DM8168 DEVOSC_DVDD18 SUPPLY

Shareef

Expert 1985 points

Hi,

In Netra's EVM RevG boards, Is there any specific reason as to why 1.8V supply for DEVOSC_DVDD18 pin is genrated locally from 3.3V using an LDO instead of using the common 1.8V EVM supply?

Regards,

Khader Shareef

over 14 years ago

0 Steve Clynes over 14 years ago

TI__Mastermind 43875 points

The common 1.8V is generated from a switching regulator which will have a high frequency noise component.Any core/IO switching will also introduce a noise component on this supply.

Using an LDO significantly reduces the amount of noise on the supply, and a low noise supply is needed for all analog modules, of which the oscillator belongs.

BR,

Steve

0 Shareef over 14 years ago in reply to Steve Clynes

Expert 1985 points

Hi Steve,

Thanks for your response. That asnwers my question, since I was planning to use an EMI suppression filter in the oscillator supply path to reduce the switching noise from affecting the analog sections.

Regards,

Khader Shareef

0 Steve Clynes over 14 years ago in reply to Shareef

TI__Mastermind 43875 points

If you pay careful attention to supply filtering then you should be OK.

I would suggest an RLC filter rather than just an EMI filter though.

BR,

Steve

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DM8168 DEVOSC_DVDD18 SUPPLY