X20C17 Datasheet, PDF (8/11 Pages) Xicor Inc. – High Speed AUTOSTORE™ NOVRAM

X20C17
AUTOSTORE Feature
The AUTOSTORE feature automatically saves the con-
tents of the X20C17’s static RAM to the on-board bit-for-
bit shadow E²PROM at power-down. This circuitry in-
sures that no data is lost during accidental power-downs
or general system crashes, and is ideal for microproces-
sor caching systems, embedded software systems, and
general system back-up memory.
The X20C17 automatically initiates a nonvolatile store
cycle whenever Vcc falls below the AUTOSTORE thresh-
old voltage (V_ASTH). V_CC must remain above the
AUTOSTORE Cycle End Voltage (V_ASEND) for the dura-
tion of the store cycle (t_ASTO). The detailed timing for this
feature is illustrated in the AUTOSTORE timing dia-
gram, below. Once the AUTOSTORE cycle is initiated,
all other device functions are inhibited.
AUTOSTORE CYCLE Timing Diagram and Suggested AUTOSTORE Implementation Circuit
V _CC
5
VCC
4
AUTOSTORE CYCLE IN PROGRESS ^VASTH
VASEND
3
2 _tASTO
1
STORE TIME
TIME (ms)
2015 FHD F14
V _CC
X20C17
22µF
2015 ILL F30.4
AUTOSTORE CYCLE LIMITS
Symbol
t_ASTO ⁽⁵⁾
V_ASTH
V_ASEND ⁽⁵⁾
Parameter
AUTOSTORE Cycle Time
AUTOSTORE Threshold Voltage
AUTOSTORE Cycle End Voltage
Note: (5) t_ASTO and V_ASEND are periodically sampled and not 100% tested.
Min.
4.0
3.5
X20C17
Max.
2.5
4.3
Units
ms
V
V
2015 PGM T15
8