TPS2090, TPS2091, TPS2092 DUAL,

TPS2095, TPS2096, TPS2097 QUAD

POWER-DISTRIBUTION SWITCHES

SLVS245A – SEPTEMBER 2000 – REVISED MARCH 2001

16

POST OFFICE BOX 655303

APPLICATION INFORMATION

thermal protection (continued)

The TPS209x implements a dual thermal trip to allow fully independent operation of the power distribution

switches. In an overcurrent or short-circuit condition the junction temperature will rise. Once the die temperature

rises to approximately 140

°C, the internal thermal sense circuitry checks which power switch is in an overcurrent

condition and turns that power switch off, thus isolating the fault without interrupting operation of the adjacent

power switch. Should the die temperature exceed the first thermal trip point of 140

°C and reach 160°C, both

switches turn off. The OC open-drain output is asserted (active low) when overtemperature or overcurrent

occurs.

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 26)

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 TPS209x, 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

TPS209x 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 insures a soft start with a controlled rise time for every insertion of the card

or module.

Power

Supply

Block of

Circuitry

TPS2092

GND

IN1

IN2

EN1

OC

OUT1

OUT2

EN2

0.1

µF

1000

µF

Optimum

2.7 V to 5.5 V

PC Board

Overcurrent Response

Block of

Circuitry

0.1

µF

1000

µF

Optimum

Figure 26. Typical Hot-Plug Implementation

devices first after insertion. The typical rise time of the switch is approximately 2.5 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.