AAT3663_08 Datasheet, PDF (19/23 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications

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PRODUCT DATASHEET
AAT3663
1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications
VIN
IN
RT
TS
Battery
Pack
RNTC
T
AAT3663-4.2-1 or AAT3663-8.4-1
0 .6xV IN
Battery Cold Fault
0. 30xVIN
Battery Hot Fault
Figure 4: External Resistor and NTC Thermistor Application Circuit.
Thermal Considerations
The AAT3663 is offered in a 3x3mm TDFN package which
can provide up to 2.0W of power dissipation when it is
properly bonded to a printed circuit board and has a
maximum thermal resistance of 50°C/W. Many consider-
ations should be taken into account when designing the
printed circuit board layout, as well as the placement of
the charger IC package in proximity to other heat gener-
ating devices in a given application. The ambient tem-
perature around the charger IC will also have an effect on
the thermal limits of the battery charging operation. The
maximum limits that can be expected for a given ambient
condition can be estimated by the following discussion.
First, the maximum power dissipation for a given situa-
tion should be calculated:
P_D(MAX) =
(T_J - T_A)
θ_JA
Where:
P_D(MAX) = Maximum Power Dissipation (W)
θ_JA = Package Thermal Resistance (°C/W)
T_J
= Thermal Loop Entering Threshold (ºC) [115ºC]
T_A
= Ambient Temperature (°C)
Figure 5 shows the relationship between maximum
power dissipation and ambient temperature of AAT3663
2.50
2.00
1.50
1.00
0.50
0.00
0
25
50
75
100
T_A (°C)
Figure 5: Maximum Power Dissipation Before
Entering Thermal Loop.
Next, the power dissipation can be calculated by the fol-
lowing equation:
I_CH(MAX) =
(P_D(MAX) - V_IN · I_OP)
V_IN - V_BAT
I_CH(MAX)
=
(T_J - T_A)
θ_JA
-
V_IN
·
V_IN - V_BAT
I_OP
Where:
P_D =
V_IN =
V_BAT =
I_CH =
I_OP =
Total Power Dissipation by the Device
Input Voltage
Battery Voltage as Seen at the BAT Pin
Constant Charge Current Programmed for the
Application
Quiescent Current Consumed by the Charger IC
for Normal Operation [0.5mA]
3663.2008.01.1.2
www.analogictech.com
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