final operating junction temperature for any set of conditions can be estimated by the following thermal

equation:

T

JUNC

= T

= T

The CMPWR101 uses a standard SOIC package. When this package is mounted on a double-sided

printed circuit board with two square inches of copper allocated for "heat spreading", the resulting

85°C/W.

Based on a maximum power dissipation of 0.43W (1.7V x 250mA) with an ambient of 70°C, the resulting

junction temperature will be:

T

= 70°C + 0.43W (80°C/W)

= 70°C + 37°C = 103°C

Thermal characteristics were measured using a double-sided board with two square inches of copper area

connected to the GND pin for "heat spreading".

Measurements showing performance up to junction temperature of 125°C were performed under light

load conditions (5mA). This allows the ambient temperature to be representative of the internal junction

temperature.

Note: The use of multi-layer board construction with separate ground and power planes will further

enhance the overall thermal performance. In the event of no copper area being dedicated for heat

spreading, a multi-layer board construction, using only the minimum size pad layout, will provide the

CMPWR101 with an overall

θ