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参数资料
| 型号： | DS2490 |
| 英文描述： | USB to 1-Wire Bridge Chip |
| 中文描述： | USB与1-Wire桥接芯片 |
| 文件页数： | 6/50页 |
| 文件大小： | 530K |
| 代理商： | DS2490 |
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DS2490
6 of 50
033199
used. Once determined, the value code for the Pulldown Slew Rate Control parameter should be stored in
the host and always be loaded into the DS2490 after a power-on or master reset cycle.
1-WIRE TIMING DIAGRAMS
This section explains the waveforms generated by the DS2490 on the 1-Wire bus in detail. First the
communication wave forms such as the Reset/Presence Detect Sequence and the time slots are discussed.
After that follows a detailed description of the pulse function under various conditions. The wave forms
generated by the DS2490 may deviate slightly from specifications found in the “Book of DS19xx iButton
Standards” or in data sheets of 1-Wire slave devices. However, the DS2490 has been designed to ensure
that the timing requirements are met.
1-Wire Communication Wave Forms
One of the major features of the DS2490 is that it relieves the host from generating the timing of the 1-
Wire signals and sampling the 1-Wire bus at the appropriate times. The reset/presence detect sequence is
shown in Figure 5. This sequence is composed of four timing segments: the reset low time t
RSTL
, the
short/interrupt sampling offset t
SI
, the presence detect sampling offset t
PDT
and a delay time t
FILL
. The
timing segments t
SI
, t
PDT
and t
FILL
comprise the reset high time t
RSTH
where 1-Wire slave devices assert
their presence or interrupt pulse. During this time the DS2490 pulls the 1-Wire bus high with its weak
pullup current.
The values of all timing segments for all 1-Wire speed options are shown in the table. Since the
reset/presence sequence is slow compared to the time slots, the values for regular and flexible speed are
the same. Except for the falling edge of the presence pulse, all edges are controlled by the DS2490. The
shape of the uncontrolled falling edge is determined by the capacitance of the 1-Wire bus and the number,
speed and sink capability of the slave devices connected.
RESET/PRESENCE DETECT
Figure 5
Speed
Regular
Overdrive
Flexible
tRSTL
512 μs
64 μs
512 μs
tSI
8 μs
2 μs
8 μs
tPDT
64 μs
8 μs
64 μs
tFILL
512 μs
64 μs
512 μs
tRSTH
584 μs
74 μs
584 μs
Upon executing a 1-WIRE RESET command (see COMMUNICATION COMMANDS), the DS2490
pulls the 1-Wire bus low for t
RSTL
and then lets it go back to 5V. The DS2490 will now wait for the
short/interrupt sampling offset t
SI
to expire and then test the voltage on the 1-Wire bus to determine if
there is a short or an interrupt signal. If there is no short or interrupt (as shown in the picture), the
相关PDF资料 |
PDF描述 |
|---|---|
| DS2490S | USB to 1-Wire Bridge Chip |
| DS2502-E64 | IEEE EUI-64 Node Address Chip |
| DS26334 | 3.3V, 16-Channel, E1/T1/J1 Short and Long-Haul Line Interface Unit |
| DS26334G | 3.3V, 16-Channel, E1/T1/J1 Short and Long-Haul Line Interface Unit |
| DS26334GN | 3.3V, 16-Channel, E1/T1/J1 Short and Long-Haul Line Interface Unit |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS2490S | 功能描述:接口 - 专用 RoHS:否 制造商:Texas Instruments 产品类型:1080p60 Image Sensor Receiver 工作电源电压:1.8 V 电源电流:89 mA 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:BGA-59 |
| DS2490S+ | 制造商:Maxim Integrated Products 功能描述:USB TO 1-WIRE BRIDGE 24SOIC W - Rail/Tube 制造商:Maxim Integrated Products 功能描述:USB 1-W BRIDGE CHIP 24-SO LF 制造商:Maxim Integrated Products 功能描述:Bulk |
| DS2490S+T&R | 制造商:Maxim Integrated Products 功能描述:USB TO 1-WIRE BRIDGE 24SOIC W - Tape and Reel |
| DS2490S+TR | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:USB to 1-Wire Bridge Chip |
| DS2490X | 制造商:未知厂家 制造商全称:未知厂家 功能描述:USB to 1-Wire Bridge Chip(468.41 k) |
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