To begin the design process, determine the following:
- Input voltage range
- Use the supply voltage of the device that is driving the TXB0106 device
to determine the input voltage range. For a valid logic high the value
must exceed the VIH of the input port. For a valid logic low
the value must be less than the VIL of the input port.
- Output voltage range
- Use the supply voltage of the device that the TXB0106 device is driving
to determine the output voltage range.
- External pullop and
pulldown resistors are not recommended. If the pullup and pulldown
resistors are mandatory, the value must not be larger than 50kΩ.
- An external pulldown or pullup resistor decreases the output VOH and
VOL. Use the below equations to draft estimate the VOH
and VOL as a result of an external pulldown and pullup resistor.
Equation 1.
Equation 2.
where
- VCCx is the output port supply voltage on either VCCA or
VCCB
- RPD is the value of the external pull down resistor
- RPU is the value of the external pull up resistor
- 4.5kΩ is the counting the variation of the serial resistor 4kΩ in the I/O
line