AAT3691 Datasheet, PDF (13/18 Pages) Skyworks Solutions Inc. – Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package

DATA SHEET
AAT3691
Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package
Adapter Input Charge Inhabit and Resume
The AAT3691 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 AAT3691 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 AAT3691 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 AAT3691 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.
Enable / Disable
The AAT3691 provides an enable function to allow the
normal operating input voltage to pass through and con-
trol the IC charging. The Enable (EN) pin is active low
and is pulled down to ground by an internal 200kΩ resis-
tor. When pulled to a logic high level, the AAT3691 is
shut down and forced into the sleep state during which
input voltage up to 28V will be blocked and charging be
halted regardless of the battery voltage or charging
state. When the device is re-enabled, the OVP block will
automatically reassess the input voltage and allow the
normal operating voltage to pass through. If a battery is
also present (NOBAT is low), the charge control circuit
will automatically reset and resume charging with the
appropriate charging mode based on the battery charge
state and measured cell voltage.
Over-Temperature Shutdown
Thermal protection completely disables charging when
internal dissipation exceeds the junction over-tempera-
ture threshold, which is 140°C with 15°C of hysteresis.
Once the over-temperature fault condition is removed,
the charge function automatically recovers.
Battery Charge Status Indication
The AAT3691 has one status LED driver output. The LED
can indicate simple functions such as battery charging,
charge complete, and charge disabled.
Description
Battery charging
Charge complete
Charge disabled
EN
low
low
high
LED Status
on
off
off
Table 2. LED Status Conditions.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
201894B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012
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