ST10F271E datasheet(128/180 Pages) STMICROELECTRONICS

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Electrical characteristics

ST10F271B/ST10F271E

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24.2

Recommended operating conditions

24.3

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,

ΘJA is the Package Junction-to-Ambient Thermal Resistance, in ° C/W,

PD is the sum of PINT and PI/O (PD = PINT + PI/O),

PINT is the product of IDD and VDD, expressed in Watt. This is the Chip Internal Power,

PI/O represents the Power Dissipation on Input and Output Pins; User Determined.

Most of the time for the applications PI/O< PINT and may be neglected. On the other hand,

PI/O may be significant if the device is configured to drive continuously external modules

and/or memories.

An approximate relationship between PD and TJ (if PI/O is neglected) is given by:

PD = K / (TJ + 273°C) (2)

Therefore (solving equations 1 and 2):

K = PD x (TA + 273°C) + ΘJA x PD

(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 obtained by solving equations (1) and (2) iteratively for any value of TA.

Table 60.

Recommended operating conditions

Symbol

Parameter

Value

Unit

Min

Max

VDD

Operating supply voltage

4.5

5.5

VSTBY

Operationg stand-by supply voltage (1)

4.5

5.5

VAREF

Operating analog reference voltage (2)

Ambient temperature under bias

-40

+125

°C

Junction temperature under bias

-40

+150

°C

The value of the VSTBY voltage is specified in the range 4.5 - 5.5 Volt. Nevertheless, it is acceptable to exceed the upper

limit (up to 6.0 Volt) for a maximum of 100 hours over the global 300000 hours, representing the lifetime of the device

(about 30 years). On the other hand, it is possible to exceed the lower limit (down to 4.0 Volt) whenever RTC and 32kHz

on-chip oscillator amplifier are turned off (only Stand-by RAM powered through VSTBY pin in Stand-by mode). When

VSTBY voltage is lower than main VDD, the input section of VSTBY/EA pin can generate a spurious static consumption on

VDD power supply (in the range of tenth of

µA).

For details on operating conditions concerning the usage of A/D Converter refer to

Section 24.7.

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