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DS1248Y

1024K NV SRAM with Phantom Clock

DS1248Y

032697 1/12

FEATURES

• Real time clock keeps track of hundredths of seconds,

minutes, hours, days, date of the month, months, and

years

• 128K x 8 NV SRAM directly replaces volatile static

RAM or EEPROM

• Embedded lithium energy cell maintains calendar op-

eration and retains RAM data

• Watch function is transparent to RAM operation

• Month and year determine the number of days in each

month; valid up to 2100

• Standard 28–pin JEDEC pinout

• Full 10% operating range

• Operating temperature range 0°C to 70°C

• Accuracy is better than ±1 minute/month @ 25°C

• Over 10 years of data retention in the absence of

power

• Available in 120, 150 and 200 ns access time

ORDERING INFORMATION

DS1248Y–XXX

–120 120 ns access

–150 150 ns access

–200 200 ns access

PIN ASSIGNMENT

32–PIN ENCAPSULATED PACKAGE

740 MIL FLUSH

A15

A13

A11

A10

DQ7

DQ6

DQ5

DQ4

DQ3

RST

A16

A14

A12

DQ0

DQ1

DQ2

GND

PIN DESCRIPTION

–A

– Address Inputs

CE – Chip Enable

GND – Ground

–DQ

– Data In/Data Out

– Power (+5V)

WE – Write Enable

OE – Output Enable

NC – No Connect

RST

– Reset

DESCRIPTION

The DS1248Y 1024K NV SRAM with Phantom Clock is

a fully static nonvolatile RAM (organized as 128K words

by 8 bits) with a built–in real time clock. The DS1248Y

has a self–contained lithium energy source and control

circuitry which constantly monitors V

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, day, date, month, and year information. The date

at the end of the month is automatically adjusted for

months with less 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.

Summary of content (12 pages)

PAGE 1
DS1248Y DS1248Y 1024K NV SRAM with Phantom Clock FEATURES PIN ASSIGNMENT • Real time clock keeps track of hundredths of seconds, minutes, hours, days, date of the month, months, and years • 128K x 8 NV SRAM directly replaces volatile static RST 1 32 VCC A16 2 31 A15 A14 3 30 NC A12 4 29 WE A7 5 28 A13 A6 6 27 A8 A5 7 26 A9 A4 8 25 A11 A3 9 24 OE A2 10 23 A10 A1 11 22 CE A0 12 21 DQ7 DQ0 13 20 DQ6 DQ1 14 19 DQ5 DQ2 15 18 DQ4 GND 16 17 DQ3
PAGE 2
DS1248Y RAM READ MODE PHANTOM CLOCK OPERATION The DS1248Y executes a read cycle whenever WE (Write Enable) is inactive (high) and CE (Chip Enable) is active (low). The unique address specified by the 17 address inputs (A0–A16) defines which of the 128K bytes of data is to be accessed. Valid data will be available to the eight data output drivers within tACC (Access Time) after the last address input signal is stable, providing that CE and OE (Output Enable) access times and states are also satisfied.
PAGE 3
DS1248Y PHANTOM CLOCK REGISTER INFORMATION in a register could produce erroneous results. These read/write registers are defined in Figure 2. The Phantom Clock information is contained in 8 registers of 8 bits, each of which is sequentially accessed one bit at a time after the 64–bit pattern recognition sequence has been completed. When updating the Phantom Clock registers, each register must be handled in groups of 8 bits.
PAGE 4
DS1248Y PHANTOM CLOCK REGISTER DEFINITION Figure 2 REGISTER RANGE (BCD) 7 6 0 5 4 3 0.1 SEC 2 1 0.01 SEC 0 00–99 1 0 10 SEC SECONDS 00–59 2 0 10 MIN MINUTES 00–59 3 12/24 0 HOUR 01–12 00–23 4 0 0 5 0 0 6 0 0 7 10 A/P OSC HR RST 10 DATE 0 10 MONTH 10 YEAR AM–PM/12/24 MODE Bit 7 of the hours register is defined as the 12– or 24–hour mode select bit. When high, the 12–hour mode is selected. In the 12–hour mode, bit 5 is the AM/PM bit with logic high being PM.
PAGE 5
DS1248Y ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature –0.3V to +7.0V 0°C to 70°C –40°C to +70°C 260°C for 10 seconds (See Note 13) * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
PAGE 6
DS1248Y (0°C to 70°C; VCC = 5.
PAGE 7
DS1248Y PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS PARAMETER TYP (0°C to 70°C; VCC = 4.5 to 5.
PAGE 8
DS1248Y MEMORY READ CYCLE (NOTE 1) tRC ADDRESSES VIH VIL VIH VIL VIH VIL ÏÏÏÏÏÏ ÌÌÌÌÌÌÌÌ ÏÏÏÏÏÏ ÌÌÌÌÌÌÌÌ ÏÏÏÏÏÏÏ ÌÌÌÌÌÌÌÌÌ ÏÏÏÏÏÏÏ ÌÌÌÌÌÌÌÌÌ ÎÎÎ ÎÎÎ ÎÎÎ ÎÎÎ tOH tACC VIH CE VIH tCO VIL tOD VIH tOE VIH OE VIL tCOE tOD tCOE VOH VOL DOUT VOH VOL OUTPUT DATA VALID MEMORY WRITE CYCLE 1 (NOTES 2, 6, AND 7) tWC ADDRESS VIH VIL VIH VIL ÏÏÏÏÏÏÏÏÏ ÏÏÏÏÏÏÏÏÏ ÏÏÏÏ ÏÏÏÏ ÌÌÌÌÌÌÌÌ ÌÌÌÌÌÌÌÌ tAW CE WE VIL VIL tWP tWR VIH VIH tOEW tODW HIGH IMPEDANCE tDS DQ0–DQ7 VIH VIL 032697 8/12 V
PAGE 9
DS1248Y MEMORY WRITE CYCLE 2 (NOTES 2 AND 8) WE = VIH tWC ADDRESSES VIH VIL VIH VIL ÏÏÏÏ ÏÏÏÏ ÏÏÏÏÏÏÏÏÏ ÏÏÏÏÏÏÏÏÏ VIH VIL tAW CE tWR tWP VIH VIH VIL WE VIL ÌÌÌÌÌÌÌÌ ÌÌÌÌÌÌÌÌ tOEW VIL VIL tODW tCOE tDS DQ0–DQ7 VIH VIL tDH DATA IN STABLE VIH VIL RESET FOR PHANTOM CLOCK tRST RST READ CYCLE TO PHANTOM CLOCK tRC tRR tCO CE tOD tOE OE tODO tOEE tCOE Q ÌÌÌ ÌÌÌ OUTPUT DATA VALID ÌÌÌ ÌÌÌ 032697 9/12
PAGE 10
DS1248Y WRITE CYCLE TO PHANTOM CLOCK OE = VIH tWC tWR tWP WE tWR tCW CE ÌÌÌÌÌÌÌ ÌÌÌÌÌÌÌ tDH tDS tDH D DATA IN STABLE ÌÌÌÌÌÌ ÌÌÌÌÌÌ POWER–DOWN/POWER–UP CONDITION VCC 4.50V 3.
PAGE 11
DS1248Y NOTES: 1. WE is high for a read cycle. 2. OE = VIH or VIL. If OE = VIH during write cycle, the output buffers remain in a high impedance state. 3. tWP is specified as the logical AND of CE and WE. tWP is measured from the latter of CE or WE going low to the earlier of CE or WE going high. 4. tDH, tDS are measured from the earlier of CE or WE going high. 5. These parameters are sampled with a 50 pF load and are not 100% tested. 6.
PAGE 12
DS1248Y DS1248Y 1024K NV SRAM WITH PHANTOM CLOCK PKG 1 A C F D K J E H B 032697 12/12 G 32–PIN DIM MIN MAX A IN. MM 1.720 43.69 1.740 44.20 B IN. MM 0.720 18.29 0.740 18.80 C IN. MM 0.395 10.03 0.415 10.54 D IN. MM 0.090 2.29 0.120 3.05 E IN. MM 0.017 0.43 0.030 0.76 F IN. MM 0.120 3.05 0.160 4.06 G IN. MM 0.090 2.29 0.110 2.79 H IN. MM 0.590 14.99 0.630 16.00 J IN. MM 0.008 0.20 0.012 0.30 K IN. MM 0.015 0.38 0.021 0.