Owner manual

W27E040
Publication Release Date: May 1997
- 3 - Revision A1
Standby Mode
The standby mode significantly reduces VCC current. This mode is entered when
CE
= VIH, VPP = 5V,
and VCC = 5V. 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 W27E040 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 X X 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 X X X VCP VPP High Z
Erase VIL VIH VIL VPE VCE VPE DIH
Erase Verify VIH VIL X X VCE VPE DOUT
Erase Inhibit VIH X X X VCE VPE High Z
Product Identifier-manufacturer VIL VIL VIL VHH VCC VCC DA (Hex)
Product Identifier-device VIL VIL VIH VHH VCC VCC 86 (Hex)