MCP1702 View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

MCP1702

250 mA Low Quiescent Current LDO Regulator

Microchip Technology 

MCP1702

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.

VOUT

1.8V

IOUT

150 mA

MCP1702

GND

VIN

VOUT

COUT

1 µF Ceramic

VIN

(2.8V to 3.2V)

CIN

1 µF Ceramic

FIGURE 6-1:

Typical Application Circuit.

6.1.1 APPLICATION INPUT CONDITIONS

Package Type = SOT-23A

Input Voltage Range = 2.8V to 3.2V

VIN maximum = 3.2V

VOUT typical = 1.8V

IOUT = 150 mA maximum

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:

PLDO = VINMAX  – VOUTMIN  IOUTMAX 

Where:

PLDO = LDO Pass device internal

power dissipation

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

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:

TJMAX = PTOTAL  RJA + TAMAX

Where:

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

RJA

Thermal resistance from

junction to ambient

TAMAX = Maximum ambient temperature

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:

PDMAX = ---T----J----M----A---X--R-----–---J-T-A---A-----M----A---X------

Where:

PD(MAX) = Maximum device power

dissipation

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX)

Maximum ambient temperature

RJA = Thermal resistance from

junction to ambient

EQUATION 6-4:

TJRISE = PDMAX  RJA

Where:

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

PTOTAL = Maximum device power

dissipation

RJA

Thermal resistance from

junction to ambient

EQUATION 6-5:

TJ = TJRISE + TA

Where:

TJ = Junction Temperature

TJ(RISE) = Rise in device junction

temperature over the ambient

temperature

TA

Ambient temperature

DS22008E-page 14

 2010 Microchip Technology Inc.

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