AAT4685 Datasheet, PDF (11/17 Pages) Skyworks Solutions Inc. – thermal shutdown protection

DATA SHEET
AAT4685
Over-Voltage Protection Switch with OCP and BOVP
Enable Control (EN)
EN is an active low enable with internal 200kΩ resistor
pulled down to GND. EN is driven low, connected to
ground, or left floating for normal device operation. Set
EN low to turn the OVP switch on after turn on delay
time. Set EN high to turn the OVP switch off. In the case
of an over-voltage or UVLO condition toggling EN will not
override the fault condition and the OVP switch will
remain off. The OCP counter and the BOVP counter are
both reset when the device is re-enabled by the EN pin.
IC Input
Internally connected to GND through a 100kΩ resistor.
Connect this pin to ground.
Device Start-Up Operation
On initial power-up, if V_UVLO < IN < V_OVP, V_BAT < V_BOVP, and
EN is low, the OVP switch starts to turn on after T_ON delay
time (typical 8ms) to be stabilized for input. This turn on
uses Soft Start to control the inrush current to minimize
ringing at the input. Because of the deglitch time at
power on, if the input voltage rises rapidly past the OVP
threshold, the device does not switch on at all; instead
it goes into protection mode and indicate a fault on the
FLT pin. After successful start-up, if I_LOAD > I_OCP limit the
device turns off and the fault flag is asserted.
The Soft Start function is defined as follows: "current
limit is stepped digitally from low level to its final current
limit level for soft starting."
Power–OK Indicator (POK)
The AAT4685 contains an open-drain POK output that
goes low when a valid input source is detected at the IN
pin. The valid input range is between V_UVLO (typical 2.7V)
and V_OVP voltage (fixed 5.85V / fixed 6.8V / adjustable
OVP threshold set by external resistors). After a valid
input has been established, charging is sustained. The
POK function is always active whether the EN pin is at
low or high state.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
201960A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 16, 2012
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