HANBit
HMNR1288D(V)
Data Retention Mode
With valid V
CC
applied, the HMNR1288D(V) operates as a conventional Bytewide static RAM. Should the supply voltage
decay, the RAM will automatically deselect, write protecting itself when V
CC
falls between V
PFD
(max), V
PFD
(min) window.
All outputs become high impedance and all inputs are treated as
“
Don't care.”
Note : A power failure during a WRITE cycle may corrupt data at the current addressed location, but does not jeopardize
the rest of the RAM's content. At voltages below V
PFD
(min), the memory will be in a write protected state, provided the V
CC
fall time is not less than t
F
. The HMNR1288D(V) may respond to transient noise spikes on V
CC
that cross into the deselect
window during the time the device is sampling V
CC
. Therefore, decoupling of the power supply lines is recommended.
When V
CC
drops below V
SO
, the control circuit switches power to the internal battery, preserving data and powering the
clock. The internal energy source will maintain data in the HMNR1288D(V) for an accumulated period of at least 10 years
at room temperature. As system power rises above V
SO
, the battery is disconnected, and the power supply is switched to
external V
CC
. Write protection continues until V
CC
reaches V
PFD
(min) plus t
REC
(min). Normal RAM operation can resume
t
REC
after V
CC
exceeds V
PFD
(max).
Figure 5. Power Down/Up Mode AC Waveforms
Power Down/Up AC Characteristics
Symbol
t
F
(2)
Parameter
V
PFD
(max) to V
PFD
(min) V
CC
Fall Time
V
PFD
(min) to V
SS
V
CC
Fall Time
HMNR1288D
HMNR1288DV
Min
300
10
150
10
40
5
Max
Unit
uS
uS
uS
uS
t
FB
(3)
t
R
t
REC
(4)
V
PFD
(min) to V
PFD
(max) V
CC
Rise Time
V
PFD
(max) to RST High
V
SS
to V
PFD
(min) V
CC
Rise Time
200
uS
uS
t
RB
Note
:
1. Valid for Ambient Operating Temperature: T
A
= 0 to 70° C; V
CC
= 4.5 to 5.5V or 3.0 to 3.6V (except where noted).
2. V
PFD
(max) to V
PFD
(min) fall time of less than tF may result in deselection/write protection not occurring until 200
µ
after
s
V
CC
passes V
PFD
(min).
3. V
PFD
(min) to V
SS
fall time of less than t
FB
may cause corruption of RAM data.
URL : www.hbe.co.kr
Rev. 1.0 (April, 2002)
8
HANBit Electronics Co.,Ltd
HANBIT [ HANBIT ELECTRONICS CO.,LTD ]
