&0
3HUIRUPDQFH ,QIRUPDWLRQ FRQW¶G
7\SLFDO 7KHUPDO &KDUDFWHULVWLFV
The overall junction to ambient thermal resistance
(θ
JA
) for device power dissipation (P
D
) consists prima-
rily of two paths in series. The first path is the junction
to the case (θ
JC
) which is defined by the package style,
and the second path is case to ambient (θ
CA
) thermal
resistance which is dependent on board layout. The
final operating junction temperature for any set of con-
ditions can be estimated by the following thermal equa-
tion:
T
JUNC
= T
AMB
+ P
D
∗
(θ
JC
) + P
D
∗
(θ
CA
)
= T
AMB
+ P
D
∗
(θ
JA
)
The CM3014 uses a SOT23-5 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
θ
JA
is 175°C/W.
Based on a maximum power dissipation of 320mW
(Load x Vin-Vout = 150mA x 2.2V) with an ambient of
70°C the resulting junction temperature will be:
GROUND CURRENT [uA]
Output Voltage Change vs. Temperature (1mA Load)
50
40
OUTPUT CHANGE [mV]
30
20
10
0
-10
-20
-30
-40
-50
-50
-25
0
25
50
o
75
100 125
TEMPERATURE [ C]
Ground Current vs. Temperature
100
80
60
40
20
0
0
25
50
75
100
o
T
JUNC
= T
AMB
+ P
D
∗
(θ
JA
)
= 70°C + 315mW
∗
(175°C/W)
= 70°C + 57.75°C = 127.75°C
7KHUPDO FKDUDFWHULVWLFV ZHUH PHDVXUHG XVLQJ D GRXEOH
VLGHG ERDUG ZLWK WZR VTXDUH LQFKHV RI FRSSHU DUHD
FRQQHFWHG WR WKH *1' SLQV IRU ³KHDW VSUHDGLQJ´
Measurements showing performance up to a junction
temperature of 125°C were performed under light load
conditions (1mA). This allows the ambient temperature
to be representative of the internal junction tempera-
ture.
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 typically provide the CM3014 with
an overall
θ
JA
of 175°C/W, which allows up to 450mW
to be dissipated safely.
3OHDVH FRQVXOW &$0' 7HFKQLFDO 6XSSRUW IRU DVVLVWDQFH
ZLWK WKHUPDO DQDO\VLV RI WKH &0 ZLWK UHVSHFW WR D
VSHFLILF DSSOLFDWLRQ
125
JUNCTION TEMPERATURE [ C]
)LJXUH &0 3HUIRUPDQFH YV 7HPSHUDWXUH
2002 California Micro Devices Corp. All rights reserved.
8
430 N. McCarthy Blvd., Milpitas, CA 95035-5112
L
Tel: 408.263.3214
L
Fax: 408.263.7846
L
www.calmicro.com
12/13/02
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
