ST72734 datasheet(133/144 Pages) STMICROELECTRONICS

部件名	ST72734

功能描述	8-BIT USB MCU FOR MONITORS, WITH UP TO 60K OTP, 1K RAM, ADC, TIMER, SYNC, TMU, PWM/BRM, H/W DDC & I2C

PDF	144 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

133 / 144 page

ST72774/ST727754/ST72734

133/144

6.1 POWER CONSIDERATIONS

The average chip-junction temperature, TJ, in

degrees Celsius, may be calculated using the

following equation:

TJ = TA + (PD x θJA) (1)

Where:

– TA is the Ambient Temperature in °C,

–

θJ

A is the Package Junction-to-Ambient Thermal

Resistance, in

°C/W,

– PD is the sum of PINT and PI/O,

– PINT is the product of IDD and VDD, expressed in

Watts. This is the Chip Internal Power

– PI/O represents the Power Dissipation on Input

and Output Pins; User Determined.

For most applications PI/O<PINT and may be

neglected. PI/O may be significant if the device is

configured to drive Darlington bases or sink LED

Loads.

An approximate relationship between PD and TJ

(if PI/O is neglected) is given by:

PD = K÷ (TJ + 273°C) (2)

Therefore:

K = PD x (TA + 273°C) + θJA x PD

2 (3)

Where:

– K is a constant for the particular part, which may

be determined from equation (3) by measuring

PD (at equilibrium) for a known TA. Using this

value of K, the values of PD and TJ may be ob-

tained by solving equations (1) and (2) iteratively

for any value of TA.

Table 34. Thermal Characteristics

Symbol

Package

Value

Unit

θJ

PSDIP42

°C/W

θJ

TQFP44

°C/W

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