0

VIN-VOUT-mV

0

20

60

100

140

3.0

0.5

1.0

1.5

2.0

2.5

T =125°C

J

T =-40°C

J

T =25°C

J

160

R

=24.9k

ILIM

40

80

120

5.0

4.5

4.0

3.5

TPS2556

TPS2557

www.ti.com

SLVS931A

– NOVEMBER 2009 – REVISED FEBRUARY 2012

TYPICAL CHARACTERISTICS (continued)

Figure 18. Switch Current vs. Drain-Source Voltage Across Switch

DETAILED DESCRIPTION

OVERVIEW

The TPS2556/57 is a current-limited, power-distribution switch using N-channel MOSFETs for applications where

short circuits or heavy capacitive loads will be encountered. This device allows the user to program the

current-limit threshold between 500 mA and 5.0 A (typ) via an external resistor. This device incorporates an

internal charge pump and the gate drive circuitry necessary to drive the N-channel MOSFET. The 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 2.5 V and requires little supply current. The

driver controls the gate voltage of the power switch. The driver incorporates circuitry that controls the rise and fall

times of the output voltage to limit large current and voltage surges and provides built-in soft-start functionality.

overcurrent or short-circuit event by reducing the charge pump voltage driving the N-channel MOSFET and

voltage at OUT because N-channel MOSFET is no longer fully enhanced.

OVERCURRENT CONDITIONS

condition is detected, the device maintains a constant output current and the output voltage reduces accordingly.

Two possible overload conditions can occur.

The first condition is when a short circuit or partial short circuit is present when the device is powered-up or

enabled. The output voltage is held near zero potential with respect to ground and the TPS2556/57 ramps the

device begins to thermal cycle.

The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is

current-sense amplifier is overdriven during this time and momentarily disables the internal N-channel MOSFET.

cycle.

The TPS2556/57 thermal cycles if an overload condition is present long enough to activate thermal limiting in any

of the above cases. The device turns off when the junction temperature exceeds 135

°C (min) while in current

limit. The device remains off until the junction temperature cools 20

°C (typ) and then restarts. The TPS2556/57

cycles on/off until the overload is removed (see Figure 10) .

Copyright

© 2009–2012, Texas Instruments Incorporated

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Product Folder Link(s): TPS2556 TPS2557