EMC1001_15 datasheet(9/24 Pages) MICROCHIP

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DS20005411A-page 9

EMC1001

4.1

Temperature Monitors

Thermal diode temperature measurements are based

on the change in forward bias voltage (

V

BE) of a diode

when operated at two different currents:

EQUATION 4-1:

The change in

V

BE voltage is proportional to absolute

temperature T.

Figure 4-2 shows a detailed block diagram of the

temperature measurement circuit. The EMC1001

incorporates

switched

capacitor

technology

that

integrates the temperature diode

V

BE from different

bias currents. The negative terminal (DN) for the

temperature diode is internally biased with a forward

diode voltage referenced to ground.

The advantages of this architecture over Nyquist rate

direct-conversion ADC (FLASH) or successive approx-

imation register (SAR) converters are superb linearity

and inherent noise immunity. The linearity can be

directly attributed to the delta-sigma ADC single-bit

comparator, while the noise immunity is achieved by

the ~20 ms integration time which translates to 50 Hz

input noise bandwidth.

FIGURE 4-2:

Detailed Block Diagram.

4.2

Temperature Measurement

Results and Data

The 10-bit temperature measurement results are

stored in temperature value registers. Table 4-1 shows

the two’s complement temperature data format with an

LSB equivalent to 0.25°C.

V

BE_HIGH

BE_LOW

kT

----------

HIGH

LOW

--------------





–

Where:

k = Boltzmann’s Constant

T = Absolute Temperature in Kelvin

q = Electron Charge

 = Diode Ideality Factor

Delta VBE

Sample

Hold

IBIAS

ILOW

IHIGH

1-bit

Delta-Sigma

Modulator

Digital

Averaging

Filter

VDD

Internal or

Remote Diode

Bias

Diode

10-bit Output

TABLE 4-1:

TEMPERATURE DATA

FORMAT

Temperature

Valid Range

-40°C to +125°C

Two’s Complement

-0.25°C

1111 1111 11 (1)

0.0°C

0000 0000 00

Note 1:

Temperature measurement returns

1100 0000 00

for all temperatures

-64.00°C.

Temperature measurement returns

0111 1111 11

for all temperatures

+127.75°C.

+0.25°C

0000 0000 01

+0.50°C

0000 0000 10

+0.75°C

0000 0000 11

+1°C

0000 0001 00

...

+125°C

0111 1101 00 (2)

TABLE 4-1:

TEMPERATURE DATA

FORMAT (CONTINUED)

Temperature

Valid Range

-40°C to +125°C

Two’s Complement

Note 1:

Temperature measurement returns

1100 0000 00

for all temperatures

-64.00°C.

Temperature measurement returns

0111 1111 11

for all temperatures

+127.75°C.

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