Fast voltage translation from 3.3v to 5.7v

Question

I need to translate a 3.3v signal to 5.7v with transition of around 60ns or less. Voltage translators such as the TXS0101 usually specify the logic high level for the input as VDD x ~0.65 (= 3.7v in my case), and their upper level is usually 5.5v. I have tried with a P and N MOSFET (see diagram below) but the P MOSFET is not saturated because 3.3v - 5.7v = -2.4v which is insufficient. Adding a resistor between 5.7v and the P MOSFET source fixes the saturation but the switching time becomes too long.

Is there in fact an IC which can do what I want? I've looked around but can't find one.

One other consideration is that a voltage drop at the output (to around 4.7v) is acceptable, but doing that without burning quite a lot of watts seems to be tricky. I tried using a 4.7v zener to drop the P input to 4.7v but it wastes a lot of current.

Update with 2nd attempt here. It's not quite as quick as I'd like but think it can work. Thanks for the input, the baker clamp was new to me, works like a charm.

2nd attempt: Fall time: Rise time:

^{simulate this circuit – Schematic created using CircuitLab}

[edit] relaxed timing requirement to 40ns

[edit] relaxed timing requirement to 60ns

[edit] added 2nd attempt

Answer 1

If your capacitance loading is light (as in the 15pF load shown below) and your power budget generous, you can just use a single transistor inverter. eg.

^{simulate this circuit – Schematic created using CircuitLab}

Rise time should be in the 25ns range typically and fall time better (10%-90%). If you only need 50ns typical you can increase R1.

Do not use a larger than necessary MOSFET for M1 or the drain source capacitance and Miller capacitance (assuming some source resistance) will kill your speed.

Answer 2

This IC is quite a bit overkill, but it would do the job.

I am sure there are single-channel level shifters/translators. The issue is finding them.

You could probably also use a TTL LVDS receiver in a pinch, by biasing one of the inputs and attenuating the input signal.

Answer 3

There is one way to do this with a single transistor (NMOS), I used the BSS123 (you can get it in small sot-23 packages). You could try something like this:

This bidirectional—you could send a signal from the high voltage side to the low one, too. But say, you want to push a 0 from the DL (low side) line to the DH (high side) line, the NMOS will turn on bring the 0V level to the drain. If you leave DL floating or apply 3.3V, the NMOS will be off and DH will be high due the 10k pullup \$R_2\$.

As far as the speed, well, I did a quick test in LTSpice and found that a 0V signal propagates through (from DL to DH) at a reasonably high speed (~5ns). Of course, in practice this will depend on the input impedance of whatever you attach to the DH side.

The green plot shows a 0V signal going from the DL to the DH side (blue).

You can find readily available versions of this circuit on DigiKey for example check this out

Hope this helps.