MCP1824 datasheet(18/34 Pages) MICROCHIP

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MCP1824/MCP1824S

DS22070A-page 18

4.0

DEVICE OVERVIEW

The MCP1824/MCP1824S is a 300 mA output current,

Low Dropout (LDO) voltage regulator. The low dropout

voltage of 200 mV typical at 300 mA of current makes

it ideal for battery-powered applications. The input

voltage range is 2.1V to 6.0V. Unlike other high output

current LDOs, the MCP1824/MCP1824S only draws a

maximum of 220 µA of quiescent current. The

MCP1824 adds a shutdown control input pin and a

power good output pin. The two output voltage options

are fixed or adjustable. The adjustable option is

available on the MCP1824 devices. The adjustable out-

put voltage is set using two external resistors.

4.1

LDO Output Voltage

The MCP1824 LDO is available with either a fixed

output voltage or an adjustable output voltage. The

output voltage range is 0.8V to 5.0V for either version.

The MCP1824S LDO is available as a fixed voltage

device.

4.1.1

ADJUST INPUT

The adjustable version of the MCP1824 uses the ADJ

pin to get the output voltage feedback for output voltage

regulation. This allows the user to set the output volt-

age of the device with two external resistors. The nom-

inal voltage for ADJ is 0.41V.

Figure 4-1 shows the adjustable version of the

MCP1824. Resistors R1 and R2 form the resistor

divider network necessary to set the output voltage.

With this configuration, Equation 4-1 represents the

equation for setting VOUT.

EQUATION 4-1:

CALCULATING VOUT

FIGURE 4-1:

Typical Adjustable Output

Voltage Application Circuit.

The allowable resistance value range for resistor R2 is

from 10 k

Ω to 200 kΩ. Solving Equation 4-1 for R1

yields Equation 4-2.

EQUATION 4-2:

CALCULATING ADJ PIN

RESISTOR VALUES

4.2

Output Current and Current

Limiting

The MCP1824/MCP1824S LDO is tested and ensured

to supply a minimum of 300 mA of output current. The

MCP1824/MCP1824S has no minimum output load, so

the output load current can go to 0 mA and the LDO will

continue to regulate the output voltage to within

tolerance.

The MCP1824/MCP1824S also incorporates an output

current limit. If the output voltage falls below 0.7V due

to an overload condition (usually represents a shorted

load condition), the output current is limited to 720 mA

(typical). If the overload condition is a soft overload, the

MCP1824/MCP1824S will supply higher load currents

of up to 900 mA. The MCP1824/MCP1824S should not

be operated in this condition continuously as it may

result in failure of the device. However, this does allow

for device usage in applications that have higher

pulsed load currents having an average output current

value of 300 mA or less.

Output overload conditions may also result in an over-

temperature shutdown of the device. If the junction

temperature rises above 150°C (typical), the LDO will

shut down the output voltage. See Section 4.8 “Over-

temperature Protection” for more information on

overtemperature shutdown.

OUT

ADJ

------------------

⎝⎠

⎛⎞

Where:

VOUT

LDO Output Voltage

VADJ

=ADJ Pin Voltage

(typically 0.41V)

SHDN

GND

ADJ

1µF

VOUT

4.7 µF

VIN

Off

MCP1824-ADJ

3 4 5

OUT

ADJ

-------------

–

⎝⎠

⎛⎞

Where:

VOUT

LDO Output Voltage

VADJ

=ADJ Pin Voltage

(typically 0.41V)

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