AAT3692 Datasheet, PDF (13/19 Pages) Skyworks Solutions Inc. – Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package

DATA SHEET
AAT3692
Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package
Application Information
Charge Sources
The AAT3692 operates from sources of an adapter or
USB interface. The internal system control will always
select the adapter input to charge the battery rather
than the USB input if the adapter voltage is above 4.5V.
The normal charging input voltage range is up to typical
7.2V. The device can withstand up to 28V on the adapt-
er or USB inputs without damage to the IC. If V_ADP or V_USB
is greater than 7.2V, the internal over-voltage protection
circuitry suspends charging until the input falls below
typical 7.0V.
AC Adapter/USB System Power Charging
Adapter Mode
In the adapter mode, constant current charge levels up
to 1.6A can be programmed by the user. The fast charge
current for the adapter input mode is set by the R_ADPSET
resistor connected between ADPSET and ground. It is
programmed by the following equations:
I_{ADP_CC} =
2
R_ADPSET
· KI_ADPSET
R_ADPSET =
2
I_{ADP_CC}
· KI_ADPSET
with KI_ADPSET = 800. Table 1 gives the recommended 1%
tolerance metal film resistance values for a desired con-
stant current charge level.
Thermal Loop Control
To protect the linear charging IC from thermal problems,
a special thermal loop control system is used to maxi-
mize charging current under adapter charge mode. The
thermal management system measures the internal cir-
cuit die temperature and reduces the fast charge current
when the die exceeds the preset internal temperature
control threshold. Once the thermal loop control becomes
active, the fast charge current is initially reduced by a
factor of 0.44.
The initial thermal loop current can be estimated by the
following equation:
I_TLOOP = I_CC · 0.44
I_{CH_CC} (mA)
50
75
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
R_ADPSET (kΩ)
16
8.06
5.36
4.02
3.24
2.67
2.32
2
1.78
1.60
1.47
1.33
1.24
1.15
1.07
1
R_USBSET (kΩ)
32.4
21.5
16
8.06
5.36
4.02
3.24
Table 1: Standard 1% Metal Film Resistor Values
for Constant Current Setting.
The thermal loop control re-evaluates the circuit die
temperature every three seconds and raises the fast
charge current in small steps to the full fast charge cur-
rent level. Figure 2 illustrates the thermal loop function
at 1A fast charge current as the ambient temperature
increases and recovers. In this manner the thermal loop
controls the system charge level, and the AAT3692 pro-
vides the highest level of constant current in the fast
charge mode for any possible valid ambient temperature
condition.
1.6
1.4
Increase Ambient Temperature to 85°C
1.2
1.0
0.8
0.6
0.4
Decrease Ambient Temperature to 25°C
0.2
0.0
Time (10s/div)
Figure 2: Digital Thermal Loop Function
at 1A Fast Charge Current with Ambient
Temperature Increasing and Recovering.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
201895B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012
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