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Level Shifter or Analog Amplifier For Level Shifting

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strahd_von_zarovich

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Hi, i have a 1.8V digital output, and i want to drive 75 ohm input with that at at least 3.3V . What is the best solution ? As i researched most level shifters can't drive high currents like this. Also i need 5ns most rise and fall time.
 

Hi,

Very unusual: 3.3V into 75 Ohms (and as it seems it is single ended). What is it for?

****
Look for hig speed, low voltage SPDT analog switches (switch to GND /3V3) (like TS5A23160DGS, but take care, they are "Make-before-break")
Look for high speed low side MOSFET or IGBT drivers. (like ZXGD3001E6, I don´t know if this fits your needs. )
Or use logic driver ICs. Like SN74LVC2G07 ( = 2 x SN74LVC1G07). Two gates in parallel to drive the load.

Klaus
 

KlausST said:
Hi,

Very unusual: 3.3V into 75 Ohms (and as it seems it is single ended). What is it for?

****
Look for hig speed, low voltage SPDT analog switches (switch to GND /3V3) (like TS5A23160DGS, but take care, they are "Make-before-break")
Look for high speed low side MOSFET or IGBT drivers. (like ZXGD3001E6, I don´t know if this fits your needs. )
Or use logic driver ICs. Like SN74LVC2G07 ( = 2 x SN74LVC1G07). Two gates in parallel to drive the load.

Klaus
Click to expand...

Thanks for response Klaus,

It is for acousto optic modulator driver, and i want to control it with DAC's 1.8V outputs. I will search your suggestions thanks.
 

Hi,

Does it really need to be a push-pull output?

Klaus
 

Need to look at the rise / fall times required, whether
there is any interest in more than bang-bang levels,
and whether you have a 3.3V supply - level shifters
only work between the rails they're supplied, while
an analog amplifier provides instead a gain and output
levels not directly determined by supply (unless you
clip).
 

    V

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Adding to Klaus's suggestion of an analog mux I've used NLASB3157 in a very similar application of high speed level shifting. At the time it was the best I could come up with in terms of speed, drive strength etc and worked well.
 

    V

    Points: 2
    Helpful Answer Positive Rating
Hi,

So, i guess answer for your question is yes ?
Click to expand...

It´s half of the answer:
I assume 25mA @ 1.6V is for driving HIGH. Is this correct?

But how much current do you need to drive LOW?

Maybe a single HIGH side driver (in a simple case a PNP transistor) is sufficient.

Klaus
 

A confusing point is that you are initially asking for a digital driver but later saying it's a DAC signal. In the digital case, you can simply use multiple paralleled fast CMOS drivers.
 

KlausST said:
Hi,



It´s half of the answer:
I assume 25mA @ 1.6V is for driving HIGH. Is this correct?

But how much current do you need to drive LOW?

Maybe a single HIGH side driver (in a simple case a PNP transistor) is sufficient.

Klaus
Click to expand...

KlausST said:
Hi,

But how much current do you need to drive LOW?

Klaus
Click to expand...

Now, i understood the question. It draws current proportional to voltage at both on and off state. And ıf u don't give voltage to control input, it stays at off state so doesn't need current to drive low. So simple transistor for switching can be used ? FPGA can provide bias current for transistor, i guess.

I can use both DAC or FPGA outputs. What is paralleled CMOS drivers for? For multiple bits or something else.
 

Hi, For 5V 50 ohm drive I have had good success using MOSFET driver IC such as UCC27517. Less than 5ns res and fall times (more like 2ns). Minimum VDD is 4.5V though.

- - - Updated - - -

mwingle said:
Hi, For 5V 50 ohm drive I have had good success using MOSFET driver IC such as UCC27517. Less than 5ns res and fall times (more like 2ns). Minimum VDD is 4.5V though.
Click to expand...

I have added a scope capture of the ucc25717 vdd=5V into 50 ohms

DS2_2016124172133.png
 

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