LP38690-ADJ_16 Datasheet, PDF (12/27 Pages) Texas Instruments – 1-A Low Dropout CMOS Linear Regulator

LP38690-ADJ, LP38692-ADJ
SNVS323I – DECEMBER 2004 – REVISED FEBRUARY 2016
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7.3 Feature Description
7.3.1 Foldback Current Limiting
Foldback current limiting is built into the LP3869x-ADJ which reduces the amount of output current the part can
deliver as the output voltage is reduced. The amount of load current is dependent on the differential voltage
between V_IN and V_OUT. Typically, when this differential voltage exceeds 5 V, the load current will limit at about
450 mA. When the V_IN –V_OUT differential is reduced below 4 V, load current is limited to about 1500 mA.
CAUTION
When toggling the LP38692 EN pin after the input voltage (V_IN) is applied, the foldback
current limit circuitry is functional the first time that the EN pin is taken high. The
foldback current limit circuitry is non-functional the second, and subsequent, times that
the EN pin is taken high. Depending on the input and output capacitance values the
input inrush current may be higher than expected which can cause the input voltage to
droop.
If the EN pin is connected to the IN pin, the foldback current limit circuitry is functional
when V_IN is applied if V_IN starts from less than 0.4 V.
7.4 Device Functional Modes
7.4.1 Enable Pin (LP38692-ADJ Only)
The LP38692–ADJ has an enable pin (EN) which allows an external control signal to turn the regulator output on
and off. The enable on/off threshold has no hysteresis. The voltage signal must rise and fall cleanly, and
promptly, through the on and off voltage thresholds. The EN pin has no internal pull-up or pull-down to establish
a default condition and, as a result, this pin must be terminated either actively or passively. If the EN pin is driven
from a source that actively pulls high and low, the drive voltage must not be allowed to go below ground potential
or higher than V_IN. If the application does not require the enable function, the pin must be connected directly to
the IN pin.
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