Dallas Maxim DS12885, Maxim DS12887A, Maxim DS12C887A, Maxim DS12C887, Maxim DS12887 User Manual

General Description

The DS12885, DS12887, and DS12C887 real-time
clocks (RTCs) are designed to be direct replacements
for the DS1285 and DS1287. The devices provide a
real-time clock/calendar, one time-of-day alarm, three
maskable interrupts with a common interrupt output, a
programmable square wave, and 114 bytes of battery­backed static RAM (113 bytes in the DS12C887 and
DS12C887A). The DS12887 integrates a quartz crystal
and lithium energy source into a 24-pin encapsulated
DIP package. The DS12C887 adds a century byte at
address 32h. For all devices, the date at the end of the
month is automatically adjusted for months with fewer
than 31 days, including correction for leap years. The
devices also operate in either 24-hour or
12-hour format with an AM/PM indicator. A precision
temperature-compensated circuit monitors the status of
VCC. If a primary power failure is detected, the device
automatically switches to a backup supply. A lithium
coin-cell battery can be connected to the V

BAT

input
pin on the DS12885 to maintain time and date operation
when primary power is absent. The device is accessed
through a multiplexed byte-wide interface, which sup­ports both Intel and Motorola modes.

Applications

Embedded Systems

Utility Meters

Security Systems

Network Hubs, Bridges, and Routers

Features

♦ Drop-In Replacement for IBM AT Computer

Clock/Calendar

♦ RTC Counts Seconds, Minutes, Hours, Day, Date,

Month, and Year with Leap Year Compensation
Through 2099

♦ Binary or BCD Time Representation

♦ 12-Hour or 24-Hour Clock with AM and PM in

12-Hour Mode

♦ Daylight Saving Time Option

♦ Selectable Intel or Motorola Bus Timing

♦ Interfaced with Software as 128 RAM Locations

♦ 14 Bytes of Clock and Control Registers

♦ 114 Bytes of General-Purpose, Battery-Backed

RAM (113 Bytes in the DS12C887 and
DS12C887A)

♦ RAM Clear Function (DS12885, DS12887A, and

DS12C887A)

♦ Interrupt Output with Three Independently

Maskable Interrupt Flags

♦ Time-of-Day Alarm Once Per Second to Once

Per Day

♦ Periodic Rates from 122μs to 500ms

♦ End-of-Clock Update Cycle Flag

♦ Programmable Square-Wave Output

♦ Automatic Power-Fail Detect and Switch Circuitry

♦ Optional 28-Pin PLCC Surface Mount Package or

32-Pin TQFP (DS12885)

♦ Optional Encapsulated DIP (EDIP) Package with

Integrated Crystal and Battery (DS12887,
DS12887A, DS12C887, DS12C887A)

♦ Optional Industrial Temperature Range Available

♦ Underwriters Laboratory (UL) Recognized

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

______________________________________________

Maxim Integrated Products

1

Typical Operating Circuit

Rev 3; 2/07

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations and Ordering Information appear at end of data sheet.

DS83C520

CRYSTAL

AS

R/W

DS

CS

AD(0–7) SQW

IRQ

MOT

X2X1

DS12885

GND

V

CC

V

CC

RESET

RCLR

V

BAT

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

Voltage Range on VCCPin Relative to Ground .....-0.3V to +6.0V

Operating Temperature Range ...................................................

Commercial (noncondensing) .............................0°C to +70°C

Operating Temperature Range ...................................................

Industrial (noncondensing)...............................-40°C to +85°C

Storage Temperature Range .............................-55°C to +125°C

Soldering Temperature .......................................See IPC/JEDEC

J-STD-020 Specification (Note 1)

Soldering Temperature (leads, 10s) ................................+260°C

DC ELECTRICAL CHARACTERISTICS

(V

CC

= +4.5V to +5.5V, TA= over the operating range, unless otherwise noted.) (Note 2)

Supply Voltage V

V

BAT

Input Logic 1 V

Input Logic 0 V

VCC Power-Supply Current I

VCC Standby Current I

Input Leakage I

I/O Leakage I

Input Current I

Output at 2.4V I

Output at 0.4V I

Power-Fail Voltage V

VRT Trip Point VRT

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

(Note 3) 4.5 5.5 V

(Note 3) 2.5 4.0 V

(Note 3) 2.2

IH

(Note 3) -0.3 +0.8 V

IL

(Note 4) 15 mA

(Note 5) mA

IL

(Note 6) -1.0 +1.0 µA

(Note 7) -1.0 +500 µA

(Note 3) -1.0 mA

(Note 3) 4.0 mA

(Note 3) 4.0 4.25 4.5 V

PF

TRIP

Input Voltage V

CC

BAT

CC1

CCS

OL

MOT

OH

OL

V

+

CC

0.3

-1.0 +1.0 µA

1.3 V

V

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

_____________________________________________________________________ 3

DC ELECTRICAL CHARACTERISTICS

(VCC= 0V, V

BAT

= 3.0V, TA= over the operating range, unless otherwise noted.) (Note 2)

AC ELECTRICAL CHARACTERISTICS

(VCC= 4.5V to 5.5V, TA= over the operating range.) (Note 2)

V

Current (OSC On);

BAT

T

= +25°C, V

A

V

Current (Oscillator Off) I

BAT

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

BACKUP

= 3.0V

I

BAT

BATDR

(Note 8) 500 nA

(Note 8) 100 nA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Cycle Time t
Pulse Width, DS Low or R/W High PW
Pulse Width, DS High or R/W Low PW

Input Rise and Fall tR, t
R/W Hold Time t
R/W Setup Time Before DS/E t

Chip-Select Setup Time Before
DS or R/W

Chip-Select Hold Time t

Read-Data Hold Time t

Write-Data Hold Time t

Address Valid Time to AS Fall t

Address Hold Time to AS Fall t

Delay Time DS/E to AS Rise t

Pulse Width AS High PW

Delay Time, AS to DS/E Rise t

Output Data Delay Time from DS
or R/W

Data Setup Time t

Reset Pulse Width t

IRQ Release from DS t
IRQ Release from RESET t

CYC

EL

EH

RWH

RWS

t

CS

CH

DHR

DHW

ASL

AHL

ASD

ASH

ASED

t

DDR

DSW

RWL

IRDS

IRR

F

385 DC ns

150 ns

125 ns

30 ns

10 ns

50 ns

20 ns

0ns

10 80 ns

0ns

30 ns

10 ns

20 ns

60 ns

40 ns

20 120 ns

100 ns

5µs

2µs

2µs

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

4 _____________________________________________________________________

Motorola Bus Read/Write Timing

Intel Bus Write Timing

PW

ASH

PW

EL

PW

EH

t

CS

t

AHL

t

ASL

t

DSW

t

DHW

t

CH

t

ASD

t

ASD

t

CYC

CS

R/W

AS

DS

AD0–AD7

WRITE

t

ASED

AS

t

ASD

PW

ASH

t

ASED

t

CYC

DS

R/ W

CS

AD0–AD7

WRITE

AD0–AD7

READ

PW

PW

t

DDR

EH

t

RWH

t

CH

t

DSW

t

t

DHW

DHR

EL

t

RWS

t

CS

t

ASL

t

AHL

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

_____________________________________________________________________ 5

Intel Bus Read Timing

t

RWL

t

IRR

t

IRDS

DS

RESET

IRQ

IRQ

Release Delay Timing

OUTPUTS

INPUTS

HIGH-Z

DON'T CARE

VALID

RECOGNIZED

RECOGNIZED

VALID

V

CC

t

F

V

PF(MAX)

V

PF(MIN)

t

RPU

t

R

t

DR

Power-Up/Power-Down Timing

R/W

AD0–AD7

AS

DS

CS

PW

ASH

t

ASD

PW

t

ASD

EL

t

ASL

t

ASED

t

CS

t

CYC

PW

EH

t

CH

t

AHL

t

DDR

t

DHR

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

6 _____________________________________________________________________

POWER-UP/POWER-DOWN CHARACTERISTICS

(TA= -40°C to +85°C) (Note 2)

CAPACITANCE

(TA= +25°C) (Note 9)

DATA RETENTION

(TA= +25°C)

AC TEST CONDITIONS

WARNING: Negative undershoots below -0.3V while the part is in battery-backed mode may cause loss of data.

Note 1: 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 water­washing techniques is acceptable, provided that ultrasonic vibrations are not used to prevent crystal damage.

Note 2: Limits at -40°C are guaranteed by design and not production tested.
Note 3: All voltages are referenced to ground.
Note 4: All outputs are open.
Note 5: Specified with CS = DS = R/W = RESET = V

CC

; MOT, AS, AD0–AD7 = 0; V

BACKUP

open.

Note 6: Applies to the AD0 to AD7 pins, the IRQ pin, and the SQW pin when each is in a high-impedance state.
Note 7: The MOT pin has an internal 20kΩ pulldown.
Note 8: Measured with a 32.768kHz crystal attached to X1 and X2.
Note 9: Guaranteed by design. Not production tested.
Note 10: Measured with a 50pF capacitance load.

Recovery at Power-Up t

VCC Fall Time; V
V

PF(MIN)

VCC Rise Time; V
V

PF(MAX)

Expected Data Retention t

Capacitance on All Input Pins
Except X1 and X2

Capacitance on IRQ, SQW, and
DQ Pins

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RPU

PF(MIN)

to

to

C

C

t

t

DR

F

R

IN

IO

PF(MAX)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

20 200 ms

300 µs

0µs

10 years

5pF

7pF

PARAMETER TEST CONDITIONS

Input Pulse Levels 0 to 3.0V

Output Load Including Scope and Jig 50pF + 1TTL Gate

Input and Output Timing Measurement Reference Levels Input/Output: VIL maximum and VIH minimum

Input-Pulse Rise and Fall Times 5ns

DS12885/DS12887/DS12887A/DS12C887/DS12C887A

Real-Time Clock

_____________________________________________________________________

7

Typical Operating Characteristics

(VCC= +5.0V, TA= +25°C, unless otherwise noted.)

OSCILLATOR FREQUENCY

vs. V

CC

DS12885 toc02

VCC (V)

FREQUENCY (Hz)

5.3

5.04.8

32768.10

32768.20

32768.30

32768.40

32768.50

32768.60

32768.70

32768.00

4.5 5.5

I

BAT1

vs. V

BAT

vs. TEMPERATURE

DS12885 toc01

V

BAT

(V)

I

BAT

(nA)

3.82.8

3.0

3.3

3.5

200

300

250

150

2.5

4.0

VCC = 0V

+85°C

+25°C

0°C

-40°C

+70°C

+40°C

Functional Diagram

X1

X2

V

CC

GND

V

BAT

CS

R/W

DS

RESET

AD0–AD7

AS

MOT

RLCR

OSC

POWER

CONTROL

BUS

INTERFACE

DIVIDE

BY 8

DS12885

CLOCK/CALENDAR

UPDATE LOGIC

DIVIDE

BY 64

16:1 MUX

DIVIDE

BY 64

SQUARE-

WAVE

GENERATOR

IRQ

GENERATOR

REGISTERS A, B, C, D

CLOCK/CALENDAR AND

ALARM REGISTERS

BUFFERED CLOCK/

CALENDAR AND ALARM

REGISTERS

USER RAM
114 BYTES

SQW

IRQ