TC1017 datasheet(12/28 Pages) MICROCHIP

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TC1017

DS20001813G-page 12

 2005-2023 Microchip Technology Inc. and its subsidiaries

5.0

THERMAL CONSIDERATIONS

5.1

Thermal Shutdown

Integrated thermal protection circuitry shuts the

regulator off when the die temperature exceeds

approximately 160°C. The regulator remains off until

the die temperature drops to approximately 150°C.

5.2

Power Dissipation: SC-70

The TC1017 is available in the SC-70 package. The

thermal resistance for the SC-70 package is

approximately 450°C/W when the copper area used in

the PCB layout is similar to the JEDEC J51-7 high

thermal

conductivity

standard

semi-G42-88

standard. For applications with a larger or thicker

copper area, the thermal resistance can be lowered.

See AN792, “A Method to Determine How Much Power

a SOT-23 Can Dissipate in an Application” (DS00792),

for a method to determine the thermal resistance for a

particular application.

The TC1017 power dissipation capability is dependant

upon several variables: input voltage, output voltage,

load current, ambient temperature and maximum

junction temperature. The absolute maximum steady-

state junction temperature is rated at +125°C. The

power dissipation within the device is equal to:

EQUATION 5-1:

The VIN x IGND term is typically very small when

compared to the (VIN–VOUT) x ILOAD term, simplifying

the power dissipation within the LDO to be:

EQUATION 5-2:

To determine the maximum power dissipation

capability, the following equation is used:

EQUATION 5-3:

Given the following example:

Find:

Internal power dissipation:

Maximum allowable ambient temperature:

Maximum allowable power dissipation at

desired ambient:

In this example, the TC1017 dissipates approximately

158.5 mW and the junction temperature is raised 71°C

over the ambient. The absolute maximum power

dissipation is 155 mW when given a maximum ambient

temperature of 55°C.

Input voltage, output voltage or load current limits can

also be determined by substituting known values in the

power dissipation equations.

Figure 5-1 and Figure 5-2 depict typical maximum

power dissipation versus ambient temperature, as well

typical

maximum

current

versus

ambient

temperature, with a 1V input voltage to output voltage

differential, respectively.

FIGURE 5-1:

Power Dissipation vs.

Ambient Temperature (SC-70 package).

VIN VOUT

–

 I

LOAD

VIN IGND



VIN VOUT

–

 I

LOAD



PDMAX

TJ_MAX TA_MAX

–





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

Where:

TJ_MAX = the maximum junction

temperature allowed

TA_MAX = the maximum ambient

temperature

JA

= the thermal resistance from

junction to air

VIN = 3.0V to 4.1V

VOUT = 2.85V ±2.5%

ILOAD = 120 mA (output current)

TA = 55°C (max. desired ambient)

PDMAX

VIN_MAX VOUT_MIN

–

 I

LOAD



4.1V 2.85

0.975





–

 120mA



158.5mW

TA_MAX

TJ_MAX P

–

DMAX





125

C 158.5mW 450C/W



–



C

125

C71C

–



TJ_MAX TA

–



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

155mW

125

C55C

–

450

C/W

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

100

150

200

250

300

350

400

-40

-15

110

Ambient Temperature (°C)

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