CAT6500 Datasheet, PDF (9/13 Pages) ON Semiconductor – 3.0 A Power Selector Switch

CAT6500
PIN FUNCTIONS
SW1, SW2
SW1 and SW2 are low ON resistance power FET switches
within CAT6500 and form the power transfer path between
PS1, PS2 and PWR_OUT. SW1 and SW2 are bidirectional
allowing for current to flow in either direction. They are
controlled by the digital inputs PRIORITY, RM_EN1,
RM_EN2. While they are not device pins they are defined
here in order to make pin functions more understandable.
PS1, PS2
These are input pins for two external power sources which
supply power for battery charging and system operation. On
the basis of a PRIORITY input, CAT6500 will select from
PS1 or PS2 and route power to PWR_OUT. If power on the
preferred input is unavailable or the voltage is insufficient
and a suitable power source is available on the other power
input then CAT6500 will use the alternate source.
PS1 and PS2 can also supply power to external devices if
a reverse−mode command is given. In reverse−mode,
PWR_OUT becomes the power source and is connected to
either PS1 or PS2 in accord with the reverse−mode
command. It is possible for both PS1 and PS2 to be powered
simultaneously by PWR_OUT if commanded by the
reverse−mode inputs. This dual command state also allows
for power transfer between PS1 and PS2.
PWR_OUT
PWR_OUT is the common point between SW1 and SW2
and conducts power from either of these inputs to the
system’s power bus.
When used in reverse mode PWR_OUT can supply power
to an external load such as a USB device attached to PS1 or
PS2.
RM_EN1, RM_EN2
Reverse mode enable inputs are logic high signals which
will override autonomous voltage source selection and force
either SW1 or SW2 into an ON state. RM_EN1 and
RM_EN2 act independently of each other and therefore can
both be active at the same time.
VCC
VCC is an alternative power source for CAT6500 in the
event neither PS1 nor PS2 is powered or if CAT6500 is in
reverse−mode and is supplying power to an external device.
VCC supplies only CAT6500’s internal control logic
circuitry and is never routed to PS1, PS2 or PWR_OUT.
C1
CAT6500 can draw its operating current from several
different inputs and will switch between these sources as
they change or become available. To keep the chip’s internal
supply voltage stable during these transitions an external
filter capacitor is required. The recommended value for C1
is between 0.1 mF and 1.0 mF.
GND
The negative power input pin for CAT6500 and system
ground.
PRIORITY
PRIORITY is a logic signal input that directs power
source selection in forward mode if both PS1 & PS2 sources
of power are present at the same time. For PRIORITY low,
PS1 is selected. If only one source of power is present,
CAT6500 will default to that source.
PRIORITY can be overridden by a RM_ENx command in
which case the associated power FET SW1 or SW2 is turned
ON by the RM_EN command.
SW1_STAT, SW2_STAT
SW1_STAT and SW2_STAT are open drain LOW true
digital outputs indicating the operating state of Power
Switch 1 (SW1) and Power Switch 2 (SW2), where a LOW
indicates the switch is ON. SW1_STAT and SW2_STAT
may be pulled up to an external voltage greater than VCC or
greater than PSx as long as it does not exceed 5.5 V.
SW1_STAT and SW2_STAT are active in reverse−mode
and continue to indicate the operational status of SW1 and
SW2.
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