MCP1702 datasheet(13/26 Pages) MICROCHIP

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DS22008B-page 13

MCP1702

6.0

APPLICATION CIRCUITS AND

ISSUES

6.1

Typical Application

The MCP1702 is most commonly used as a voltage

regulator. It’s low quiescent current and low dropout

voltage makes 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 MCP1702 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

(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 MCP1702 is +125°C. To

estimate the internal junction temperature of the

MCP1702, 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-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 = 2.8V to 3.2V

VIN maximum = 3.2V

VOUT typical = 1.8V

IOUT = 150 mA maximum

MCP1702

GND

VOUT

VIN

CIN

1µF Ceramic

COUT

1µF Ceramic

VOUT

VIN

(2.8V to 3.2V)

1.8V

IOUT

150 mA

PLDO

VIN 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

TJMAX

()

PTOTAL RθJA

TAMAX

Where:

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

θJA

Thermal resistance from

junction to ambient

TAMAX = Maximum ambient temperature

PDMAX

()

TJMAX

()

TAMAX

()

–

()

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

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

TJRISE

()

PDMAX

()

Where:

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

PTOTAL = Maximum device power

dissipation

θJA

Thermal resistance from

junction to ambient

TJRISE

()

Where:

TJ = Junction Temperature

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

Ambient temperature

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