Re: [Mspgcc-users] Low noise power supply.

[bernard mondan]

The noise of a power supply is not depending only from the regulator.
You have to use some capacitor to reduce the noise of your system.
A noise level around 20 mV ppk  seems to be very hight you probably have
a component that generate that noise and you have to put a ceramic capacitor
at the power pin.


Bernard Mondan.


Claudio Grasso wrote:

    Hi all!

    I am trying to build an application that uses the ADC12 and I need
    a low noise power supply. I am using a TPS77733 regulator but it
    has a high frequency noise of about 10mV uncharged (in the
    oscilloscope one can see regular isolated pulses). When I charge
    it with an MSP430f149, noise increases up to 20 mV peak to peak
    (but now you don't see isolated pulses but a regular oscillation
    -reflecting the MSP operation for sure- ). This variation is also
    reflected in Vref and results in fluctuations in measurements of
    steady voltages. Can anybody please suggest me where to find an
    example of a low noise power supply? I've been searching in the
    application notes but I only found examples powered by batteries
    (what is not an option in my case).

    I can't understand either, why the noise in the output of the TPS
    increases so much when charged by the MSP (it drains just a few
    uA). My test circuit has all the capacitors suggested in the User
    guide.

    Any help will be greatly welcome.

    Best regards,

                            Claudio

    PS: Sorry this is quite off topic but I'm really lost L