AM5728: VTT termination circuit

shigehiro tsuda

Part Number: AM5728
Other Parts Discussed in Thread: TPS51200

Hi,

Please tell me why the VDDS_DDR and the capacitor(0.22uF) are connected in the VTT termination circuit of DDR3 of AM5728EVM.
Should this circuit be better?

Best Regards,
Shigehiro Tsuda

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Hi,

These are decoupling capacitors. The Vtt regulator both sources and sinks current, that's why it's preferred to decouple both to GND and to VDD_DDR. If you look at the TPS51200, you will see that there is also decoupling to GND on Vtt.

0 shigehiro tsuda over 6 years ago in reply to Biser Gatchev-XID

Mastermind 9490 points

Hi Biser,

Thank you for quick reply.
I understood that these are decoupling capacitors.
Is it correct with the understanding of the purpose of noise removal?

Best Regards,
Shigehiro Tsuda

0 Biser Gatchev-XID over 6 years ago in reply to shigehiro tsuda

TI__Guru**** 393215 points

Noise removal, voltage ripples, etc... The purpose of decoupling is to help handle current surges during voltage transitions.

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AM5728: VTT termination circuit