LP2985LV

150mA LOW NOISE, LOW DROPOUT REGULATOR

WITH SHUTDOWN FOR OUTPUT VOLTAGES <2.3 V

SLVS552 − OCTOBER 2004

11

POST OFFICE BOX 655303

APPLICATION INFORMATION

ON/OFF operation

The LP2985LV allows for a shutdown mode via the ON/OFF pin. Driving the pin LOW (

≤0.3 V) turns the device

OFF, conversely, a HIGH (

≥1.6 V) turns the device ON. If the shutdown feature is not used, the ON/OFF pin

should be connected to the input to ensure that the regulator is on at all times. For proper operation, do not leave

the ON/OFF pin unconnected and apply a signal with a slew rate of

≥40 mV/µs.

reverse input-output voltage

There is an inherent diode present across the PNP pass element of the LP2985LV.

VOUT

VIN

With the anode connected to the output, this diode is reverse biased during normal operation since the input

voltage is higher than the output. However, if the output is pulled higher than the input for any reason, this diode

will be forward biased and can cause a parasitic silicon-controlled rectifier (SCR) to latch, resulting in high

current flowing from the output to the input. Thus, to prevent possible damage to the regulator in any application

where the output may be pulled above the input, an external Schottky diode must be connected between the

output and input. With the anode on output, this Schottky limits the reverse voltage across the output and input

pins to

0.3 V, preventing the regulator’s internal diode from forward biasing.

VOUT

VIN

Schottky

LP2985LV