DS1822/T&R

更新时间： 2024-02-03 20:10:59

品牌	Logo	应用领域
美信 - MAXIM		/
页数	文件大小	规格书
21页	223K
描述
Serial Switch/Digital Sensor, 12 Bit(s), 2Cel, Rectangular, 3 Pin, Through Hole Mount, TO92-3

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数据手册

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DS1822/T&R 技术参数

是否无铅：	不含铅	是否Rohs认证：	符合
生命周期：	Active	包装说明：	SOP8,.25
Reach Compliance Code：	compliant	ECCN代码：	EAR99
HTS代码：	8542.39.00.01	Factory Lead Time：	6 weeks
风险等级：	1.59	Samacsys Description：	Board Mount Temperature Sensors Econo 1-Wire Digital Thermometer
最大精度（摄氏度）：	2 Cel	其他特性：	COMPLIANCE TO MIL-150
主体宽度：	3.91 mm	主体高度：	1.55 mm
主体长度或直径：	4.88 mm	外壳：	PLASTIC
JESD-609代码：	e3	安装特点：	SURFACE MOUNT
位数：	12	端子数量：	8
最大工作电流：	1.5 mA	最高工作温度：	125 °C
最低工作温度：	-55 °C	输出接口类型：	1-WIRE INTERFACE
封装主体材料：	PLASTIC/EPOXY	封装等效代码：	SOP8,.25
封装形状/形式：	RECTANGULAR	电源：	3.3/5 V
传感器/换能器类型：	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL	子类别：	Other Sensors/Transducers
最大供电电压：	5.5 V	最小供电电压：	3 V
表面贴装：	YES	端子面层：	Matte Tin (Sn)
端接类型：	SOLDER

DS1822/T&R 数据手册

DS1822

OPERATION—ALARM SIGNALING

After the DS1822 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_Hand T_Lregisters (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_Hand T_Lregisters are NV (EEPROM) so they will retain data when the device is

powered down. T_Hand T_Lcan be accessed through bytes 2 and 3 of the scratchpad as explained in the

MEMORY section of this data sheet.

T_HAND T_LREGISTER FORMAT Figure 3

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

2⁶

2⁵

2⁴

2³

2²

2¹

2⁰

Only bits 11 through 4 of the temperature register are used in the T_Hand T_Lcomparison since T_Hand T_L

are 8-bit registers. If the measured temperature is lower than or equal to T_Lor higher than or equal to T_H,

an alarm condition exists and an alarm flag is set inside the DS1822. 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 DS1822s on the bus by issuing an Alarm Search

[ECh] command. Any DS1822s with a set alarm flag will respond to the command, so the master can

determine exactly which DS1822s have experienced an alarm condition. If an alarm condition exists and

the T_Hor T_Lsettings have changed, another temperature conversion should be done to validate the alarm

condition.

POWERING THE DS1822

The DS1822 can be powered by an external supply on the V_DDpin, or it can operate in “parasite power”

mode, which allows the DS1822 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 DS1822’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 DS1822 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

DS1822 is used in parasite power mode, the V_DDpin must be connected to ground.

In parasite power mode, the 1-Wire bus and C_PPcan provide sufficient current to the DS1822 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 DS1822 is performing temperature conversions or copying data from the

scratchpad memory to EEPROM, the operating current can be as high as 1.5mA. 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 DS1822 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

10μs (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= 10ms). No other

activity can take place on the 1-Wire bus while the pullup is enabled.

The DS1822 can also be powered by the conventional method of connecting an external power supply to

the V_DDpin, 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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与DS1822/T&R相关器件

型号	品牌	描述	获取价格	数据表
DS1822/T&R	MAXIM	Econo 1-Wire Digital Thermometer	获取价格
DS1822_V01	MAXIM	Econo 1-Wire Digital Thermometer	获取价格
DS1822+	MAXIM	Econo 1-Wire Digital Thermometer	获取价格
DS1822+PAR	MAXIM	Serial Switch/Digital Sensor, 12 Bit(s), 2Cel, Rectangular, 3 Pin, Through Hole Mount, TO-	获取价格
DS1822+T	MAXIM	Econo 1-Wire Digital Thermometer	获取价格
DS1822+T&R	MAXIM	Econo 1-Wire Digital Thermometer	获取价格

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