 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
DS1820 Datasheet(PDF) 4 Page - Dallas Semiconductor |
|
|
|||||||||||||||||||||||||||||
DS1820 Datasheet(HTML) 4 Page - Dallas Semiconductor |
|
|
4 / 27 page  DS1820 030598 4/27 USING VDD TO SUPPLY TEMPERATURE CONVERSION CURRENT Figure 3 +5V DS1820 I/O 4.7K µP VDD TO OTHER 1–WIRE DEVICES EXTERNAL +5V SUPPLY OPERATION – MEASURING TEMPERATURE The DS1820 measures temperature through the use of an on–board proprietary temperature measurement technique. A block diagram of the temperature mea- surement circuitry is shown in Figure 4. The DS1820 measures temperature by counting the number of clock cycles that an oscillator with a low tem- perature coefficient goes through during a gate period determined by a high temperature coefficient oscillator. The counter is preset with a base count that corre- sponds to –55 °C. If the counter reaches zero before the gate period is over, the temperature register, which is also preset to the –55 °C value, is incremented, indicat- ing that the temperature is higher than –55 °C. At the same time, the counter is then preset with a value determined by the slope accumulator circuitry. This cir- cuitry is needed to compensate for the parabolic behav- ior 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 non–linear behavior of the oscillators over temperature, yielding a high resolution temperature measurement. This is done by changing the number of counts neces- sary 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 accumu- lator) at a given temperature must be known. Internally, this calculation is done inside the DS1820 to provide 0.5 °C resolution. The temperature reading is provided in a 16–bit, sign–extended two’s complement reading. Table 1 describes the exact relationship of out- put data to measured temperature. The data is trans- mitted serially over the 1–Wire interface. The DS1820 can measure temperature over the range of –55 °C to +125 °C in 0.5°C increments. For Fahrenheit usage, a lookup table or conversion factor must be used. Note that temperature is represented in the DS1820 in terms of a 1/2°C LSB, yielding the following 9–bit format: MSB LSB 1 1 1 0 0 1 1 1 0 = –25 °C The most significant (sign) bit is duplicated into all of the bits in the upper MSB of the two–byte temperature reg- ister in memory. This “sign–extension” yields the 16–bit temperature readings as shown in Table 1. Higher resolutions may be obtained by the following procedure. First, read the temperature, and truncate the 0.5 °C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter may then be read. This value is the count remaining (COUNT_REMAIN) after the gate period has ceased. The last value needed is the number of counts per degree C (COUNT_PER_C) at that temperature. The actual temperature may be then be calculated by the user using the following: TEMPERATURE = TEMP_READ – 0.25 ) (COUNT_PER_C – COUNT_REMAIN) COUNT_PER_C |
Similar Part No. - DS1820 |
|
Similar Description - DS1820 |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
