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BQ24083_16 Datasheet, PDF (15/24 Pages) Texas Instruments – ADJUSTABLE BATTERY VOLTAGE
◁
bq24083
www.ti.com .............................................................................................................................................................. SLUS848A – MAY 2008 – REVISED APRIL 2009
SOURCE
INPUT
VDC
GND
C1
0.1 mF
1.5 kW
bq24083
1 IN
OUT 10
1.5 kW
2 NC
CE 9
3 STAT1 PG 8
4 STAT2 VBSEL 7
5 VSS
ISET 6
100 kW
1.5 kW
PACK+
C2
+
0.1 mF PACK–
1.13 kW
RSET
HI, VOUT = 4.06
LO, VOUT = 4.2
Charge Current
Translator Output
Thermal Considerations
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 (RθJA) measured (or
modeled) from the device junction to the air surrounding the package surface (ambient). The mathematical
expression for RθJA is:
RqJA
=
TJ - T
P
A
(5)
Where:
• TJ = device junction temperature
• TA = ambient temperature
• P = device power dissipation
Factors that can greatly influence the measurement and calculation of RθJA 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:
P = (V(IN) - V(OUT)) x IO(OUT)
(6)
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.
Copyright © 2008–2009, Texas Instruments Incorporated
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