TWO-LEVEL CURRENT-LIMIT CIRCUIT

OUT

IN

GND

FAULT

ILIM

EN

ControlSignal

Input

Fault Signal

PowerPad

Output

CurrentLimit

ControlSignal

0.1 F

m

R

100k

FAULT

W

R1

210kW

R2

22.1kW

Q1

2N7002

TPS2552

TPS2553, TPS2552-1, TPS2553-1

Some applications require different current-limit thresholds depending on external system conditions. Figure 27

shows an implementation for an externally controlled, two-level current-limit circuit. The current-limit threshold is

set by the total resistance from ILIM to GND (see previously discussed "Programming the Current-Limit

Threshold" section). A logic-level input enables/disables MOSFET Q1 and changes the current-limit threshold by

modifying the total resistance from ILIM to GND. Additional MOSFET/resistor combinations can be used in

parallel to Q1/R2 to increase the number of additional current-limit levels.

NOTE:

ILIM should never be driven directly with an external signal.

Figure 27. Two-Level Current-Limit Circuit

Copyright © 2008, Texas Instruments Incorporated

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