PCA9601DP,118 NXP Semiconductors, PCA9601DP,118 Datasheet - Page 22

• Manufacturer Part Number: PCA9601DP,118
• Description: IC DUAL BI-DIR BUS BUFFER 8-TSSO
• Manufacturer: NXP Semiconductors

Specifications of PCA9601DP,118

• Number Of Channels Per Chip: 2
• Supply Voltage (max): 15 V
• Supply Voltage (min): 2.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TSSOP-8
• Interface: I2C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-5302-2

NXP Semiconductors
PCA9601_1
Product data sheet
Fig 25. Wiring transients limited by the diodes in PCA9601
Question: We have 2 meters of cable in a bus that joins the TX/RX sides of two
PCA9601 devices. When one TX drives LOW the other PCA9601 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 PCA9601s is a ‘transmission line’ that will
have a characteristic impedance around 100 Ω and it will be terminated by pull-up
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 PCA9601, to around −0.8 V and that will
not cause problems for PCA9601. 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 PCA9601 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.
All information provided in this document is subject to legal disclaimers.
voltage
(V)
Rev. 01 — 28 May 2010
−2
SX
6
4
2
0
5 V
horizontal scale = 62.5 ns/div
RX
PCA9601
TX
send
send
5 V
300 Ω
2 meter
cable
receive
5 V
300 Ω
receive
time (ns)
GND
Dual bidirectional bus buffer
Figure
RX
TX
002aaf079
5 V
SX
25, the transient
PCA9601
© NXP B.V. 2010. All rights reserved.
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