P82B96TD/S900,118 NXP Semiconductors, P82B96TD/S900,118 Datasheet - Page 21
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P82B96TD/S900,118
Manufacturer Part Number
P82B96TD/S900,118
Description
IC INTERFACE
Manufacturer
NXP Semiconductors
Type
Bufferr
Datasheet
1.P82B96TD118.pdf
(32 pages)
Specifications of P82B96TD/S900,118
Tx/rx Type
I²C Logic
Delay Time
5.0ns
Capacitance - Input
7pF
Voltage - Supply
2 V ~ 15 V
Current - Supply
900µA
Mounting Type
Surface Mount
Package / Case
8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
568-5123-2
NXP Semiconductors
P82B96_8
Product data sheet
Fig 23. Wiring transients limited by the diodes in P82B96
Question: We have 2 meters of cable in a bus that joins the Tx/Rx sides of two P82B96
devices. When one Tx drives LOW the other P82B96 Tx/Rx is driven to 0.8 V for over
50 ns. What is the expected value and the theoretically allowed value of undershoot?
Answer: Because the cable joining the two P82B96s is a ‘transmission line’ that will
have a characteristic impedance around 100
resistors that are larger than that characteristic impedance there will always be negative
undershoot generated. The duration of the undershoot is a function of the cable length
and the input impedance of the connected IC. As shown in
undershoot will be limited, by the diodes inside P82B96, to around 0.8 V and that will
not cause problems for P82B96. Those transients will not be passed inside the IC to the
Sx/Sy side of the IC.
Question: If we input 800 mV undershoot at Tx, Rx pins, what kind of problem is
expected?
Answer: When that undershoot is generated by another P82B96 and is simply the
result of the system wiring, then there will be no problems.
Question: Will we have any functional problem or reliability problem?
Answer: No.
voltage
Rev. 08 — 10 November 2009
(V)
Sx
6
4
2
0
2
5 V
horizontal scale = 62.5 ns/div
P82B96
Rx
Tx
send
send
5 V
300
2 meter
cable
receive
and it will be terminated by pull-up
5 V
300
receive
GND
time (ns)
Dual bidirectional bus buffer
Figure
Rx
Tx
002aaf065
5 V
Sx
23, the transient
© NXP B.V. 2009. All rights reserved.
P82B96
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