Diodes AP2152A Manuel d'utilisateur télécharger pdf (Page 12)

AP2142A/ AP2152A

Document number: DS32191 Rev. 3 - 2

12 of 16

www.diodes.com

March 2013

AP2142A/ AP2152A

Application Information (cont.)

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 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.

Ordering Information

Part Number

Package

Code

Packaging

7”/13” Tape and Reel

Quantity Part Number Suffix

AP21X2ASG-13 S SO-8 250/Tape & Reel -13

AP21X2AMPG-13 MP MSOP-8EP 2500/Tape & Reel -13

AP21X2AFGEG-7 FGE U-DFN3030-8 3000/Tape & Reel -7

1 2 ... 7 8 9 10 11 12 13 14 15 16

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Diodes AP2152A Manuel d'utilisateur Page 12

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