參數(shù)資料
型號(hào)： DS18B20Z
廠商： DALLAS SEMICONDUCTOR
元件分類： Switch/Digital Output Temperature Sensor
英文描述： DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, SURFACE MOUNT
封裝： 0.150 INCH, SOIC-8
文件頁(yè)數(shù)： 15/20頁(yè)
文件大?。?/td> 149K
代理商： DS18B20Z
DS18B20
4 of 20
OPERATION – ALARM SIGNALING
After the DS18B20 performs a temperature conversion, the temperature value is compared to the user-
defined two’s complement alarm trigger values stored in the 1-byte TH and TL registers (see Figure 3).
The sign bit (S) indicates if the value is positive or negative: for positive numbers S = 0 and for negative
numbers S = 1. The TH and TL registers are nonvolatile (EEPROM) so they will retain data when the
device is powered down. TH and TL can be accessed through bytes 2 and 3 of the scratchpad as explained
in the MEMORY section of this datasheet.
TH AND TL REGISTER FORMAT Figure 3
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
S
2
6
2
5
2
5
2
5
2
1
2
0
Only bits 11 through 4 of the temperature register are used in the TH and TL comparison since TH and TL
are 8-bit registers. If the result of a temperature measurement is higher than TH or lower than TL, an
alarm condition exists and an alarm flag is set inside the DS18B20. This flag is updated after every
temperature measurement; therefore, if the alarm condition goes away, the flag will be turned off after the
next temperature conversion.
The master device can check the alarm flag status of all DS18B20s on the bus by issuing an Alarm Search
[ECh] command. Any DS18B20s with a set alarm flag will respond to the command, so the master can
determine exactly which DS18B20s have experienced an alarm condition. If an alarm condition exists
and the TH or TL settings have changed, another temperature conversion should be done to validate the
alarm condition.
POWERING THE DS18B20
The DS18B20 can be powered by an external supply on the VDD pin, or it can operate in “parasite power”
mode, which allows the DS18B20 to function without a local external supply.
Parasite power is very
useful for applications that require remote temperature sensing or that are very space constrained. Figure
1 shows the DS18B20’s parasite-power control circuitry, which “steals” power from the 1-wire bus via
the DQ pin when the bus is high. The stolen charge powers the DS18B20 while the bus is high, and some
of the charge is stored on the parasite power capacitor (CPP) to provide power when the bus is low.
When the DS18B20 is used in parasite power mode, the VDD pin must be connected to ground.
In parasite power mode, the 1-wire bus and CPP can provide sufficient current to the DS18B20 for most
operations as long as the specified timing and voltage requirements are met (refer to the DC
ELECTRICAL CHARACTERISTICS and the AC ELECTRICAL CHARACTERISTICS sections of this
data sheet). However, when the DS18B20 is performing temperature conversions or copying data from
the scratchpad memory to EEPROM, the operating current can be as high as 1.5 mA. This current can
cause an unacceptable voltage drop across the weak 1-wire pullup resistor and is more current than can be
supplied by CPP. To assure that the DS18B20 has sufficient supply current, it is necessary to provide a
strong pullup on the 1-wire bus whenever temperature conversions are taking place or data is being
copied from the scratchpad to EEPROM. This can be accomplished by using a MOSFET to pull the bus
directly to the rail as shown in Figure 4. The 1-wire bus must be switched to the strong pullup within 10
s (max) after a Convert T [44h] or Copy Scratchpad [48h] command is issued, and the bus must be held
high by the pullup for the duration of the conversion (tconv) or data transfer (twr = 10 ms).
No other
activity can take place on the 1-wire bus while the pullup is enabled.
The DS18B20 can also be powered by the conventional method of connecting an external power supply
to the VDD pin, as shown in Figure 5. The advantage of this method is that the MOSFET pullup is not
required, and the 1–wire bus is free to carry other traffic during the temperature conversion time.
相關(guān)PDF資料
PDF描述
DS18B20 DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, THROUGH HOLE MOUNT
DS18B20U+T&R DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, SQUARE, SURFACE MOUNT
DS18B20-SL+T&R DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, THROUGH HOLE MOUNT
DS18B20/T&R DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, THROUGH HOLE MOUNT
DS18B20U DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, SQUARE, SURFACE MOUNT
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS18B20Z/T&R 制造商:Maxim Integrated Products 功能描述:HI RES MICROLAN DIG THERM 8-SOIC TR - Tape and Reel 制造商:Maxim Integrated Products 功能描述:IC THERM MICROLAN PROG-RES 8SOIC 制造商:Maxim Integrated Products 功能描述:Board Mount Temperature Sensors Prgmble Resolution 1-Wire Parasite Pwr
DS18B20Z/T&R 功能描述:板上安裝溫度傳感器 Prgmble Resolution 1-Wire Parasite Pwr RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
DS18B20Z+ 功能描述:板上安裝溫度傳感器 Prgmble Resolution 1-Wire Parasite Pwr RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
DS18B20Z+ 制造商:Maxim Integrated Products 功能描述:SEMICONDUCTOR ((NW))
DS18B20Z+T&R 制造商:Maxim Integrated Products 功能描述:HI RES MICROLAN DIG THERM 8-SOIC TR 制造商:Maxim Integrated Products 功能描述:TEMP SENSOR DGTL SERL (1-WIRE) 8SOIC N - Tape and Reel 制造商:Maxim Integrated Products 功能描述:IC THERM MICROLAN PROG-RES 8SOIC 制造商:Maxim Integrated Products 功能描述:Board Mount Temperature Sensors Prgmble Resolution 1-Wire Parasite Pwr
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*