TPS756: Ripple Noise Introduced impacting other systems

Gavi Siddu

Part Number: TPS756

Hi Team,

We have used TPS75633KC on our custom board. The supply to the regulator is provided from a common point, to which different boards have been connected. We are observing heavy noise introduced in the output and when we isolated the custom board by providing supply from an external source, the noise in the output was absent completely.

We also used an oscilloscope and high impedance probe to measure the ripple noise and it measures around 600mv.

We followed the same application circuit mentioned on the datasheet of the regulator.

Can u help me with this?

over 4 years ago

0 JCHK over 4 years ago

TI__Mastermind 44630 points

HI Gavi,

Are you sure the regulator is stable? The TPS756 requires ESR in the output capacitor for stability.

How much and what type(s) of capacitors are being used at the output of your device?

We do have a newer (max 4A) device the TPS7A85A which has a much faster transient response. This device is much less impacted by the ESR at COUT.

I hope this gives you some ideas. If not, can you share a schematic and layout?

Regards,

0 Gavi Siddu over 4 years ago in reply to JCHK

Prodigy 240 points

Thank you for the reply.

We have used 1uf and 10uf at the input and 47uf and 0.1uf at the output. These Ceramic capacitors.

We are not sure about the stability and we havent provided any ESR as u asked for Capacitor stability.

0 Gavi Siddu over 4 years ago in reply to Gavi Siddu

Prodigy 240 points

Can you suggest any regulator whuch is pin compatible with the TPS75633KC ?

0 JCHK over 4 years ago in reply to Gavi Siddu

TI__Mastermind 44630 points

Hi Gavi,

It is the output capacitor that is required for loop stability. With 47.1uF of capacitance, a minimum ESR of 200mOhms is required. Is it possible to add ~0.5Ohms of resistance in series with the capacitance at the output?

Regards,

0 JCHK over 4 years ago in reply to Gavi Siddu

TI__Mastermind 44630 points

HI Gavi,

I don't believe so, the TPS756 is a unique device.

We are planning on a newer high current device in the future (i.e. years out) but the initial target packages will be QFN.

Sorry,

Power management

Power management forum

TPS756: Ripple Noise Introduced impacting other systems