MCP1702 datasheet(14/26 Pages) MICROCHIP

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MCP1702

DS22008E-page 14

 2010 Microchip Technology Inc.

6.0

APPLICATION CIRCUITS AND

ISSUES

6.1

Typical Application

The MCP1702 is most commonly used as a voltage

regulator. Its 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



JA). 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

1 µF Ceramic

COUT

1µF Ceramic

VOUT

VIN

(2.8V to 3.2V)

1.8V

IOUT

150 mA

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



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



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



Thermal resistance from

junction to ambient

JRISE



Where:

TJ = Junction Temperature

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

Ambient temperature

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