tr - Rise Time (ns)

0

50

100

150

200

250

300

0

100

200

300

400

D001

VCCB = 3.3 V

TCA9800

TCA9801

TCA9802

TCA9803

tr - Rise Time (ns)

0

50

100

150

200

250

300

0

100

200

300

400

D001

VCCB = 1.65 V

TCA9800

TCA9801

TCA9802

TCA9803

26

TCA9803

SCPS267B – MARCH 2017 – REVISED FEBRUARY 2020

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Copyright © 2017–2020, Texas Instruments Incorporated

Table 8. Design Requirements for Bus B (continued)

Parameter

Description

Acceptable Range

Example Value/Target

fSCL

I2C clock frequency

400 kHz

Table 9. Design Requirements for Bus C

Parameter

Description

Acceptable Range

Example Value/Target

CL

Load capacitance (bus capacitance) on B-

side

up to 400 pF

40 pF

tr

Rise time

up to 300 ns

≤ 300 ns

VCCA

VCCA supply voltage

0.8 V-3.6 V

1.65 V

VCCB

VCCB supply voltage

1.65 V-3.6 V

1.65 V

fSCL

I2C clock frequency

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

Figure 32. Selection Guide Based On Example Design

Requirements for Bus B

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 IEXT-I section.