TCA9800 Datasheet, PDF (23/36 Pages) Texas Instruments – Level-Translating I2C Bus Buffer/Repeater

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400
TCA9800
TCA9801
TCA9802
300
TCA9803
V_CCB = 3.6 V
200
TCA9800
SCPS264 – MARCH 2017
100
0
0
50
100
150
200
250
300
t_r - Rise Time (ns)
D001
Figure 28. Maximum Load Capacitance vs Rise Time (400-kHz I²C, V_CCB = 3.6 V)
10.2.2 Buffering Without Level-Shifting
The TCA980x family supports buffering use cases which do not need level-shifting or voltage-translation.
It is critical to note that there are no external sources of current allowed on the B-side ports, since this can affect
device operation as shown in the I_EXT-I section.
2.5 V
5k
SDA
BUS
SCL
MASTER
400 kHz
5k
VCCA VCCB
TCA980x
SDAA SDAB
SDA
SCLA SCLB
SCL
SLAVE
EN
400 kHz
Copyright © 2017, Texas Instruments Incorporated
Figure 29. Buffering Use Case Without Level-Shifting
NOTE
Decoupling capacitors are not shown to keep the illustration simple. Decoupling capacitors
(1 µF and 0.1 µF) must be placed close to each power supply pin.
10.2.2.1 Design Requirements
The system designer must first select the correct variant of the TCA980x family for the load. In order to do this,
the information in Table 7 must be known. The setup in Figure 29 is used for these example design
requirements.
Parameter
C_L
t_r
V_CCA
Table 7. Design Requirements
Description
Load capacitance (bus capacitance) on B-
side
Rise time
VCCA supply voltage
Acceptable Range
up to 400 pF
up to 300 ns
0.8 V-3.6 V
Example Value/Target
200 pF
≤ 300 ns
2.5 V
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