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TPS53355: What is the sensitivity of this supply to variations on VIN?

Marc Sanfacon
Prodigy 10 points
Part Number: TPS53355
Other Parts Discussed in Thread: TINA-TI

In section 9 Power Supply Recommendations, the datasheet states "This input supply must be well regulated".

What is your definition of "well regulated"?  If I have a VIN = 12V nominal, how much variation am I allowed on VIN?  Note, the design is for VOUT=1.5V nominal.

If there is an instantaneous drop on the 12V on VIN, is there a risk that VOUT might fall out of regulation?  If so, what might this look like?

Thanks,

Marc

  • 0
    TI__Guru**** 191445 points
    For some reason I did not get a notification of this post. It happens sometimes as it is an "automated system".

    Generally, these devices are ment to be powered from other similar dc/dc converters with well regulated outputs. If the input supply has large amounts of low frequency ac ripple, such as you might see on an unregulated wall wart for example, you may see some ripple components on the output at that frequency.

    For very slowly changing Vin, the change to Vout, is considered line regulation. See figure 11 in the TPS53355 datasheet.

    A sudden change or drop in input voltage would be considered a line transient. We have several examples of load transient response, but I do not see any date for line transients. It would be reasonable to expect a change in output voltage in the case of a line transient. It may or may not drop out of regulation temporarily. It would depend a lot on the external components and the amplitude and slew rate of the line transient. Your best bet would be to test it out on a prototype. Alternately, you could simulate it using Pspice or TINA-TI models available here:

    www.ti.com/.../toolssoftware