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.
RTC with Constant-Voltage Trickle Charger
DS12R885/DS12CR887/DS12R887
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
CC
Pin Relative to Ground .....-0.3V to +6.0V
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature .......................................See IPC/JEDEC
J-STD-020A Specification
Soldering Temperature (leads, 10s) ................................+260°C
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.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage (Note 2)
V
BACKUP
Input Voltage
(DS12R885 Only)
Input Logic 1
Input Logic 0
V
CC
Power-Supply Current
(Note 3)
V
CC
Standby Current (Note 4)
Input Leakage
I/O Leakage
Input Current
Output Current at 2.4V
Output Current at 0.4V
Power-Fail Voltage (Note 2)
VRT Trip Point
Trickle-Charger Current-Limiting
Resistor
Trickle-Charger Output Voltage
SYMBOL
V
CC
V
BACKUP
V
IH
V
IL
I
CC1
I
CCS
I
IL
I
OL
I
MOT
I
OH
I
OL
V
PF
VRT
TRIP
R1
V
OUT
(Note 5)
(Note 6)
(Note 2)
(Note 2)
-33
-5
-33
-5
DS12R885 Only
DS12R885 Only
2.7
4.05
2.88
4.33
1.3
10
3.05
-33
-5
(Note 2)
(Note 2)
(Note 2)
-33
-5
-5
-33
-1.0
-1.0
-1.0
-1.0
4.0
2.97
4.5
CONDITIONS
MIN
2.97
4.5
2.0
2.2
-0.3
0.7
0.8
0.250
0.140
TYP
3.3
5.0
MAX
3.63
5.5
V
OUT
V
CC
+
0.3
+0.8
2
2
0.5
0.3
+1.0
+1.0
+500
UNITS
V
V
V
V
mA
mA
µA
µA
µA
mA
mA
V
V
kΩ
V
2
_____________________________________________________________________
RTC with Constant-Voltage Trickle Charger
DC ELECTRICAL CHARACTERISTICS (DS12R885 Only)
(V
CC
= 0V, V
BACKUP
= 3.2V,
T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
V
BACKUP
Current (OSC On);
T
A
= +25°C, V
BACKUP
= 3.0V
V
BACKUP
Current (Oscillator Off)
SYMBOL
I
BACKUP2
(Note 7)
CONDITIONS
MIN
TYP
800
MAX
1000
100
UNITS
nA
nA
DS12R885/DS12CR887/DS12R887
I
BACKUPDR
(Note 7)
AC ELECTRICAL CHARACTERISTICS
(V
CC
= 4.5V to 5.5V,
T
A
= -40°C to +85°C.) (Note 1)
PARAMETER
Cycle Time
Pulse Width, DS Low or R/W High
Pulse Width, DS High or R/W Low
Input Rise and Fall
R/W Hold Time
R/W Setup Time Before DS/E
Chip-Select Setup Time Before
DS or R/W
Chip-Select Hold Time
Read-Data Hold Time
Write-Data Hold Time
Address Valid Time to AS Fall
Address Hold Time to AS Fall
Delay Time DS/E to AS Rise
Pulse Width AS High
Delay Time, AS to DS/E Rise
Output Data Delay Time from DS
or R/W
Data Setup Time
Reset Pulse Width
IRQ
Release from DS
IRQ
Release from
RESET
SYMBOL
t
CYC
PW
EL
PW
EH
t
R
, t
F
t
RWH
t
RWS
t
CS
t
CH
t
DHR
t
DHW
t
ASL
t
AHL
t
ASD
PW
ASH
t
ASED
t
DDR
t
DSW
t
RWL
t
IRDS
t
IRR
(Note 8)
0
10
5
0
5
0
20
5
10
30
35
15
50
5
0
0
2
2
60
35
CONDITIONS
MIN
180
80
65
30
TYP
MAX
DC
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
µs
µs
µs
_____________________________________________________________________
3
RTC with Constant-Voltage Trickle Charger
DS12R885/DS12CR887/DS12R887
AC ELECTRICAL CHARACTERISTICS
(V
CC
= 2.97V to 3.63V,
T
A
= -40°C to +85°C.) (Note 1)
PARAMETER
Cycle Time
Pulse Width, DS Low or R/W High
Pulse Width, DS High or R/W Low
Input Rise and Fall
R/W Hold Time
R/W Setup Time Before DS
Chip-Select Setup Time Before
DS or R/W
Chip-Select Hold Time
Read-Data Hold Time
Write-Data Hold Time
Address Valid Time to AS Fall
Address Hold Time to AS Fall
Delay Time DS to AS Rise
Pulse Width AS High
Delay Time, AS to DS Rise
Output Data Delay Time from DS
or R/W
Data Setup Time
Reset Pulse Width
IRQ
Release from DS
IRQ
Release from
RESET
SYMBOL
t
CYC
PW
EL
PW
EH
t
R
, t
F
t
RWH
t
RWS
t
CS
t
CH
t
DHR
t
DHW
t
ASL
t
AHL
t
ASD
PW
ASH
t
ASED
t
DDR
t
DSW
t
RWL
t
IRDS
t
IRR
(Note 8)
0
15
8
0
5
0
30
15
15
45
55
20
70
5
0
0
2
2
80
55
CONDITIONS
MIN
280
130
90
30
TYP
MAX
DC
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
µs
µs
µs
4
_____________________________________________________________________
Microcontroller MCU
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