MCP1710 datasheet(16/24 Pages) MICROCHIP

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MCP1710

DS20005158D-page 16

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EQUATION 5-5:

EQUATION 5-6:

5.3

Typical Application Examples

Internal power dissipation, junction temperature rise,

junction temperature and maximum power dissipation

are calculated in the following example. The power

dissipation, as a result of ground current, is small

enough to be neglected.

5.3.1

POWER DISSIPATION EXAMPLES

EXAMPLE 5-1:

5.3.1.1

Device Junction Temperature Rise

The internal junction temperature rise is a function of

internal power dissipation and the thermal resistance,

from junction-to-ambient, for the application. The

thermal resistance, from junction-to-ambient (R

JA), is

derived from the EIA/JEDEC standards for measuring

thermal resistance. The EIA/JEDEC specification is

JESD51. The standard describes the test method and

board specifications for measuring the thermal

resistance from junction-to-ambient. The actual ther-

mal resistance for a particular application can vary

depending on many factors, such as copper area and

thickness. Refer to AN792, “A Method to Determine

How Much Power a SOT23 Can Dissipate in an Appli-

cation” (DS00792), for more information regarding this

subject.

EXAMPLE 5-2:

5.3.1.2

Junction Temperature Estimate

To estimate the internal junction temperature, the

calculated temperature rise is added to the ambient or

offset temperature. For this example, the worst-case

junction temperature is estimated below:

EXAMPLE 5-3:

5.3.1.3

Maximum Package Power

Dissipation at +60°C Ambient

Temperature

EXAMPLE 5-4:

Package

Package Type = 2 x 2 VDFN-8

Input Voltage

VIN =3.3V ± 5%

LDO Output Voltage and Current

VOUT =2.5V

IOUT =200 mA

Maximum Ambient Temperature

TA(MAX) =+60°C

Internal Power Dissipation

PLDO(MAX) =(VIN(MAX) – VOUT(MIN))x IOUT(MAX)

PLDO = ((3.3V x 1.05) – (2.5V x 0.975))

x200 mA

PLDO = 0.206 Watts

TJRISE



PDMAX







TJ(RISE) = Rise in the device’s junction

temperature over the ambient

temperature

PD(MAX) = Maximum power dissipation of the

device

JA = Thermal resistance from

junction-to-ambient

TJRISE



TJ = Junction temperature

TJ(RISE) = Rise in the device’s junction

temperature over the ambient

temperature

TA = Ambient temperature

TJ(RISE) =PTOTAL xRJA

TJ(RISE) = 0.206W x 73.1°C/W

TJ(RISE) =15.1°C

TJ =TJ(RISE) +TA(MAX)

TJ = 15.1°C + 60.0°C

TJ =75.1°C

2x2 VDFN-8 (73.1°C/W R

JA):

PD(MAX) = (85°C – 60°C)/73.1°C/W

PD(MAX) = 0.342W

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