AAT3693 Advanced Analogic Technologies, Inc., AAT3693 Datasheet - Page 18

• Manufacturer Part Number: AAT3693
• Description: 1.6a Lithium-ion/polymer Battery Charger In 2.2x2.2 Tdfn
• Manufacturer: Advanced Analogic Technologies, Inc.

Figure 6 shows the maximum charge current at different
ambient temperatures.
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a decou-
pling capacitor closer to the IC and between the IN pin
and GND.
An input capacitor in the range of 1μF to 22μF is recom-
mended. If the source supply is unregulated, it may be
necessary to increase the capacitance to keep the input
voltage above the under-voltage lockout threshold dur-
ing device enable and when battery charging is initiated.
If the AAT3693 adapter input is used in a system with an
external power supply source, such as a typical AC-to-
DC wall adapter, then a C
18
BatteryManager
Figure 6: Maximum Charging Current Before the
Digital Thermal Loop Becomes Active.
1000
800
600
400
200
4.25
0
T
4.5
A
= 85°C
4.75
5
TM
T
A
5.25
= 60°C
IN
T
capacitor in the range of 10μF
A
5.5
V
= 45°C
IN
5.75
(V)
6
1.6A Lithium-Ion/Polymer Battery Charger in 2.2x2.2 TDFN
6.25
T
A
6.5
= 25°C
6.75
w w w . a n a l o g i c t e c h . c o m
7
should be used. A larger input capacitor in this applica-
tion will minimize switching or power transient effects
when the power supply is “hot plugged”.
Output Capacitor
The AAT3693 only requires a 1μF ceramic capacitor on
the BAT pin to maintain circuit stability. This value should
be increased to 10μF or more if the battery connection is
made any distance from the charger output. If the
AAT3693 is to be used in applications where the battery
can be removed from the charger, such as with desktop
charging cradles, an output capacitor greater than 10μF
may be required to prevent the device from cycling on
and off when no battery is present. It is good design
practice to place the decoupling capacitor closer to the
IC and between the BAT pin and GND.
PCB Layout Considerations
For the best results, it is recommended to physically
place the battery pack as close as possible to the
AAT3693 BAT pin. To minimize voltage drops on the PCB,
keep the high current carrying traces adequately wide.
When designing with >500mA charging current system,
a multilayer ground plane PCB design is highly recom-
mended. Putting thermal vias on the thermal pad design
will effectively transfer heat from the top metal layer of
the PCB to the inner or bottom layers. The number of
thermal vias will depend on the application and power
dissipation. The AAT3693 evaluation board is a layout
example for reference.
PRODUCT DATASHEET
AAT3693
3693.2009.04.1.1