USB Flash and SD Cards: Controller, NAND and Chip-off
On USB sticks and SD cards, the controller handles wear levelling and bad-block mapping. When it dies, the NAND is usually still good.
Two failure classes
Controller failure: the device is not detected or shows wrong capacity, while NAND is intact. NAND failure: bad blocks, charge loss, or physical damage — much rarer.
Chip-off reading
Read the NAND directly, then rebuild the mapping using the controller's known algorithms or by scanning for file structures in the raw dump. Monolithic packages need pinout work.
FAQ
Can a dead USB stick be read?
Often yes if the NAND is intact; the controller is the usual casualty.
Is a 'RAW' card recoverable?
Usually — that is a metadata problem, not a media one.