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CompactFlash, SD, MMC, USB flash storage. Anything that does not have moving parts inside.
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Which resistor at R25 on C20V-2.0-SM3257EN USB flash drive?

April 7th, 2021, 11:54

Hi there,

We received this not detected USB 2.0 flash drive for data recovery and have serious reasons to think that the resistor at location R25 could be missing.
Does anyone have this board model and could take a good quality picture of the resistor, or tell us the resistance value?

flash_drive_SM3257EN.jpg
C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0

Circuit board:
Code:
C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0 2011-02-25

Controller: Silicon Motion SM3257EN

flash_drive_with_resitor_torn_off.jpg
R25 location on C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0 board

Reasons for us to think that a resistor at R25 is missing:
  • Under the microscope, the resistor at R25 appears having been torn off: the weld is not smooth but abrupt shaped.
  • The customer told us the flash drive was intermittently working during some time when he pressed on it.
  • Another picture of the same circuit shows the presence of a resistor at R25: http://www.datasheetcafe.com/wp-content ... EN-DI1.gif
    Unfortunately it is too blurry to allow reading the resistor value (if printed on it).
  • There are no other apparent damage and replacing the USB connector does not bring anything.

On the shell, one cannot read the brand name anymore and the customer cannot remember it, but likely a popular model from Emtec or so.
shell-from-flash-drive.jpg
Plastic shell from C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0

Thank you for your kind help.

Re: Which resistor at R25 on C20V-2.0-SM3257EN USB flash dri

April 7th, 2021, 15:49

The resistor appears to be in series with the +5V supply. Typically it would be 2R2 (2.2 ohm) or 1 ohm. You could use a wire link or a fuse, but first verify that there is no short between ground and the load side of the resistor.

See pin #37.

http://www.datasheetcafe.com/sm3257-datasheet-pdf/

http://j5d2v7d7.stackpathcdn.com/wp-content/uploads/2015/10/SM3257-datasheet.gif
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