LMZ14201 tracking

Ben Campbell84

Other Parts Discussed in Thread: LMZ14201

Hello everyone,

I have an application where I would like to use the LMZ14201 to track another voltage. The 'special features' section of its product page states 'tracking'. But the datasheet does not mention how to achieve tracking. Could anyone provide some details please?

Specifically, I would like the LMZ14201 to track an external voltage, but be 2.7V higher than the external voltage. The tracking circuit will also need to limit the output voltage of the LMZ14201 to 6V (the maximum allowed output voltage). The external voltage is a charging capacitor, which can take values from 0V up to 4.2V.

Thank you for any help,

Ben

over 8 years ago

0 Anston Lobo over 8 years ago

TI__Genius 16025 points

Hi Ben,

We are looking into your question now, stay tuned.

Thanks,
Anston

0 Arief Hernadi over 8 years ago

TI__Mastermind 23815 points

Hi Ben,

You might use the SS pin, below 0.8V the FB will follow SS pin but after that the FB will stay at 0.8V.
It seem like you want the converter output to track this external voltage (adjustable output voltage) is this true?

Thx

0 Ben Campbell84 over 8 years ago in reply to Arief Hernadi

Prodigy 40 points

Hello Arief,

Thank you for that information. I can see how that feature can be used.

Yes, I would like the converter output to track an external voltage (Ve) plus 2.7V: Vout = Ve + 2.7V.

Ben

0 Arief Hernadi over 8 years ago in reply to Ben Campbell84

TI__Mastermind 23815 points

Hi Ben,

Yes in this case if you want to keep on tracking the external voltage plus 2.7V, using the soft start pin might not be feasible.
The SS pin will only adjust the rate of rise of the output voltage based on external ramp. This is what it means by tracking.

In your case, you might want to play around with feedback or inject something on the FB node such that it will track another voltage + 2.7V, as long the other voltage is lower than VIN to LMZ14201.
Here is maybe an idea to do it:
powerelectronics.com/.../601PET21.pdf

You can change the DAC into somekind of voltage source with opamp buffer.

Thanks
-Arief

0 Ben Campbell84 over 8 years ago in reply to Arief Hernadi

Prodigy 40 points

Thanks for the link and for your help Arief. I will try the approach you suggest.

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LMZ14201 tracking