AAT3692 Datasheet, PDF (15/19 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
Enable / Disable
The AAT3692 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 AAT3692 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.
Battery Charge and
Power OK Status Indications
The AAT3692 has two open drain outputs, STAT and
POK, for battery charge status and power OK indications.
The battery charger status LED can indicate simple func-
tions 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 3: STAT LED Indications.
POK is an open drain output to indicate valid power for
charging. The valid power source range for charging is
not only related to the normal operating range, but also
to the battery voltage. If the input power source is
higher than the UVLO threshold, lower than the OVP
threshold, and greater than typical 220mV of V_BAT, POK
will be pulled down.
The LED anodes should be connected to either V_USBCH or
V_ADPCH, depending upon system design requirements. The
LEDs should be biased with as little current as necessary
to create reasonable illumination; therefore, a ballast
resistor should be adopted to limit the current flowing
through the LED by connecting it with the LED in series
between STAT and V_USBCH or V_ADPCH. LED current con-
sumption will add to the overall thermal power budget
for the device package, so LED drive current should be
kept to a minimum. 2mA should be sufficient to drive
most low-cost green or red LEDs. It is not recommended
to exceed 8mA for driving an individual status LED. The
required ballast resistor value can be estimated using
the following formulas:
To connect to ADPCH:
R=
V_ADPCH - V_FLED
I_LED
To connect to USBCH:
R=
V_USBCH - V_FLED
I_LED
For example, using a red LED with 2.0V V_F @ 2mA, cal-
culate R under 5.5V V_ADPCH:
R=
5.5V - 2.0V
2mA
= 1.75kΩ
Capacitor Selection
Input Capacitor
An input capacitor is used to filter the input voltage by
placing a decoupling capacitor between the ADP, ADPCH,
USB and USBCH pins and ground. An input capacitor in
the range of 1μF to 10μF is recommended. 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. This input capac-
itor range is also suitable for a system with an external
power supply source, such as a typical AC-to-DC wall
adapter. It will minimize switching or power bounce
effects when the power supply is “hot plugged”. Likewise,
a 2.2μF or greater input capacitor is recommended for
the USB input to help buffer the effects of USB source
power switching, noise, and input cable impedance.
Output Capacitor
The AAT3692 requires a 1μF ceramic capacitor on the
BAT pin to maintain circuit stability. This value should be
increased to 10μF or more if the battery connection is
made any distance from the charger output. In a fast
charge application with current above 1A, a 22μF output
capacitor is required to obtain an accurate recharge volt-
age threshold. If the AAT3692 is used in applications
where the battery can be removed from the charger,
such as in the case of desktop charging cradles, an out-
put capacitor value greater than 10μF may be required
to prevent the device from cycling on and off when no
battery is present.
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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