TCA9802 Datasheet, PDF (26/36 Pages) Texas Instruments – Level-Translating I2C Bus Buffer/Repeater

TCA9802
SCPS266 – MARCH 2017
Parameter
C_L
t_r
V_CCA
V_CCB
f_SCL
Table 9. Design Requirements for Bus C
Description
Load capacitance (bus capacitance) on B-
side
Rise time
VCCA supply voltage
VCCB supply voltage
I²C clock frequency
Acceptable Range
up to 400 pF
up to 300 ns
0.8 V-3.6 V
1.65 V-3.6 V
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Example Value/Target
40 pF
≤ 300 ns
1.65 V
1.65 V
400 kHz
10.2.3.2 Detailed Design Procedure
Selecting the pull-up resistor required for the A-side (Bus A) is well documented already, see the I2C Bus Pullup
Resistor Calculation application report. The rest of this section deals only with selection of a device based on the
B-side design requirements.
Selection process of each device is identical to the procedure described in the Device Selection Guide section,
except that it must be done for each individual TCA980x. This section jumps straight to the selection graphs to
show the selection process. See the Detailed Design Procedure section for single device for detailed information.
Based on Figure 32, the TCA9802 or the TCA9803 are the devices which are able to meet the design
requirements. The TCA9802 is the most optimized selection, but the TCA9803 can be used without issue.
Based on Figure 33, all 4 variants of the TCA980x family meet the design requirements. The TCA9800 is the
most optimized selection, but any of the variants can be used without issue.
As the system designer, the choice can be made to go for the most optimized part selections (TCA9802 for bus
B and TCA9800 for bus C), but it is also ok to use the TCA9802 or the TCA9803 on both busses, because they
both satisfy the design requirements of both busses.
10.2.3.3 Application Curves
400
TCA9800
TCA9801
TCA9802
300
TCA9803
V_CCB = 3.3 V
200
400
TCA9800
TCA9801
TCA9802
300
TCA9803
V_CCB = 1.65 V
200
100
100
0
0
50
100
150
200
250
300
t_r - Rise Time (ns)
D001
Figure 32. Selection Guide Based On Example Design
Requirements for Bus B
0
0
50
100
150
200
250
300
t_r - Rise Time (ns)
D001
Figure 33. Selection Guide Based On Example Design
Requirements for Bus C
10.2.4 Series Device Use Case
The TCA980x family supports multiple TCA980x used in series. It is acceptable to connect A sides together, or
have A sides connect to B sides, but B-sides may never be connected together.
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.
NOTE: B-sides of TCA980x devices may never be connected to each other, because the I_EXT-I specification limit
is violated. See the I_EXT-I for more information.
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