Datasheet

Power
Supply
0.1 µF
1000 µF
Optimum
2.7 V to 5.5 V
PC Board
Overcurrent Response
TPS2042B
OC1
GND
EN1
IN
EN2
OUT1
OUT2
OC2
Block of
Circuitry
Block of
Circuitry
TPS2041B, TPS2042B
TPS2043B, TPS2044B, TPS2051B
TPS2052B, TPS2053B, TPS2054B
www.ti.com SLVS514L –JUNE 2010– REVISED JUNE 2011
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 TPS204xB/TPS205xB, 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 TPS204xB/TPS205xB also ensures that the switch is off after the card has been removed, and that the
switch is 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.
Figure 40. Typical Hot-Plug Implementation (Example, TPS2042B)
By placing the TPS204xB/TPS205xB between the V
CC
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 1 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.
DETAILED DESCRIPTION
Power Switch
The power switch is an N-channel MOSFET with a low on-state resistance. Configured as a high-side switch, the
power switch prevents current flow from OUT to IN and IN to OUT when disabled. The power switch supplies a
minimum current of 500 mA.
Charge Pump
An internal charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate
of the MOSFET above the source. The charge pump operates from input voltages as low as 2.7 V and requires
little supply current.
Driver
The driver controls the gate voltage of the power switch. To limit large current surges and reduce the associated
electromagnetic interference (EMI) produced, the driver incorporates circuitry that controls the rise times and fall
times of the output voltage.
Enable (ENx)
The logic enable pin disables the power switch and the bias for the charge pump, driver, and other circuitry to
reduce the supply current. The supply current is reduced to less than 1 μA or 2 μA when a logic high is present
on EN. A logic zero input on EN restores bias to the drive and control circuits and turns the switch on. The
enable input is compatible with both TTL and CMOS logic levels.
Copyright © 2010–2011, Texas Instruments Incorporated 27