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.
| 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 | ✔ | ✔ ＊except SBL66C |
||
| SPDT | TC7MBL Series | ✔ | ✔ | ||||
| SP4T | TC7MBL Series | ✔ | ✔ | ||||
| 5 V | SPDT | 1.65～5.5 | ✔ | － | |||
| SPDT | TC7SB Series | ✔ | － | ||||
| Dual Supply level shifting |
SPST | VCCA 1.65～5.0 |
VCCB 2.3～5.5 |
N-ch | ✔ | ✔ | |
| SPDT | TC7MPB Series | ✔ | ✔ | ||||
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
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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