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Datasheet difference of AD9978 and AD9978A

Question asked by aimPoint on Feb 26, 2015
Latest reply on Mar 5, 2015 by aimPoint

Hi all

 

I have questions about datasheet difference of AD9978 and AD9978A.

 

 

(1) update timing

I thought the AD9978 and the AD9978A same specification, but there is a difference in the  update timing of register contents.

What same meaning RCP and VD?

 

AD9978 Datasheet description

RCP update. Many registers are updated at the next RCP falling edge. By updating these values at the next RCP edge, the current field is not corrupted, and the new register values are applied to the next field.

The RCP update can be further delayed past the RCP falling edge by using the UPDATE[11:0] register (Address 0x57).

This delays the RCP-updated register updates to any HD line in the field

 

AD9978A Datasheet description

VD update. Many registers are updated at the next VD falling edge. By updating these values at the next VD edge, the current field is not corrupted, and the new register values are applied to the next field.

The VD update can be further delayed past the VD falling edge by using the UPDATE[11:0] register (Address 0x57).

This delays the VD-updated register updates to any HD line in the field.

 

 

(2) starup registers?

The following register group setting is different in the AD9978 and AD9978A.

. Address 0x43 bit[9]

. Address 0x4E bit[11:4]

. Address 0x4F bit[11:3]

. Address 0xE9 bit[11:0]

 

This is because of the silicon is different, and I think that each requires a different value?

Also for writing the recommended timing, it has been described in page 24 "RECOMMENDED POWER-UP SEQUENCE" of AD9978A, but there is no information on the AD9978.

 

 

(3) 0xE4 LVDS_TEST_PAT[15:4] is delete in AD9978A

The following registers are not described in the AD9978A Sp.0 data sheet.

0xE4 [11:0] LVDS_TEST_PAT[15:4] 12 MSBs of fixed test pattern for AFE outputs

 

Do fixed test pattern would be that has been removed in AD9978A?

 

 

BestRegards

aimPoint

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