MCP1754 datasheet(21/42 Pages) MICROCHIP

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DS22276A-page 21

MCP1754/MCP1754S

5.0

APPLICATION CIRCUITS &

ISSUES

5.1

Typical Application

The MCP1754/MCP1754S is most commonly used as

a voltage regulator. It’s low quiescent current and low

dropout voltage make it ideal for many battery-powered

applications.

FIGURE 5-1:

Typical Application Circuit.

5.1.1

APPLICATION INPUT CONDITIONS

5.2

Power Calculations

5.2.1

POWER DISSIPATION

The internal power dissipation of the MCP1754/

MCP1754S 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 (56.0 µA x VIN). The following equation

can be used to calculate the internal power dissipation

of the LDO.

EQUATION

The

maximum

continuous

operating

junction

temperature specified for the MCP1754/MCP1754S is

+150°C. To estimate the internal junction temperature

of the MCP1754/MCP1754S, the total internal power

dissipation is multiplied by the thermal resistance from

junction to ambient (R

JA). The thermal resistance from

junction to ambient for the SOT23A pin package is

estimated at 336 °C/W.

EQUATION

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

Package Type = SOT23

Input Voltage Range = 3.6V to 4.8V

VIN maximum = 4.8V

VOUT typical = 1.8V

IOUT = 50 mA maximum

MCP1754S

GND

VOUT

VIN

CIN

1µF Ceramic

COUT

1µF Ceramic

VOUT

VIN

3.6V to 4.8V

1.8V

IOUT

50 mA

LDO

IN MAX

)

()

OUT MIN

()

–

() I

OUT MAX

)

()

PLDO = LDO Pass device internal power dissipation

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

JMAX

()

TOTAL

AMAX

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

JA = Thermal resistance from junction to ambient

TAMAX = Maximum ambient temperature

DMAX

()

JMAX

()

AMAX

()

–

()

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

PD(MAX) = Maximum device power dissipation

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX) = Maximum ambient temperature

JA = Thermal resistance from junction to ambient

JRISE

()

DMAX

()

TJ(RISE) = Rise in device junction temperature over

the ambient temperature

PD(MAX) = Maximum device power dissipation

JA = Thermal resistance from junction to ambient

JRISE

()

TJ = Junction Temperature

TJ(RISE) = Rise in device junction temperature over

the ambient temperature

TA = Ambient temperature

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