W27C512
Standby Mode
The standby mode significantly reduces V current. This mode is entered when
CC
CE
high. In standby
PP
/V .
OE
mode, all outputs are in a high impedance state, independent of
Two-line Output Control
Since EPROMs are often used in large memory arrays, the W27C512 provides two control inputs for
multiple memory connections. Two-line control provides for lowest possible memory power
dissipation and ensures that data bus contention will not occur.
System Considerations
An EPROM's power switching characteristics require careful device decoupling. System designers are
SB
CC
interested in three supply current issues: standby current levels (I ), active current levels (I ), and
CE
transient current peaks produced by the falling and rising edges of
. Transient current magnitudes
depend on the device output's capacitive and inductive loading. Two-line control and proper
decoupling capacitor selection will suppress transient voltage peaks. Each device should have a 0.1 m
CC
F ceramic capacitor connected between its V
and GND. This high frequency, low inherent-
inductance capacitor should be placed as close as possible to the device. Additionally, for every eight
m
devices, a 4.7 F electrolytic capacitor should be placed at the array's power supply connection
CC
between V and GND. The bulk capacitor will overcome voltage slumps caused by PC board trace
inductances.
TABLE OF OPERATING MODES
(VPP = 12V, VPE = 14V, VHH = 12V, VCP = 5V, VCE = 5V, X = VIH or VIL)
MODE
PINS
A0
A9
VCC
OUTPUTS
CE
OE/VPP
IL
IL
CC
OUT
D
Read
V
V
X
X
X
X
X
X
X
X
X
X
X
X
X
X
PE
V
IL
V
IH
CC
V
Output Disable
Standby (TTL)
Standby (CMOS)
Program
V
High Z
High Z
High Z
IH
CC
V
V
X
X
CC
V
CC
±
0.3V
V
IL
V
PP
CP
V
IN
D
V
IL
V
IL
V
CC
V
OUT
D
Program Verify
Program Inhibit
Erase
IH
PP
CP
V
V
V
High Z
IL
PE
IL
CE
V
IH
D
V
V
V
V
V
IL
IL
V
OUT
D
Erase Verify
X
X
X
3.75
IH
IL
PE
CE
V
Erase Inhibit
V
V
X
High Z
IL
V
IL
HH
V
CC
V
Product Identifier-manufacturer
Product Identifier-device
V
V
V
DA (Hex)
08 (Hex)
IL
IL
V
IH
V
HH
V
CC
V
Publication Release Date: November 1999
Revision A4
- 3 -
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