DS18B20数字温度传感器技术手册
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更新于2024-07-29
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"DS18B20温度传感器手册提供了该传感器的详细技术规格和使用方法。"
DS18B20温度传感器是一款由Dallas Semiconductor（现Maxim Integrated）生产的单线数字温度传感器，其特点包括：
1. **独特的1-Wire接口**：这种传感器只需要一个端口引脚即可实现通信，简化了硬件设计，减少了布线复杂性。
2. **唯一的64位序列码**：每个DS18B20设备都有一个内置的非易失性ROM，存储着独一无二的64位序列码，方便识别和管理多个传感器。
3. **多滴模式功能**：支持多个传感器并联在同一总线上，使得分布式温度传感应用变得简单。
4. **无需外部组件**：DS18B20可以无需额外的元件就能工作，只需在数据线上提供电源，工作电压范围为3.0V至5.5V。
5. **宽温测量范围**：可测量从-55°C到+125°C的温度，适用于各种环境条件。
6. **高精度**：在-10°C到+85°C范围内，精度可达±0.5°C，确保了测量的准确性。
7. **用户可选分辨率**：温度计的分辨率可在9至12位之间选择，提供灵活的精度配置。
8. **快速转换时间**：能够在750毫秒内将温度转换为12位数字值，响应速度快。
9. **可编程报警设置**：用户可以定义非易失性报警设置，当温度超出预设范围时，传感器能触发报警。
10. **报警搜索命令**：通过执行报警搜索命令，可以快速识别并定位温度超出设定限值的设备。
11. **软件兼容性**：DS18B20与DS1822软件兼容，意味着已有的DS1822应用可以轻松升级到DS18B20。
12. **应用广泛**：适用于恒温控制器、工业系统、消费产品、温度计等各种对温度敏感的系统。
在实际应用中，DS18B20的引脚分配为：
- GND - 接地
- DQ - 数据输入/输出
- VDD - 电源电压
- NC - 不连接
DS18B20是一款高性能、易于集成的温度测量解决方案，广泛应用于各种需要精确温度监测的场合。用户可以根据需求调整其工作模式，实现高效可靠的温度监控。
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 T
H
and T
L
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 T
H
and T
L
registers are nonvolatile (EEPROM) so they will retain data when the
device is powered down. T
H
and T
L
can be accessed through bytes 2 and 3 of the scratchpad as explained
in the MEMORY section of this datasheet.
T
H
AND T
L
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
2
2
1
2
0
Only bits 11 through 4 of the temperature register are used in the T
H
and T
L
comparison since T
H
and T
L
are 8-bit registers. If the result of a temperature measurement is higher than T
H
or lower than T
L
, 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 T
H
or T
L
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 V
DD
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 (C
PP
) to provide power when the bus is low.
When the DS18B20 is used in parasite power mode, the V
DD
pin must be connected to ground.
In parasite power mode, the 1-wire bus and C
PP
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 C
PP
. 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
µs (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 (t
conv
) or data transfer (t
wr
= 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 V
DD
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.
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