DS1644-120+ Maxim Integrated Products, DS1644-120+ Datasheet - Page 2

• Manufacturer Part Number: DS1644-120+
• Description: IC RAM TIMEKEEP NV 120NS 28-EDIP
• Manufacturer: Maxim Integrated Products
• Type: Clock/Calendar/NVSRAMr

Specifications of DS1644-120+

• Memory Size: 256K (32K x 8)
• Time Format: HH:MM:SS (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 28-DIP Module (600 mil), 28-EDIP
• Function: Clock/Calendar/NV Timekeeping RAM
• Rtc Memory Size: 32768 Byte
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 4.5 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: Through Hole
• Rtc Bus Interface: Parallel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PIN DESCRIPTION
DESCRIPTION
The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both
accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any
JEDEC standard 32k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and
EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real
time clock information resides in the eight uppermost RAM locations. The RTC registers contain year,
month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the
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 DS1644
also contains its own power-fail circuitry, which deselects the device when the V
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by
low V
PDIP
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
1
2
3
4
5
6
7
8
9
-
-
-
CC
PIN
as errant access and update cycles are avoided.
PowerCap
1-3,33,34
32
30
25
24
23
22
21
20
19
18
16
15
14
17
13
12
11
10
28
29
27
26
31
9
8
7
6
5
4
X1, X2,
NAME
GND
DQ0
DQ1
DQ2
DQ3
DQ4
DQ5
DQ6
DQ7
V
RST
A14
A12
A10
A11
A13
WE
V
NC
CE
OE
A7
A6
A5
A4
A3
A2
A1
A0
A9
A8
BAT
CC
Address Input
Data Input/Output
Ground
Data Input/Output
Active Low Chip-Enable Input
Address Input
Active Low Output-Enable Input
Address Input
Active-Low Write-Enable Input
Power-Supply Input
Active-Low Reset Output, Open Drain. Requires a pull-up resistor for
proper operation.
No Connection
Crystal Connection V
2 of 14
BAT
Battery Connection
FUNCTION
CC
supply is in an out-of-
DS1644/DS1644P