using LMZ22010/LMZ23610 in inverting configuration and current sharing

Can the LMZ22010 or LMZ23610 be using in an inverting configuration with current sharing?  If so, is there any level shift that must be perofrmed on the current share line?

  • The LMZ12010; LMZ22010; LMZ13610; LMZ23610 can all be used in an inverting configuration with current sharing.

    There is no level shifting that needs to be done on the current sharing line.  In the inverting configuration all logic signals are now referenced from the negative output voltage

     

    Level shifting will need to be done on the enable pin, and synchronization pin, unless the enable and sync circuitry is referenced from the negative voltage.

    Application Note AN-2027 has details on the level shifting circuitry.  http://www.ti.com/lit/an/snva425/snva425.pdf.

    If you look at Figure 3, the PNP level shifter.  Adjust RENT so that the synchronization signal logic high does not exceed the 5.5V maximum value of the logic with reference to the negative output voltage. The same is true for the enable logic.

    For example:  The input clock is from 0V to 5V, and the device is configured for -3.3V out. Let RENB=10K.

                              RENT should be selected such that the voltage divider lowers the logic high 5V to (5V-3.3V) = 1.7V.

                              RENT = RENB * (Logic High -  Vset) / (Vset-Vout)

                              RENT = 10Kohm * (5V - 1.7V)/(1.7V-(-3.3v) = 6.6K

                              Quick re-check. Set Voltage = (10K * (5V - -3.3V) / 16.6K) - 3.3V = 1.7V

     

     

    One last thing to consider is that in this configuration the sum of the input current and the output current must be less than the current limit of the device.

    Regards,