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DS2490

USB to 1-Wire Bridge Chip

Maxim Integrated 

DS2490

the various 1-Wire bus topologies simple multi-drop to complex 1-Wire Network. 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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