DS2480B+ Maxim Integrated Products, DS2480B+ Datasheet - Page 16

• Manufacturer Part Number: DS2480B+
• Description: IC LINE DRVR W/SENSOR 1-W 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Line Driver, Transmitterr

Specifications of DS2480B+

• Number Of Drivers/receivers: 1/0
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1-WIRE COMMUNICATION WAVEFORMS
One of the major features of the DS2480B 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. How this is done for the
reset/presence detect sequence is shown in Figure 6a. This sequence is composed of four timing
segments: the reset low time t
offset t
where 1-Wire slave devices assert their presence or interrupt pulse. During this time the DS2480B pulls
the 1-Wire bus high with its weak pullup current.
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 standard and flexible speed are
the same. Except for the falling edge of the presence pulse all edges are controlled by the DS2480B. 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.
Figure 6a. RESET/PRESENCE DETECT
After having received the command code for generating a reset/presence sequence, the DS2480B 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 (as shown in the picture), the
DS2480B will wait for t
result of the presence test, the DS2480B will then wait for t
response byte to the host.
If the test for interrupt or short reveals a logic 0, the DS2480B will wait for 4096s and then test the
1-Wire bus again. If a logic 0 is detected, the 1-Wire bus is shorted and a command response byte with
the code for SHORT will be sent immediately. If a logic 1 is detected, the device will wait for t
expire, after which it will send the command response byte with the code for an alarming presence pulse.
No additional testing for a presence pulse will be done. The DS2480B will perform the short/interrupt
testing as described also at Overdrive speed, although interrupt signaling is only defined for standard
speed.
The idle time following the Reset/Presence Detect sequence depends on the serial communication speed
and the host’s response time.
Overdrive
Standard
Flexible
Speed
PDT
and a delay time t
512µs
512µs
t
64µs
RSTL
PDT
RSTL
and test the voltage on the 1-Wire bus for a presence pulse. Regardless of the
FILL
RSTL
and then lets it go back to 5V. The DS2480B will now wait for the
. The timing segments t
SI
to expire and then test the voltage on the 1-Wire bus to determine if
, the short/interrupt sampling offset t
8µs
2µs
8µs
t
SI
16 of 32
SI
, t
PDT
64µs
64µs
t
8µs
PDT
FILL
and t
to expire and then send the command
FILL
comprise the reset high time t
SI
, the presence detect sampling
512µs
512µs
64µs
t
FILL
584µs
584µs
t
74µs
RSTH
FILL
RSTH
to