HANBit
HMNR1288D(V)
Data Retention Mode
With valid VCC 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 VCC falls between VPFD (max), VPFD (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 VPFD (min), the memory will be in a write protected state, provided the VCC
fall time is not less than tF. The HMNR1288D(V) may respond to transient noise spikes on VCC that cross into the deselect
window during the time the device is sampling VCC. Therefore, decoupling of the power supply lines is recommended.
When VCC drops below VSO, 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 VSO, the battery is disconnected, and the power supply is switched to
external VCC . Write protection continues until VCC reaches VPFD (min) plus tREC (min). Normal RAM operation can resume
tREC after VCC exceeds VPFD (max).
Figure 5. Power Down/Up Mode AC Waveforms
Power Down/Up AC Characteristics
Symbol
Parameter
Min
300
10
Max
Unit
uS
uS
uS
uS
uS
uS
(2)
tF
VPFD (max) to VPFD (min) VCC Fall Time
HMNR1288D
HMNR1288DV
VPFD (min) to VPFD (max) VCC Rise Time
(3)
tFB
VPFD (min) to VSS VCC Fall Time
150
10
tR
(4)
tREC
VPFD (max) to RST High
40
200
tRB
VSS to VPFD (min) VCC Rise Time
5
Note :
1. Valid for Ambient Operating Temperature: TA = 0 to 70°C; VCC = 4.5 to 5.5V or 3.0 to 3.6V (except where noted).
2. VPFD (max) to VPFD (min) fall time of less than tF may result in deselection/write protection not occurring until 200µs after
VCC passes VPFD (min).
3. VPFD (min) to VSS fall time of less than tFB 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 ]
