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LMZ14201 Acceptable input ripple

Jeff Starkell
Intellectual 505 points
Other Parts Discussed in Thread: LMZ14201

We are using a LMZ14201  in a 24Vac (HVAC system)

The output voltage is 3.3V, and load current is 500ma

For long term reliability we would prefer to avoid electrolytic and instead use ceramic capacitors for the input filter capacitor(s).

Using ceramic capacitors, we are space limited to 50uF and this results in a fair bit of ripple on the input to the LMX14201 as shown below:

With our maximum specified input voltage of 28Vac, the min and max values are as follows:

Vin (Yellow):

  • Min = 33V
  • Max = 40V

Venable (Magenta):

  • Min = 5.0V
  • Max = 6.3V

With our minimum specified input voltage of 20Vac, the min and max values are as follows:

  • Min = 19V
  • Max = 28V

Venable (Magenta):

  • Min = 3.0V
  • Max = 4.4V

So within the specified range for both Vin and enable, do you envision any issues running this device with the 7 to 10V input ripple as shown?

  • 0
    TI__Genius 15810 points
    Hello,
    The LMZ14201 is rated up to 42V at the input. As long as you have a good layout and good bypassing you should be okay with a max input of 40V. The max voltage limitation on the EN pin is 7V, so you should be okay with that. You could potentially add more protection there in form a zener diode too if you were worried about it.

    Regards,
    Akshay