Q
We have programmed the fuses of the AD8555 with following values:first gain stage = 0x7F
second gain stage = 0x7
Output gain offset = 0
We left the Parity fuse unprogrammed. After reading back the programmed values
we got the exact values back. However after programming the master fuse (read
back of OTHER gives us 0x3), the device appears to be 'dead' (i.e. Vout = Vss),
just as if the parity fuse would have the wrong value.
What went wrong?
A
Firstly, the AD8555 is not recommended for new designs. The alternative is theAD8556, which features internal EMI filters on the VNEG, VPOS, FILT, and VCLAMP
pins. These built-in filters on the pins limit the interference bandwidth and
provide good RFI suppression without reducing performance within the pass-band
of the instrumentation amplifier.
Regarding the AD8555 issue, if I understand correctly, the simulation works and
when you actually permanently program the device, it doesn't work.As per the
AD8556 and AD8557, the AD8555 programming should also be done near room
temperature (between 10°C and 40°C). The fuses themselves have a
temperature-dependent resistance and this dependency will affect the blow
process too.
Refer to further details at following Engineerzone query:
http://ez.analog.com/message/67426#67426
