AAT3686IXN-4.2-3-T1 ANALOGICTECH [Advanced Analogic Technologies], AAT3686IXN-4.2-3-T1 Datasheet - Page 18

• Manufacturer Part Number: AAT3686IXN-4.2-3-T1
• Description: USB Port/AC Adapter Lithium-Ion/Polymer Battery Charger
• Manufacturer: ANALOGICTECH [Advanced Analogic Technologies]

Data Timing
The system microcontroller should assert an active low
data request pulse for minimum duration of 200ns; this
is specified by the SQ
of the end of the data request pulse, the AAT3686 status
data control will reply the data word back to the system
microcontroller after a delay defined by the data report
time specification T
group of data pulses will be defined by the T
cation.
Thermal Considerations
The AAT3686 is offered in a 3x4mm TDFN package and a
4x4mm TDFN package, each of which can provide up to
2.7W of power dissipation when it is properly bonded to
a printed circuit board and has a maximum thermal resis-
tance of 37°C/W. Many considerations should be taken
into account when designing the printed circuit board
layout, as well as the placement of the charger IC pack-
age in proximity to other heat generating devices in a
given application design. The ambient temperature
around the charger IC will also have an effect on the
thermal limits of a battery charging application. The
maximum limits that can be expected for a given ambient
condition can be estimated by the following discussion.
Timing Diagram
18
BatteryManager
SQ
CK
Data
DATA(RPT)
PULSE
TM
T
T
DATA(RPT)
OFF
. Upon sensing the rising edge
. The period of the following
> 2 P
= T
DATA
T
System Reset
System Start
SQ
SYNC
SYNC
PULSE
+ T
USB Port/AC Adapter Lithium-Ion/Polymer Battery Charger
LAT
< 2.5 P
T
LAT
DATA
w w w . a n a l o g i c t e c h . c o m
DATA
specifi-
P
DATA
N=1
First, the maximum power dissipation for a given situa-
tion should be calculated:
Where:
Next, the maximum operating ambient temperature for
a given application can be estimated based on the ther-
mal resistance of the 3x4mm and 4x4mm TDFN pack-
ages when sufficiently mounted to a PCB layout and the
internal thermal loop temperature threshold.
Where:
T
T
P
θ
P
V
V
I
I
CC
OP
A
JA
D
J
D
IN
BAT
= Maximum device junction temperature below the
= Ambient temperature in degrees C
= Total power dissipation by the device
= Package thermal resistance in °C/W
= Total power dissipation by the device
= Either V
= Battery voltage as seen at the BAT pin
= Maximum constant fast charge current pro-
= Quiescent current consumed by the charger IC for
thermal loop threshold
selected
grammed for the application
normal operation
N=2
Eq. 1:
ADP
P
Eq. 2:
D
N=3
or V
= [(V
PRODUCT DATASHEET
USB,
T
T
IN
OFF
A
- V
= T
depending on which mode is
BAT
J
AAT3686
- (θ
) · I
JA
CC
· P
+ (V
D
3686.2007.12.1.11
)
IN
· I
OP
)]