pca9646 NXP Semiconductors, pca9646 Datasheet - Page 12

• Manufacturer Part Number: pca9646
• Description: Pca9646 Buffered 4-channel 2-wire Bus Switch
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9646
Product data sheet
Figure 16
systems using P82B715 I
capacitance limit. P82B715 alone provides a ‘10 impedance transformation’
no isolation of the loadings on either side. P82B715 systems have a finite capacitance
limit and its system calculations can be relatively complex. The buffering action of
PCA9646 simplifies calculations and allows the isolated bus rise time to meet the
Fast-mode requirement even when that is not possible on the long cable section.
Of course it is possible to create a much larger system by connecting existing long
P82B715 cable systems to each of the four channels and driving all of them from one
isolated Master.
Fig 16. PCA9646 isolating the standard I
PCA9646 provides bus isolation and simplifies calculation of bus RC components.
shows how PCA9646 can be used to combine or extend existing long cable
SDA
SCL
isolated I
All information provided in this document is subject to legal disclaimers.
5 V
2
C-bus
R1
1.8 kΩ
Rev. 1 — 1 March 2011
2
C-bus extenders when they have reached their maximum
R2
1.8 kΩ
3
U1
SCL
SDA
RESET
A[2:0]
PCA9646
V
DD
2
C-bus from a P82B715 used as a line driver
SC0
SC1
SC2
SC3
SD0
SD1
SD2
SD3
no pull-up
required
Buffered 4-channel 2-wire bus switch
U2
SX
SY
P82B715
V
CC
LX
LY
R3
long cable run
PCA9646
© NXP B.V. 2011. All rights reserved.
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