Datasheet

1
2
3
4
10
9
8
IN
NC
OUT
V
SS
STAT1
STAT2
7
6
VBSEL
ISET
1.13k
R
W
SET
bq24083
+
PACK+
HI,V =4.06
LO
OUT
,V =4.2
OUT
PACK–
C
0.1 F
1
m
C
0.1 F
2
m
100kW
VDC
GND
SOURCE
INPUT
CE
PG
1.5kW
1.5kW
1.5kW
5
ChargeCurrent
TranslatorOutput
Thermal Considerations
P
TT
R
AJ
JA
-
=
q
(5)
P =(V -V )xI
(IN) (OUT) O(OUT)
(6)
bq24083
www.ti.com .............................................................................................................................................................. SLUS848A – MAY 2008 – REVISED APRIL 2009
The bq24083 is in a thermally enhanced MLP package. The package includes a thermal pad to provide an
effective thermal contact between the device and the printed-circuit board (PCB). Full PCB design guidelines for
this package are provided in the application report entitled, QFN/SON PCB Attachment (TI Literature Number
SLUA271 ).
The most common measure of package thermal performance is thermal impedance (R
θ JA
) measured (or
modeled) from the device junction to the air surrounding the package surface (ambient). The mathematical
expression for R
θ JA
is:
Where:
• T
J
= device junction temperature
• T
A
= ambient temperature
• P = device power dissipation
Factors that can greatly influence the measurement and calculation of R
θ JA
include:
• Orientation of the device (horizontal or vertical)
• Volume of the ambient air surrounding the device under test and airflow
• Whether other surfaces are in close proximity to the device being tested
• Use multiple 10 – 13 mil vias in the PowerPAD™ to copper ground plane.
• Avoid cutting the ground plane with a signal trace near the power IC.
• The PCB must be sized to have adequate surface area for heat dissipation.
• FR4 (figerglass) thickness should be minimized.
The device power dissipation, P, is a function of the charge rate and the voltage drop across the internal Power
FET. It can be calculated from the following equation:
Due to the charge profile of Li-xx batteries, the maximum power dissipation is typically seen at the beginning of
the charge cycle when the battery voltage is at its lowest. See Figure 6 .
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