Rev 2; 10/08
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
General Description
The DS3234 is a low-cost, extremely accurate SPI™ bus
real-time clock (RTC) with an integrated temperature-com-
pensated crystal oscillator (TCXO) and crystal. The
DS3234 incorporates a precision, temperature-compen-
sated voltage reference and comparator circuit to monitor
V
CC
. When V
CC
drops below the power-fail voltage (V
PF
),
the device asserts the
RST
output and also disables read
and write access to the part when V
CC
drops below both
V
PF
and V
BAT
. The
RST
pin is monitored as a pushbutton
input for generating a µP reset. The device switches to the
backup supply input and maintains accurate timekeeping
when main power to the device is interrupted. The integra-
tion of the crystal resonator enhances the long-term accu-
racy of the device as well as reduces the piece-part count
in a manufacturing line. The DS3234 is available in com-
mercial and industrial temperature ranges, and is offered
in an industry-standard 300-mil, 20-pin SO package.
The DS3234 also integrates 256 bytes of battery-backed
SRAM. In the event of main power loss, the contents of
the memory are maintained by the power source con-
nected to the V
BAT
pin. The RTC maintains seconds,
minutes, hours, day, date, month, and year information.
The date at the end of the month is automatically adjust-
ed for months with fewer than 31 days, including correc-
tions for leap year. The clock operates in either the
24-hour or 12-hour format with
AM/PM
indicator. Two
programmable time-of-day alarms and a programmable
square-wave output are provided. Address and data are
transferred serially by an SPI bidirectional bus.
Features
♦
Accuracy ±2ppm from 0°C to +40°C
♦
Accuracy ±3.5ppm from -40°C to +85°C
♦
Battery Backup Input for Continuous
Timekeeping
♦
Operating Temperature Ranges
Commercial: 0°C to +70°C
Industrial: -40°C to +85°C
♦
Low-Power Consumption
♦
Real-Time Clock Counts Seconds, Minutes,
Hours, Day, Date, Month, and Year with Leap Year
Compensation Valid Up to 2099
♦
Two Time-of-Day Alarms
♦
Programmable Square-Wave Output
♦
4MHz SPI Bus Supports Modes 1 and 3
♦
Digital Temp Sensor Output: ±3°C Accuracy
♦
Register for Aging Trim
♦
RST
Input/Output
♦
300-Mil, 20-Pin SO Package
♦
Underwriters Laboratories (UL
®
) Recognized
DS3234
Ordering Information
PART
DS3234S#
DS3234SN#
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-
PACKAGE
20 SO
20 SO
TOP
MARK
DS3234S
DS3234SN
Applications
Servers
Telematics
Utility Power Meters
GPS
#
Denotes a RoHS-compliant device that may include lead that
is exempt under the RoHS requirements. Lead finish is JESD97
Category e3, and is compatible with both lead-based and
lead-free soldering processes. A "#" anywhere on the top mark
denotes a RoHS-compliant device.
Typical Operating Circuit
TOP VIEW
V
CC
V
CC
SS
SCLK
MOSI
MISO
RST
μP
PUSH-
BUTTON
RESET
CS
SCLK
DIN
DOUT
RST
N.C.
N.C.
N.C.
N.C.
N.C.
V
CC
INT/SQW
32kHz
V
BAT
V
PU
CS 1
N.C. 2
32kHz 3
V
CC
4
INT/SQW 5
RST 6
N.C.
N.C.
N.C.
N.C.
N.C. 7
N.C. 8
N.C. 9
N.C. 10
Pin Configuration
20 SCLK
19 DOUT
18 SCLK
17 DIN
DS3234
16 V
BAT
15 GND
14 N.C.
13 N.C.
12 N.C.
11 N.C.
DS3234
GND
SPI is a trademark of Motorola, Inc.
UL is a registered trademark of Underwriters Laboratories, Inc.
SO
______________________________________________
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.
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
DS3234
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground......-0.3V to +6.0V
Operating Temperature Range
(noncondensing) .............................................-40°C to +85°C
Junction Temperature ......................................................+125°C
Storage Temperature Range ...............................-40°C to +85°C
Soldering Temperature
(leads, 10s) ...........................................................+260°C/10s
Soldering Temperature (reflow, 2 times max) .......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.) (Notes 1, 2)
PARAMETER
Supply Voltage
Logic 1 Input
CS,
SCLK, DIN
Logic 0 Input
CS,
SCLK, DIN,
RST
SYMBOL
V
CC
V
BAT
V
IH
2.0V
V
CC
3.63V
5.5V
CONDITIONS
MIN
2.0
2.0
0.7 x
V
CC
-0.3
-0.3
TYP
3.3
3.0
MAX
5.5
3.8
V
CC
+
0.3
+0.2 x
V
CC
+0.7
UNITS
V
V
V
IL
V
3.63V < V
CC
ELECTRICAL CHARACTERISTICS
(V
CC
= 2.0V to 5.5V, V
CC
= active supply (see Table 1), T
A
= -40°C to +85°C, unless otherwise noted.) (Typical values are at
V
CC
=
3.3V, V
BAT
= 3.0V,
and T
A
= +25°C, unless otherwise noted. TCXO operation guaranteed from 2.3V to 5.5V on V
CC
and 2.3V to 3.8V on
V
BAT
.) (Notes 1, 2)
PARAMETER
Active Supply Current
SYMBOL
I
CCA
CONDITIONS
SCLK = 4MHz, BSY = 0
(Notes 3, 4)
CS
= V
IH
, 32kHz output off,
SQW output off
(Note 4)
SPI bus inactive, 32kHz
output off, SQW output off
V
CC
= 3.63V
V
CC
= 5.5V
V
CC
= 3.63V
V
CC
= 5.5V
V
CC
= 3.63V
V
CC
= 5.5V
2.45
2.575
25
MIN
TYP
MAX
400
700
120
µA
160
500
600
2.70
100
µA
V
nA
UNITS
µA
Standby Supply Current
I
CCS
Temperature Conversion Current
Power-Fail Voltage
V
BAT
Leakage Current
I
CCSCONV
V
PF
I
BATLKG
(V
CC
= 2.0V to 5.5V, T
A
= -40°C to +85°C, unless otherwise noted.) (Notes 1 and 2)
Logic 1 Output, 32kHz
I
OH
= -500µA
I
OH
= -250µA
I
OH
= -125µA
V
CC
> 3.63V,
3.63V > V
CC
> 2.7V,
2.7V > (V
CC
or V
BAT)
> 2.0V
(BB32kHz = 1)
V
OH
0.85 x V
CC
V
2
_____________________________________________________________________
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.0V to 5.5V, V
CC
= active supply (see Table 1), T
A
= -40°C to +85°C, unless otherwise noted.) (Typical values are at
V
CC
=
3.3V, V
BAT
= 3.0V,
and T
A
= +25°C, unless otherwise noted. TCXO operation guaranteed from 2.3V to 5.5V on V
CC
and 2.3V to 3.8V on
V
BAT
.) (Notes 1, 2)
PARAMETER
Logic 0 Output, 32kHz
Logic 1 Output, DOUT
Logic 0 Output, DOUT,
INT/SQW
Logic 0 Output,
RST
Output Leakage Current 32kHz,
INT/SQW,
DOUT
Input Leakage DIN,
CS,
SCLK
RST
Pin I/O Leakage
Output Frequency
Frequency Stability vs.
Temperature
Frequency Stability vs. Voltage
Trim Register Frequency
Sensitivity per LSB
Temperature Accuracy
Crystal Aging
SYMBOL
V
OL
V
OH
V
OL
V
OL
I
LO
I
LI
I
OL
f
OUT
Δf/f
OUT
Δf/V
-40°C
Δf/LSB
Specified at:
+25°C
+70°C
+85°C
Temp
Δf/f
OUT
After reflow,
not production tested
First year
0–10 years
-3
±1.0
±5.0
RST
high impedance (Note 5)
V
CC
= 3.3V or V
BAT
= 3.3V
0°C to +40°C
V
CC
= 3.3V or
V
BAT
= 3.3V
-40°C to 0°C and
+40°C to +85°C
-2
-3.5
1
0.7
0.1
0.4
0.8
+3
°C
ppm
ppm
I
OL
= 1mA
I
OH
= -1.0mA
I
OL
= 3mA
I
OL
= 1.0mA
Output high impedance
-1
-1
-200
32.768
+2
+3.5
ppm
ppm/V
0
0.85 x V
CC
0.4
0.4
+1
+1
+10
CONDITIONS
MIN
TYP
MAX
0.4
UNITS
V
V
V
V
µA
µA
µA
kHz
DS3234
TCXO (V
CC
= 2.3V to 5.5V, V
BAT
= 2.3V to 3.8V, T
A
= -40°C to +85°C, unless otherwise noted.) (Notes 1 and 2)
ELECTRICAL CHARACTERISTICS
(V
CC
= 0V, V
BAT
= 2.0V to 3.8V,
T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
Timekeeping Battery Current
(Note 4)
Temperature Conversion Current
Data-Retention Current
SYMBOL
I
BATT
I
BATTC
I
BATTDR
CONDITIONS
EOSC
= 0, BBSQW = 0,
CRATE1 = CRATE0 = 0
EOSC
= 0, BBSQW = 0
EOSC
= 1
V
BAT
= 3.4V
V
BAT
= 3.8V
MIN
TYP
1.5
1.5
MAX
2.3
2.5
400
100
UNITS
μA
μA
nA
_____________________________________________________________________
3
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
DS3234
AC ELECTRICAL CHARACTERISTICS
(V
CC
= 2.0V to 5.5V, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SCLK Clock Frequency
Data to SCLK Setup
SCLK to Data Hold
SCLK to
CS
Setup
SCLK to Data Valid (Note 6)
SCLK Low Time
SCLK High Time
SCLK Rise and Fall
CS
to SCLK Setup
SCLK to
CS
Hold
CS
Inactive Time
CS
to Output High Impedance
Pushbutton Debounce
Reset Active Time
Oscillator Stop Flag (OSF) Delay
Temperature Conversion Time
SYMBOL
f
SCL
t
DC
t
CDH
t
CCS
t
CDD
t
CL
t
CH
t
R
, t
F
t
CC
t
CCH
t
CWH
t
CDZ
PB
DB
t
RST
t
OSF
t
CONV
(Note 8)
(Note 7)
250
250
100
125
200
2.7V
2.0V
V
CC
5.5V
V
CC
<
2.7V
400
100
200
400
40
2.7V
2.0V
2.7V
2.0V
2.7V
2.0V
V
CC
V
CC
V
CC
5.5V
5.5V
5.5V
110
220
110
220
200
V
CC
<
2.7V
V
CC
<
2.7V
V
CC
<
2.7V
2.7V
2.0V
V
CC
CONDITIONS
5.5V
30
30
30
80
160
V
CC
<
2.7V
MIN
TYP
MAX
4
2
UNITS
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
ms
ms
ms
POWER-SWITCH CHARACTERISTICS
(T
A
= -40°C to +85°C)
PARAMETER
V
CC
Fall Time; V
PF(MAX)
to
V
PF(MIN)
V
CC
Rise Time; V
PF(MIN)
to
V
PF(MAX)
Recovery at Power-Up
SYMBOL
t
VCCF
t
VCCR
t
REC
(Note 9)
CONDITIONS
MIN
300
0
125
300
TYP
MAX
UNITS
µs
µs
ms
CAPACITANCE
(T
A
= +25°C)
PARAMETER
Capacitance on All Input Pins
Capacitance on All Output Pins
SYMBOL
C
IN
C
IO
(Note 10)
Outputs high impedance (Note 10)
CONDITIONS
MIN
TYP
MAX
10
10
UNITS
pF
pF
4
_____________________________________________________________________
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
Pushbutton Reset Timing
RST
DS3234
PB
DB
t
RST
Power-Switch Timing
V
CC
V
PF(MAX)
V
PF(MIN)
V
PF
V
PF
t
VCCF
t
VCCR
t
REC
RST
WARNING: Negative undershoots below -0.3V while the part is in battery-backed mode may
cause loss of data.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Limits at -40°C are guaranteed by design and not production tested.
All voltages are referenced to ground.
Measured at V
IH
= 0.8 x V
CC
or V
IL
= 0.2 x V
CC
, 10ns rise/fall time, DOUT = no load.
Current is the averaged input current, which includes the temperature conversion current. CRATE1 = CRATE0 = 0.
The
RST
pin has an internal 50kΩ (nominal) pullup resistor to V
CC
.
Measured at V
OH
= 0.8 x V
CC
or V
OL
= 0.2 x V
CC
. Measured from the 50% point of SCLK to the V
OH
minimum of DOUT.
With 50pF load.
The parameter t
OSF
is the period of time the oscillator must be stopped for the OSF flag to be set over the voltage range of
0V
≤
V
CC
≤
V
CC(MAX)
and 2.3V
≤
V
BAT
≤
V
BAT(MAX)
.
Note 9:
This delay only applies if the oscillator is enabled and running. If the
EOSC
bit is 1, t
REC
is bypassed and
RST
immediately
goes high.
Note 10:
Guaranteed by design and not production tested.
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