What is the difference between the bus switch type and the buffer type of the voltage-level transformation IC (level shifter)?
The bus switch type uses MOSFETs as switches and performs voltage level shifting with external pull-up resistors. Since it is just a switch, it has no current drive capability. On the other hand, the buffer type outputs from the CMOS structure circuit and level shifts. Therefore, it has a product-specific drive capability, and the output is a digital signal.
Bus Switch Type Voltage translation IC (Level Shifter)
The bus switch type product (TC7SPB9306TU) can perform voltage level shift by switching on/off and using pull-up resistors. The OE pin is a control input that switches on/off.
With the connection shown in Fig. 1, we will explain the operation using an example of the waveform that is output from the right side (Input B) when an input signal is input from the left side (Input A).
The input/output transfer operation is divided into two operations, depending on the input voltage level, using VOHU (input level up characteristic) specified in the product data sheet (Table- 1) as a threshold.
0V to VOHU : The internal switch is on and transfers a signal from A to B without changing its voltage.
VOHU or higher: The internal switch is off. The external pull-up resistor on the VCCB side pulls up the input voltage to the VCCB level.
Table-1 VOHU and VOHD characteristics shown in the datasheet (TC7SPB9306TU)
Buffer-type voltage-translation IC (level shifter)
Buffer type products output from the CMOS structure circuit and level shift. Therefore, it has a product-specific drive capability, and the output is a digital signal (Fig. 2). For specific values of drive capability, refer to the output current described in the operating range of the datasheet.
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