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Original question:

LMH1297: PSRR for Internal LDO

LMH1297: LDO Noise Sensitivity as a Function of Input Power Supply Frequency

Iain Davis1
Prodigy 245 points
Part Number: LMH1297
Other Parts Discussed in Thread: TPS62150

Hello,

In a related thread, information regarding the PSRR of the internal LDO for the LMH1297 was requested - the response received was the LDO can handle a maximum of 20mV Noise.

The chosen power supply is TPS62150, which has options to Run at 1.25MHz and 2.5MHz - is the 20mV noise requirement independent of Frequency?

....such that either 1.25MHz or 2.5MHz could be chosen?

Thank you in advance,

Iain

  • 0
    TI__Guru* 93570 points

    Hi Iain,

    Maximum supply noise is 20mVpp up to 1MHz. From 1.1MHz to 50MHz it is 10mVpp. Therefor there is noise/frequency dependency.

    To check device supply noise sensitivity, we unsoldered DC power supply coupling capacitors and then super imposed sine wave over DC supply. In reality, with DC supply coupling caps this noise gets heavily attenuated and would not get even close to 10 or 20mV noise. Therefor please follow data sheet recommended supply coupling caps and place these as close to the device as possible. I would not expect noise level to be way less than 10 or 20mV.

    Regards,, Nasser