AP2142AMPG-13 Diodes Zetex, AP2142AMPG-13 Datasheet - Page 12

• Manufacturer Part Number: AP2142AMPG-13
• Manufacturer: Diodes Zetex

Specifications of AP2142AMPG-13

• Short Circuit Current Limit: 700mA
• Input Voltage Range: 2.7 to 5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Supplier Unconfirmed

AP2142A/AP2152A
0.5A DUAL CHANNEL CURRENT-LIMITED POWER
SWITCH WITH OUTPUT DISCHARGE
Application Note
(Continued)
Thermal Protection
Thermal protection prevents the IC from damage when heavy-overload or short-circuit faults are present for
extended periods of time. The AP2142A/AP2152A implements a thermal sensing to monitor the operating junction
temperature of the power distribution switch. Once the die temperature rises to approximately 140°C due to
excessive power dissipation in an over-current or short-circuit condition the internal thermal sense circuitry turns
the power switch off, thus preventing the power switch from damage. Hysteresis is built into the thermal sense
circuit allowing the device to cool down approximately 25°C before the switch turns back on. The switch continues
to cycle in this manner until the load fault or input power is removed. The FLG open-drain output is asserted when
an over-temperature shutdown or over-current occurs with 7-ms deglitch.
Under-voltage Lockout (UVLO)
Under-voltage lockout function (UVLO) keeps the internal power switch from being turned on until the power
supply has reached at least 2V, even if the switch is enabled. Whenever the input voltage falls below
approximately 2V, the power switch is quickly turned off. This facilitates the design of hot-insertion systems where
it is not possible to turn off the power switch before input power is removed.
Discharge Function
The discharge function of the device is active when enable is disabled or de-asserted. The discharge function with
the N-MOS power switch implementation is activated and offers a resistive discharge path for the external storage
capacitor. This is designed for discharging any residue of the output voltage when either no external output
resistance or load resistance is present at the output.
Host/Self-Powered HUBs
Hosts and self-powered hubs (SPH) have a local power supply that powers the embedded functions and the
downstream ports. This power supply must provide from 5.25V to 4.75V to the board side of the downstream
connection under both full-load and no-load conditions. Hosts and SPHs are required to have current-limit
protection and must report over-current conditions to the USB controller. Typical SPHs are desktop PCs,
monitors, printers, and stand-alone hubs.
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 AP2142A/AP2152A, 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
AP2142A/AP2152A 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 AP2142A/AP2152A between the V
input and the rest of the circuitry, the input power reaches
CC
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.
AP2142A/2152A
12 of 17
October 2010
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Document number: DS32191 Rev. 2 - 2