ap2281 Diodes, Inc., ap2281 Datasheet - Page 9

• Manufacturer Part Number: ap2281
• Description: Single Slew Rate Controlled Load Switch
• Manufacturer: Diodes, Inc.

Application Note
Input Capacitor
A 1μF capacitor is recommended to connect between IN
and GND pins to decouple input power supply glitch and
noise. The input capacitor has no specific type or
ESR (Equivalent
However, for higher current application, ceramic
capacitors are recommended due to their capability to
withstand input current surges from low impedance
sources, such as batteries in portable applications. This
input capacitor must be located as close as possible to
the device to assure input stability and less noise. For
PCB layout, a wide copper trace is required for both
IN and GND.
Output Capacitor
A 0.1μF capacitor is recommended to connect between
OUT and GND pins to stabilize and accommodate load
transient condition. The output capacitor has no specific
type or ESR requirement. The amount of the
capacitance may be increased without limit. For
PCB layout, the output capacitor must be placed as
close as possible to OUT and GND pins, and keep the
traces as short as possible.
ENABLE/SHUTDOWN Operation
The AP2281 is turned on by setting the EN pin high, and
is turned off by pulling it low. To ensure proper operation,
the signal source used to drive the EN pin must be able
to swing above and below the specified turn-on/off
voltage thresholds listed in the Electrical Characteristics
section under V
DISCHARGE Operation
The AP2281-3 offers discharge option that helps to
discharge the output charge when disabled.
AP2281 Rev. 2
IL
and V
Series
IH
.
Resistance)
requirement.
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9 of 11
Single Slew Rate Programmable Load Switch
Power Dissipation
The device power dissipation and proper sizing of the
thermal plane is critical to avoid thermal shutdown and
ensure reliable operation. Power dissipation of the
device depends on input voltage and load conditions and
can be calculated by:
However, the maximum power dissipation that can be
handled by the device depends on the maximum
junction to ambient thermal resistance, maximum
ambient temperature, and maximum device junction
temperature, which can be approximated by the
equation below:
For example at V
I
using equation (1) is P
θ
temperature rise from ambient is approximately 49°C.
Since the maximum junction temperature is 125°C, the
operating ambient temperature must be kept below 76°C
to safely operate the device.
On the other hand, at T
calculated maximum power dissipation from equation (2)
is approximately P
operating maximum continuous current is 1.81A. For
other
recalculate the device maximum power dissipation
based on the operating conditions.
OUT
JA
= 153°C/W and equation (2), the calculated junction
= 2A, the maximum power dissipation calculated
P
D
application
(max@
P =
D
IN
I
OUT
= 5V, the typical R
T
Dmax
A
conditions,
)
2
xR
D
=
A
= 0.26W. Hence the safe
= 0.32W. Based on SOT26
(
DSON
+
= 85°C and V
125
θ
the
°
JA
C
©
AP2281
DSON
Diodes Incorporated
−
users
(1)
T
= 80mΩ. For
A
MAY 2008
IN
)
= 5V, the
(2)
should