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PLL or IMO? | Cypress Semiconductor

PLL or IMO?

Summary: 5 Replies, Latest post by danaaknight on 05 Oct 2015 04:56 AM PDT
Verified Answers: 3
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rahulram's picture
Cypress Employee
115 posts

 Hi folks,

which is better and why? A 3Mhz from PLL or 3Mhz  from IMO?

hli
user_78878863's picture
User
2759 posts

The PLL cannot generate a frequency on its own. So the question to this answer might be 'only the IMO can be used as generator'.

The PLL might introduce a small jitter to the generated clock, but I doubt it will be noticeable for normal uses.

TDBConsulting_1416776's picture
User
51 posts

For those interested, IMO stands for Internal Main Oscillator.

 

user_14586677's picture
User
7648 posts

This might assist -

 

http://www.cypress.com/documentation/application-notes/an60631-psoc-3-and-psoc-5lp-clocking-resources    AN60631 - PSoC® 3 and PSoC 5LP Clocking Resources

 

Regards, Dana.

pvkv's picture
Cypress Employee
82 posts

Hi,

Note that PLL can output only above > 24 MHz. 

As Dana pointed out, AN60631  describes all clock sources. IMO provides only few frequencies, they are 3 MHz, 6 MHz, 12 MHz, 24 MHz, 48 MHz, 62 MHz and 74 MHz. While PLL can generated ratio multile of it's souce clock. PLL can provide you clock between 24 MHz to 80 MHz. 

You can also note below statement from AN60631.

"The PLL introduces no frequency inaccuracy, and consumes less power at a given output frequency than the IMO. Thus, when a clock is desired within the operational range of the PLL, it is recommended that the IMO be run at the minimum speed of 3 MHz, and the PLL be used to generate the desired output frequency. The resulting PLL output clock will be within the accuracy specification percentages of the input clock"

user_14586677's picture
User
7648 posts

A summary of PSOC III clocking, attached.

 

Regards, Dana.

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