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RSCL
RSDA
9thClockPulse- AcknowledgeFromSlave
TSCL
TSDA
9thClockPulse- AcknowledgeFromSlave
V
OL
OfSlave
V
OL
OfDriver T
TSDA
TSCL
TMDS141
RSDA
RSCL
EN
SDA_SINK
SCL_SINK
TMDS442
SDA
SCL
EN
SDA
SCL
BUS
MASTER
SDA
SCL
BUS
SLAVE
TSDA
TSCL
TMDS141
RSDA
RSCL
EN
3.3V
3.3V
3.3V
Source Sink
Repeater
Rup
SOURCE
Rup
2
Rup
1
C
1
C
2
C
3
C
3
C
1
5V
5V
C
2
5V
Rup
SINK
C
2
5V
Rup
SINK
C
2
Rup
SOURCE
I
2
C Pull-up Resistors
R
up(min)
+ V
DD
ńlsink
(1)
TMDS442
SLLS757A – AUGUST 2006 – REVISED MARCH 2007
Figure 37. Bus R Waveform
Figure 38 illustrates the waveforms seen on the T-side I
2
C-bus under the same operation in Figure 37 . On the
T-side of the I
2
C repeater, the clock and data lines would have a positive offset from ground equal to the V
OL
of
the driver T. After the 8th clock pulse, the data line is pulled to the V
OL
of the slave device which is very close to
ground in this example. At the end of the acknowledge, the slave device releases and the bus level rises back to
the V
OL
set by the driver until the R-side rises above V
CC
/2, after which it continues to high. It is important to note
that any arbitration or clock stretching events require that the low level on the T-side bus at the input of the
TMDS442 I
2
C repeater is below 0.4 V to be recognized by the device and then transmitted to the R-side I
2
C bus.
Figure 38. Bus T Waveform
The I
2
C circuitry inside the TMDS442 allows multiple stage operation as shown in Figure 39 . I
2
C-Bus slave
devices can be connected to any of the bus segments. The number of devices that can be connected in series is
limited by repeater delay/time of flight considerations for the maximum bus speed requirements.
Figure 39. Typical Series Application
The pull-up resistor value is determined by two requirements:
1. The maximum sink current of the I
2
C buffer:
The maximum sink current is 3 mA or slightly higher for an I
2
C driver supporting standard-mode I
2
C
operation,.
2. The maximum transition time on the bus:
The maximum transition time, T, of an I
2
C bus is set by an RC time constant, where R is the pull-up resistor
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