DS1284N - Maxim Integrated Products, Inc.

DS1284/DS1286

Watchdog Timekeepers

1 of 18 REV: 032406

GENERAL DESCRIPTION

www.maxim-ic.com

The DS1284/DS1286 watchdog timekeepers are

self-contained real-time clocks, alarms, watchdog

timers, and interval timers in a 28-pin JEDEC DIP

and encapsulated DIP package. The DS1286

contains an embedded lithium energy source and a

quartz crystal, which eliminates the need for any

external circuitry. The DS1284 requires an external

quartz crystal and a VBAT source, which could be a

lithium battery. Data contained within 64 8-bit

registers can be read or written in the same manner

as byte-wide static RAM. Data is maintained in the

watchdog timekeeper by intelligent control circuitry

that detects the status of VCC and write protects

memory when VCC is out of tolerance. The lithium

energy source can maintain data and real time for

over 10 years in the absence of VCC. Watchdog

timekeeper information includes hundredths of

seconds, seconds, minutes, hours, day, date, month,

and year. The date at the end of the month is

automatically adjusted for months with fewer than

31 days, including correction for leap year. The

DS1284/DS1286 operate in either 24-hour or 12-

hour format with an AM/PM indicator. The devices

provide alarm windows and interval timing between

0.01 seconds and 99.99 seconds. The real-time

alarm provides for preset times of up to one week.

ORDERING INFORMATION

FEATURES

 Keeps Track of Hundredths of Seconds,

Seconds, Minutes, Hours, Days, Date of the

Month, Months, and Years; Valid Leap Year

Compensation Up to 2100

 Watchdog Timer Restarts an Out-of-Control

Processor

 Alarm Function Schedules Real-Time-Related

Activities

 Embedded Lithium Energy Cell Maintains

Time, Watchdog, User RAM, and Alarm

Information

 Programmable Interrupts and Square-Wave

Outputs Maintain JEDEC Footprint

 All Registers are Individually Addressable via

the Address and Data Bus

 Accuracy is Better than ±1 Minute/Month at

+25°C (EDIP)

 Greater than 10 Years of Timekeeping in the

Absence of VCC

 50 Bytes of User NV RAM

 Underwriters Laboratory (UL) Recognized

 -40°C to +85°C Industrial Temperature Range

Option

Pin Configurations appear at end of data sheet.

PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK*

DS1284 0°C to +70°C 5.0 28 DIP (600 mils) DS1284

DS1284N -40°C to +85°C 5.0 28 DIP (600 mils) DS1284 N

DS1284Q 0°C to +70°C 5.0 28 PLCC DS1284Q

DS1284Q+ 0°C to +70°C 5.0 28 PLCC DS1284Q

DS1284Q/T&R 0°C to +70°C 5.0 28 PLCC/Tape and Reel DS1284Q

DS1284Q+T&R 0°C to +70°C 5.0 28 PLCC/Tape and Reel DS1284Q

DS1284QN -40°C to +85°C 5.0 28 PLCC DS1284QN

DS1284QN+ -40°C to +85°C 5.0 28 PLCC DS1284QN

DS1284QN/T&R -40°C to +85°C 5.0 28 PLCC/Tape and Reel DS1284QN

DS1284QN+T&R -40°C to +85°C 5.0 28 PLCC/Tape and Reel DS1284QN

DS1286 0°C to +70°C 5.0 28 EDIP (720 mils) DS1286

DS1286I -40°C to +8 5°C 5.0 28 EDIP (720 mils) DS1286 IND

DS1286I+ -40°C to +8 5°C 5.0 28 EDIP (720 mils) DS1286 IND

+ Denotes a lead(Pb)-free/RoHS-compliant package.

* A “+” anywhere on the top mark indicates a lead-free package.

DS1284/DS1286

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OPERATION—READ REGISTERS

The DS1284/DS1286 execute a read cycle whenever WE (write enable) is inactive (high) and CE (chip

enable) and OE (output enable) are active (low). The unique address specified by the six address inputs

(A0–A5) defines which of the 64 registers is to be accessed. Valid data is available to the eight data

output drivers within tACC (access time) after the last address input signal is stable, provided that CE and

OE access times are also satisfied. If OE and CE access times are not satisfied, then data access must be

measured from the latter occurring signal (CE or OE) and the limiting parameter is either tCO for CE or tOE

for OE rather than address access.

OPERATION—WRITE REGISTERS

The DS1284/DS1286 are in the write mode whenever the WE and CE signals are in the active-low state

after the address inputs are stable. The latter occurring falling edge of CE or WE determines the start of

the write cycle. The write cycle is terminated by the earlier rising edge of CE or WE. All address inputs

must be kept valid throughout the write cycle. WE must return to the high state for a minimum recovery

state (tWR) before another cycle can be initiated. Data must be valid on the data bus with sufficient data

setup (tDS) and data hold time (tDH) with respect to the earlier rising edge of CE or WE. The OE control

signal should be kept inactive (high) during write cycles to avoid bus contention. However, if the output

bus has been enabled (CE and OE active), then WE will disable the outputs in tODW from its falling edge.

DATA RETENTION

The watchdog timekeeper provides full functional capability when VCC is greater than VTP. Data is

maintained in the absence of VCC without any additional support circuitry. The DS1284/DS1286

constantly monitor VCC. Should the supply voltage decay, the watchdog timekeeper automatically write

protects itself, and all inputs to the registers become “don’t care.” Both INTA and INTB (INTB) are

open-drain outputs. The two interrupts and the internal clock continue to run regardless of the level of

VCC. However, it is important to ensure that the pullup resistors used with the interrupt pins are never

pulled up to a value greater than VCC + 0.3V. As VCC falls below the battery voltage, a power-switching

circuit turns on the lithium energy source to maintain the clock and timer data functionality. Also ensure

that during this time (battery-backup mode), the voltage present at INTA and INTB (INTB) never

exceeds the battery voltage. If the active-high mode is selected for INTB (INTB), this pin only goes high

in the presence of VCC. During power-up, when VCC rises above approximately 3.0V, the power-switching

circuit connects external VCC and disconnects the VBAT energy source. Normal operation can resume after

VCC exceeds VTP for tREC.

WATCHDOG TIMEKEEPER REGISTERS

The watchdog timekeeper has 64 8-bits-wide registers that contain all the timekeeping, alarm, watchdog,

control, and data information. The clock, calendar, alarm, and watchdog registers are memory locations

that 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 (see Figure 1). The command register bits are affected by both internal and

external functions. This register is discussed later. The 50 bytes of RAM registers can only be accessed

from the external address and data bus. Registers 0, 1, 2, 4, 6, 8, 9, and A contain time-of-day and date

information (see Figure 2). Time-of-day information is stored in binary-coded decimal (BCD). Registers

3, 5, and 7 contain the time-of-day alarm information. Time-of-day alarm information is stored in BCD.

watchdog alarm registers and information stored in these two registers is in BCD. Registers E to 3F are

user bytes and can be used to contain data at the user’s discretion.

DS1284/DS1286

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PIN DESCRIPTION

DIP EDIP PLCC NAME FUNCTION

1 1 1 INTA Active-Low Interrupt Output A. This open-drain pin requires a

pullup resistor for proper operation.

2, 3 — 2, 3 X1, X2

Connections for Standard 32.768kHz Quartz Crystal. The internal

oscillator circuitry is designed for operation with a crystal having

a specified load capacitance (CL) of 6pF. The crystal is connected

directly to the X1 and X2 pins. There is no need for external

capacitors or resistors. For more information on crystal selection

and crystal layout considerations, refer to Application Note 58:

Crystal Considerations with Dallas Real Time Clocks.

4 2, 3, 4,

21, 24,

25 4 N.C. No Connection

5–10 5–10 5–10 A5–A0 Address Inputs

11, 12,

13, 15,

16–19

11, 12,

13, 15,

16–19

11, 12,

13, 15,

16–19

DQ0, DQ1,

DQ2, DQ3,

DQ4–DQ7 Data Input/Output

14, 21 14 14, 21 GND Ground

20 20 20 CE Active-Low Chip-Enable Input

22 22 22 OE Active-Low Output-Enable Input

23 23 23 SQW

Square-Wave Output. Push-pull output. High impedance when

VCC is below VTP.

24 — 24 RCLR

Active-Low RAM Clear. Used to clear (set to logic 1) all 50

bytes of user NV RAM, but does not affect the registers

involved with time, alarm, and watchdog functions. To clear the

RAM, RCLR must be forced to an input logic 0 (-0.3V to

+0.8V) during battery-backup mode when VCC is not applied.

The RCLR function is designed to be used via human interface

(shorting to ground or by switch) and not be driven with external

buffers. This pin is internally pulled up and should be left

floating when not in use.

25 — 25 VBAT

Input for Any Standard 3V Lithium Cell or Other Energy

Source. Input voltage must be held between the minimum and

maximum limits for proper operation. The supply should be

connected directly to the VBAT pin. A diode must not be placed

in series with the battery to the VBAT pin. Furthermore, a diode is

not necessary because reverse charging current-protection

circuitry is provided internal to the device and has passed the

requirements of Underwriters Laboratories for UL listing. This

pin should be grounded but can be left floating.

26 26 26 INTB

(INTB)

Active-Low (Active-High) Interrupt Output B. When the active-

high state is selected (IBH = 1), an open-drain pullup transistor

connected to VCC sources current when the output is active.

When the active-low state is selected (IBH = 0), an open-drain

pulldown transistor connected to ground sinks current when the

output is active. If active-high output operation is selected, a

pulldown resistor is required for proper operation. When active-

low output operation is selected, a pullup resistor is required for

proper operation.

27 27 27 WE Active-Low Write-Enable Input

DS1284/DS1286

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DIP EDIP PLCC NAME FUNCTION

28 28 28 VCC

Primary Power-Supply Input. When voltage is applied within

normal limits, the device is fully accessible and data can be

written and read. When a backup supply is connected to the

device and VCC is below VTP, read and writes are inhibited.

However, the timekeeping function continues unaffected by the

lower input voltage.

Figure 1. Block Diagram

Internal RegistersInternal Counters

Internal Registers

Oscillator 

8 

40.96



40.96 PF delay



Update seconds through

years and check time of

day alarm

User RAM

50 Bytes

Command

External Registers,

clock, calendar,

time of day alarm

ddress Decode and Control

Power

Switch



Swap

pins

External

Registers

Hundredths of

Seconds

External

Registers

Watchdog Alarm

Internal Counters

Data I/O Buffers

0-A5

VCC

BAT

SQW

NTA

NTB/

(INTB)

1024Hz

TD INT

WD INT

DS1286

only

100Hz 100Hz

DS1286 only

GND

DQ0–DQ7

DS1284/DS1286

IBH

DS1284/DS1286

5 of 18

HUNDREDTHS-OF-SECONDS GENERATOR

The hundredths-of-seconds generator circuit shown in the Block Diagram (Figure 1) is a state machine

that divides the incoming frequency (4096Hz) by 41 for 24 cycles and 40 for 1 cycle. This produces a

100Hz output that is slightly off during the short term, and is exactly correct every 250ms. The divide

ratio is given by: Ratio = [41 x 24 + 40 x 1] / 25 = 40.96

Thus, the long-term average frequency output is exactly 100Hz.

Figure 2. Watchdog Timekeeper Registers

DS1284/DS1286

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TIME-OF-DAY REGISTERS

Registers 0, 1, 2, 4, 6, 8, 9, and A contain time-of-day data in BCD. Ten bits within these eight registers

are not used and always read 0 regardless of how they are written. Bits 6 and 7 in the months register (9)

are binary bits. When set to logic 0, EOSC (bit 7) enables the RTC oscillator. This bit is set to logic 1 as

shipped from Dallas Semiconductor to prevent lithium energy consumption during storage and shipment.

The user normally turns this bit on during device initialization. However, the oscillator can be turned on

and off as necessary by setting this bit to the appropriate level. Bit 6 of this same byte controls the square-

wave output (pin 23). When set to logic 0, the square-wave output pin outputs a 1024Hz square-wave

signal. When set to logic 1, the square-wave output pin is in a high-impedance state. Bit 6 of the hours

the 12-hour format, bit 5 is the AM/PM bit with logic 1 being PM. In the 24-hour mode, bit 5 is the

second 10-hour bit (20–23 hours). The time-of-day registers are updated every 0.01 seconds from the

RTC, except when the TE bit (bit 7 of register B) is set low or the clock oscillator is not running. The

preferred method of synchronizing data access to and from the watchdog timekeeper is to access the

command register by doing a write cycle to address location 0B and setting the TE (transfer enable) bit to

a logic 0. Doing so freezes the external time-of-day registers at the present recorded time, allowing access

to occur without danger of simultaneous update. When the watch registers have been read or written, a

second write cycle to location 0B, setting the TE bit to a logic 1, puts the time-of-day registers back to

being updated every 0.01 second. No time is lost in the RTC because the internal copy of the time-of-day

An alternate method of reading and writing the time-of-day registers is to ignore synchronization.

However, any single read may give erroneous data as the RTC may be in the process of updating the

external memory registers as data is being read. The internal copies of seconds through years are

incremented and time-of-day alarm is checked during the period that hundreds of seconds read 99 and are

transferred to the external register when hundredths of seconds roll from 99 to 00. A way of making sure

data is valid is to do multiple reads and compare. Writing the registers can also produce erroneous results

for the same reasons. A way of making sure that the write cycle has caused proper update is to do read

verifies and re-execute the write cycle if data is not correct. While the possibility of erroneous results

from reads and write cycles has been stated, it is worth noting that the probability of an incorrect result is

kept to a minimum due to the redundant structure of the watchdog timekeeper.

TIME-OF-DAY ALARM REGISTERS

Registers 3, 5, and 7 contain the time-of-day alarm registers. Bits 3, 4, 5, and 6 of register 7 always read 0

regardless of how they are written. Bit 7 of registers 3, 5, and 7 are mask bits (Figure 3). When all the

mask bits are logic 0, a time-of-day alarm only occurs when registers 2, 4, and 6 match the values stored

in registers 3, 5, and 7. An alarm is generated every day when bit 7 of register 7 is set to logic 1.

Similarly, an alarm is generated every hour when bit 7 of registers 7 and 5 is set to logic 1. When bit 7 of

registers 7, 5, and 3 is set to logic 1, an alarm occurs every minute when register 1 (seconds) rolls from 59

to 00.

Time-of-day alarm registers are written and read in the same format as the time-of-day registers. The

time-of-day alarm flag and interrupt is always cleared when alarm registers are read or written.

DS1284/DS1286

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WATCHDOG ALARM REGISTERS

Registers C and D contain the time for the watchdog alarm. The two registers contain a time count from

to 99.99 seconds in BCD. The value written into the watchdog alarm registers can be written or read in

any order. Any access to Registers C or D causes the watchdog alarm to reinitialize and clears the

watchdog flag bit and the watchdog interrupt output. When a new value is entered or the watchdog

registers are read, the watchdog timer starts counting down from the entered value to 0. When 0 is

reached, the watchdog interrupt output goes to the active state. The watchdog timer countdown is

interrupted and reinitialized back to the entered value every time either of the registers is accessed. In this

manner, controlled periodic accesses to the watchdog timer can prevent the watchdog alarm from ever

going to an active level. If access does not occur, the countdown alarm is repetitive. The watchdog alarm

registers always read the entered value. The actual countdown register is internal and is not readable.

Writing Registers C and D to 0 disables the watchdog alarm feature.

COMMAND REGISTER (0Bh)

Bit #: BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

Name: TE IPSW IBH PU/LVL WAM TDM WAF TDF

Note: The initial state of these bits is not defined.

Bit 7: Transfer Enable (TE). This bit when set to logic 1 allows the internal time and date counters to

update the user accessible registers. When set to logic 0, the external, user-accessible time and date

registers remain static when being read or written, while the internal counters continue to run. The

function of this bit is further described in the time-of-day regi sters section

Bit 6: Interrupt Pin Swap (IPSW). This bit directs which type of interrupt is present on interrupt pins

INTA or INTB (INTB). When set to logic 1, INTA becomes the time-of-day alarm interrupt pin and

INTB (INTB) becomes the watchdog interrupt pin. When bit 6 is set to logic 0, the interrupt functions are

reversed such that the time-of-day alarm is output on INTB (INTB) and the watchdog interrupt is output

on INTA. Caution should be exercised when dynamically setting this bit as the interrupts are reversed

even if in an active state.

Bit 5: Interrupt B Active High/Low (IBH). When bit 5 is set to logic 1, the B interrupt output sources

current when active. When bit 5 is set to logic 0, the B interrupt output sinks current when active.

Bit 4: Pulse/Level Output (PU/LVL). When set to logic 1, the pulse mode is selected and INTA sinks

cur rent for a minimu m of 3ms and then releases. Output INTB (INTB) either sinks or sources current for

a minimum of 3ms depending on the level of bit 5. The watchdog timer continues to run and WAF is

cleared at the end of the pulse. When set to a logic 0, both INTA and INTB (INTB), when active, output

an active low (INTB (INTB) active high when IBH = 1) until the interrupt is cleared.

Bit 3: Watchdog Alarm Mask (WAM). When this bit is written to logic 1, the watchdog interrupt

output is deactivated regardless of the state of WAF. When WAM is set to logic 0 and the WAF bit is set

to a 1, the watchdog interrupt output goes to the active state, which is determined by bits 1, 4, 5, and 6 of

the command register.

Bit 2: Time-of-Day Alarm Mask (TDM). When this bit is written to logic 1, the time-of-day alarm-

interrupt output is deactivated regardless of the state of TDF. When TDM is set to logic 0, the time-of-day

DS1284/DS1286

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interrupt output goes to the active state, which is determined by bits 0, 4, 5, and 6 of the command

Bit 1: Watchdog Alarm Flag (WAF). When this bit is set internally to logic 1, a watchdog alarm has

occurred. This bit is read-only and writing this register has no effect on the bit. The bit is reset when any

of the watchdog alarm registers are accessed. The WAM bit has no effect on the operation of this bit. If

pulse mode (PU/LVL = 1) is selected, the watchdog continues to run and the flag is internally written to 0

at the end of the pulse. The WAM bit has no effect on the operation of this bit.

Bit 0: Time-of-Day Alarm Flag (TDF). When this bit is set internally to a logic 1, indicates that a match

with the time-of-day alarm registers has occurred. This bit is read-only and writing this register has no

effect on the bit. The time of the alarm can be determined by reading the time-of-day alarm registers. The

bit is reset when any of the time-of-day alarm registers are read. The TDM bit has no effect on the

operation of this bit.

Figure 3. Time-of-Day Alarm Mask Bits

(03h)

MINUTES (05h)

HOURS (07h)

DAYS FUNCTION

1 1 1 Alarm once per minute

0 1 1 Alarm when minutes match

0 0 1 Alarm when hours and minutes match

0 0 0 Alarm when hours, minutes, and days match

DS1284/DS1286

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ABSOLUTE MAXIMUM RATINGS

Voltage Range on Any Pin Relative to Ground……………………………………………..-0.3V to +7.0V

Operating Temperature Range

Commercial………………………………………………………………………………..0C to +70C

Industrial………………………………………………………………………………...-40°C to +85°C

Storage Temperature Range………………………………………………………………...-40°C to +85°C

Soldering Temperature………………..……………...See IPC/JEDEC J-STD-020 Specification (Note 13)

Stresses beyond those listed as “Absolute Maxim Ratings” may cause permanent damage to the device. These are stress ratings only, any

functional operation of the device at these or any other conditions beyond the those indicated in operations section of the specifications is no

implied. Exposure to absolute maximum ratings for extended periods may affect device reliability.

RECOMMENDED DC OPERATING CONDITIONS

(TA = -40°C to +85°C or 0°C to +70°C.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Power-Supply Voltage VCC 4.5 5.0 5.5 V 10

Input Logic 1 VIH 2.2

VCC +

0.3 V 10

Input Logic 0 VIL -0.3 +0.8 V 10

VBAT Input Voltage VBAT 2.4 3.0 3.5 V 10

DC ELECTRICAL CHARACTERISTICS

(VCC = 5V 10%, TA = -40C to +85C or 0°C to +70°C.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Leakage Current IIL -1.0 +1.0

A

Output Leakage Current ILO -1.0 +1.0

A

I/O Leakage Current

CE  VIH  VCC ILIO -1.0 +1.0

A

Output Current at 2.4V IOH -1.0 mA

Output Current at 0.4V IOL 2.0 mA

Standby Current CE = 2.2V ICCS1 3.0 7.0 mA

Standby Current CE > VCC - 0.5 ICCS2 4.0 mA

Active Current ICC 15 mA

Write-Protection Voltage VTP 1.088

x VBAT 1.26 x

VBAT 1.324

x VBAT V

DC ELECTRICAL CHARACTERISTICS

(VCC = 0V, VBAT = 2.4V to 3.5V, TA = 0°C to +70°C.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Battery Current (EOSC = 0) IBAT +0.5 +0.6

A

DS1284/DS1286

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CAPACITANCE

(TA = +25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CIN 7 10 pF

Output Capacitance COUT 7 10 pF

Input/Output Capacitance CI/O 7 10 pF

AC ELECTRICAL CHARACTERISTICS

(VCC = 4.5V to 5.5V, TA = -40C to +85C or 0°C to +70°C.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Read Cycle Time tRC 150 ns 1

Address Access Time tACC 150 ns

CE Access Time tCO 150 ns

OE Access Time tOE 60 ns

OE or CE to Output Active tCOE 10 ns

Output High-Z from Deselect tOD 60 ns

Output Hold from Address Change tOH 10 ns

Write Cycle Time tWC 150 ns

Write Pulse Width tWP 140 ns 3

Address Setup Time tAW 0 ns

Write Recovery Time tWR 10 ns

Output High-Z from WE t

ODW 50 ns

Output Active from WE t

OEW 10 ns

Data Setup Time tDS 45 ns 4

Data Hold Time tDH 0 ns 4,5

INTA, INTB Pulse Width tIPW 3 ms 11,12

DS1284/DS1286

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READ CYCLE (NOTE 1)

WRITE CYCLE 1 (NOTES 2, 6, 7)

DS1284/DS1286

12 of 18

WRITE CYCLE 2 (NOTES 2, 8)

TIMING DIAGRAM: INTERRUPT

OUTPUTS PULSE MODE (NOTES 11, 12)

DS1284/DS1286

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POWER-UP/POWER-DOWN CONDITION

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

CE at VIH before Power-Down tPD 0

s

VCC Slew from 4.5V to 0V (CE at VIH) tF 350 s

VCC Slew from 0V to 4.5V (CE at VIH) tR 100 s

CE at VIH after Power-Up tREC 150 ns

POWER-DOWN/POWER-UP CONDITION

(TA = +25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Expected Data-Retention Time

(DS1286) tDR 10 years 9

WARNING: Under no circumstances are negative undershoots, of any amplitude, allowed

when device is in battery-backup mode.

DS1284/DS1286

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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. tDS or tDH are measured from the earlier of CE or WE going high.

5. tDH is measured from WE going high. If CE is used to terminate the write cycle, then tDH = 20ns.

6. If the CE low transition occurs simultaneously with or later than the WE low transition in write cycle

1, the output buffers remain in a high-impedance state during this period.

7. If the CE high transition occurs prior to or simultaneously with the WE high transition, the output

buffers remain in a high-impedance state during this period.

8. If WE is low or the WE low transition occurs prior to or simultaneously with the CE low transition,

the output buffers remain in a high-impedance state during this period.

9. Each DS1284/DS1286 is marked with a four-digit date code AABB. AA designates the year of

manufacture. BB designates the week of manufacture. The expected tDR is defined as starting at the

date of manufacture.

10. All voltages are referenced to ground.

11. Applies to both interrupt pins when the alarms are set to pulse.

12. Interrupt output occurs within 100ns on the alarm condition existing.

13. RTC modules can be successfully processed through conventional wave-soldering techniques as long

as temperature exposure to the lithium energy source contained within does not exceed +85°C.

However, post-solder cleaning with water-washing techniques is acceptable, provided that ultrasonic

vibrations are not used to prevent crystal damage.

AC TEST CONDITIONS

Output Load: 100pF + 1TTL Gate

Input Pulse Levels: 0 to 3.0V

Timing Measurement Reference Levels

Input: 1.5V

Output: 1.5V

Input Pulse Rise and Fall Times: 5ns

PACKAGE INFORMATION

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 PDIP P28+9 21-0044

28 PLCC Q28+11 21-0049

28 EDIP MDP28+1 21-0241

DS1284/DS1286

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PIN CONFIGURATIONS

DQ0

PLCC

BAT

CLR

SQW

GND

DQ7

N.C.

INTA

VCC

INTB

(

INTB

)

DQ1

DQ2

GND

DQ3

DQ4

DQ5

DQ6

4 3 2 1 28 27 26

12 13 14 15 16 17 18

DS1284

DIP

(600 mils)

DQ0

DQ1

GND

DQ2

INTB

(

INTB

)

SQW

GND

DQ7

DQ6

DQ5

DQ3

DQ4

N.C.

NTA

VBAT

CLR

DS1284

EDIP

(720 mils)

N.C.

DQ0

DQ1

GND

DQ2

VCC

NTB

(

INTB

)

N.C.

SQW

N.C.

DQ7

DQ6

DQ5

DQ3

DQ4

N.C.

NTA

DS1286

TOP VIEW

DS1284/DS1286

16 of 18

PACKAGE INFORMATION

PKG 28-PIN PLCC

DIM MIN MAX

A IN.

MM 0.300 BSC

7.62

B IN.

MM 0.442

17.68 0.462

11.73

D IN.

MM 0.480

12.2 0.500

12.7

D2 IN.

MM 0.390

9.91 0.430

10.92

E IN.

MM 0.090

2.29 0.120

3.05

E2 IN.

MM 0.390

9.91 0.430

10.92

F IN.

MM 0.015

0.38 0.020

0.518

H IN.

MM 0.100

2.54 0.020

0.518

DS1284/DS1286

17 of 18

PACKAGE INFORMATION (continued)

PKG 28-PIN DIP

DIM MIN MAX

A IN.

MM 1.445 1.470

B IN.

MM 0.530 0.550

C IN.

MM 0.140 0.160

D IN.

MM 0.600 0.625

E IN.

MM 0.015 0.040

F IN.

MM 0.120 0.145

G IN.

MM 0.090 0.110

H IN.

MM 0.625 0.675

J IN.

MM 0.008 0.012

K IN.

MM 0.015 0.022

DS1284/DS1286

18 of 18

Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.

No circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation.

PACKAGE INFORMATION (continued)

PKG 28-PIN EDIP

DIM MIN MAX

A IN.

MM 1.520

38.61 1.540

39.12

B IN.

MM 0.695

17.65 0.720

18.29

C IN.

MM 0.350

8.89 0.375

9.52`

D IN.

MM 0.100

2.54 0.130

3.30

E IN.

MM 0.015

0.38 0.030

0.76

F IN.

MM 0.110

2.79 0.140

3.56

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

0.53

NOTE: PINS 2, 3, 21, 24, AND 25 ARE MISSING BY DESIGN.