ADP1712/ADP1713/ADP1714
Rev. A | Page 13 of 16
THERMAL CONSIDERATIONS
To guarantee reliable operation, the junction temperature of the
ADP1712/ADP1713/ADP1714 must not exceed 125°C. To
ensure the junction temperature stays below this maximum value,
the user needs to be aware of the parameters that contribute to
junction temperature changes. These parameters include ambient
temperature, power dissipation in the power device, and thermal
resistances between the junction and ambient air (θ
JA
). The θ
JA
number is dependent on the package assembly compounds used
and the amount of copper to which the GND pin of the package
is soldered on the PCB. Table 5 shows typical θ
JA
values of the
5lead TSOT package for various PCB copper sizes.
Table 5.
Copper Size (mm
2
)
θ
JA
(°C/W)
0
1
170
50 152
100 146
300 134
500 131
1
Device soldered to minimum size pin traces.
The junction temperature of the ADP1712/ADP1713/ADP1714
can be calculated from the following equation:
T
J
= T
A
+ (P
D
× θ
JA
) (3)
where:
T
A
is the ambient temperature.
P
D
is the power dissipation in the die, given by
P
D
= [(V
IN
– V
OUT
) × I
LOAD
] + (V
IN
× I
GND
) (4)
where:
I
LOAD
is the load current.
I
GND
is the ground current.
V
IN
and V
OUT
are input voltage and output voltage, respectively.
Power dissipation due to ground current is quite small and can
be ignored. Therefore, the junction temperature equation
simplifies to the following:
T
J
= T
A
+ {[(V
IN
– V
OUT
) × I
LOAD
] × θ
JA
} (5)
As shown in Equation 4, for a given ambient temperature, input-
to-output voltage differential, and continuous load current,
there exists a minimum copper size requirement for the PCB to
ensure the junction temperature does not rise above 125°C. The
following figures show junction temperature calculations for
different ambient temperatures, load currents, input-to-output
voltage differentials, and areas of PCB copper.
140
0
0.5 5.0
V
IN
– V
OUT
(V)
T
J
(°C)
120
100
80
60
40
20
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
1mA
10mA
30mA
80mA
100mA
200mA
300mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06455-029
Figure 33. 500 mm
2
of PCB Copper, T
A
= 25°C
140
0
0.5 5.0
V
IN
– V
OUT
(V)
T
J
(°C)
120
100
80
60
40
20
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
1mA
10mA
30mA
80mA
100mA
200mA
300mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06455-030
Figure 34. 100 mm
2
of PCB Copper, T
A
= 25°C
140
0
0.5 5.0
V
IN
– V
OUT
(V)
T
J
(°C)
120
100
80
60
40
20
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
1mA
10mA
30mA
80mA
100mA
200mA
300mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06455-031
Figure 35. 0 mm
2
of PCB Copper, T
A
= 25°C
