AAT3685IWP-4.2-T1 Analogic Tech, AAT3685IWP-4.2-T1 Datasheet - Page 17

• Manufacturer Part Number: AAT3685IWP-4.2-T1
• Description: Battery Management Lithium-Ion/Polymer Battery Charger
• Manufacturer: Analogic Tech

Specifications of AAT3685IWP-4.2-T1

• Package / Case: TDFN33-12
• Mounting Style: SMD/SMT
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Timing Diagram
BatteryManager
Thermal Considerations
The AAT3685 is packaged in a Pb-free, 3x3mm TDFN
package which can provide up to 2.0W of power dissipa-
tion when it is properly bonded to a printed circuit board
and has a maximum thermal resistance of 50°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 package in proximity to
other heat generating devices in a given application
design. The ambient temperature around the charger IC
will also have an affect 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.
First, the maximum power dissipation for a given situa-
tion should be calculated:
Where:
P
V
V
I
I
Next, the maximum operating ambient temperature for
a given application can be estimated based on the ther-
mal resistance of the 3x3mm TDFN package when suf-
3685.2007.12.1.4
CC
OP
D
IN
BAT
= Total Power Dissipation by the Device
= Input Voltage Level, V
= Battery Voltage as Seen at the BAT Pin
= Maximum
= Quiescent Current Consumed by the Charger IC
Programmed for the Application
for Normal Operation
Eq. 4:
SQ
CK
Data
P
D
= [(V
Constant
TM
T
T
IN
DATA(RPT)
OFF
- V
> 2 P
BAT
ADP/USB
= T
) · I
DATA
T
Fast
System Reset
System Start
SQ
SYNC
SYNC
CC
PULSE
+ T
+ (V
Charge
LAT
IN
< 2.5 P
· I
T
LAT
OP
)]
w w w . a n a l o g i c t e c h . c o m
DATA
Current
P
DATA
N=1
ficiently mounted to a PCB layout and the internal ther-
mal loop temperature threshold.
Where:
Example:
For an application where the fast charge current is set to
500mA, V
at 3.0V, what is the maximum ambient temperature at
which the thermal limiting will become active?
Given:
Using Equation 4, calculate the device power dissipation
for the stated condition:
T
T
P
θ
V
V
I
I
T
θ
CC
OP
JA
JA
A
J
D
J
USB
BAT
Eq. 6:
= Ambient Temperature in Degrees C
= Maximum Device Junction Temperature Protected
= Total Power Dissipation by the Device
= Package Thermal Resistance in °C/W
= 5.0V
= 3.0V
= 500mA
= 0.75mA
= 140°C
= 50°C/W
Lithium-Ion/Polymer Battery Charger
by the Thermal Limit Control
N=2
P
USB
D
= (5.0V - 3.0V) (500mA) + (5.0V · 0.75mA)
= 1.00375W
= 5.0V and the worst case battery voltage
Eq. 5:
N=3
PRODUCT DATASHEET
T
T
OFF
A
= T
J
AAT3685
- (θ
JA
· P
D
)
17