DS1720

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ORDER INFORMATION

ORDERING

NUMBER

PACKAGE

MARKING

DESCRIPTION

DS1720S+

DS1720 (see note)

DS1720 in Lead-Free 208mil 8-pin SO

DS1720S+T&R

DS1720 (see note)

DS1720 in Lead-Free 208mil 8-pin SO, 2500 Piece

Tape-and-Reel

DS1720S

DS1720

DS1720 in 208mil 8-pin SO

DS1720S/T&R

DS1720

DS1720 in 208mil 8-pin SO, 2500 Piece Tape-and-Reel

Note: A “+” symbol will also be marked on the package near the Pin 1 indicator.

OPERATION–MEASURING TEMPERATURE

A block diagram of the DS1720 is shown in Figure 1. The DS1720 measures temperatures through the

use of an on–board proprietary temperature measurement technique. A block diagram of the temperature

measurement circuitry is shown in Figure 2.

The DS1720 measures temperature by counting the number of clock cycles that an oscillator with a low

temperature coefficient goes through during a gate period determined by a high temperature coefficient

oscillator. The counter is preset with a base count that corresponds to –5

5°C. If the counter reaches zero

before the gate period is over, the temperature register, which is also preset to the –5

5°C value, is

incremented, indicating that the temperature is higher than –5

5°C. At the same time, the counter is then

preset with a value determined by the slope accumulator circuitry. This circuitry is needed to compensate

for the parabolic behavior of the oscillators over temperature. The counter is then clocked again until it

reaches zero. If the gate period is still not finished, then this process repeats.

The slope accumulator is used to compensate for the nonlinear behavior of the oscillators over

temperature, yielding a high resolution temperature measurement. This is done by changing the number

of counts necessary for the counter to go through for each incremental degree in temperature. To obtain

the desired resolution, therefore, both the value of the counter and the number of counts per degree C (the

value of the slope accumulator) at a given temperature must be known.