Doubt

Hello All,

I had a small doubt..

The amplitude of the clock frequency depends on which voltage in any DSP either 3.3V or 1.9V (i.e core voltage). and why??

Regards,

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Prathyush Kumar-

> I had a small doubt..
>
> The amplitude of the clock frequency depends on which voltage in any DSP
> either 3.3V or 1.9V (i.e core voltage). and why??

Which 54xx DSP? Some of the 54x devices have Vcc-PLL input separate from Vcc-Core,
others do not.

-Jeff Start a New Thread

Prathyush Kumar-

> I am using TMS320VC5441 DSP.

The C5441 has a separate Vcc-PLL input (VCCA pin).

> But could please clarify me why it (i.e Vcc Pll diferent from Vcc
> core) will be different in some devices.
>
> Is there any special reason for that??

PLL is an analog circuit, and -- even though it takes same voltage as Vcc-Core for
C5441 (1.6V) -- it must be kept well isolated from any variations in the main
Vcc-Core net. Even very small fluctuations in level or ripple could cause an analog
PLL circuit to destabilize (lose sync).

I know some designers back in 2000-2002 time-frame would even use separate V-reg for
Vcc-PLL input. TI's newer devices appear to be less sensitive, using 3.3V for the
V-PLL level and requiring only an EMI filter.

-Jeff
> Jeff Brower wrote:
>
> Prathyush Kumar-
>
> > I had a small doubt..
> >
> > The amplitude of the clock frequency depends on which voltage in any
> DSP
> > either 3.3V or 1.9V (i.e core voltage). and why??
>
> Which 54xx DSP? Some of the 54x devices have Vcc-PLL input separate from
> Vcc-Core,
> others do not.
>
> -Jeff
> Start a New Thread