DS2490Y Maxim Integrated Products, DS2490Y Datasheet - Page 7

• 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

DS2490
DS2490 will then wait for t
to expire and then, depending on the value of embedded 1-WIRE RESET
FILL
command bits PST, NTF, and ICP, generate a command response byte that is available to the host.
If the test for interrupt or short reveals a logic 0, the DS2490 will wait for 4096µs and then test the 1-
Wire bus again. If a logic 0 is detected, the 1-Wire bus is shorted and the DS2490 feedback response for
the 1-WIRE RESET communication command will indicate a short detection. If a logic 1 is detected, the
device will wait for t
to expire, after which it will load the feedback response value for the 1-WIRE
FILL
RESET command with an alarming presence pulse detect value. See the DEVICE FEEDBACK section
for additional details. No additional testing for a presence pulse will be done. The DS2490 will perform
the short/interrupt testing as described also at overdrive speed, although interrupt signaling is only
defined for regular speed.
As shown in Figure 6, a Write-1 and Read Data time slot is comprised of the segments t
, t
, and
LOW1
DSO
t
. During Write-1 time slots, after the Write-1 low time (t
) expires, the DS2490 waits for the
HIGH
LOW1
duration of the data sample offset and then samples the 1-Wire voltage to read the response. After this,
the waiting time t
must expire before the time slot is complete. As shown in Figure 7, a Write-0 time
HIGH1
slot consists of the two segments t
and t
.
LOW0
REC0
Since the defaults for regular speed exceed the 1-Wire sampling maximum for most 1-Wire devices
(t
+ t
= 20µs) it is recommended to always use flexible speed. The minimum flexible speed
LOW1
DSO
settings t
= 4µs and t
= 10µs suffice for most applications. If the network is large or heavily
LOW1
DSO
loaded, Write-1 low time (t
) should be extended to more than 8µs to allow the 1-Wire bus to
LOW1
completely discharge. Since a large or heavily loaded network needs more time to recharge, it is also
recommended to delay sampling the bus for reading. A higher Data Sample Offset value (t
) will
DSO
increase the voltage margin and also provide extra energy to the slave devices when generating a long
series of Write-0 time slots. However, the total of t
+ t
should not exceed 15µs. Otherwise, the
LOW1
DSO
slave device responding may have stopped pulling the bus low when transmitting a logic 0. Note that
some long line loading conditions can extend the line recovery so the total t
+ t
can be extended.
LOW1
DSO
Care must be taken to not violate the t
of the attached 1-Wire devices.
MSR
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