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LMZ31710: LMZ31710

Amos Daskal
Prodigy 70 points
Part Number: LMZ31710
Other Parts Discussed in Thread: LMZ31704, , TPSM84A21

Hi,

Using the DC to DC converter LMZ31710 (or might be LMZ31704), I want to control the output voltage by inserting a digital potentiometer as Rset (between VADJ and AGND).

Using the LMZ31710 as the power supply of a Tec device. Input voltage is 12Vdc.

The application is controlling Tec device and so, the target is controilling the Tec temperature output by controlling the LMZ31710 output voltage.

My questions are:

1. Can I do it and in this way to control the output voltage between 0.6V to 5.5V ?

2. If it can be done, do I need to control the Rrt resistor as well? Can I do it with the digital potentiometer as well?

3. If it can be done, what is the setup time of each ouput voltage change? How much time it takes to change output voltage from 0.6V to 5.5V?

4.If it can be done, what is your recommendations for capacitors configuration (input and output), asuming using all the available voltage range (0.6V to 5.5V)?

Thanks in advance,

Amos Daskal

  • 0
    TI__Guru 50120 points

    Hi Amos,

    It sounds like you want to have dynamic control of the output. If you aren't aware of an available application note, attached is the link. In the app note, the TPSM84A21 is used with a DAC to demonstrate this concept. Please have a look at the app note and let me know if this answered your questions.

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Prodigy 70 points
    Hi Jimmy,
    Thanks a lot for your fast response.
    The TPSM84A21 & TPSM8422 are not good enough for my needs since I need output voltage range of 0.6V to 5V. (It is supported in the LMZ31710)
  • 0 in reply to Amos Daskal
    TI__Guru 50120 points

    Hi Amos,

    I should have linked this app note instead of the previous one. My mistake. The app note that I will link in this message uses the LMZ31710 with the LM1001 DAC. However I am not convinced that you can do 0.6V to 5V on the fly. The reason is that the slew rate of the voltage adjustment can result in the converter hitting an overcurrent limit especially if you have large output capacitance. The app note provides practical applications of output voltage control(deltaVout = 1.1V) such that Vout range is between 0.7V to 1.8V.  Because of the possibility of tripping overcurrent limit protection, it is recommended to take small steps to reach the desired output voltage(eg. 0.7V to 1.8V slew then from 1.8V to perhaps 3.0V slew etc.) 

    Regards,

    Jimmy