NXP Semiconductors

PCA9600

Dual bidirectional bus buffer

002aaf082

time (ns)

2

0

4

6

voltage

(V)

- 2

horizontal scale = 62.5 ns/div

send

receive

5 V

RX

TX

SX

PCA9600

send

300 Ω

5 V

2 meter

cable

5 V

300 Ω

GND

receive

SX

RX

TX

5 V

Figure 24. Wiring transients limited by the diodes in PCA9600

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 PCA9600 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.

Question: If we add 100 Ω to 200 Ω at signal line, the overshoot becomes slightly

smaller. Is this a good idea?

Answer: No, it is not necessary to add any resistance. When the logic signal

generated by TX or TY of PCA9600 drives long traces or wiring with ICs other than

PCA9600 being driven, then adding a Schottky diode (BAT54A) as shown in Figure 25

will clamp the wiring undershoot to a value that will not cause conduction of the IC’s

internal diodes.

PCA9600

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© NXP B.V. 2021. All rights reserved.

Product data sheet

Rev. 6.1 — 20 December 2021

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