Does the bus switch have a tolerant function?

Some bus switches have a tolerant function, while others do not. Table 1 lists whether each series of bus switches has a tolerant function or not, so please refer to it. However, for details, please check the data sheet of the device you are using. If there is a possibility that a signal may be input to the I/O terminal of the bus switch when the power is turned off, select a product with a tolerant function.

Table-1 tolerant function of bus switches
Category Switch
Configuration		 VCC (V) Type Product Series Tolerant Function
Control Pin Switch I/O
Low Voltage SPST 1.65～3.6 N-ch＋P-ch

TC7SBL Series

TC7WBL Series

TC7MBL Series

 ✔

✔

＊except SBL66C
SPDT TC7MBL Series ✔ ✔
SP4T TC7MBL Series ✔ ✔
5 V SPDT 1.65～5.5

TC7SB Series

TC7WB Series

 ✔ －
SPDT TC7SB Series ✔ －
Dual Supply
level shifting		 SPST

VCCA

1.65～5.0

VCCB

2.3～5.5

 N-ch

TC7SPB Series

TC7WPB Series

TC7QPB Series

TC7MPB Series

 ✔ ✔
SPDT TC7MPB Series ✔ ✔
Table-2 TC7MBL3257CFT operating ranges

The tolerant function of the input/output terminals (I/O terminals) of the bus switch

As for how to check the tolerant function of the bus switch, please check the rating of the "switch input/output voltage" item in the operating ranges of the data sheet. Table 2 shows the operating range of TC7MBL3257CFT as an example of a device with a tolerant function. When VCC = 0 V or switch = OFF, the switch input/output voltage (VS) does not depend on the power supply voltage and can input signals within the range of the power supply voltage. Therefore, even if a signal is input when the power is off, the device will not be damaged.

Table-2 TC7MBL3257CFT operating ranges

Table-3 TC7WB66CFK operating ranges

And Table-3 lists the operating ranges of TC7WB66CFK as an example of a device that does not have a tolerant function. When VCC = 0 V or the switch is OFF, the switch input/output voltage (VS) is 0 to VCC, so the input signal depends on the input voltage. In other words, the input signal cannot be input when the power is cut off.

Table-3 TC7WB66CFK operating ranges

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