19-6007; Rev 2; 2/12
Low-Current, SPI-Compatible Real-Time Clock
General Description
The DS1347 SPI-compatible real-time clock (RTC) con-
tains a real-time clock/calendar and 31 x 8 bits of static
random-access memory (SRAM). The real-time
clock/calendar provides seconds, minutes, hours, day,
date, month, year, and century information. A time/date
programmable polled ALARM is included in the device.
The end-of-the-month date is automatically adjusted for
months with fewer than 31 days, including corrections
for leap year. The clock operates in either the 24hr or
12hr format with an
AM/PM
indicator. The device oper-
ates with a supply voltage of +2V to +5.5V, are avail-
able in the ultra-small 8-pin TDFN package, and work
over the -40°C to +85°C industrial temperature range.
Features
o
RTC Counts Seconds, Minutes, Hours, Day of Week,
Date of Month, Month, Year, and Century
o
Leap-Year Compensation
o
+2V to +5.5V Wide Operating Voltage Range
o
SPI (Mode 1 or 3) Interface: 4MHz at 5V, 1MHz at 2V
o
31 x 8-Bit SRAM for Scratchpad Data Storage
o
Uses Standard 32.768kHz Watch Crystal
o
Low Timekeeping Current (400nA at 2V)
o
Single-Byte or Multiple-Byte (Burst Mode) Data
Transfer for Read or Write of Clock Registers or
SRAM
o
Ultra-Small, 3mm x 3mm x 0.8mm, 8-Pin TDFN
Package
o
Programmable Time/Date Polled ALARM Function
o
No External Crystal Bias Resistors or Capacitors
Required
DS1347
Applications
Point-of-Sale Equipment
Intelligent Instruments
Fax Machines
Battery-Powered Products
Portable Instruments
Typical Operating Circuit
+3.3V 0.1µF
6
Ordering Information
PART
DS1347T+
TEMP RANGE
-40°C to +85°C
OSC C
L
(pF)
12.5
PIN-PACKAGE
8 TDFN-EP*
1
SCLK
CS
DOUT
DIN
+3.3V
V
CC
DS1347
µc
5
2
3
X1
8
32.768kHz
CRYSTAL
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
X2
7
GND
4
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Low-Current, SPI-Compatible Real-Time Clock
DS1347
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
All Other Pins to GND ................................-0.3V to (V
CC
+ 0.3V)
Current into Any Pin..........................................................±20mA
Rate of Rise, V
CC
............................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
TDFN (derate 24.4mW/°C above +70°C)...................1.375mW
Junction Temperature .....................................................+150°C
Storage Temperature Range…………………… -55°C to +125°C
ESD Protection (All Pins, Human Body Model)................±2000V
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+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
= +2.0V to +5.5V, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Operating Voltage
Range
Active Supply Current
(Note 2)
Timekeeping Supply
Current (Note 3)
SYMBOL
V
CC
I
CC
V
CC
= +2V
V
CC
= +5V
V
CC
= +2V
I
TK
V
CC
= +3.6V
V
CC
= +5V
SPI DIGITAL INPUTS (SCLK, DIN,
CS)
Input High Voltage
Input Low Voltage
Input Leakage Current
V
IH
V
IL
I
IL
V
CC
= +2V
V
CC
= +5V
V
CC
= +2V
V
CC
= +5V
V
IN
= 0 to V
CC
(Note 4)
CS
= V
IH
(Note 4)
V
CC
= +2V, I
SINK
= 1.5mA
V
CC
= +5V, I
SINK
= 4mA
V
CC
= +2V, I
SOURCE
= -0.4mA
V
CC
= +5V, I
SOURCE
= -1mA
1.8
4.5
-0.1
15
0.4
0.4
-0.1
10
+0.1
1.4
2.2
0.6
0.8
+0.1
V
V
µA
pF
µA
pF
V
V
0.35
0.35
0.4
CONDITIONS
MIN
2
TYP
MAX
5.5
0.1
0.25
0.7
0.7
0.8
µA
UNITS
V
mA
Input Capacitance
C
IN
SPI DIGITAL OUTPUT (DOUT)
Output Leakage Current
Output Capacitance
Output Low Voltage
Output High Voltage
I
O
C
OUT
V
OL
V
OH
2
_______________________________________________________________________________________
Low-Current, SPI-Compatible Real-Time Clock
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +2.0V to +5.5V, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
(Figure 5, Notes 1, 5)
PARAMETER
SPI SERIAL TIMING
Input Rise Time
Input Fall Time
Output Rise Time
Output Fall Time
SCLK Period
SCLK High Time
SCLK Low Time
SCLK Fall to DOUT
Valid
DIN to SCLK Setup
Time
DIN to SCLK Hold
Time
SCLK Rise to
CS
Rise Hold Time
CS
High Pulse Width
CS
High to DOUT
High Impedance
CS
to SCLK Setup
Time
t
rIN
t
fIN
t
rOUT
t
fOUT
t
CP
t
CH
t
CL
t
DO
t
DS
t
DH
t
CSH
t
CSW
t
CSZ
t
CSS
100
V
CC
= +2V
V
CC
= +5V
V
CC
= +2V, C
LOAD
= 100pF
V
CC
= +5V, C
LOAD
= 100pF
100
20
200
50
200
100
DIN, SCLK,
CS
DIN, SCLK,
CS
DOUT, C
LOAD
= 100pF
DOUT, C
LOAD
= 100pF
V
CC
= +2V
V
CC
= +5V
1000
238
100
100
300
100
5
5
10
10
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DS1347
CRYSTAL CHARACTERISTICS
PARAMETER
Nominal Frequency
Series Resistance
Load Capacitance
SYMBOL
f
O
ESR
C
L
12.5
CONDITIONS
MIN
TYP
32.768
100
MAX
UNITS
kHz
k
pF
Note 1:
All parameters are 100% tested at T
A
= +25°C. Limits over temperature are guaranteed by design and characterization and
not production tested.
Note 2:
I
CC
is specified with DOUT open,
CS
= DIN = GND, SCLK = 4MHz at V
CC
= +5V; SCLK = 1MHz at V
CC
= +2.0V.
Note 3:
Timekeeping current is specified with
CS
= V
CC
, SCLK = DIN = GND, DOSF = 0, EGFIL = 1.
Note 4:
Guaranteed by design and not 100% production tested.
Note 5:
All values referred to V
IH(MIN)
and V
IL(MAX)
levels.
_______________________________________________________________________________________
3
Low-Current, SPI-Compatible Real-Time Clock
DS1347
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS1347 toc01
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
T
A
= +25°C,
CS = V
CC
EGFIL = 1,
DOSF = 0
DS1347 toc02
120
100
SUPPLY CURRENT (µA)
80
60
40
f
SCLK
= 1MHz
20
0
2
3
4
SUPPLY VOLTAGE (V)
5
6
f
SCLK
= 4MHz
T
A
= +25°C,
I
OUT
= 0mA,
CS = DIN = GND
400
SUPPLY CURRENT (nA)
350
300
250
EGFIL = 0,
DOSF = 0
EGFIL = 0,
DOSF = 1
200
2
3
4
SUPPLY VOLTAGE (V)
5
6
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
CS = V
CC
,
EGFIL = DOSF = 0
SUPPLY CURRENT (nA)
+85°C
DS1347 toc03
500
400
+70°C
+25°C
300
0°C
200
2
3
4
SUPPLY VOLTAGE (V)
5
-40°C
6
4
_______________________________________________________________________________________
Low-Current, SPI-Compatible Real-Time Clock
Pin Configuration
TOP VIEW
+
SCLK
DOUT
DIN
1
2
8
7
X1
X2
V
CC
CS
DS1347
DS1347
3
EP
6
5
GND 4
TDFN
Pin Description
PIN
1
2
3
4
5
6
7
8
—
NAME
SCLK
DOUT
DIN
GND
CS
V
CC
X2
X1
EP
FUNCTION
Serial-Clock Input. SCLK is used to synchronize data movement on the serial interface for either 3-wire or
SPI communications.
Serial-Data Output. When SPI communication is enabled, the DOUT pin is the serial-data output for the SPI
bus.
Serial-Data Input. When SPI communication is enabled, the DIN pin is the serial-data input for the SPI bus.
Ground
Active-Low Chip Select. The chip-enable signal must be asserted low during a read or a write for SPI
communications.
Power-Supply Input
Connections for Standard 32.768kHz Quartz Crystal (see the
Crystal Characteristics
table).
Exposed Pad. Connect to GND or leave unconnected.
_______________________________________________________________________________________
5
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