Rev 1; 4/04
RTC with Constant-Voltage Trickle Charger
General Description
The DS12R885 is a functional drop-in replacement for
the DS12885 real-time clock (RTC). The device pro-
vides an RTC/calendar, one time-of-day alarm, three
maskable interrupts with a common interrupt output, a
programmable square wave, and 114 bytes of battery-
backed static RAM. The date at the end of the month is
automatically adjusted for months with fewer than 31
days, including correction for leap years. It also oper-
ates in either 24-hour or 12-hour format with an AM/PM
indicator. A precision temperature-compensated circuit
monitors the status of V
CC
. If a primary power failure is
detected, the device automatically switches to a back-
up supply. The V
BACKUP
pin supports a rechargeable
battery or a super cap and includes an integrated,
always enabled trickle charger. The DS12R885 is
accessed through a multiplexed byte-wide interface,
which supports both Intel and Motorola modes. The
DS12CR887 and DS12R887 integrate the DS12R885
die with a crystal and battery.
Features
♦
Trickle-Charge Capability for a Rechargeable
Battery or Super Cap
♦
Selectable Intel or Motorola Bus Timing
♦
RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year with Leap-Year Compensation to
2100
♦
Interrupt Output with Three Independently
Maskable Interrupt Flags
♦
Time-of-Day Alarm is Once-per-Second to Once-
per-Day
♦
Periodic Rates from 122µs to 500ms
♦
End-of-Clock Update Cycle Flag
♦
14 Bytes of Clock and Control Registers
♦
114 Bytes of General-Purpose RAM with Clear Input
♦
Programmable Square-Wave Output
♦
Automatic Power-Fail Detect and Switch Circuitry
♦
+5.0V or +3.3V Operation
♦
Industrial Temperature Range
♦
DS12CR887 Encapsulated DIP (EDIP) Module with
Integrated Battery and Crystal
♦
DS12R887 BGA Module Surface-Mountable
Package with Integrated Crystal and Rechargeable
Battery
DS12R885/DS12CR887/DS12R887
Applications
Embedded Systems
Utility Meters
Security Systems
Network Hubs, Bridges, and Routers
Typical Operating Circuit
CRYSTAL
V
CC
Ordering Information
PART
DS12R885-5
DS12R885-33
DS12CR887-5
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
24 SO
(300 mils)
24 SO
(300 mils)
24 EDIP
(700 mils)
24 EDIP
(700 mils)
TOP MARK
DS12R885-5
DS12R885-33
DS12CR887-5
DS12CR887-33
DS12R887-5
DS12R887-33
X1
AS
R/W
DS
X2
V
CC
RESET
RCLR
DS83C520
CS
AD(0–7)
IRQ
MOT
DS12R885
SQW
V
BACKUP
±
DS12CR887-33
SUPER
CAP
DS12R887-5*
DS12R887-33*
-40°C to +85°C 48 BGA
-40°C to +85°C 48 BGA
GND
*Future
product—contact factory for availability.
Pin Configurations appear at end of data sheet.
______________________________________________
Maxim Integrated Products
1
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.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
