TPS2491DGSG4【PDF 11/25 页】IC POS HV HOT-SWAP CTRLR 10-MSOP

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VCCCH1

VCC10V/div

Timer1V/div

1A/div

10V/div

OUT

10 V/div

TPS2490

TPS2491

www.ti.com

SLVS503D NOVEMBER 2003REVISED JULY 2012

APPLICATION INFORMATION

BASIC OPERATION

The TPS2490/91 provides all the features needed for a positive hotswap controller. These features include: 1)

under-voltage lockout; 2) adjustable (system-level) enable; 3) turn-on inrush limit; 4) high-side gate drive for an

external N-channel MOSFET; 5) MOSFET protection (power limit and current limit); 6) adjustable overload

timeoutalso called an electronic circuit breaker; 7) charge-complete indicator for downstream converter

coordination; and 8) an optional automatic restart mode. The TPS2490/91 features superior power-limiting

MOSFET protection that allows independent control of current limit (to set maximum full-load current), power limit

(to control junction temperature rise), and overload time (to control case temperature rise).

The typical application circuit, and oscilloscope plots of Figure 13 through Figure 17 demonstrate many of the

functions described above.

Board Plug-In (Figure 13)

Only the bypass capacitor charge current and small bias currents are evident when a board is first plugged in.

The TPS2490/91 is held inactive, and GATE, PROG, TIMER, and PG are held low for less than 1 ms while

internal voltages stabilize. A startup cycle is ready to take place after the stabilization.

GATE, PROG, TIMER, and PG are released after stabilization in this example because both the internal UVLO

threshold and the external EN (enable) thresholds have been exceeded. The part begins sourcing current from

the GATE pin and M1 begins to turn on while the voltage across it, V

(SENSEOUT)

, and current through it,

(VCCSENSE)

, are monitored. Current initially rises to the value which satisfies the power limit engine (P

LIM

VCC

)

since the output capacitor was discharged.

TIMER and PG Operation (Figure 13)

The TIMER pin charges C

as long as limiting action continues, and discharges at a 1/10 charge rate when

limiting stops. If the voltage on C

reaches 4 V before the output is charged, M1 is turned off and either a latch-

off or restart cycle commences, depending on the part type. The open-drain PG output provides a deglitched

end-of-charge indication which is based on the voltage across M1. PG is useful for preventing a downstream

dc/dc converter from starting while C

is still charging. PG goes active (open drain) about 9 ms after C

charged. This delay allows M1 to fully turn on and any transients in the power circuits to end before the converter

starts up. The resistor pull-up shown on pin PG in the typical application diagram only demonstrates operation;

the actual connection to the converter depends on the application. Timing can appear to terminate early in some

designs if operation transitions out of the power limit mode into a gate charge limited mode at low V

values.

Figure 13. Basic Board Insertion

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