DS1251 Datasheet, PDF (2/22 Pages) Dallas Semiconductor – 4096k NV SRAM with Phantom Clock

DS1251/DS1251P
ORDERING INFORMATION
DS1251YP–XXXY (5V)
- IND Industrial
- 70 70ns access
blank 32-Pin DIP Module
P 34-Pin PowerCap Module board*
DS1251WP-XXXY (3.3V)
- IND Industrial
- 120 120ns access
PIN DESCRIPTION
A₀–A₁₈
- Address Inputs
CE
- Chip Enable
OE
- Output Enable
WE
V_CC
GND
DQ₀–DQ₇
NC
X1, X2
V_BAT
- Write Enable
- Power Supply Input
- Ground
- Data In/Data Out
- No Connection
- Crystal Connection
- Battery Connection
RST
- Reset
blank 32-Pin DIP Module
P 34-Pin PowerCap Module board*
*DS9034PCX (PowerCap) Required:
(Must be ordered separately.)
DESCRIPTION
The DS1251 4096k NV SRAM with Phantom Clock is a fully static nonvolatile RAM (organized as 512k
words by 8 bits) with a built-in real-time clock. The DS1251Y has a self-contained lithium energy source
and control circuitry, which constantly monitors V_CC for an out-of-tolerance condition. When such a
condition occurs, the lithium energy source is automatically switched on and write protection is
unconditionally enabled to prevent garbled data in both the memory and real-time clock.
The phantom clock provides timekeeping information including hundredths of seconds, seconds, minutes,
hours, days, dates, months, and years. The date at the end of the month is automatically adjusted for
months with fewer than 31 days, including correction for leap years. The phantom clock operates in either
24-hour or 12-hour format with an AM/PM indicator.
PACKAGES
The DS1251 is available in two packages: 32-pin DIP and 34-pin PowerCap module. The 32-pin DIP
style module integrates the crystal, lithium energy source, and silicon in one package. The 34-pin
PowerCap module board is designed with contacts for connection to a separate PowerCap (DS9034PCX)
that contains the crystal and battery. This design allows the PowerCap to be mounted on top of the
DS1251P after the completion of the surface mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery because of the high temperatures required for
solder reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module Board and
PowerCap are ordered separately and shipped in separate containers.
2 of 22