HT27C512 Просмотр технического описания (PDF) - Holtek Semiconductor
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HT27C512 Datasheet PDF : 10 Pages
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HT27C512
stable for at least tACC-tOE.
Standby mode
The HT27C512 has CMOS standby mode which
reduces the maximum VCC current to 10µA. It
is placed in CMOS standby when CE is at
VCC±0.3V. The HT27C512 also has a TTL-
standby mode which reduces the maximum
VCC current to 1.0mA. It is placed in TTL-
standby when CE is at VIH. When in standby
mode, the outputs are in a high-impedance
state, independent of the OE input.
Two-line output control function
To accommodate multiple memory connections,
a two-line control function is provided to allow
for:
• Low memory power consumption
• Assurance that output bus contention will not
occur.
It is recommended that CE be decoded and used
as the primary device-selection function, while
OE be made a common connection to all devices
in the array and connected to the READ line
from the system control bus. This assures that
all deselected memory devices are in their low-
power standby mode and that the output pins
are only active when data is desired from a
particular memory device.
System considerations
During the switch between active and standby
conditions, transient current peaks are pro-
duced on the rising and falling edges of Chip
Enable. The magnitude of these transient cur-
rent peaks is dependent on the output capaci-
tance loading of the device. At a minimum, a
0.1µF ceramic capacitor (high frequency, low
inherent inductance) should be used on each
device between VCC and VPP to minimize tran-
sient effects. In addition, to overcome the volt-
age drop caused by the inductive effects of the
printed circuit board traces on EPROM arrays,
a 4.7µF bulk electrolytic capacitor should be
used between VCC and VPP for each eight de-
vices. The location of the capacitor should be
close to where the power supply is connected to
the array.
Operation mode truth table
All the operation modes are shown in the table following.
Mode
CE
OE/VPP
A0
A9
Output
Read
Output Disable
Standby (TTL)
Standby (CMOS)
Program
Program Verify
Product Inhibit
Manufacturer Code (3)
Device Type Code (3)
VIL
VIL
VIH
VCC± 0.3V
VIL
VIL
VIH
VIL
VIL
VIL
X (2)
X
VIH
X
X
X
X
X
X
X
X
VPP
X
X
VIL
X
X
VPP
X
X
VIL
VIL VH (1)
VIL
VIH VH (1)
Dout
High Z
High Z
High Z
DIN
DOUT
High Z
1C
83
Notes: (1) VH = 12.0V ± 0.5V
(2) X=Either VIH or VIL
(3) For Manufacturer Code and Device Code, A1=VIH, When A1=VIL, both codes will read 7F
7
6th May ’99
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