A question regarding 1.2v and DGND pins in ADSP-21262......

Hi!

I don't whether this post can be posted here or not But i know these posts only........

I have a custom board with ADSP-21262...the board is designed from the reference schematics given by Analog devices (ADSP-21262 Ez kit lite)....

I have Problem in this board....Iam presently in the stage of soldering the Board...........Before Giving the Details of my doubt i will some details..

1. In the Board,First I have Soldered PowerSupply section which is having 1.2v regulator and 3.3v regulator and i have checked whether supply coming or not...it is OK..Next i have soldered the IC(ADSP-21262) then actually 1.2v regulator is toomuch heating....Upto my knowledge this means 1.2v and GND are somewhere shorted in the board ...this thing i conformed by checking with the multimeter ,But i can't able to find the Short....
But I have conformed that SHORT is in Processor only...Soldering of the IC is OK....We have taken care when soldering the IC.. "this is one situation"

2.This time we have taken a new board but the same board as before and we have soldered only ADSP-21262 without any other section in the board Now also there is a SHORT in 1.2v and DGND pins of the Processor (I have conformed by using the Multimeter)....IC soldering is nice and OK.....And the Board before soldering the IC also OK...and it is BBC tested OK board....
The impedence i have ckecked with the multimeter is very very less between 1.2v and DGND ....It is around 50ohm..

I don't have much IDEA regarding these things and Iam not thatmuch experienced also......
I just want any suggestion....................????????\
thank u for hearing me............ Start a New Thread

I don't think you have a short. The core impedance is going to be fairly
low, about 18 ohms if I recall correctly.
How did you create your core voltage? If from an LDO, you may have not
consider the power dissipation across the regulator. It should be fine
if you have a well designed switcher.

Al Clark
Danville Signal Processing, Inc.

m...@yahoo.co.in wrote:
>
> Hi!
>
> I don't whether this post can be posted here or not But i know these
> posts only........
>
> I have a custom board with ADSP-21262...the board is designed from the
> reference schematics given by Analog devices (ADSP-21262 Ez kit lite)....
>
> I have Problem in this board....Iam presently in the stage of
> soldering the Board...........Before Giving the Details of my doubt i
> will some details..
>
> 1. In the Board,First I have Soldered PowerSupply section which is
> having 1.2v regulator and 3.3v regulator and i have checked whether
> supply coming or not...it is OK..Next i have soldered the
> IC(ADSP-21262) then actually 1.2v regulator is toomuch heating....Upto
> my knowledge this means 1.2v and GND are somewhere shorted in the
> board ...this thing i conformed by checking with the multimeter ,But i
> can't able to find the Short....
> But I have conformed that SHORT is in Processor only...Soldering of
> the IC is OK....We have taken care when soldering the IC.. "this is
> one situation"
>
> 2.This time we have taken a new board but the same board as before and
> we have soldered only ADSP-21262 without any other section in the
> board Now also there is a SHORT in 1.2v and DGND pins of the Processor
> (I have conformed by using the Multimeter)....IC soldering is nice and
> OK.....And the Board before soldering the IC also OK...and it is BBC
> tested OK board....
> The impedence i have ckecked with the multimeter is very very less
> between 1.2v and DGND ....It is around 50ohm..
>
> I don't have much IDEA regarding these things and Iam not thatmuch
> experienced also......
> I just want any suggestion....................????????\
> thank u for hearing me............
>

> Start a New Thread

First of all thank u for u r reply........

Iam using LD1117S12TR which LDO POS 800mA 1.2V regulator

Iam giving more details:

1) 1.2V regulator is heating but it is giving 1.2V to the Circuit

2) When the Power is applied the Regulator starts heating(Anyway it is generating the 1.2V) and after some time the ADSP-21262 chip also gets heated.....
Hi!
>
>I don't whether this post can be posted here or not But i know these posts only........
>
>I have a custom board with ADSP-21262...the board is designed from the reference schematics given by Analog devices (ADSP-21262 Ez kit lite)....
>
>I have Problem in this board....Iam presently in the stage of soldering the Board...........Before Giving the Details of my doubt i will some details..
>
>1. In the Board,First I have Soldered PowerSupply section which is having 1.2v regulator and 3.3v regulator and i have checked whether supply coming or not...it is OK..Next i have soldered the IC(ADSP-21262) then actually 1.2v regulator is toomuch heating....Upto my knowledge this means 1.2v and GND are somewhere shorted in the board ...this thing i conformed by checking with the multimeter ,But i can't able to find the Short....
>But I have conformed that SHORT is in Processor only...Soldering of the IC is OK....We have taken care when soldering the IC.. "this is one situation"
>
>2.This time we have taken a new board but the same board as before and we have soldered only ADSP-21262 without any other section in the board Now also there is a SHORT in 1.2v and DGND pins of the Processor (I have conformed by using the Multimeter)....IC soldering is nice and OK.....And the Board before soldering the IC also OK...and it is BBC tested OK board....
>The impedence i have ckecked with the multimeter is very very less between 1.2v and DGND ....It is around 50ohm..
>
>I don't have much IDEA regarding these things and Iam not thatmuch experienced also......
>I just want any suggestion....................????????\
>thank u for hearing me............
>
> Start a New Thread

Hello

I'm not very exprinced too but look :

If we have a 1.2V LDO and a 3.3V power supply , voltage drop on regulator equals 3.3V - 1.2V = 2.1V

ADSP-21262 'eats' more than 200mA ( IDDIN can be 400mA ) @ 1.2V VDDINT (see the spec. note on ADI site).

Let's calculate some Power disp. on Voltage Reg.
Pht = 2.1V * 0.2A = 0.42W @ 200mA

and

Pht = 2.1V * 0.4A = 0.84W @ 400mA (almost a 1W from small Vreg )

Hi!
>
>I don't whether this post can be posted here or not But i know these posts only........
>
>I have a custom board with ADSP-21262...the board is designed from the reference schematics given by Analog devices (ADSP-21262 Ez kit lite)....
>
>I have Problem in this board....Iam presently in the stage of soldering the Board...........Before Giving the Details of my doubt i will some details..
>
>1. In the Board,First I have Soldered PowerSupply section which is having 1.2v regulator and 3.3v regulator and i have checked whether supply coming or not...it is OK..Next i have soldered the IC(ADSP-21262) then actually 1.2v regulator is toomuch heating....Upto my knowledge this means 1.2v and GND are somewhere shorted in the board ...this thing i conformed by checking with the multimeter ,But i can't able to find the Short....
>But I have conformed that SHORT is in Processor only...Soldering of the IC is OK....We have taken care when soldering the IC.. "this is one situation"
>
>2.This time we have taken a new board but the same board as before and we have soldered only ADSP-21262 without any other section in the board Now also there is a SHORT in 1.2v and DGND pins of the Processor (I have conformed by using the Multimeter)....IC soldering is nice and OK.....And the Board before soldering the IC also OK...and it is BBC tested OK board....
>The impedence i have ckecked with the multimeter is very very less between 1.2v and DGND ....It is around 50ohm..
>
>I don't have much IDEA regarding these things and Iam not thatmuch experienced also......
>I just want any suggestion....................????????\
>thank u for hearing me............
>
> Start a New Thread