Datasheet

ADP1710/ADP1711
Rev. 0 | Page 11 of 16
Current and thermal limit protections are intended to protect
the device against accidental overload conditions. For reliable
operation, device power dissipation must be externally limited
so junction temperatures do not exceed 125°C.
THERMAL CONSIDERATIONS
To guarantee reliable operation, the junction temperature of the
ADP1710/ADP1711 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 pins of the package
are soldered on the PCB. Table 5 shows typical θ
JA
values of the
5lead 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 ADP1710/ADP1711 can be
calculated from the following equation:
T
J
= T
A
+ (P
D
× θ
JA
) (2)
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
) (3)
where:
I
LOAD
is the load current.
I
GND
is the ground current.
V
IN
and V
OUT
are the 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
} (4)
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, V
IN
to V
OUT
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
125mA
150mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06310-023
Figure 23. 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
125mA
150mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06310-024
Figure 24. 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
125mA
150mA
(LOAD CURRENT)
MAX T
J
(DO NOT OPERATE ABOVE THIS POINT)
06310-025
Figure 25. 0 mm
2
of PCB Copper, T
A
= 25°C