LP38503-ADJ_15 Datasheet, PDF (14/27 Pages) Texas Instruments – LP3850x-ADJ, LP3850xA-ADJ 3-A FlexCap Low Dropout Linear Regulator for 2.7-V to 5.5-V Inputs

LP38501-ADJ, LP38503-ADJ
SNVS522I – AUGUST 2007 – REVISED AUGUST 2015
Feature Description (continued)
www.ti.com
Figure 22. 10-µF Ceramic Paralleled by 220-µF OSCON
7.3.3 Dropout Voltage
The dropout voltage of a regulator is defined as the input-to-output differential required by the regulator to keep
the output voltage within 2% of the nominal value. For CMOS LDOs, the dropout voltage is the product of the
load current and the R_DS(on) of the internal MOSFET pass element.
Because the output voltage is beginning to “drop out” of regulation when it drops by 2%, electrical performance
of the device is reduced compared to the values listed in Electrical Characteristics for some parameters (line and
load regulation and PSRR would be affected).
7.3.4 Reverse Current Path
The internal MOSFET pass element in the LP38501-ADJ and LP38503-ADJ has an inherent parasitic diode.
During normal operation, the input voltage is higher than the output voltage and the parasitic diode is reverse
biased. However, if the output is pulled above the input in an application, then current flows from the output to
the input as the parasitic diode gets forward biased. The output can be pulled above the input as long as the
current in the parasitic diode is limited to 200-mA continuous and 1-A peak. The regulator output pin must not be
taken below ground potential. If the LP38501-ADJ and LP38503-ADJ is used in a dual-supply system where the
regulator load is returned to a negative supply, the output must be diode-clamped to ground.
7.3.5 Short-Circuit Protection
The LP38501-ADJ and LP38503-ADJ contain internal current limiting which reduces output current to a safe
value if the output is overloaded or shorted. Depending upon the value of V_IN, thermal limiting may also become
active as the average power dissipated causes the die temperature to increase to the limit value (about 170°C).
The hysteresis of the thermal shutdown circuitry can result in a “cyclic” behavior on the output as the die
temperature heats and cools.
7.4 Device Functional Modes
7.4.1 Enable Operation (LP38501-ADJ Only)
The ENABLE pin (EN) must be actively terminated by either a 10-kΩ pullup resistor to V_IN, or a driver which
actively pulls high and low (such as a CMOS rail to rail comparator). If active drive is used, the pullup resistor is
not required. This pin must be tied to V_IN if not used (it must not be left floating).
14
Submit Documentation Feedback
Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: LP38501-ADJ LP38503-ADJ