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PWM level converter

Nagaraju T
Prodigy 20 points
Other Parts Discussed in Thread: LM8330, LSF0102

Hi,

I have a PWM out put of 3.3V and i would like to convert it to 5V. which device i should use for this purpose ?

The 3.3V PWM is variable from 0 to 3.3 at any time. Back light power 4W Max.

Application: LCD back light control.

regards

Nagaraju

  • 0
    TI__Guru* 97046 points

    Hi Nagaraju,

    Thanks for your post.  We will need additional information to make a well informed suggestion.  

    What frequency is the PWM signal operating at?

    How much current can the input driver deliver?

    With a 4 W at 5 V, the output will require 800 mA (max) -- do you want the translator to drive that or will you be using an external drive circuit?

    Any additional info you have such as a schematic or other parts numbers in the circuit would be helpful.

  • 0 in reply to Emrys Maier
    Prodigy 120 points

    Emrys,

    I have a similar question.

    I got three PWMs coming out of LM8330, and I need to boost it up to be 12V PWM.

    LM8330 is power with a 1.8Vdc, so I assume that the PWMs is at 1.8Vdc.

    Is there some part from TI that I can use for that...?

    I'm looking at LSF0102, but the part only do 1.8V to 5V translation

    Is there a 5V to 12V translation part...?

    Thanks
    Kevin

  • 0 in reply to KEVIN NGUYEN
    TI__Guru* 97046 points
    Hi Kevin,
    Sorry for the delay in getting back to you. I have done some level translation in the range you are talking about, but I wanted to get some more information fom you before I made any suggestions.

    What frequency is the PWM signal operating at?

    How much current will the 12V signal be driving?

    I assume this is only up-translation, and is single directional (ie you don't need to translate back from 12V to 1.8V on the same line). Is that correct?
  • 0 in reply to Emrys Maier
    Prodigy 120 points
    Hi Emrys,

    PWM will be at 32 kHz, going out from 1.8V to 12V direction only.

    100mA drive current or less.

    Up translation only, from 1.8V to 12V.

    Thanks
    Kevin
  • 0 in reply to KEVIN NGUYEN
    TI__Guru* 97046 points
    I think your best bet will be to use the TPL7407 -- this is basically an open-drain MOSFET array. Each FET is fully on with a 1.5V input, and they can sink well over 100mA per channel (up to 2A for the whole chip, 500mA max each). The down side to this is that it will only drive the output when the input is high - when the input is low the output is high impedance. This is generally not a problem for motor driving or LED driving though.

    In case you are driving motors, just know that we are having a bit of trouble with the last channel on this device (OUT7) on inductive loads -- so just don't use that channel and you will be fine.