Load

Transient

Line

Transient

NOM

~89%

~85%

Power-

Up

Power-

Down

~2.25V

~1.25V

~2.50V

LP38513

www.ti.com

SNVS361E – JULY 2007 – REVISED NOVEMBER 2015

7.4 Device Functional Modes

7.4.1 Enable Operation

The Enable on/off threshold is typically 850 mV and has no hysteresis. The voltage signal must rise and fall

cleanly, and promptly, through this threshold. The EN pin has no internal pullup or pulldown 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 single ended device (such as the collector of a discrete transistor) a pullup resistor

as the pullup or pulldown resistor to establish default condition for the EN pin. The resistor value selected must

be appropriate to swamp out any leakage in the external single-ended device, as well as any stray capacitance.

If the EN pin is driven from a source that actively pulls high and low (such as a CMOS rail-to-rail comparator

output), the pullup or pulldown resistor is not required.

If the application does not require the enable function, the EN pin must be connected directly to the adjacent IN

pin.

7.4.2 ERROR Flag Operation

The internal ERROR flag comparator has an open-drain output stage. Hence, the ERROR pin requires an

external pullup resistor. The value of the pullup resistor must be in the range of 2 k

Ω to 20 kΩ and must be

connected to the LP38513 OUT pin. The ERROR flag pin must not be pulled up to any voltage source higher

voltage is less than typically 1.25 V the status of the ERROR flag output is not reliable. The ERROR flag pin

must be connected to ground if this function is not used.

The timing diagram in Figure 16 shows the relationship between the ERROR flag and the output voltage when a

pullup resistor is connected to the output voltage pin.

The timing diagram in Figure 17 shows the relationship between the ERROR flag and the output voltage when

the pullup resistor is connected to the input voltage.

Figure 16. ERROR Flag Operation (see Figure 18)

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