AN2115

Pin function

Doc ID 11165 Rev 5

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Pin function

Table 1.

Pin description

Pin n°

Name

Description

1

RUN

Shutdown input. When connected to a low level voltage (less than 0.5 V) the device stops

working. When high (above 1.3 V) the device is enabled. This pin must not be left floating.

2

COMP

Error amplifier output. A compensation network must be connected to this pin. Usually a 220 pF

capacitor is sufficient to guarantee loop stability (see related section).

3

VFB

Error amplifier inverting input. The output voltage can be adjusted by connecting this pin to an

external resistor divider from 0.6 V up to the input voltage.

4

GND

Ground.

5

LX

Switch output node. This pin is internally connected to the drain of the internal switches.

6

VCC

Input voltage. The start-up input voltage is 2.2 V (typ.) while the operating input voltage ranges

from 2 V to 5.5 V. An internal UVLO circuit generates a 200 mV (typ.) hysteresis.

7

SYNC

Operating mode selector input. When high (above 1.3 V) Low Consumption Mode is selected.

When low (less than 0.5 V), Low Noise Mode is selected. If connected to an appropriate external

synchronization signal (from 1 MHz up to 2 MHz) the internal synchronization circuit is activated

and the device works at the same switching frequency. This pin must not be left floating.

8

PGOOD

Power good comparator output. It is an open drain output. A pull-up resistor should be

low when the output voltage is lower than 90% of the regulated output voltage, and goes high

when the output voltage is greater than 90% of the regulated output voltage. The pin can be left

floating if not needed.