THEORY OF OPERATIION
The SP619 is a switch capable of handling
up to 800mA of current.
The SP619
is targeted as a for
5V
USB
protection
power distribution switch.
And
can be used in general
power distribution
applications where short circuits are likely
to be encountered.
Short circuit operation
When the SP619 enters a short circuit con-
dition, the switch is disabled. The output
of the SP619 will not restart until the out-
enable pin can be used to re-enable the
SP619 into any load condition that is not
a fault condition. Refer to the truth table on
page 4 for more information on the differ-
ent SP619 switch states. The typical deac-
tivation time is about 2ms.
inrush current that can be encountered.
At 6 volts in, the inrush current was about
250mA into a 100µF capacitor.
Output Voltage Rise Time
The output voltage of the SP619 has an
output capacitance dependency on the
slope of V
OUT
. A simple RC circuit is cre-
ated when the switch is turned on.
V(t)=V
O
+V
IN
(
-t
1-e
R
DS
(
ON
) • C
OUT
(
Where V
O
is initial Voltage condition typi-
cally 0V
V
IN
is the input voltage
R
DS
(
ON
) is the switch resistance
C
OUT
is the output capacitance
For 4.2V V
IN
and 100µF output capacitance
4.17
Enable
The enable pin allows easy control of the
SP619. The enable pin should not be en-
abled high prior to a voltage being pres-
ent on the input of the device. The enable
pin should not exceed the input voltage by
-
ode. Doing so will affect the operation of
the SP619 and could damage the device.
3.33
V
OUT
2.5
1.67
0.83
0
0
0.33
0.67
1
time in uS
1.33
1.67
2
This is comparable to actual measured
This resistor will pull the enable low when
an enable signal is not present. This pre-
vents the SP619 from falsely turning on.
The enable pin can also be used to restart
the part into a load condition that is high in
current. Please refer to the truth table on
page 4 for more details.
Inrush Current
The SP619 is a simple resistive switch.
When the switch is turned on into a highly
April 2008 Rev L
SP619 High Current Power Switch
© 2008
EXAR
Corporation
4
EXAR [ EXAR CORPORATION ]
