Reduce noise in dc/dc supply

Sofia Teixeira

Other Parts Discussed in Thread: TPS7A33, TPS7A47

Hi i currently have an power supply in which i nedd to reduce the noise, and was wondering if the TPS7A4 and TPS7A33 would do the job.

Output power supply +15V and -15V, 65 mA, noise=50mVp-p

I need t reduce it to 100uV and 12V, -12V.

thanks

if not, can anybody recomend an power supply that uses an external battery (12,24,36 and 48)V and outputs from [12,15]V both positive and negative and noise bellow 100uVsqrt(Hz)

over 9 years ago

0 Ryan Eslinger over 9 years ago

TI__Guru 55940 points

Hi Sofia,

You can certainly use an LDO in this application! What you will be most interested in is looking at the PSRR curves in the datasheet. These curves show the rejection provided by the LDO over a number of conditions vs frequency. For example Figure 13 of TPS7A47 shows the PSRR vs frequency with a number of different output currents.

Very Respectfully,

Ryan

0 Sofia Teixeira over 9 years ago in reply to Ryan Eslinger

Prodigy 70 points

i was more interestep in noise values, since the sensor that i use requires a ultra low noise supply. I was only thinking of using these to reduce the noise of the supply that i found.

0 Ryan Eslinger over 9 years ago in reply to Sofia Teixeira

TI__Guru 55940 points

Hi Sofia,

At what frequency is your DC/DC switching at? With 50mVpp, you are likely seeing the switching noise. The PSRR of an LDO will attenuate this noise.

Very Respectfully,

Ryan

0 Sofia Teixeira over 9 years ago in reply to Ryan Eslinger

Prodigy 70 points

100 to 650 kHz which LDO do you recomend?

thanks

0 Ryan Eslinger over 9 years ago in reply to Sofia Teixeira

TI__Guru 55940 points

Hi Sofia,

You can use TPS7A4701 for the positive and TPS7A3301 for the negative rail. Both provide greater than 40dB of PSRR in your frequency range.

Very Respectfully,

Ryan

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Reduce noise in dc/dc supply