TC1263-3.0VET View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC1263-3.0VET

500 mA, Fixed-Output, CMOS LDO with Shutdown

Microchip Technology 

TC1263

5.0 THERMAL CONSIDERATIONS

5.1 Thermal Shutdown

Integrated thermal protection circuitry shuts the

regulator off when the die temperature exceeds 160°C.

The regulator remains off until the die temperature

drops to approximately 150°C.

5.2 Power Dissipation

The amount of power the regulator dissipates is

primarily a function of input and output voltage and out-

put current. The following equation is used to calculate

worst-case actual power dissipation:

EQUATION 5-1:

PD = VINMAX – VOUTMINILOADMAX

Where:

PD = Worst-case actual power dissipation

VINMAX = Maximum voltage on VIN

VOUTMIN = Minimum regulator output voltage

ILOADMAX = Maximum output (load) current

The maximum allowable power dissipation

(Equation 5-2) is a function of the maximum ambient

temperature (TAMAX), the maximum allowable die

temperature (TJMAX) and the thermal resistance from

junction-to-air (JA).

EQUATION 5-2:

Where: PDMAX = T----J---M----A---X----–-J---A-T---A----M----A---X-

PD = Worst-case actual power dissipation

VINMAX = Maximum voltage on VIN

VOUTMIN = Minimum regulator output voltage

ILOADMAX = Maximum output (load) current

Table 5-1 and Table 5-2 show various values of JA for

the TC1263 package types.

TABLE 5-1:

THERMAL RESISTANCE

GUIDELINES FOR TC1263 IN

8-PIN SOIC PACKAGE

Copper

Area

(Topside)*

Copper

Area

(Backside)

Board

Area

Thermal

Resistance

JA)

2500 sq mm 2500 sq mm 2500 sq mm 60°C/W

1000 sq mm 2500 sq mm 2500 sq mm 60°C/W

225 sq mm 2500 sq mm 2500 sq mm 68°C/W

100 sq mm 2500 sq mm 2500 sq mm 74°C/W

* Pin 2 is ground. Device is mounted on top-side.

TABLE 5-2:

THERMAL RESISTANCE

GUIDELINES FOR TC1263 IN

5-PIN DDPAK/TO-220

PACKAGE

Copper

Area

(Topside)*

Copper

Area

(Backside)

Board

Area

Thermal

Resistance

JA)

2500 sq mm 2500 sq mm 2500 sq mm 25°C/W

1000 sq mm 2500 sq mm 2500 sq mm 27°C/W

125 sq mm 2500 sq mm 2500 sq mm 35°C/W

* Tab of device attached to top-side copper

Equation 5-1 can be used in conjunction with

Equation 5-2 to ensure regulator thermal operation is

within limits. For example:

Given:

VINMAX = 3.3V ± 10%

VOUTMIN = 2.7V ± 0.5%

ILOADMAX = 275 mA

TJMAX = 125°C

TAMAX = 95°C

JA = 60° C/W (SOIC)

Find:

1. Actual power dissipation

2. Maximum allowable dissipation

Actual power dissipation:

PD  VINMAX – VOUTMINILOADMAX

PD = 3.3  1.1 – 2.7  .995275  10–3

PD = 260 mW

Maximum allowable power dissipation:

PDMAX = T----J---M----A---X----–-J---A-T---A----M----A---X-

PDMAX = ---1---2---5-6----–0----9---5----

PDMAX = 500 mW

In this example, the TC1263 dissipates a maximum of

260 mW below the allowable limit of 500 mW. In a

similar manner, Equation 5-1 and Equation 5-2 can be

used to calculate maximum current and/or input

voltage limits. For example, the maximum allowable

VIN is found by substituting the maximum allowable

power dissipation of 500 mW into Equation 5-1, from

which VINMAX = 4.6V.

DS21374D-page 8

 2002-2012 Microchip Technology Inc.

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