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參數(shù)資料
| 型號： | DS2490Y |
| 廠商： | Maxim Integrated Products |
| 文件頁數(shù)： | 45/50頁 |
| 文件大小： | 0K |
| 描述： | IC BRIDGE CLIP USB TO 1-W 24SOIC |
| 標(biāo)準(zhǔn)包裝： | 1,000 |
| 應(yīng)用： | USB |
| 接口： | 1 線 |
| 電源電壓： | 3 V ~ 5.5 V |
| 封裝/外殼： | 24-SOIC（0.295"，7.50mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 24-SOIC W |
| 包裝： | 管件 |
| 安裝類型： | 表面貼裝 |
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DS2490
5 of 50
ACTIVE PULLUP Figure 3
5V
0V
1-Wire bus
is discharged
VIAPO
VIAPTO
t
APUOT
t 1
t2
t3
The circuit operates as follows: At t1, 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 IWEAKPU provided by the
DS2490. The slope is determined by the load on the bus and the value of the pullup current. At t2, the
voltage crosses the threshold voltage VIAPO. Now, the DS2490 switches over from the weak pullup
current IWEAKPU to the higher current IACTPU. As a consequence, the voltage on the bus now rises faster.
As the voltage on the bus crosses the threshold VIAPTO at t3, a timer is started. As long as this timer is on
(tAPUOT), the IACTPU 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 IWEAKPU. Then, at regular and overdrive speed it will generate a falling edge at
a slew rate of typically 15 V/s. This value is acceptable for short 1-Wire busses and adequate for
communication at overdrive speed. For 1-Wire networks of more than roughly 30m 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
tF
5V
0V
low slew rate
high slew rate
0.8 V
pull-down begins
weak pull-up ends,
1-Wire bus
is pulled up
Target for
long lines:
4 ± 0.5 s
t 1
Extensive tests have shown that 1-Wire networks with lengths of up to 300m will perform best if the fall
time tF is in the range of 4 ± 0.5s. This translates into a slew rate of approximately 1V/s. This slew rate
is typically achieved by selecting a PULLDOWN SLEW RATE parameter code of 0 x 4 (see MODE
COMMANDS). If the actual measured fall time is longer than the target value, a parameter code of 0 x 3
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| DS2490Y+ | 制造商:Maxim Integrated Products 功能描述:USB TO 1-WIRE BRIDGE 24SOIC W - Tape and Reel |
| DS24B33 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:1-Wire 4Kb EEPROM |
| DS24B33 R | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:1-Wire 4Kb EEPROM |
| DS24B33 T | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:1-Wire 4Kb EEPROM |
| DS24B33 TR | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:1-Wire 4Kb EEPROM |
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