N270 datasheet(52/57 Pages) INTEL

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Thermal Specifications and Design Considerations

Datasheet

Table 15. Thermal Diode Interface

Signal Name

Pin/Ball Number

Signal Description

THERMDA

Thermal diode anode

THERMDC

Thermal diode cathode

Table 16. Thermal Diode Parameters using Transistor Model

Symbol

Parameter

Min

Typ

Max

Unit

Notes

IFW

Forward Bias Current

—

200

μA

Emitter Current

—

200

μA

Transistor Ideality

0.997

1.001

1.015

2,3,4

Beta

0.25

—

0.65

2,3

Series Resistance

2.79

4.52

6.24

2,5

NOTES:

Intel does not support or recommend operation of the thermal diode under reverse

bias.

Characterized across a temperature range of 50–100°C.

Not 100% tested. Specified by design characterization.

The ideality factor, nQ, represents the deviation from ideal transistor model behavior as

exemplified by the equation for the collector current:

= I

* (e

qVBE/nQkT –1)

where IS = saturation current, q = electronic charge, VBE = voltage across the

transistor base emitter junction (same nodes as VD), k = Boltzmann Constant, and

T = absolute temperature (Kelvin).

The series resistance, RT, provided in the Diode Model Table (Table 16) can be used for

more accurate readings as needed.

When calculating a temperature based on the thermal diode measurements, a number

of parameters must be either measured or assumed. Most devices measure the diode

ideality and assume a series resistance and ideality trim value, although are capable

of also measuring the series resistance. Calculating the temperature is then

accomplished using the equation listed under Table 16. In most sensing devices, an

expected value for the diode ideality is designed-in to the temperature calculation

equation. If the designer of the temperature sensing device assumes a perfect diode,

the ideality value (also called ntrim) will be 1.000. Given that most diodes are not

perfect, the designers usually select an ntrim value that more closely matches the

behavior of the diodes in the processor. If the processor diode ideality deviates from

that of the ntrim, each calculated temperature will be offset by a fixed amount. This

temperature offset can be calculated with the equation:

Terror(nf) = Tmeasured * (1 – nactual/ntrim)

Where Terror(nf) is the offset in degrees C, Tmeasured is in Kelvin, nactual is the measured

ideality of the diode, and ntrim is the diode ideality assumed by the temperature

sensing device.

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