Datasheet ADP1720-EP (Analog Devices) - 10

link to page 10 link to page 10 link to page 11
ADP1720-EP Data Sheet APPLICATIONS INFORMATION THERMAL CONSIDERATIONS 140 MAX TJ (DO NOT OPERATE ABOVE THIS POINT)
To guarantee reliable operation, the junction temperature of
120
the ADP1720-EP must not exceed 125°C. To ensure that the
°C)
junction temperature stays below this maximum value, the user
( 100
needs to be aware of the parameters that contribute to junction
URE T A
temperature changes. These parameters include ambient tempera-
R 80 E P
ture, power dissipation in the power device, and thermal
M E 60
resistances between the junction and ambient air (θ
N T
JA). The θJA
IO
number is dependent on the package assembly compounds used
40
and the amount of copper to which the GND pins of the package
JUNCT
are soldered on the PCB. Table 5 shows typical θ
20
JA values of the
1mA 10mA 30mA 50mA
022 8-lead MSOP package for various PCB copper sizes.
5mA 20mA 40mA (LOAD CURRENT) 0
09723-
0 4 8 12 16 20 24 28 Table 5. Typical θJA Values for ADP1720-EP VIN – VOUT (V) Copper Size (mm2) θ (°C/W) JA
Figure 19. 500 mm2 of PCB Copper, TA = 25°C 25 246 50 216
140 MAX TJ (DO NOT OPERATE ABOVE THIS POINT)
100 186
120
300 178
°C)
500 169
( 100 URE T
The junction temperature of the ADP1720-EP can be calculated
A R 80 E
from the following equation:
P M E 60
T
N T
J = TA + (PD × θJA) (3)
IO
where:
40
T
JUNCT
A is the ambient temperature.
20
P
1mA 10mA 30mA 50mA
023 D is the power dissipation in the die, given by
5mA 20mA 40mA (LOAD CURRENT)
P
0
09723- D = [(VIN – VOUT) × ILOAD] + (VIN × IGND) (4)
0 4 8 12 16 20 24 28
where:
VIN – VOUT (V)
I Figure 20. 300 mm2 of PCB Copper, T LOAD is the load current. A = 25°C IGND is the ground current.
140
V
MAX T
IN and VOUT are input and output voltages, respectively.
J (DO NOT OPERATE ABOVE THIS POINT)
Power dissipation due to ground current is quite small and
120
can be ignored. Therefore, the junction temperature equation
°C) ( 100
simplifies to the following:
URE T A
T
R 80 E
J = TA + {[(VIN – VOUT) × ILOAD] × θJA} (5)
P M
As shown in Equation 5, for a given ambient temperature,
E 60 N T
input-to-output voltage differential, and continuous load
IO
current, there exists a minimum copper size requirement for
40
the PCB to ensure that the junction temperature does not rise
JUNCT 20
above 125°C. Figure 19 to Figure 24 show junction temperature
1mA 10mA 30mA 50mA
024 calculations for different ambient temperatures, load currents,
5mA 20mA 40mA (LOAD CURRENT) 0
09723- V
0 4 8 12 16 20 24 28
IN to VOUT differentials, and areas of PCB copper for the
V
ADP1720-EP.
IN – VOUT (V)
Figure 21. 100 mm2 of PCB Copper, TA = 25°C Rev. A | Page 10 of 12 Document Outline Features Enhanced Product Features Applications Typical Application Circuits General Description Revision History Specifications Absolute Maximum Ratings Thermal Resistance ESD Caution Pin Configurations and Function Descriptions Typical Performance Characteristics Applications Information Thermal Considerations Outline Dimensions Ordering Guide