MCP1802 datasheet(17/26 Pages) MICROCHIP

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DS22053B-page 17

MCP1802

6.0

APPLICATION CIRCUITS &

ISSUES

6.1

Typical Application

The MCP1802 is most commonly used as a voltage

regulator. Its low quiescent current and low dropout

voltage make it ideal for many battery-powered

applications.

FIGURE 6-1:

Typical Application Circuit.

6.1.1

APPLICATION INPUT CONDITIONS

6.2

Power Calculations

6.2.1

POWER DISSIPATION

The internal power dissipation of the MCP1802 is a

function of input voltage, output voltage and output

current. The power dissipation, as a result of the

quiescent current draw, is so low, it is insignificant

(25.0 µA x VIN). The following equation can be used to

calculate the internal power dissipation of the LDO.

EQUATION 6-1:

The maximum continuous operating temperature

specified for the MCP1802 is +85°C. To estimate the

internal junction temperature of the MCP1802, the total

internal power dissipation is multiplied by the thermal

resistance from junction to ambient (R

θJA). The thermal

resistance from junction to ambient for the SOT-23-5

package is estimated at 256°C/W.

EQUATION 6-2:

The maximum power dissipation capability for a

package can be calculated given the junction-to-

ambient thermal resistance and the maximum ambient

temperature for the application. The following equation

can be used to determine the package maximum

internal power dissipation.

EQUATION 6-3:

EQUATION 6-4:

EQUATION 6-5:

Package Type =

SOT-23-5

Input Voltage Range =

2.4V to 5.0V

VIN maximum =

5.0V

VOUT typical =

1.8V

IOUT =50 mA maximum

MCP1802

GND

VOUT

VIN

CIN

1µF

COUT

1 µF Ceramic

VOUT

VIN

2.4V to 5.0V

1.8V

IOUT

50 mA

SHDN

Ceramic

LDO

IN MAX

)

()

OUT MIN

()

–

() I

OUT MAX

)

()

Where:

PLDO = LDO Pass device internal power

dissipation

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

JMAX

()

TOTAL

AMAX

Where:

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

θJA = Thermal resistance from

junction to ambient

TAMAX = Maximum ambient temperature

DMAX

()

JMAX

()

AMAX

()

–

()

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

Where:

PD(MAX) = Maximum device power

dissipation

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX) = Maximum ambient temperature

θJA = Thermal resistance from

junction to ambient

JRISE

()

DMAX

()

Where:

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

PTOTAL = Maximum device power

dissipation

θJA = Thermal resistance from

junction to ambient

JRISE

()

Where:

TJ = Junction Temperature

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

TA = Ambient temperature

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