AAT4672 Datasheet, PDF (20/24 Pages) Advanced Analogic Technologies – Power Supply Selector Switch

SmartSwitch^TM
Functional Block Diagram
MAIN
IMAIN
PWRSEL
IAUX
AUX
Thermal
and Current
Sense
Switch 1
Logic
Control
Switch 2
PRODUCT DATASHEET
AAT4672
Power Supply Selector Switch
OUT
EN
GND
Truth Table
Y = Yes, N = No, X = don’t care.
V_MAIN > UVLO
N
Y
N
Y
Y
Input Conditions
V_AUX > UVLO
N
N
Y
Y
Y
Functional Description
To power the OUT pin, at least one of the two input sup-
plies (MAIN/AUX) must be greater than the UVLO thresh-
old. If only one supply is greater than the UVLO thresh-
old, the load will be connected to that particular supply
when the device is enabled. If both supplies are above
the UVLO threshold, the AAT4672 will connect the supply
from the MAIN pin to the OUT pin when the device is
enabled and the MAIN voltage is greater than the AUX
voltage plus 0.2V (typical); otherwise, the AAT4672 will
connect the supply from the AUX pin to the OUT pin.
The two internal power switches are current limited; the
current limits are programmed by the resistors on the
IMAIN and IAUX pins respectively.
V_MAIN > V_AUX + 0.2V
X
X
X
Y
N
AAT4672
V_OUT
Floating
V_MAIN
V_AUX
V_MAIN
V_AUX
Applications Information
Input Capacitors
A 1µF or greater capacitor is generally recommended
between MAIN and GND (C_MAIN), and between AUX and
GND (C_AUX). An input capacitor is not required for basic
operation; however, it is useful in preventing load tran-
sients from affecting up-stream circuits. Ceramic, tanta-
lum, or aluminum electrolytic capacitors may be selected
for C_MAIN/C_AUX. There is no specific capacitor equivalent
series resistance (ESR) requirement for C_MAIN/C_AUX.
However, for higher current operation, ceramic capaci-
tors are recommended for C_MAIN/C_AUX due to their inher-
ent capability over tantalum capacitors to withstand
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