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LSF0102-Q1: LSF0102-Q1 VOLTAGE LEVEL SHIFTER

ASHISH JOHNSON
Prodigy 30 points
Part Number: LSF0102-Q1
Other Parts Discussed in Thread: TXU0202

I have a doubt while switching EN of ISOLATOR will fail the device VREFA and VREF B supply's will be provided separately and controlled via a switching circuit. Design attachment provided 3.3V to 1.8 V level shifter

  • 0
    TI__Mastermind 25140 points

    Hi Ashish,

    Please see Using the Enable Pin with the LSF Family as using an open-drain driver shorted to VrefB through the 200K is the correct configuration.

    However, your signals seems to be for fixed direction and the TXU0202 would be a more suitable recommendation, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 30 points

    But it just a sample circuit i having 9 more level shifters which not having fixed direction so is there will be an issue while switch EN signal with the transistor circuit attached in the post (signal is PUSH PULL that's why used a switching circuit)

  • 0 in reply to Michael Ikwuyum
    Prodigy 30 points

    But it just a sample circuit i having 9 more level shifters which not having fixed direction so is there will be an issue while switch EN signal with the transistor circuit attached in the post (signal is PUSH PULL that's why used a switching circuit)

  • 0 in reply to ASHISH JOHNSON
    TI__Mastermind 20301 points

    Hey Ashish.

    While Michael is out, I will try my best to substitute and understand your question.

    Your current schematic will be problematic as Michael mentioned- the EN pin needs to be shorted to VREFB through a 200k pullup resistor. If you want to control the EN pin externally, an open-drain driver w/o a pullup resistor can be used on the EN pin so that it is only capable of driving a LOW to disable the device.

    If your signals are not truly auto-bidirectional per channel, it is recommended to use a fixed-direction/ direction controlled translator instead. Typically, GPIO signals are fixed direction, meaning each all data in each channel is only going one way permanently. If that is the case, The TXU0202 as Michael mentioned would be a more suitable device to use. 

    ASHISH JOHNSON said:
    But it just a sample circuit i having 9 more level shifters which not having fixed direction so is there will be an issue while switch EN signal with the transistor circuit attached in the post (signal is PUSH PULL that's why used a switching circuit)

    There isn't any issues with using auto-bidirectional signals with this device when the EN pin is shorted to VREFB through a 200k pullup resistor. 

    Regards,

    Jack