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DS2490

USB to 1-Wire Bridge Chip

Maxim Integrated 

DS2490

SECTION

ELECTRICAL CHARACTERISTICS

APPLICATION INFORMATION

APPENDIX 1

APPENDIX 2

APPENDIX 3

APPENDIX 4

SUMMARY

DC and AC specifications

HW application example

CONTROL COMMANDS—USB setup packet encoding

COMMUNICATION COMMANDS—USB setup packet

encoding

MODE COMMANDS—USB setup packet encoding

USB command and command type constant codes

OVERVIEW

The DS2490 directly interfaces a USB port to a 1-Wire bus. As shown in Figure 1, the DS2490

incorporates a USB physical interface, a USB device controller coupled with a 1-Wire-specific USB

function core, and a 1-Wire bus interface controller. The 1-Wire interface controller shapes the slopes of

the 1-Wire waveforms, applies strong pullup to 5V, and reads the 1-Wire bus using a non-TTL threshold

to maximize the noise margin for best performance on large 1-Wire Networks. 1-Wire waveform timing

is accurately controlled with a crystal-based oscillator.

The DS2490 also supports USB remote wake-up which enables the DS2490-based USB peripheral to

send resume signaling to a suspended host system. If the remote wake-up function is enabled and the host

system is in a suspended state, a 1-Wire device attachment will cause the DS2490 to perform a host

system wake-up and allow the 1-Wire device to be serviced.

DS2490 FUNCTIONAL BLOCK DIAGRAM Figure 1

SUSO

D+

D-

USB

XCVR

USB

DESC

ROM

USB

DEVICE

CONTROLLER

USB

1-WIRE

FUNCTION

CORE

EP

FIFOS

1-WIRE

I/F

CONTROLLER

1-WIRE

VB

PWR

CNTL

OSC

CLK

GEN

VD

XI XO

GND

VVDPP2

Typical application examples of the DS2490 are shown in Figure 2 (a to c). As shown in all the examples,

all host control and communication with the device is accomplished over a USB communication link. A

USB vendor-specific command set, as defined in this document, is used to select operational modes

(MODE COMMANDS), control command processing (CONTROL COMMANDS), and communicate

over the 1-Wire interface (COMMUNICATION COMMANDS). Shown in Figure 2, example (a) is a

DS2490-based USB peripheral application. The peripheral function is a USB to 1-Wire adapter and

provides both USB and 1-Wire I/O connections. In this example, the peripheral is attached to the USB

enabled host computer 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

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