PRODUCT DATASHEET
AAT3687
BatteryManagerTM
Lithium-Ion/Polymer Battery Charger
Given:
Thermal Considerations
VADP = 5.0V
VBAT = 3.6V
ICC = 1A
IOP = 0.75mA
TJ = 110°C
θJA = 50°C/W
The AAT3687 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 con-
siderations 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 effect on the thermal limits of a battery charg-
ing application. The maximum limits that can be expect-
ed for a given ambient condition can be estimated by the
following discussion.
Using Equation 5, calculate the device power dissipation
for the stated condition:
Eq. 7:
PD = (5.0V - 3.6V)(1A) + (5.0V · 0.75mA)
= 1.40375W
First, the maximum power dissipation for a given situa-
tion should be calculated:
The maximum ambient temperature before the AAT3687
thermal loop becomes active can now be calculated
using Equation 6:
P = [(V - VBAT) · ICC + (VIN · IOP)]
IN
Eq. 5:
D
Eq. 8:
TA = 110°C - (50°C/W · 1.40375W)
= 39.8125°C
Where:
PD = Total Power Dissipation by the Device
VIN = Input Voltage Amplitude, VADP
VBAT = Battery Voltage as Seen at the BAT Pin
ICC = Maximum Constant Fast Charge Current
Programmed for the Application
Therefore, under the stated conditions for this worst
case power dissipation example, the AAT3687 will enter
the thermal loop and lower the fast charge constant cur-
rent when the ambient operating temperature rises
above 39.8°C.
IOP = Quiescent Current Consumed by the Charger IC
for Normal Operation
Capacitor Selection
Input Capacitor
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-
ficiently mounted to a PCB layout and the internal ther-
mal loop temperature threshold.
In general, it is good design practice to place a decou-
pling capacitor between the ADP pin and ground. 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 during
device enable and when battery charging is initiated.
Eq. 6:
TA = TJ - (θJA · PD)
Where:
TA = Ambient Temperature in °C
TJ = Maximum Device Junction Temperature Below the
Thermal Loop Threshold
PD = Total Power Dissipation by the Device
θJA = Package Thermal Resistance in °C/W
If the AAT3687 adapter input is to be used in a system
with an external power supply source, such as a typical
AC-to-DC wall adapter, then a CIN capacitor in the range
of 10µF should be used. A larger input capacitor in this
application will minimize switching or power transient
effects when the power supply is “hot plugged” in.
Example:
For an application where the fast charge current for the
adapter mode is set to 1A, VADP = 5.0V and the battery
voltage at 3.6V, what is the maximum ambient tempera-
ture at which the thermal loop will become active?
w w w . a n a l o g i c t e c h . c o m
16
3687.2008.04.1.12
5秒后页面跳转
SG3525资料手册详解：SG3525参数分析、引脚说明、应用介绍
AT89C51单片机资料手册详细解析及应用示例
CP2102资料手册解读：CP2102引脚说明、关键参数分析
资料手册解读：UC3842参数和管脚说明
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
技术参数
数据手册
如果您发现信息不准确，
