HANBIT HMNR28D-85

HANBit
HMNR28D(V)
5.0 or 3.3V, 16K bit (2 Kbit x 8) TIMEKEEPER NVSRAM
Part No. HMNR28D(V)
GENERAL DESCRIPTION
The HMNR28D(V) TIMEKEEPER SRAM is a 2Kb x 8 non-volatile static RAM and real time clock organized as 2,048
words by 8 bits. The special DIP package provides a fully integrated battery back-up memory and real time clock solution.
The HMNR28D(V) directly replaces industry standard 2Kbit x 8 SRAMs. It also provides the non-volatility of Flash without
any requirement for special WRITE timing or limitations on the number of WRITEs that can be performed.
FEATURES
■ INTEGRATED LOW POWER SRAM, REAL TIME CLOCK, POWER-FAIL CONTROL CIRCUIT, BATTERY and
CRYSTAL
■ BCD CODED YEAR, MONTH, DAY, DATE, HOURS, MINUTES, and SECONDS
■ AUTOMATIC POWER-FAIL CHIP DESELECT and WRITE PROTECTION VOLTAGES :
(VPFD = Power-fail Deselect Voltage)
– HMNR28D : VCC = 4.5 to 5.5V
4.2V ≤ VPFD ≤ 4.5V
– HMNR28DV: VCC = 3.0 to 3.6V
2.7V ≤ VPFD ≤ 3.0V
■ CONVENTIONAL SRAM OPERATION : UNLIMITED WRITE CYCLES
■ SOFTWARE CONTROLLED CLOCK CALIBRATION FOR HIGH ACCURACY APPLICATIONS
■ 10 YEARS OF DATA RETENTION and CLOCK OPERATION IN THE ABSENCE OF POWER PIN and FUNCTION
COMPATIBLE WITH INDUSTRY STANDARD 2K x 8 SRAMS
■ SELF-CONTAINED BATTERY and CRYSTAL IN DIP PACKAGE
OPTIONS
MARKING
PIN ASSIGNMENT
w Timing
70 ns
-70
85 ns
-85
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
Vss
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
Vcc
A8
A9
/WE
/OE
A10
/CE
DQ7
DQ6
DQ5
DQ4
DQ3
24-pin Encapsulated Package
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
1
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
FUNCTIONAL DESCRIPTION
The HMNR28D(V) is a full function, year 2000 compliant (Y2KC), real– time clock/calendar (RTC) and 2k x 8 non-volatile
static RAM. User access to all registers within the HMNR28D(V) is accomplished with a bytewide interface . The Realtime clock (RTC) information and control bits reside in the sixteen upper most RAM locations. The RTC registers contain
century, year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the date of
each month and leap year are made automatically. The RTC clock registers are double buffered to avoid access of
incorrect data that can occur during clock update cycles. The double buffered system also prevents time loss as the
timekeeping countdown continues unabated by access to time register data.
The HMNR28D(V) also contains its own power-fail circuitry which deselects the device when the VCC supply is in an out of
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by low VCC as
errant access and update cycles are avoided.
BLOCK DIAGRAM
16 x 8
TIMEKEEPER
REGISTER
OSCILLATOR AND
CLOCK CHAIN
32.768KHz
CRYSTAL
A0 ~ A10
POWER
2,032 x 8
SRAM ARRAY
LITHIUM
CELL
VPFD
/CE
VOLTAGE SENSE
AND
SWITCHING
CIRCURITY
/WE
/OE
Vcc
Vss
A0-A10 : Address Input
/WE : Write Enable
/CE : Chip Enable
/OE : Output Enable
Vss : Ground
VCC : Power (+5V or +3.3V)
DQ0-DQ7 : Data In / Data Out
NC : No Connection
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
DQ0 ~ DQ7
2
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Absolute Maximum Ratings
Symbol
Parameter
Value
Unit
TA
AmbientOperatingTemperature
0 to 70
°C
TSTG
Storage Temperature(Vcc Off, Oscillator Off)
-40 to 70
°C
Lead Solder Temperature for 10 seconds
260
°C
Input or Output Voltage
TSLD
(1)
VIO
VCC
Supply Voltage
-0.3 to Vcc+0.3
V
HMNR28D
4.5 to 5.5
V
HMNR28DV
3.0 to 3.6
V
IO
Output Current
20
mA
PD
Power Dissipation
1
W
Note : Permanent device damage may occur if Absolute Maximum Ratings are exceeded.
Functional operation should be restricted to the Recommended DC Operating Conditions detailed in this data sheet.
Exposure to higher than recommended voltage for extended periods of time could affect device reliability.
(1) Soldering temperature not to exceed 260° C for 10 seconds (Total thermal budget not to exceed 150° C for longer
than 30 seconds).
Caution : Negative undershoots below – 0.3V are not allowed on any pin while in the Battery Back-up mode.
Operating and AC Measurement Conditions
Parameter
HMNR28D
HMNR28DV
Unit
VCC Supply Voltage
4.5 to 5.5
3.0 to 3.6
V
Ambient Operating Temperature
0 to 70
0 to 70
°C
Load Capacitance (CL )
100
50
pS
Input Rise and Fall Times
≤ 5
≤ 5
nS
Input Pulse Voltages
0 to 3
0 to 3
V
Input and Output Timing Ref. Voltages
1.5
1.5
V
AC Measurement Load Circuit
Note : 50pF for HMNR28DV
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
3
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Capacitance
Symbol
Parameter
Max
Unit
Input Capacitance
10
pF
Input/Output Capacitance
10
pF
CIN
(3)
COUT
(1,2)
Min
Note :
1.
Effective capacitance measured with power supply at 5V (HMNR28D) or 3.3V (HMNR28DV). Sampled only, not
100% tested.
2.
At 25° C, f = 1MHz.
3.
Outputs deselected.
DC Characteristics
HMNR28D
HMNR28DV
Parameter
ILI
Input Leakage Current
0V ≤ VIN ≤ VCC
± 1
± 1
uA
Output Leakage Current
0V ≤ VOUT ≤ VCC
± 1
± 1
uA
Supply Current
Outputs open
10
mA
ILO
(2)
ICC
ICC1
ICC2
Supply Current (Standby)
TTL
Supply Current (Standby)
CMOS
Test Condition
(1)
Symbol
Min
8
3
2
mA
800
nA
100
nA
0.8
V
575
VIH
Input High Voltage
2.2
Output High Voltage
800
575
100
-0.3
VOH
Unit
/CE=VCC-0.2
Input Low Voltage
(open drain) (4)
4
Max
mA
VIL
Output Low Voltage
15
Typ
3
OFF
VOL
Min
5
Battery Current OSC
Output Low Voltage
Max
/CE=VIH
Battery Current OSC ON
IBAT
Typ
0.8
VCC
+0.3
-0.3
VCC
2.0
+0.3
V
IOL=2.1mA
0.4
0.4
V
IOL=10mA
0.4
0.4
V
IOH=-1.0mA
2.4
2.0
2.4
VOHB
VOH Battery Back-up
IOUT2=-1.0uA
3.6
V
IOUT1
VOUT Current (Active)
VOUT1 > VCC-0.3
100
70
mA
VOUT2>VBAT-0.3
100
100
uA
3.0
V
IOUT2
VPFD
VSO
VBAT
VOUT Current (Battery
Back-up)
Power-fail Deselect
4.1
Voltage
3.6
V
4.35
4.5
2.0
2.7
2.9
VPFD-
Battery Back-up
3.0
Switchover Voltage
100
V
mV
Battery Voltage
3.0
3.0
V
Note: 1. Valid for Ambient Operating Temperature: TA =0 to 70° C or 40 to 85°C ;
VCC = 4.5 to 5.5V or 3.0 to 3.6V (except where noted).
2. Outputs deselected.
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
4
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
OPERATING MODES
The 24-pin, 600mil DIP Hybrid houses a controller chip, SRAM, quartz crystal, and a long life lithium button cell in a single
package. The clock locations contain the year, month, date, day, hour, minute, and second in 24 hour BCD format.
Corrections for 28, 29 (leap year-compliant until the year 2100), 30, and 31 day months are made automatically. Byte
7F8h is the clock control register. This byte controls user access to the clock information and also stores the clock
calibration setting. The seven clock bytes (7FFh-7F9h) are not the actual clock counters, they are memory locations
consisting of READ/WRITE memory cells within the static RAM array. The HMNR28D includes a clock control circuit which
updates the clock bytes with current information once per second. The information can be accessed by the user in the
same manner as any other location in the static memory array. The HMNR28D(V) also has its own Power-Fail Detect
circuit. This control circuitry constantly monitors the supply voltage for an out of tolerance condition.
When VCC is out of tolerance, the circuit write protects the TIMEKEEPER register data and SRAM, providing data security
in the midst of unpredictable system operation. As VCC falls, the control circuitry automatically switches to the battery,
maintaining data and clock operation until valid power is restored.
Operating Modes
Mode
Deselect
WRITE
READ
READ
Deselect
Deselect
VCC
4.5V to 5.5V
or
3.0V to 3.6V
VSO to VPFD (min)
≤ VSO (1)
/CE
/OE
/WE
DQ7 – DQ0
Power
VIH
X
X
High-Z
Standby
VIL
X
VIL
DIN
Active
VIL
VIL
VIH
DOUT
Active
VIL
VIH
VIH
High
X
X
X
X
X
X
High
High
Active
CMOS
Standby
Battery Backup
Note : X = VIH or VIL; VSO = Battery Back-up Switchover Voltage.
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
5
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
READ Mode
The HMNR28D(V) is in the READ Mode whenever /WE (WRITE Enable) is high and /CE (Chip Enable) is low. The unique
address specified by the 15 Address Inputs defines which one of the 32,768 bytes of data is to be accessed. Valid data
will be available at the Data I/O pins within Address Access Time (tAVQV) after the last address input signal is stable,
providing the /CE and /OE access times are also satisfied. If the /CE and /OE access times are not met, valid data will be
available after the latter of the Chip Enable Access Times (tELQV) or Output Enable Access Time (tGLQV). The state of the
eight three-state Data I/O signals is controlled by /CE and /OE. If the outputs are activated before tAVQV, the data lines will
be driven to an indeterminate state until tAVQV. If the Address Inputs are changed while /CE and /OE remain active, output
data will remain valid for Output Data Hold Time (tAXQX) but will go indeterminate until the next Address Access.
READ Mode AC Waveforms
A0-A10
/CE
/OE
Note : /WE = High.
READ Mode AC Characteristics
HMNR28D
Symbol
Parameter
HMNR28DV
-70
Min
Unit
-85
Max
Max
tAVAV
READ Cycle Time
tAVQV
Address Valid to Output Valid
70
85
nS
tELQV
Chip Enable Low to Output Valid
70
85
nS
tGLQV
Output Enable Low to Output Valid
25
35
nS
(2)
tELQX
70
Min
85
nS
Chip Enable Low to Output Transition
5
5
nS
tGLQX
(2)
Output Enable Low to Output Transition
0
0
nS
tEHQZ
(2)
Chip Enable High to Output Hi-Z
tGHQZ
(2)
tAXQX
20
Output Enable High to Output Hi-Z
20
Address Transition to Output Transition
5
5
25
nS
25
nS
nS
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. CL = 5pF.
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
6
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
WRITE Mode
The HMNR28D(V) is in the WRITE Mode whenever /WE (WRITE Enable) and /CE (Chip Enable) are low state after the
address inputs are stable. The start of a WRITE is referenced from the latter occurring falling edge of /WE or /CE. A
WRITE is terminated by the earlier rising edge of /WE or /CE. The addresses must be held valid throughout the cycle. /CE
or /WE must return high for a minimum of tEHAX from Chip Enable or tWHAX from WRITE Enable prior to the initiation of
another READ or WRITE cycle. Data-in must be valid tDVWH prior to the end of WRITE and remain valid for tWHDX afterward.
/OE should be kept high during WRITE cycles to avoid bus contention; although, if the output bus has been activated by a
low on /CE and /OE a low on /WE will disable the outputs tWLQZ after /WE falls.
WRITE AC Waveforms, WRITE Enable Controlled
A0-A10
WRITE AC Waveforms, Chip Enable Controlled
A0-A10
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
7
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
WRITE Mode AC Characteristics
Parameter
Symbol
HMNR28D
HMNR28DV
-70
-85
(1)
Min
Max
Min
Unit
Max
tAVAV
WRITE Cycle Time
70
85
nS
tAVWL
Address Valid to WRITE Enable Low
0
0
nS
tAVEL
Address Valid to Chip Enable Low
0
0
nS
tWLWH
WRITE Enable Pulse Width
45
55
nS
tELEH
Chip Enable Low to Chip Enable High
50
60
nS
tWHAX
WRITE Enable High to Address Transition
0
0
nS
tEHAX
Chip Enable High to Address Transition
0
0
nS
tDVWH
Input Valid to WRITE Enable High
25
30
nS
tDVEH
Input Valid to Chip Enable High
25
30
nS
tWHDX
WRITE Enable High to Input Transition
0
0
nS
tEHDX
Chip Enable High to Input Transition
0
0
nS
tWLQZ
(2,3)
WRITE Enable Low to Output High-Z
20
25
nS
tAVWH
Address Valid to WRITE Enable High
55
65
nS
tAVEH
Address Valid to Chip Enable High
55
65
nS
WRITE Enable High to Output Transition
5
5
nS
tWHQX
(2,3)
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. CL = 5pF.
3. If /CE goes low simultaneously with /WE going low, the outputs remain in the high impedance state.
Data Retention Mode
With valid VCC applied, the HMNR28D(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 HMNR28D(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 HMNR28D(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).
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
8
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Power Down/Up Mode AC Waveforms
Power Down/Up AC Characteristics
Symbol
Parameter
Min
(2)
tF
VPFD (max) to VPFD (min) VCC Fall Time
300
uS
HMNR28D
10
uS
HMNR28DV
(3)
tFB
VPFD (min) to VSS VCC Fall Time
tR
tREC
Unit
150
uS
VPFD (min) to VPFD (max) VCC Rise Time
10
uS
VPFD (max) to RST High
40
VSS to VPFD (min) VCC Rise Time
5
(4)
tRB
Max
200
uS
uS
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.
Power Down/Up Trip Points DC Characteristics
Parameter
Symbol
VPFD
VSO
Power-fail Deselect Voltage
(1,2)
Min
Typ
Max
Unit
HMNR28D
4.2
4.35
4.5
V
HMNR28DV
2.7
2.9
3.0
V
Battery Back-up Switchover
HMNR28D
3.0
V
Voltage
HMNR28DV
VPFD-100mV
V
TDR(3)
Expected Data Retention Time
10
YEARS
Note: 1. All voltages referenced to VSS .
2. 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).
3. At 25° C.
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
9
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Register Map
Address
Funtion /
Data
D7
D6
7FE
0
0
7FD
0
0
7FC
0
FT
7FB
0
0
7FA
0
7F9
ST
7F8
W
R
S
7F7
0
0
0
0
0
0
0
0
7F6
0
0
0
0
0
0
0
0
7F5
0
0
0
0
0
0
0
0
7F4
0
0
0
0
0
0
0
0
7F3
0
0
0
0
0
0
0
0
7F2
0
0
0
0
0
0
0
0
BL
0
7FF
D4
D3
D2
10Years
7F1
7F0
D5
0
0
0
Year
Year
00-99
Month
01-12
Date : Day of Month
Date
01-31
0
10 Hours
Day
01-07
Hours(24 Hour Format)
Day
Hours
00-23
Minutes
Minutes
00-59
Seconds
Seconds
00-59
10 Minutes
10 Seconds
Calibration
1000 Years
0
0
0
D0
Month
10M
10 Date
D1
Range BCD Format
Control
100 Years
0
0
Century
0
00-99
Flag
Keys :
R = READ Bit
W = WRITE Bit
ST = Stop Bit
0 = Must be set to ’0’
BL = Battery Low Flag
S = Sign Bit
CLOCK OPERATIONS
The HMNR28D(V) offers 16 internal registers which contain TIMEKEEPER, and Control data. These registers are memory
locations which contain external (user accessible) and internal copies of the data. The external copies are independent of
internal functions except that they are updated periodically by the simultaneous transfer of the incremented internal copy.
TIMEKEEPER Registers store data in BCD. Control Registers store data in Binary Format.
Reading the Clock
Updates to the TIMEKEEPER registers should be halted before clock data is read to prevent reading data in transition.
The TIMEKEEPER cells in the RAM array are only data registers and not the actual clock counters, so updating the
registers can be halted without disturbing the clock itself. Updating is halted when a ’1’is written to the READ Bit, D6 in the
Control Register (7F8h). As long as a ’1’remains in that position, updating is halted. After a halt is issued, the registers
reflect the count; that is, the day, date, and time that were current at the moment the halt command was is-sued. All of the
TIMEKEEPER registers are updated simultaneously. A halt will not interrupt an update in progress. Updating occurs
approximately 1 second after the READ Bit is reset to a ’0.’
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
10
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Setting the Clock
Bit D7 of the Control Register (7F8h) is the WRITE Bit. Setting the WRITE Bit to a ’1,’like the READ Bit, halts updates to
the TIMEKEEPER reg-isters. The user can then load them with the correct day, date, and time data in 24-hour BCD
format. Resetting the WRITE Bit to a ’0’then transfers the
values of all time registers (7Fh-7F9h, 7F1h) to the actual TIMEKEEPER counters and allows normal operation to resume.
After the WRITE Bit is reset, the next clock update will occur approximately one second later.
Note: Upon power-up following a power failure, both the WRITE Bit and the READ Bit will be reset to ’0.’
Stopping and Starting the Oscillator
The oscillator may be stopped at any time. If the device is going to spend a significant amount of time on the shelf, the
oscillator can be turned off to minimize current drain on the battery. The STOP Bit is located at Bit D7 within the Seconds
Register (7F9h). Setting it to a ’1’stops the oscillator. When reset to a ’0,’the HMNR28D oscillator starts within one
second.
Note : It is not necessary to set the WRITE Bit when setting or resetting the STOP Bit (ST).
Calibrating the Clock
The HMNR28D(V) is driven by a quartz controlled oscillator with a nominal frequency of 32,768Hz. The devices are
factory calibrated at 25° C and tested for accuracy. Clock accuracy will not exceed 35 ppm (parts per million) oscillator
frequency error at 25° C, which equates to about ± 1.53 minutes per month. When the Calibration circuit is properly
employed, accuracy improves to better than +1/-2 ppm at 25° C. The oscillation rate of crystals changes with temperature.
The HMNR28D design employs periodic counter correction. The calibration circuit adds or subtracts counts from the
oscillator divider circuit at the divide by 256 stage. The number of times pulses are blanked (subtracted, negative
calibration) or split (added, positive calibration) depends upon the value loaded into the five Calibration bits found in the
Control Register.
Adding counts speeds the clock up, subtracting counts slows the clock down. The Calibration bits occupy the five lower
order bits (D4-D0) in the Control Register 7F8h. These bits can be set to represent any value between 0 and 31 in binary
form. Bit D5 is a Sign bit; '1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs within a 64
minute cycle. The first 62 minutes in the cycle may, once per minute, have one second either shortened by 128 or
lengthened by 256 oscillator cycles. If a binary '1' is loaded into the register, only the first 2 minutes in the 64 minute cycle
will be modified; if a binary 6 is loaded, the first 12 will be affected, and so on. Therefore, each calibration step has the
effect of adding 512 or subtracting 256 oscillator cycles for every 125, 829, 120 actual oscillator cycles; that is, +4.068 or 2.034 ppm of adjustment per calibration step in the calibration register. Assuming that the oscillator is running at exactly
32,768Hz, each of the 31 increments in the Calibration byte would represent +10.7 or -5.35 seconds per month which
corresponds to a total range of +5.5 or -2.75 minutes per month. One method for ascertaining how much calibration a
given HMNR28D(V) may require involves setting the clock, letting it run for a month and comparing it to a known accurate
reference and recording deviation over a fixed period of time. This allows the designer to give the end user the ability to
calibrate the clock as the environment requires, even if the final product is packaged in a nonuser serviceable enclosure.
The designer could provide a simple utility that accesses the Calibration bits.
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
11
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
Battery Low Warning
The HMNR28D(V) automatically performs battery voltage monitoring upon power-up and at factory-programmed time
intervals of approximately 24 hours. The Battery Low (BL) Bit, Bit D4 of Flags Register 7F0h, will be asserted if the battery
voltage is found to be less than approximately 2.5V. The BL Bit will remain asserted until completion of battery
replacement and subsequent battery low monitoring tests, either during the next power-up sequence or the next
scheduled 24hour interval. If a battery low is generated during a power-up sequence,
this indicates that the battery is below approximately 2.5V and may not be able to maintain
data integrity in the SRAM. Data should be considered suspect and verified as correct. A fresh battery should be installed.
If a battery low indication is generated during the 24-hour interval check, this indicates that the battery is near end of life.
However, data is not compromised
due to the fact that a nominal VCC is supplied. In order to insure data integrity during
Power Supply Decoupling and Undershoot Protection
Note: ICC transients, including those produced by output
switching, can produce voltage fluctuations, resulting in spikes
on the VCC bus. These transients can be reduced if capacitors
are used to store energy which stabilizes the VCC bus. The
energy stored in the bypass capacitors will be released as low
going spikes are generated or energy will be absorbed when
overshoots occur. A ceramic bypass capacitor value of 0.1uF
is recommended in order to provide the needed filtering. In
addition to transients that are caused by normal
SRAM operation, power cycling can generate negative
voltage spikes on VCC that drive it to values below VSS by as
much as one volt. These negative spikes can cause data
corruption in the SRAM while in battery backup mode. To
protect from these voltage spikes, ST recommends
connecting a schottky diode from VCC to VSS (cathode connected to VCC, anode to VSS). (Schottky diode 1N5817 is
recommended for through hole and MBRS120T3 is recommended for surface mount).
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
12
HANBit Electronics Co.,Ltd.
HANBit
HMNR28D(V)
PACKAGE DIMENSION
Dimension
Min
Max
A
1.470
1.500
B
0.710
0.740
C
0.365
0.375
D
0.012
-
E
0.008
0.013
F
0.590
0.630
G
0.017
0.023
H
0.090
0.110
I
0.075
0.110
J
0.120
0.150
J
A
I
H
G
B
C
D
E
F
ORDERING INFORMATION
H M N R 2 8 D V – 70 I
Operating Temperature : I = Industrial Temp. (-40~85 °C )
Blank = Commercial Temp. (0~70°C)
Speed options : 70 = 70 ns
85 = 85 ns
Operating Voltage : Blank = 5V
V = 3.3V
Dip type package
Device : 2K x 8
Nonvolatile Timekeeping SRAM
HANBit Memory Module
URL : www.hbe.co.kr
Rev. 0.0 (March, 2002)
13
HANBit Electronics Co.,Ltd.