pca9601 NXP Semiconductors, pca9601 Datasheet - Page 21

• Manufacturer Part Number: pca9601
• Description: Dual Bidirectional Bus Buffer
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9601_1
Product data sheet
10.2.1 Example with questions and answers
Fig 24. Transients generated by the bus wiring
Question: On a falling edge of TX we measure undershoot at −800 mV at the linked
TX, RX pins of the PCA9601 that is generating the LOW, but the PCA9601 data sheet
specifies minimum −0.3 V. Does this mean that we violate the data sheet absolute
value?
Answer: For PCA9601 the −0.3 V Absolute Maximum rating is not intended to apply to
transients, it is a DC rating. As shown in
undershoot at the IC that is driving the bus LOW and no significant undershoot should
be observed when using reasonable care with the ground connection of the ‘scope. It is
more likely that undershoot observed at a driving PCA9601 is caused by local stray
inductance and capacitance in the circuit and by the oscilloscope connections. As
shown, undershoot will be generated by PCB traces, wiring, or cables driven by a
PCA9601 because the allowed value of the I
than that required to correctly terminate the wiring. In this example, with no IC
connected at the end of the wiring, the undershoot is about 2 V.
All information provided in this document is subject to legal disclaimers.
voltage
(V)
Rev. 01 — 28 May 2010
−2
6
4
2
0
horizontal scale = 62.5 ns/div
SX
5 V
RX
PCA9601
TX
send
send
5 V
Figure
300 Ω
2 meter
2
cable
C-bus pull-up resistor generally is larger
receive
24, there is no theoretical reason for any
time (ns)
5 V
002aaf078
300 Ω
receive
GND
Dual bidirectional bus buffer
PCA9601
© NXP B.V. 2010. All rights reserved.
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