MCP1725 datasheet(14/32 Pages) MICROCHIP

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MCP1725

DS22026A-page 14

3.0

PIN DESCRIPTION

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Input Voltage Supply (VIN)

Connect the unregulated or regulated input voltage

source to VIN. If the input voltage source is located

several inches away from the LDO, or the input source

is a battery, it is recommended that an input capacitor

be used. A typical input capacitance value of 1 µF to

10 µF should be sufficient for most applications.

3.2

Shutdown Control Input (SHDN)

The SHDN input is used to turn the LDO output voltage

on and off. When the SHDN input is at a logic-high

level, the LDO output voltage is enabled. When the

SHDN input is pulled to a logic-low level, the LDO

output voltage is disabled. When the SHDN input is

pulled low, the PWRGD output also goes low and the

LDO enters a low quiescent current shutdown state

where the typical quiescent current is 0.1 µA.

3.3

Ground (GND)

Connect the GND pin of the LDO to a quiet circuit

ground. This will help the LDO power supply rejection

ratio and noise performance. The ground pin of the

LDO only conducts the quiescent current of the LDO

(typically 120 µA), so a heavy trace is not required.

For applications have switching or noisy inputs tie the

GND pin to the return of the output capacitor. Ground

planes help lower inductance and voltage spikes

caused by fast transient load currents and are

recommended for applications that are subjected to

fast load transients.

3.4

Power Good Output (PWRGD)

The PWRGD output is an open-drain output used to

indicate when the LDO output voltage is within 92%

(typically) of its nominal regulation value. The PWRGD

threshold has a typical hysteresis value of 2%. The

PWRGD output is typically delayed by 200 µs (typical,

no capacitance on CDELAY pin) from the time the LDO

output is within 92% + 3% (max hysteresis) of the

regulated output value on power-up. This delay time is

controlled by the CDELAY pin.

3.5

Power Good Delay Set-Point Input

(CDELAY)

The CDELAY input sets the power-up delay time for the

PWRGD output. By connecting an external capacitor

from the CDELAY pin to ground, the typical delay times

for the PWRGD output can be adjusted from 200 µs (no

capacitance) to 300 ms (0.1 µF capacitor). This allows

for the optimal setting of the system reset time.

Fixed Output

Adjustable

Output

Name

Description

VIN

Input Voltage Supply

VIN

Input Voltage Supply

SHDN

Shutdown Control Input (active-low)

GND

Ground

PWRGD

Power Good Output (open-drain)

CDELAY

Power Good Delay Set-Point Input

—

ADJ

Voltage Sense Input (adjustable version)

—

Sense

Voltage Sense Input (fixed voltage version)

VOUT

Regulated Output Voltage

Exposed Pad

Exposed Pad of the DFN Package (ground potential)

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