When I apply 4.8 V (Arduino 5 V) to the B side of my level shifter TXB0108, I always get 1.2 V (which is the minimum) on the A side.

Is it possible to get something like 3.3 V or at least 1.8 V (it's the minimal required for my device)? enter image description here Back side enter image description here

  • \$\begingroup\$ Are you supplying 3.3V on the VA pin? \$\endgroup\$
    – Dave Tweed
    Feb 3 at 4:17
  • \$\begingroup\$ Are you trying to use a TXB0108 as a DC/DC converter? It isn't, it's a bidirectional logic level shifter without direction control input. \$\endgroup\$
    – greybeard
    Feb 3 at 7:18
  • \$\begingroup\$ i use 5V, @greybeard what do you mean? It's supposed to reduce the voltage right? Power via VB to VA, and signal for the reset? \$\endgroup\$
    – Unicorn
    Feb 3 at 7:44
  • 1
    \$\begingroup\$ A logic level shifter is not supposed to reduce supply voltage. The datasheet you hyperlinked shows separate supplies \$V_{CCA} \ \le V_{CCB}\ \$ supplied externally and describes shifting levels between port terminals. \$\endgroup\$
    – greybeard
    Feb 3 at 7:50
  • 1
    \$\begingroup\$ (Doesn't an Arduino supply 3.3 V in addition to 5 V?) \$\endgroup\$
    – greybeard
    Feb 3 at 7:53

1 Answer 1


Feeding 5 V into VB, it is not possible to get 3.3 V from VA:
Both VA and VB are power supply inputs.

There is no supply output:
This is a bidirectional logic level shifter without direction control input.

Converting one level voltage to another is a job for a (voltage) converter,
5 V DC to 3 V DC would be DC/DC converter, efficiency of 0.85 should be well possible.

Voltage regulators have been used for this; a "linear" one would have an efficiency below 0.6 here.

The use of a logic level shifter is to connect logic level terminals of sub-circuits with incompatible logic levels.
The supplier of the TXB0108 once published a Voltage Level Translation Guide.

  • \$\begingroup\$ Ok thanks, so not for my need. When then i will need those level shifter? And in the meantime I discover SPX3819 for voltage regulator. \$\endgroup\$
    – Unicorn
    Feb 3 at 22:42
  • \$\begingroup\$ SPX3819 looks good enough. Keep in mind that you need to get rid of the power dissipated - in a 70°C environment going from 5 V to 3.3 V, that limits current to about 99 mA even with the DFN package. \$\endgroup\$
    – greybeard
    Feb 4 at 5:11

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