MCP1810 datasheet(22/32 Pages) MICROCHIP

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MCP1810

DS20005623A-page 22

 2016 Microchip Technology Inc.

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 EXAMPLE

EXAMPLE 5-1:

5.3.1.1

Device Junction Temperature Rise

The internal junction temperature rise is a function of

internal power dissipation and of the thermal resistance

from junction to ambient for the application. The

thermal resistance from junction to ambient (R

JA) is

derived from 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 thermal

resistance for a particular application can vary

depending on many factors such as copper area and

thickness. Refer to Application Note AN792, “A Method

to Determine How Much Power a SOT23 Can

Dissipate in an Application”

(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-Lead

Input Voltage

VIN =3.3V ± 5%

LDO Output Voltage and Current

VOUT =2.5V

IOUT =150 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))

x150 mA

PLDO = 0.154 Watts

JRISE



DMAX







Where:

TJ(RISE) = Rise in the device junction

temperature over the ambient

temperature

PD(MAX) = Maximum power dissipation of the

device

JA = Thermal resistance from junction to

ambient

JRISE



Where:

TJ = Junction temperature

TJ(RISE) = Rise in the device junction

temperature over the ambient

temperature

TA = Ambient temperature

TJ(RISE) =PTOTAL xRJA

TJ(RISE) = 0.154W x 73.1°C/W

TJ(RISE) = 11.3°C

TJ =TJ(RISE) +TA(MAX)

TJ = 11.3°C + 60.0°C

TJ =71.3°C

2x2 VDFN 8-Lead (73.1°C/W R



JA):

PD(MAX) = (85°C – 60°C)/73.1°C/W

PD(MAX) = 0.342W

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