AP2181D Просмотр технического описания (PDF) - Diodes Incorporated.
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AP2181D Datasheet PDF : 18 Pages
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AP2181D/AP2191D
1.5A SINGLE CHANNEL CURRENT-LIMITED POWER
SWITCH WITH OUTPUT DISCHARGE
Application Note (Continued)
Power Dissipation and Junction Temperature
The low on-resistance of the internal MOSFET allows the small surface-mount packages to pass large current.
Using the maximum operating ambient temperature (TA) and RDS(ON), the power dissipation can be calculated by:
PD = RDS(ON)× I2
Finally, calculate the junction temperature:
TJ = PD x RθJA + TA
Where:
TA= Ambient temperature °C
RθJA = Thermal resistance
PD = Total power dissipation
Generic Hot-Plug Applications
In many applications it may be necessary to remove modules or pc boards while the main unit is still operating.
These are considered hot-plug applications. Such implementations require the control of current surges seen by
the main power supply and the card being inserted. The most effective way to control these surges is to limit and
slowly ramp the current and voltage being applied to the card, similar to the way in which a power supply normally
turns on. Due to the controlled rise times and fall times of the AP2181D/AP2191D, these devices can be used to
provide a softer start-up to devices being hot-plugged into a powered system. The UVLO feature of the
AP2181D/AP2191D also ensures that the switch is off after the card has been removed, and that the switch is off
during the next insertion.
By placing the AP2181D/AP2191D between the VCC input and the rest of the circuitry, the input power reaches
these devices first after insertion. The typical rise time of the switch is approximately 1ms, providing a slow
voltage ramp at the output of the device. This implementation controls system surge current and provides a hot-
plugging mechanism for any device.
AP2181D/2191D
Document number: DS32251 Rev. 1 - 2
11 of 18
www.diodes.com
June 2010
© Diodes Incorporated
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