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参数资料
| 型号： | DS2480 |
| 英文描述： | Serial 1.Wire Line Driver |
| 中文描述： | 串行、1-Wire线驱动器 |
| 文件页数： | 12/26页 |
| 文件大小： | 185K |
| 代理商： | DS2480 |
DS2480
042498 12/26
CONTROLLED EDGES
One of the tasks of the DS2480 is to actively shape the
edges of the 1–Wire communication waveforms. This
speeds up the recharging of the 1–Wire bus (rising
edges) and reduces ringing of long lines (falling edges).
The circuitry for shaping rising edges is always on. The
slew rate of falling edges is actively controlled only at
flexible speed and requires the parameter for slew rate
control being different from its power–on default value.
All Rising Edges
The active pull–up of the rising edges reduces the rise
time on the 1–Wire bus significantly compared to a sim-
ple resistive pull–up. Figure 4 shows how the DS2480 is
involved in shaping a rising edge.
ACTIVE PULL–UP
Figure 4
5V
V
IAPTO
V
IAPO
0V
1–WIRE BUS
IS DISCHARGED
t
1
t
2
t
3
t
APUOT
The circuit operates as follows: At t
1
the pull–down
(induced by the DS2480 or a device on the bus) ends.
From this point on the 1–Wire bus is pulled high by the
weak pull–up current I
WEAKPU
provided by the DS2480.
The slope is determined by the load on the bus and the
value of the pull–up current. At t
2
the voltage crosses the
threshold voltage V
IAPO
. Now the DS2480 switches
over from the weak pull–up 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 DS2480
will switch back to the weak pull–up current.
Falling Edges (DS2480–initiated)
Whenever the DS2480 begins pulling the 1–Wire bus
low to initiate a time slot, for example, it first turns off the
weak pull–up current I
WEAKPU
. Then, at regular and
Overdrive speed it will generate a falling edge at a slew
rate of typically 15V/
μ
s. 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 one should always use
flexible speed. One of the parameters that is adjustable
at flexible speed is the slew rate of DS2480–initiated fal-
ling edges. The effect of the slew rate control is shown in
Figure 5.
SLEW RATE CONTROL
Figure 5
5V
HIGH SLEW RATE
0.8V
0V
1–WIRE BUS
IS PULLED UP
WEAK PULL–UP ENDS,
PULL–DOWN BEGINS
t
1
LOW SLEW RATE
TARGET FOR
LONG LINES:
4
±
0.5
μ
s
t
F
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
μ
s. This translates into a slew
rate of approximately 1V/
μ
s. This slew rate is typically
achieved by setting the configuration parameter 001
(Pull–Down Slew Rate Control) to a value of 100 (see
Table 4). If the actual measured fall time is longer than
the target value, one should use a value code of 011 or
lower. If the fall time is shorter, one should use a value
code of 101 or higher.
Once determined, the value code for the Pull–Down
Slew Rate Control parameter should be stored in the
host and always be loaded into the DS2480 after a
power–on or master reset cycle.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS2480B | 功能描述:缓冲器和线路驱动器 RoHS:否 制造商:Micrel 输入线路数量:1 输出线路数量:2 极性:Non-Inverting 电源电压-最大:+/- 5.5 V 电源电压-最小:+/- 2.37 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Reel |
| DS2480B | 制造商:Maxim Integrated Products 功能描述:IC SERIAL LINE DRIVER 2480 SOIC8 |
| DS2480B/T&R | 功能描述:缓冲器和线路驱动器 RoHS:否 制造商:Micrel 输入线路数量:1 输出线路数量:2 极性:Non-Inverting 电源电压-最大:+/- 5.5 V 电源电压-最小:+/- 2.37 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Reel |
| DS2480B+ | 功能描述:缓冲器和线路驱动器 Serial - 1-Wire Line Driver RoHS:否 制造商:Micrel 输入线路数量:1 输出线路数量:2 极性:Non-Inverting 电源电压-最大:+/- 5.5 V 电源电压-最小:+/- 2.37 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Reel |
| DS2480B+R | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Serial to 1-Wire Line Driver |
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