TPS2592AX datasheet(14/28 Pages) TI

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ILIM

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TPS2592Ax

TPS2592Bx

SLVSC11A – JUNE 2013 – REVISED JUNE 2013

www.ti.com

EN/UVLO > VENR

VIN>VUVR

BFET Mode

Charge

Discharge

EN/UVLO: As an input pin, it controls both the ON/OFF state of the internal MOSFET and that of the external

blocking FET. In its high state, the internal MOSFET is enabled and charging begins for the gate of external FET.

A low on this pin will turn off the internal MOSFET and pull the gate of the external FET to GND via the built-in

discharge resistor. High and Low levels are specified in the parametric table of the datasheet. The EN/UVLO pin

is also used to clear a thermal shutdown latch in the TPS2592xL by toggling this pin (H

→L).

The internal de-glitch delay on EN/UVLO falling edge is intentionally kept low (1us typical) for quick detection of

power failure. When used with a resistor divider from supply to EN/UVLO to GND, power-fail detection on

EN/UVLO helps in quick turn-off of the BFET driver, thereby stopping the flow of reverse current (see typical

application diagram, Figure 47). For applications where a higher de-glitch delay on EN/UVLO is desired, or when

the supply is particularly noisy, it is recommended to use an external bypass capacitor from EN/UVLO to GND

ILIM: The device continuously monitors the load current and keeps it limited to the value programmed by RILIM.

After start-up event and during normal operation, current limit is set to IOL (over-load current limit).

(3)

When power dissipation in the internal MOSFET [PD = (VVIN -VOUT) × IOUT] exceeds 10W, there is a 2% – 12%

thermal foldback in the current limit value so that IOL drops to ISC. In each of the two modes, MOSFET gate

voltage is regulated to throttle short-circuit and overload current flowing to the load. Eventually, the device shuts

down due to over temperature.

Figure 43. Thermal Foldback in Current Limit

During a transient short circuit event, the current through the device increases very rapidly. The current-limit

amplifier cannot respond very quickly to this event due to its limited bandwidth. Therefore, the TPS2592

incorporates a fast-trip comparator, which shuts down the pass device very quickly when IOUT > IFASTRIP, and

terminates the rapid short-circuit peak current. The trip threshold is set to 60% higher than the programmed over-

load current limit (IFASTRIP = 1.6 x IOL). After the transient short-circuit peak current has been terminated by the

fast-trip comparator, the current limit amplifier smoothly regulates the output current to IOL (see figure below).

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TPS2592AX Datasheet(PDF) 14 Page - Texas Instruments

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