supply monitor with reset, and 512 bytes of EEPROM.
The clock provides hundredths of seconds, seconds,
minutes, and hours, and operates in 24-hour or 12-hour
format with an AM/PM indicator. The calendar provides
day, date, month, and year information. The date at the
end of the month is automatically adjusted for months
with fewer than 31 days, including corrections for leap
year. A watchdog timer provides a reset for an unre-
sponsive microprocessor. It is programmable in 10ms
intervals from 0.01 to 99.99 seconds. A temperature-
compensated voltage reference and comparator circuit
monitors the status of V
CC
. If a primary power failure is
detected, the device automatically switches to the
backup supply and drives the reset output to the active
state. The backup supply maintains time and date
operation in the absence of V
CC
. When V
CC
returns to
nominal levels, the reset is held low for a period to allow
the power supply and processor to stabilize. The
device also has a pushbutton reset controller, which
debounces a reset input signal. The device is
accessed through an I
2
C serial interface.
♦
Fast (400kHz) I
2
C Interface
♦
RTC Counts Hundredths of Seconds, Seconds,
Minutes, Hours, Day, Date, Month, and Year with
Leap Year Compensation Valid Up to 2100
♦
Programmable Watchdog Timer
♦
Automatic Power-Fail Detect and Switch Circuitry
♦
Reset Output with Pushbutton Reset Input
Capability
♦
512 x 8 Bits of EEPROM
♦
Integrated Trickle-Charge Capability for Backup
Supply
♦
Three Operating Voltages: 5.0V, 3.3V, and 3.0V
♦
Low Timekeeping Voltage Down to 1.3V
♦
-40°C to +85°C Temperature Range
♦
UL Recognized
Features
DS1388
Ordering Information
PART
DS1388Z-3
DS1388Z-33
DS1388Z-5
DS1388Z-5+
DS1388Z-3+
TEMP RANGE
PIN-
PACKAGE
TOP
MARK
DS1388-3
DS138833
DS1388-5
DS1388-5
DS138833
DS1388-3
Applications
Portable Instruments
Point-of-Sale Equipment
Network Interface Cards
Wireless Equipment
-40°C to +85°C 8 SO (150 mils)
-40°C to +85°C 8 SO (150 mils)
-40°C to +85°C 8 SO (150 mils)
-40°C to +85°C 8 SO (150 mils)
-40°C to +85°C 8 SO (150 mils)
DS1388Z-33+ -40°C to +85°C 8 SO (150 mils)
Pin Configuration
TOP VIEW
A ’+’ symbol near the pin one indicator indicates lead-free.
+ = Lead free.
Typical Operating Circuit
V
CC
V
CC
CRYSTAL
V
CC
X1
1
X2
V
BACKUP
GND
2
3
4
8
V
CC
RST
SCL
SDA
CPU
RPU
RPU
X1
X2
V
CC
DS1388
7
6
5
SCL
SDA
DS1388
RST
V
BACKUP
SO
Purchase of I
2
C components from Maxim Integrated Products,
Inc., or one of its sublicensed Associated Companies, conveys
a license under the Philips I
2
C Patent Rights to use these com-
ponents in an I
2
C system, provided that the system conforms
to the I
2
C Standard Specification as defined by Philips.
GND
RPU = t
r
/C
B
______________________________________________
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.
I
2
C RTC/Supervisor with Trickle Charger
and 512 Bytes EEPROM
DS1388
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
CC
Pin Relative to Ground .....-0.3V to +6.0V
Voltage Range on Inputs Relative
to Ground ...............................................-0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
(noncondensing) .............................................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature .....................See IPC/JEDEC J-STD-020
Specification
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.
RECOMMENDED DC OPERATING CONDITIONS
(T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
SYMBOL
V
CC
(Note 2)
CONDITIONS
DS1388Z-5
DS1388Z-33
DS1388Z-3
Logic 1
Logic 0
Pullup Voltage (SCL, SDA),
V
CC
= 0V
V
BACKUP
Voltage
Power-Fail Voltage
V
IH
V
IL
V
PU
V
BACKUP
V
PF
(Note 2)
DS1388Z-5
(Note 2)
DS1388Z-33
DS1388Z-3
1.3
4.15
2.70
2.45
3.0
4.33
2.88
2.60
(Note 2)
(Note 2)
MIN
4.5
2.97
2.7
0.7 x
V
CC
-0.3
TYP
5
3.3
3
MAX
5.5
3.63
3.3
V
CC
+
0.3
+0.3 x
V
CC
5.5
5.5
4.50
2.97
2.70
V
V
V
V
V
V
UNITS
DC ELECTRICAL CHARACTERISTICS
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
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