TC2117-1.8DB Ver la hoja de datos (PDF) - Microchip Technology

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componentes Descripción

Fabricante

TC2117-1.8DB

800 mA Fixed Low Dropout Positive Regulator

Microchip Technology 

TC2117

TABLE 4-2:

THERMAL RESISTANCE

GUIDELINES FOR TC2117 IN

3-PIN DDPAK PACKAGE

Copper

Area

(Topside)*

Copper

Area

(Backside)

Board Area

2500 sq mm 2500 sq mm 2500 sq mm

1000 sq mm 2500 sq mm 2500 sq mm

125 sq mm 2500 sq mm 2500 sq mm

*Tab of device attached to topside copper.

Thermal

Resistance

(θJA)

25°C/W

27°C/W

35°C/W

Equation 4-1 can be used in conjunction with

Equation 4-2 to ensure regulator thermal operation is

within limits. For example:

Given:

VINMAX = 5.0V ± 5%

VOUTMIN = 3.3V ± 0.5%

ILOADMAX = 400 mA

TJMAX = 125°C

TAMAX = 55°C

θJA = 59°C/W (SOT-223)

Find: 1. Actual power dissipation

2. Maximum allowable dissipation

Actual power dissipation:

PD ≈ (VINMAX – VOUTMIN)ILOADMAX

= [(5.0 x 1.05) – (3.3 x .995)] 400 x 10-3

= 786 mW

Maximum allowable power dissipation:

PDMAX = (TJMAX – TAMAX)

θJA

= (125 – 55)

59

= 1.186W

In this example, the TC2117 dissipates a maximum of

only 786 mW; below the allowable limit of 1.186W. In a

similar manner, Equation 4-1 and Equation 4-2 can be

used to calculate maximum current and/or input volt-

age limits.

DS21665C-page 8

© 2006 Microchip Technology Inc.

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