AAT3692 Datasheet, PDF (14/19 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
Adapter Input Charge Inhabit and Resume
The AAT3692 has an under-voltage lockout feature so
that if the charger input supply ADP pin drops below the
UVLO threshold, the charger will suspend charging.
When the UVLO condition is removed and V_ADPCH > V_BAT,
the system charge control assesses the state of charge
of the battery cell and automatically resumes charging in
the appropriate phase (pre-conditioning trickle charge,
constant current charge, constant voltage charge or end
of charge) according to the condition of the battery.
USB Mode
The AAT3692 also provides an input for intelligent USB
charging. When no voltage is present on the adapter
input pin or adapter input is below 4.5V, the charge con-
troller will automatically switch to accepting power from
the USB input. The USB charge may be user programmed
to any level between 50mA and 500mA by selecting the
appropriate resistor values for R_USBSET.
I_{USB_CC} =
2
R_USBSET
· KI_USBSET
R_USBSET =
2
I_{USB_CC}
·
KI_USBSET
Among them, KI_USBSET is 800. Refer to Table 1 for recom-
mended R_USBSET values for the desired USB input constant
current charge levels.
USB Charge Reduction
In many instances, product system designers do not
know the real properties of a potential USB port used to
supply power to the battery charger. Typically, powered
USB ports found on desktop and notebook PCs should
supply up to 500mA. If a USB port being used to supply
the charger is unable to provide the programmed fast
charge current or if the system under charge must share
supply current with other functions, the AAT3692 auto-
matically reduces USB fast charge current to maintain
port integrity and protect the host system.
The USB charge reduction system becomes active when
the voltage on the USBCH input falls below the USB
charge reduction threshold, typically 4.5V. The charge
reduction system reduces the fast charge current level in
a linear fashion until the voltage sensed on the USB input
recovers above the charge reduction threshold voltage.
USB Input Charge Inhibit and Resume
The AAT3692 UVLO and power on reset feature functions
when the USB input pin voltage level drops below the
UVLO threshold. At this point, the charger suspends
charging and shuts down. When power is re-applied to
the USB pin or the UVLO condition recovers, the system
charge control will assess the state of charge on the bat-
tery cell and automatically resume charging in the
appropriate mode for the condition of the battery.
Programmable Charge Termination
Current Percentage
The charge termination current percentage of fast charge
current can be programmed by an external resistor from
TERM to GND. The resistance can be calculated by
R_TERM = 133 ·
I_{CH_TERM}
I_{CH_CC}
·
10³
Among them, I_{CH_CC} is the fast charge current of valid
source; e.g., if the design target of charge termination
current is 100mA for 1A ADP fast charge current, then
R_TERM
=
133
·
100mA
1A
·
10³
=
13.3kΩ
At this R_TERM setting, when USB is the active charging
source, charge termination current percentage is still
10% of the USB fast charge current. So if the USB fast
charge current is 500mA, the charge termination current
is 50mA.
Table 2 shows some standard metal resistor values for
different charge termination current percentages.
Charge Termination Current
Percentage (%)
10
15
20
25
30
35
40
45
50
R_TERM (kΩ)
13.3
20
26.7
34
41.2
47.5
53.6
60.4
66.5
Table 2: Standard 1% Metal Film Resistor
Values for Charge Termination Current
Percentage Settings.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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201895B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012