MCP1754_13 datasheet(21/44 Pages) MICROCHIP

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DS22276B-page 21

MCP1754/MCP1754S

5.0

APPLICATION CIRCUITS &

ISSUES

5.1

Typical Application

The MCP1754/MCP1754S 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 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 that 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 of a pack-

age is 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 dis-

sipation.

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

1 µF Ceramic

VOUT

VIN

3.6V to 4.8V

1.8V

IOUT

50 mA

PLDO

VIN MAX



VOUT MIN



–

 I

OUT MAX





PLDO = LDO Pass device internal power dissipation

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

TJMAX



PTOTAL RJA



TAMAX



TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

JA = Thermal resistance from junction to ambient

TA(MAX) = Maximum ambient temperature

PDMAX



TJMAX



TAMAX



–





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

PD(MAX) = Maximum device power dissipation

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX) = Maximum ambient temperature

JA = Thermal resistance from junction to ambient

TJRISE



PDMAX







TJ(RISE) = Rise in device junction temperature over

the ambient temperature

PD(MAX) = Maximum device power dissipation

JA = Thermal resistance from junction to ambient

TJRISE



TJ = Junction Temperature

TJ(RISE) = Rise in device junction temperature over

the ambient temperature

TA = Ambient temperature

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