DS1920
DS1920 BLOCK DIAGRAM Figure 1
PARASITE POWER
The block diagram (Figure 1) shows the parasite-powered circuitry. This circuitry “steals” power
whenever the data contact is high. Data will provide sufficient power as long as the specified timing and
voltage requirements are met (see the 1-Wire Bus System section). The advantage of parasite power is that
no local power source is needed for remote sensing of temperature.
In order for the DS1920 to be able to perform accurate temperature conversions, sufficient power must be
provided over the data line when a temperature conversion is taking place. The DS1920 requires a current
during conversion of up to 1mA, therefore, the data line will not have sufficient drive due to the 5 k ?
pullup resistor. This problem is particularly acute if several DS1920s are on the same data line and
attempting to convert simultaneously.
The way to assure that the DS1920 has sufficient supply current is to provide a strong pullup on the data
line whenever temperature conversion or copying to the EEPROM is taking place. This may be
accomplished by using a MOSFET to connect the data line directly to the power supply as shown in
Figure 2. The data line must be switched over to the strong pullup within 10 μ s maximum after issuing a
command that involves copying to the EEPROM or initiates a temperature conversion.
3 of 22
相关PDF资料
DS1921G-F5# IBUTTON THERMOCHRON F5
DS1921H-F5# IBUTTON THERMOCHRON F5
DS1921K# KIT IBUTTON THERMOCHRON
DS1922E-F5# IBUTTON TEMP LOGGER 4KBit F5
DS1922L-F5# IBUTTON TEMP LOGGER
DS1923-F5# IBUTTON TEMP/HUMIDITY LOGGER F5
DS1961S-F3# IBUTTON EEPROM 1KBit F3
DS1963S-F5+ IBUTTON MONETARY SHA-1
相关代理商/技术参数
DS1921 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:High-Resolution Thermochron iButton
DS1921G 制造商:未知厂家 制造商全称:未知厂家 功能描述:Thermochron iButton
DS1921G_11 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Logs Up to 2048 Consecutive Temperature Thermochron iButton
DS1921G_1109 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Thermochron iButton
DS1921G_12 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Thermochron iButton
DS1921G-F5 功能描述:iButton RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5# 功能描述:iButton Thermochron iButton RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5#W 功能描述:iButton RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated