MCP1703AT-1202ESLASHMB datasheet(14/31 Pages) MICROCHIP

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MCP1703A

DS20005122B-page 14

 2012-2013 Microchip Technology Inc.

6.0

APPLICATION CIRCUITS AND

ISSUES

6.1

Typical Application

The MCP1703A 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 MCP1703A is a

function of input voltage, output voltage and output

current. As a result of the quiescent current draw, the

power dissipation is so low that it is insignificant (2.0 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

junction

temperature specified for the MCP1703A is +125°C. To

estimate the internal junction temperature of the

MCP1703A, the total internal power dissipation is

multiplied by the thermal resistance from junction to

ambient (RθJA). The thermal resistance from junction

to ambient for the SOT-23A pin package is estimated at

336°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-23A

Input Voltage Range = 2.7V to 4.8V

VIN maximum = 4.8V

VOUT typical = 1.8V

IOUT = 50 mA maximum

GND

VOUT

VIN

CIN

1 µF Ceramic

COUT

1µF Ceramic

VOUT

VIN

2.7V to 4.8V

1.8V

IOUT

50 mA

MCP1703A

LDO

IN MAX

() VOUT 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

RθJA = Thermal resistance from

junction-to-ambient

TA(MAX) = Maximum ambient temperature

DMAX

()

JMAX

() TAMAX

()

–

()

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

Where:

PD(MAX) = Maximum device power dissipation

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX) = Maximum ambient temperature

RθJA = 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

RθJA = 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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