MCP1710 datasheet(15/24 Pages) MICROCHIP

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DS20005158D-page 15

MCP1710

5.0

APPLICATION

CIRCUITS/ISSUES

5.1

Typical Application

The MCP1710 is used for applications that require ultra

low quiescent current draw.

FIGURE 5-1:

Typical Application Circuit.

5.2

Power Calculations

5.2.1

POWER DISSIPATION

The internal power dissipation within the MCP1710 is a

function of input voltage, output voltage, output current

and quiescent current. Equation 5-1 can be used to

calculate the internal power dissipation for the LDO.

EQUATION 5-1:

In addition to the LDO pass element power dissipation,

there is power dissipation within the MCP1710 as a

result of quiescent or ground current. The power

dissipation as a result of the ground current can be

calculated using Equation 5-2:

EQUATION 5-2:

The total power dissipated within the MCP1710 is the

sum of the power dissipated in the LDO pass device

and the P(IGND) term. Because of the CMOS

construction, the typical IGND for the MCP1710 is

200 µA at full load. Operating at a maximum VIN of 5.5V

results in a power dissipation of 1.1 mW. For most

applications, this is small compared to the LDO pass

device power dissipation and can be neglected.

The maximum continuous operating junction tempera-

ture specified for the MCP1710 is +85°C. To estimate the

internal junction temperature of the MCP1710, the total

internal power dissipation is multiplied by the thermal

resistance from junction-to-ambient (R

JA) of the device.

The thermal resistance from junction-to-ambient for the

2 x 2 VDFN-8 package is estimated at 73.1°C/W.

EQUATION 5-3:

The maximum power dissipation capability for a

package

can

calculated

given

the

junction-to-ambient thermal resistance and the maxi-

mum ambient temperature for the application.

Equation 5-4 can be used to determine the package

maximum internal power dissipation.

EQUATION 5-4:

VIN

VOUT

GND

CIN

COUT

SHDN

PLDO

VIN MAX



VOUT MIN



–

 I

OUT MAX





Where:

PLDO = Internal power dissipation of the

LDO pass device

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

IOUT(MAX) = Maximum output current

PIGND



VIN MAX



IGND



Where:

PI(GND) = Power dissipation due to the

quiescent current of the LDO

VIN(MAX) = Maximum input voltage

IGND = Current flowing in the GND pin

TJMAX



PTOTAL RJA



TAMAX



Where:

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total power dissipation of the device

JA = Thermal resistance from junction to

ambient

TA(MAX) = Maximum ambient temperature

PDMAX



TJMAX



TAMAX



–





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

Where:

PD(MAX) = Maximum power dissipation of the

device

TJ(MAX) = Maximum continuous junction

temperature

TA(MAX) = Maximum ambient temperature

JA = Thermal resistance from

junction-to-ambient

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