TCA9802 Datasheet, PDF (24/36 Pages) Texas Instruments – Level-Translating I2C Bus Buffer/Repeater

TCA9802
SCPS266 – MARCH 2017
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Parameter
V_CCB
f_SCL
Table 7. Design Requirements (continued)
Description
VCCB supply voltage
I²C clock frequency
Acceptable Range
1.65 V-3.6 V
Example Value/Target
2.5 V
400 kHz
10.2.2.2 Detailed Design Procedure
Selecting the pull-up resistor required for the A-side 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.
As shown in Figure 30, the shaded region is the appropriate region based on design requirements listed in
Table 7. Any line that touches this shaded region is able to meet the design requirements. In this example, the
TCA9803, TCA9802, and TCA9801 are able to satisfy the design requirements, since they all touch the shaded
region. The TCA9800 falls below the shaded region.
Based on the selection graph shown above, the TCA9801 is selected, since it is the lowest-power device which
touches the shaded region (red trace). The TCA9803 or the TCA9802 may also be used without any
consequences.
10.2.2.3 Application Curve
400
TCA9800
TCA9801
TCA9802
300
TCA9803
V_CCB = 2.5 V
200
100
0
0
50
100
150
200
250
300
t_r - Rise Time (ns)
D001
Figure 30. Selection Guide Based On Example Design Requirements
10.2.3 Parallel Device Use Case
The TCA980x family supports multiple TCA980x used in parallel. The A-sides of the TCA980x are allowed to 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 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 section for more information.
NOTE: The B-side may not be connected to another translator if it uses a static-voltage offset. The R_ILC spec is
violated since the static voltage offset adjusts the output resistance to ground to be outside of the R_ILC spec
requirement, causing the TCA980x to be unable to recognize a low.
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