DS2490S/TR データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS2490S/TR

USB to 1-WireTM Bridge Chip

Dallas Semiconductor -> Maxim Integrated 

DS2490

either directly at a root port or through a USB HUB. The 1-Wire bus interface provided by the DS2490

supports all 1-Wire devices manufactured by Dallas Semiconductor as well as the various 1-Wire bus

topologies simple multi-drop to complex MicroLAN. Example (b) and (c) in Figure 2 are variations of

example (a) in which the DS2490 is embedded in the host computer or a USB HUB.

DS2490 Application Examples Figure 2

1-WIRE INTERFACE CONTROLLER

1-Wire communication commands sent to the DS2490 are ultimately processed by the 1-Wire interface

controller. One of the tasks of the interface controller 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 active. 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. See the MODE COMMANDS section for

parameter control and power-on defaults.

All Rising Edges

The active pullup of the rising edges reduces the rise time on the 1-Wire bus significantly compared to a

simple resistive pullup. Figure 3 shows how the DS2490 is involved in shaping a rising edge.

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