LP2989

www.ti.com

SNVS083O – FEBRUARY 2005 – REVISED MARCH 2015

Feature Description (continued)

7.3.4 Short Circuit Protection (Current Limit)

The internal current limit circuit is used to protect the LDO against high-load current faults or shorting events. The

LDO is not designed to operate in a steady-state current limit. During a current-limit event, the LDO sources

constant current. Therefore, the output voltage falls when load impedance decreases. Note also that if a current

limit occurs and the resulting output voltage is low, excessive power may be dissipated across the LDO, resulting

in a thermal shutdown of the output. A foldback feature limits the short-circuit current to protect the regulator from

damage under all load conditions. If OUT is forced below 0 V before EN goes high and the load current required

exceeds the foldback current limit, the device may not start correctly.

7.3.5 Thermal Protection

The device contains a thermal shutdown protection circuit to turn off the output current when excessive heat is

dissipated in the LDO. The thermal time-constant of the semiconductor die is fairly short, and thus the output

cycles on and off at a high rate when thermal shutdown is reached until the power dissipation is reduced. The

internal protection circuitry of the device is designed to protect against thermal overload conditions. The circuitry

is not intended to replace proper heat sinking. Continuously running the device into thermal shutdown degrades

its reliability.

7.4 Device Functional Modes

7.4.1 Operation With 16 V

7.4.2 Operation with Shutdown Control

If the voltage on the SHUTDOWN pin is less than 0.18 V, the output is ensured to be OFF. When the voltage on

the SHUTDOWN pin is more than 1.6 V the output is ensured to be ON. Operating with the SHUTDOWN pin

voltage between 0.18 V and 1.6 V is strongly discouraged as the status of the output is not ensured.

7.4.3 Shutdown Input Operation

The LP2989 is shut off by driving the SHUTDOWN pin low, and turned on by pulling it high. If this feature is not

To assure proper operation, the signal source used to drive the Shutdown input must be able to swing above and

To prevent mis-operation, the turn-on (and turn-off) voltage signals applied to the Shutdown input must have a

slew rate which is

≥ 40 mV/µs.

CAUTION

The regulator output voltage cannot be ensured if a slow-moving AC (or DC) signal is

applied that is in the range between the specified turn-on and turn-off voltages listed

Copyright © 2005–2015, Texas Instruments Incorporated

Submit Documentation Feedback

15

Product Folder Links: LP2989