CMPWR280 查看數據表（PDF） - California Micro Devices Corp

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CMPWR280

1.5A SmartOR™ Dual Regulator with VAUX Drive

California Micro Devices Corp 

CMPWR280

Typical Thermal Characteristics

Thermal dissipation of junction heat consists primarily

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

the case (θJC) thermal resistance which is defined by

the package style, and the second path is the case to

ambient (θCA) thermal resistance, which is dependent

on board layout.

The overall junction to ambient (θJA) thermal resis-

tance is equal to:

θJA = θJC + θCA

For a given package style and board layout, the operat-

ing junction temperature is a function of junction power

dissipation PJUNC, and the ambient temperature,

resulting in the following thermal equation:

TJUNC = TAMB + PJUNC (θJC ) + PJUNC (θCA )

= TAMB + PJUNC (θJA )

The CMPWR280TO is housed in a TO-263 5-lead

package, which provides a θJC of 3°C/W. The ground

tab is soldered down to the PCB. When the device is

mounted on a double-sided printed circuit board with

two square inches of copper allocated for “heat spread-

ing”, the resulting θJA is 25°C/W.

Based on a maximum power dissipation of 2.85W

(1.9Vx1.5A) with an ambient of 70°C the resulting junc-

tion temperature will be:

TJUNC = TAMB + PJUNC (θJA )

= 70°C + 2.85W (25°C/W)

= 70°C + 71°C = 141°C

All thermal characteristics of the CMPWR280TO were

measured using a double-sided board with two square

inches of copper area connected to the GND pins 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 tempera-

ture.

Note: The use of multi-layer board construction with

power planes will further enhance the thermal perfor-

mance of the package. In the event of no copper area

being dedicated for heat spreading, a multi-layer board

construction will typically provide the CMPWR280TO

with an overall θJA of 25°C/W which allows up to 2.5W

to be safely dissipated.

Output Voltage vs. Temperature. Figure 19 shows

the regulator VOUT performance up to the maximum

rated junction temperature. The overall 125°C variation

in junction temperature causes an output voltage

change of about 25mV.

g

p

g

p

3.340

3.320

3.300

5mA load

3.280

3.260

0

25

50

75

100

125

Junction Temperature [° C]

Figure 19. Output Voltage vs. Temperature

Output Voltage (Rated) vs. Temperature. Figure 20

shows the regulator steady state performance when

fully loaded (1.5A) in an ambient temperature up to the

rated maximum of 70°C. The output variation at maxi-

mum load is approximately 13mV across the normal

temperature range.

Fig 3.2. Output Voltage (Rated) vs.

Temperature

3.340

3.320

3.300

3.280

1.5A load

3.260

0

10 20 30 40 50 60 70

Ambient Temperature [° C]

Figure 20. Output Voltage (Rated) vs. Temperature

© 2004 California Micro Devices Corp. All rights reserved.

10 430 N. McCarthy Blvd., Milpitas, CA 95035-5112 ● Tel: 408.263.3214 ● Fax: 408.263.7846 ● www.calmicro.com 08/16/04

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