bq2204A
X4 SRAM Nonvolatile Controller Unit
General Description Features Г¤ Power monitoring and switching for 3-volt battery-backup applications Г¤ Write-protect control
Г¤ 2-input decoder for control of up
to 4 banks of SRAM
Г¤ 3-volt primary cell inputs
Г¤ Le t han 10ns chip-e nable
propagation delay
Г¤ 5% or 10% supply operation The CMOS bq2204A SRAM Nonvolatile Controller Unit provides all
necessary functions for converting
up to four banks of standard CMOS
SRAM into nonvolatile read/write
memory.
A precision comparator monitors the 5V
VCC input for an out-of-tolerance condition. When out-of-tolerance is detected,
the four conditioned chip-enable outputs
are forced inactive to write-protect up to
four banks of SRAM. Pin Connections During a power failure, the external
SRAMs are switched from the VCC
supply to one of two 3V backup supplies. On a subsequent power-up, the
SRAMs are write-protected until a
power-valid condition exists.
During power-valid operation, a …
