ltc4065l Linear Technology Corporation, ltc4065l Datasheet - Page 14

• Manufacturer Part Number: ltc4065l
• Description: Standalone 250ma Li-ion Battery Charger In 2 ? 2 Dfn
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LTC4065L/LTC4065LX
Example: Consider an LTC4065L operating from a 5.5V
wall adapter providing 250mA to a 3V Li-Ion battery. The
ambient temperature above which the LTC4065L will
begin to reduce the 250mA charge current is approxi-
mately:
Charging at such high ambient temperatures is not recom-
mended by battery manufacturers.
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in the
Programming Charge Current section.
It is important to remember that LTC4065L applications
do not need to be designed for worst-case thermal condi-
tions since the IC will automatically reduce power dissipa-
tion when the junction temperature reaches approximately
115°C.
14
T
T
T
A
A
A
= 115°C – (5.5V – 3V) • (250mA) • 60°C/W
= 115°C – 0.625W • 60°C/W = 115°C – 37.5°C
= 77.5°C
U
U
W
U
Board Layout Considerations
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4065L package is soldered to the PC
board ground. Correctly soldered to a 2500mm
sided 1 oz. copper board the LTC4065L has a thermal
resistance of approximately 60°C/W. Failure to make
thermal contact between the Exposed Pad on the backside
of the package and the copper board will result in thermal
resistances far greater than 60°C/W.
V
Many types of capacitors can be used for input bypassing;
however, caution must be exercised when using multi-
layer ceramic capacitors. Because of the self-resonant and
high Q characteristics of some types of ceramic capaci-
tors, high voltage transients can be generated under some
start-up conditions, such as connecting the charger input
to a live power source. For more information, refer to
Application Note 88.
CC
Bypass Capacitor
2
double-
4065lxfa