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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： | 5/50页 |
| 文件大小： | 530K |
| 代理商： | DS2490 |
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DS2490
5 of 50
033199
ACTIVE PULLUP
Figure 3
5V
0V
1-Wire bus
is discharged
V
IAPO
V
IAPTO
t
APUOT
t
1
t
2
t
3
The circuit operates as follows: At t
1
the pulldown (induced by the DS2490 or a device on the bus) ends.
From this point on the 1-Wire bus is pulled high by the weak pullup current I
WEAKPU
provided by the
DS2490. The slope is determined by the load on the bus and the value of the pullup current. At t
2
the
voltage crosses the threshold voltage V
IAPO
. Now the DS2490 switches over from the weak pullup
current I
WEAKPU
to the higher current I
ACTPU
. As a consequence, the voltage on the bus now rises faster.
As the voltage on the bus crosses the threshold V
IAPTO
at t
3
, a timer is started. As long as this timer is on
(t
APUOT
), the I
ACTPU
current will continue to flow. After the timer is expired, the DS2490 will switch back
to the weak pullup current.
Falling Edges (DS2490-initiated)
Whenever the DS2490 begins pulling the 1-Wire bus low to initiate a time slot, for example, it first turns
off the weak pullup current I
WEAKPU
. Then, at regular and Overdrive speed it will generate a falling edge
at a slew rate of typically 15 V/μs. This value is acceptable for short 1-Wire busses and adequate for
communication at Overdrive speed. For MicroLAN networks of more than roughly 30 meters length,
flexible speed should always be used. One of the parameters that is adjustable at flexible speed is the
slew rate of DS2490-initiated falling edges. The effect of the slew rate control is shown in Figure 4.
SLEW RATE CONTROL
Figure 4
5V
0V
0.8 V
t
F
low slew rate
high slew rate
pull-down begins
weak pull-up ends,
1-Wire bus
is pulled up
Target for
long lines:
4 ± 0.5 μs
t
1
As extensive tests have shown, MicroLAN networks at a length of up to 300 meters will perform best if
the fall time t
F
is in the range of 4 ± 0.5 μs. This translates into a slew rate of approximately 1 V/μs. This
slew rate is typically achieved by selecting a PULLDOWN SLEW RATE parameter code of 0x4 (see
MODE COMMANDS). If the actual measured fall time is longer than the target value, a parameter code
of 0x3 or lower should be used. If the fall time is shorter, a parameter code of 0x5 or higher should be
相关PDF资料 |
PDF描述 |
|---|---|
| DS2490S | USB to 1-Wire Bridge Chip |
| DS2502-E64 | IEEE EUI-64 Node Address Chip |
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| DS26334G | 3.3V, 16-Channel, E1/T1/J1 Short and Long-Haul Line Interface Unit |
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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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