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Original question:

LSF0108: LSF0108 questions regarding behavior at same voltage

LSF0108: Partial Power Down and IOFF device support

Dineshkumar R
Prodigy 80 points
Part Number: LSF0108
Other Parts Discussed in Thread: LSF0204

Tool/software:

Hi,

I have a few questions regarding the LSF0108 IC.

1. I planned to connect the VCCA = VCCB at same voltage level. Is LSF0108 IC supports same voltage level. I didn't see anything regarding what would happen if VccA= VccB. Please provide your feedback.

2. If the low voltage power rail 1V8_power_A domain in my case is enabled first then there is a long delay before the 1V8_power_B domain rail. Is there are risk of high current flow through the MOSFET body diode and through the target ICs(SoC)  ESD TVS diodes?  Is there are chance there can be problems in this scenario? please provide your feedback.

3. LSF0108 device supports I2S communication. If yes any preventive measures requirement to take care in design. provide your feedback.

4. LSF0204 device supports IOFF and partial power down mode(attached image for reference) . Similarly, LSF0108 supports the same features. Please confirm.

  • 0
    TI__Mastermind 40766 points

    Hi Dineshkumar,

    1. This is considered a switch configuration mode where VREFA= VREFB. It is possible to configure the device to work in this manner, see example setup below: 

    2. This will depend on how the EN pin is configured. If VREFA is up and EN is still driven low through external GPIO, then the device will still be in HIGH-Z state and the leakage current will be a minimum. 

    3. The device has open drain outputs, and the sizing of the external pullups should be chosen to be appropriate per your I2S speeds and acceptable VOL levels. 

    4. LSF0108 can be placed in IOFF mode if VREFB is driven low (assuming that it follows the proper biasing setup with VREFB and EN shorted together and pulled up to your VCCB voltage). If VREFA is low and VREFB node is still supplied a voltage, IOFF would not be supported.

    Regards,

    Jack