cat6500 ON Semiconductor, cat6500 Datasheet - Page 11

• Manufacturer Part Number: cat6500
• Description: Cat6500 3.0 A Power Selector Switch
• Manufacturer: ON Semiconductor

Over−Voltage
18 V on the PS1 or PS2 inputs. In the event of such a fault
condition, SW1 or SW2, whichever is exposed to the fault
will shut OFF. This fault protection is voltage sensitive,
activating at 7 V typically and overrides control inputs
PRIORITY, RM_EN1 and RM_EN2.
constant and independent of the rise time of the overvoltage
event, however the voltage transient seen at PWR_OUT will
vary depending upon the operating conditions at the time of
the event. Case 1 and Case 2 of Figure 5 illustrates this. In
Case 1, an overvoltage is applied to a PS input as would
happen if a malfunctioning or improper charger were used
to recharge a handheld appliance. The internal FET switch
is initially off and the application of voltage at the PS input
Break−Before−Make Switching
automatic control (PRIORITY) or in override (RM_EN),
CAT6500 disables the active switch before the new
connection is made. This ensures there will be no unintended
cross conduction between PS1 and PS2. Even when SW1
and SW2 are commanded to be ON simultaneously there is
a brief interval when both SW1 and SW2 are OFF. Figure 6
illustrates this.
Table 6. POWER SWITCH CONTROL AND SELECTION
PWR_OUT
PWR_OUT
CAT6500 is designed to withstand input voltages of up to
The response time of the over voltage detection circuit is
When switching between power sources either under
for voltage rising at PS
L ≤ 1.7 V
PS1
Hi−Z
H
H
H
H
L
L
L
PWR_OUT
PWR_OUT
H ≥ 1.7 V
PS2
Hi−Z
H
H
H
H
L
L
L
RM_EN1
Inputs
if left floating
0
0
0
0
0
0
0
1
0
1
Default = 0
RM_EN2
0
0
0
0
0
0
0
0
1
1
if left floating
PRIORITY
Default = 1
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X
0
1
X
11
0 = Open
SW1
initiates turning it ON, but the delay associated with turning
ON the switch is very long compared to the overvoltage
comparator’s response time. The resulting voltage transient
at PWR_OUT is very small to non−existent because the FET
switch never gets the chance to turn fully ON.
internal FET switch is ON. If for some reason the applied
voltage surges above the overvoltage threshold the FET will
be turned OFF but a transient will be seen at PWR_OUT.
The degree to which the voltage at PWR_OUT exceeds the
overvoltage threshold depends upon the rate of voltage rise
at PS compared to the comparator’s response time.
OFF SW1 and SW2 when either PS1 or PS2 goes negative
by more than 0.7 V.
Thermal Considerations
dissipate some amount of heat which is a function of the
current through the switch and RON. Typical heating curves
are shown in Figure 19.
temperature sensor. Should the chip’s temperature reach
145°C CAT6500 will shut off both power switches until the
die temperature drops to below approximately 135°C, at
which time the power switches will be returned to their
original operating state. If the temperature again exceeds the
thermal shutdown limit both switches will be disabled and
this cycling will continue until current flowing through the
switch is reduced, the load is removed or the switch is turned
off under system control.
0
1
0
1
1
0
0
1
0
1
Connections
Case 2 assumes voltage is applied to a PS input and the
CAT6500 is tolerant to negative voltages as well and shuts
Under normal operating conditions SW1 and SW2 will
CAT6500 is protected against overheating by an internal
1 = Closed
SW2
0
0
1
0
0
1
1
0
1
1
PWR_OUT
PS1
PS2
PS1
PS1
PS2
PS2
X
X
X
0
SW1_STAT
Outputs
1
0
1
0
0
1
1
0
1
0
SW2_STAT
1
1
0
1
1
0
0
1
0
0