DS2490Y Maxim Integrated Products, DS2490Y Datasheet - Page 6

• Manufacturer Part Number: DS2490Y
• Description: IC BRIDGE CLIP USB TO 1-W 24SOIC
• Manufacturer: Maxim Integrated Products

Specifications of DS2490Y

• Applications: USB
• Interface: 1-Wire
• Voltage - Supply: 3 V ~ 5.5 V
• Package / Case: 24-SOIC (7.5mm Width)
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

or lower should be used. If the fall time is shorter, a parameter code of 0x5 or higher should be used.
Once determined, the value code for the PULLDOWN SLEW RATE control parameter should be stored
in the host and always be loaded into the DS2490 after a power-on or master reset cycle.
1-WIRE TIMING DIAGRAMS
This section explains the 1-Wire bus waveforms generated by the DS2490. First, the communication
waveforms such as the reset/presence detect sequence and read/write data time slots are discussed
followed by a detailed description of the Pulse function under various conditions.
1-Wire Communication Wave Forms
One of the major features of the DS2490 is that it relieves the host from generating the timing of the 1-
Wire signals and sampling the 1-Wire bus at the appropriate times. The reset/presence detect sequence is
shown in Figure 5. This sequence is composed of four timing segments: the reset low time t
short/interrupt sampling offset t
timing segments t
their presence or interrupt pulse. During this time, the DS2490 pulls the 1-Wire bus high with a weak
pullup current.
Reset/presence timing values are shown in Figure 5. The values of all timing segments for all 1-Wire
speed options are shown in the table. Since the reset/presence sequence is slow compared to the time
slots, the values for regular and flexible speed are the same. Except for the falling edge of the presence
pulse, all edges are controlled by the DS2490. The shape of the uncontrolled falling edge is determined
by the capacitance of the 1-Wire bus and the number, speed, and sink capability of the slave devices
connected.
RESET/PRESENCE DETECT Figure 5
Upon executing a 1-WIRE RESET command (see COMMUNICATION COMMANDS), the DS2490
pulls the 1-Wire bus low for t
short/interrupt sampling offset t
there is a short or an interrupt signal. If there is no short or interrupt the DS2490 will wait for t
the voltage on the 1-Wire bus for a presence pulse. Regardless of the result of the presence test, the
SPEED
REGULAR
OVERDRIVE
FLEXIBLE
SI
, t
PDT
and t
FILL
RSTL
SI
SI
t
512µs
64µs
512µs
, the presence detect sampling offset t
RSTL
to expire and then test the voltage on the 1-Wire bus to determine if
comprise the reset high time t
NOMINAL TIMING VALUES
and then lets it go back to 5V. The DS2490 will now wait for the
t
8µs
2µs
8µs
SI
6 of 50
t
64µs
8µs
64µs
PDT
RSTH
t
512µs
64µs
512µs
FILL
where 1-Wire slave devices assert
PDT
and a delay time t
t
584µs
74µs
584µs
RSTH
PDT
FILL
RSTL
and test
. The
, the