TPS2010A, TPS2011A, TPS2012A, TPS2013A

POWER-DISTRIBUTION SWITCHES

SLVS189A – DECEMBER 1998 – REVISED NOVEMBER 1999

19

POST OFFICE BOX 655303

APPLICATION INFORMATION

undervoltage lockout (UVLO)

An undervoltage lockout ensures that the power switch is in the off state at power up. Whenever the input voltage

falls below approximately 2 V, the power switch will be 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. The

UVLO will also keep the switch from being turned on until the power supply has reached at least 2 V, even if

the switch is enabled. Upon reinsertion, the power switch will be turned on, with a controlled rise time to reduce

EMI and voltage overshoots.

generic hot-plug applications (see Figure 36)

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. Because of the controlled rise times and fall times of the TPS201xA series, 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 TPS201xA also ensures the switch will be off after the card has been removed, and the switch will be off

during the next insertion. The UVLO feature guarantees a soft start with a controlled rise time for every insertion

of the card or module.

Power

Supply

Block of

Circuitry

TPS2013A

GND

IN

IN

EN

OUT

OUT

OUT

OUT

0.1

µF

1000

µF

Optimum

2.7 V to 5.5 V

PC Board

Figure 36. Typical Hot-Plug Implementation

device first after insertion. The typical rise time of the switch is approximately 9 ms, providing a slow voltage

ramp at the output of the device. This implementation controls system surge currents and provides a

hot-plugging mechanism for any device.