How can I achieve level shifting from 2.5 V to 1.8 V and vice versa?

Step-down (2.5 V→1.8 V) and step-up (1.8 V→2.5 V) voltage translation can be achieved by using a CMOS logic IC with tolerant function, single- or dual-supply level shifters (Buffer type), and dual-supply bus switches.

Fig. 1 Step-down voltage translation using an input-tolerant function
Fig. 1 Step-down voltage translation using an input-tolerant function

The following is a brief example.
For detailed selection methods, please use the following application notes.
→　Tips for Selecting Level Shifters(Voltage Translation ICs) (PDF:2.62MB)

Step-down voltage conversion:
The input-tolerant function allows level shifting from a higher voltage to a lower voltage such as from 2.5 V to 1.8 V. For example, the input-tolerant function allows 3.3 V to be applied to an input without drawing extra current even when VCC = 0 V. (Fig. 1）
For Step-down voltage translation using the input-tolerant function of a CMOS logic IC, ensure that the maximum low-level input voltage is within the VIL range. (Table-1) 

Table-1 input voltage specification (74LCX244)

Table-1 input voltage specification (74LCX244)

Fig. 2 Step-up voltage translation (1.8 V → 2.5 V)
Fig. 2 Step-up voltage translation (1.8 V → 2.5 V)

Step-up voltage translation:
Level shifting from a lower voltage to a higher voltage such as from 1.8 V to 2.5 V can be performed if the high-level output voltage (VOH) of the preceding IC satisfies the high-level input voltage (VIH) of level translation IC because VOH is almost equal to the supply voltage (VCC).
(Fig. 2)

Table-2 Example of VIH specifications of a CMOS logic IC (74LCX00FT)

Table-2 Example of VIH specifications of a CMOS logic IC (74LCX00FT)

Related Links

The following documents also contain related information.

FAQs

Product Lists

Application Notes

Product page General Purpose Logic ICs
Products
e-Learning Basics of CMOS Logic ICs
e-Learning
e-Learning Usage Considerations of CMOS Logic ICs
e-Learning

Back to FAQs of General-Purpose Logic ICs

A new window will open