W27E257 Datasheet, PDF (3/14 Pages) Winbond – 32K X 8 ELECTRICALLY ERASABLE EPROM

W27E257
Standby Mode
The standby mode significantly reduces VCC current. This mode is entered when CE = VIH. In
standby mode, all outputs are in a high impedance state, independent of OE.
Two-line Output Control
Since EPROMs are often used in large memory arrays, the W27E257 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
EPROM power switching characteristics require careful device decoupling. System designers are
interested in three supply current issues: standby current levels (ISB), active current levels (ICC), and
transient current peaks produced by the falling and rising edges of CE. 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 µ
F ceramic capacitor connected between its VCC and GND. This high frequency, low inherent-
inductance capacitor should be placed as close as possible to the device. Additionally, for every eight
devices, a 4.7 µF electrolytic capacitor should be placed at the array's power supply connection
between VCC 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, X = VIH or VIL)
MODE
PINS
CE
OE A0 A9 VCC VPP OUTPUTS
Read
VIL
VIL X
X VCC VCC DOUT
Output Disable
VIL
VIH X
X VCC VCC High Z
Standby (TTL)
VIH
XX
X VCC VCC High Z
Standby (CMOS)
VCC ±0.3V X X
X VCC VCC High Z
Program
VIL
VIH X
X VCP VPP DIN
Program Verify
VIH
VIL X
X VCP VPP DOUT
Program Inhibit
VIH
VIH X
X VCP VPP High Z
Erase
VIL
VIH VIL VPE VCC VPE DIH
Erase Verify
VIH
VIL X
X VCC VPE DOUT
Erase Inhibit
VIH
VIH X
X VCP VPP High Z
Product Identifier-manufacturer
VIL
VIL VIL VHH VCC VCC DA (Hex)
Product Identifier-device
VIL
VIL VIH VHH VCC VCC 02 (Hex)
Publication Release Date: January 1997
-3-
Revision A3