LP2981-N_16 Datasheet, PDF (15/30 Pages) Texas Instruments – Micropower 100-mA Ultralow Dropout Regulator

www.ti.com
LP2981-N
SNOS773N – MARCH 2000 – REVISED APRIL 2016
Feature Description (continued)
7.3.3 Ultra-Low-Dropout Voltage
Generally speaking, the dropout voltage often refers to the voltage difference between the input and output
voltage (VDO = V_IN – V_OUT), where the main current pass-FET is fully on in the ohmic region of operation and is
characterized by the classic R_DS(ON) of the FET. VDO indirectly specifies a minimum input voltage above the
nominal programmed output voltage at which the output voltage is expected to remain within its accuracy
boundary.
7.3.4 Low Ground Current
LP2981-N uses a vertical PNP process which allows for quiescent currents that are considerably lower than
those associated with traditional lateral PNP regulators, typically 600 μA at 100-mA load and 80 μA at 1-mA load.
7.3.5 Sleep Mode
When pulling the ON/OFF pin to low level, LP2981-N will enter sleep mode, and less than 1-μA quiescent current
is consumed. This function is designed for the application which needs a sleep mode to effectively enhance
battery life cycle.
7.3.6 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. 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 up correctly.
7.3.7 Thermal Protection
The LP2981-N 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 LM2981-N 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 V_OUT(TARGET) + 1 V ≤ V_IN < 16 V
The device operates if the input voltage is equal to, or exceeds, V_OUT(TARGET) + 0.6 V. At input voltages below the
minimum V_IN requirement, the device does not operate correctly and output voltage may not reach target value.
7.4.2 Operation With ON/OFF Control
If the voltage on the ON/OFF pin is less than 0.15 V, the device is disabled, and the shutdown current does not
exceed 1 μA. Raising ON/OFF above 1.4 V initiates the start-up sequence of the device.
Copyright © 2000–2016, Texas Instruments Incorporated
Product Folder Links: LP2981-N
Submit Documentation Feedback
15