Maxim Integrated DS3234, DS3234S, DS3234SN User Manual

DS3234

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-com­pensated crystal oscillator (TCXO) and crystal. The
DS3234 incorporates a precision, temperature-compen­sated voltage reference and comparator circuit to monitor
VCC. When VCCdrops below the power-fail voltage (VPF),
the device asserts the RST output and also disables read
and write access to the part when VCCdrops below both
VPFand 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 integra­tion of the crystal resonator enhances the long-term accu­racy of the device as well as reduces the piece-part count
in a manufacturing line. The DS3234 is available in com­mercial 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 con­nected 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 adjust­ed for months with fewer than 31 days, including correc­tions 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.

Applications

Servers Utility Power Meters
Telematics GPS

Benefits and Features

• Highly Accurate RTC with Integrated Crystal and

SRAM Completely Manages All Timekeeping
Functions

• Accuracy ±2ppm from 0°C to +40°C

• Accuracy ±3.5ppm from -40°C to +85°C

• Real-Time Clock Counts Seconds, Minutes, Hours,

Day, Date, Month, and Year, with Leap Year
Compensation Valid Up to 2099

• Digital Temp Sensor Output: ±3°C Accuracy

• Register for Aging Trim

• RST Input/Output

• Two Time-of-Day Alarms

• Programmable Square-Wave Output

• Simple Serial Interface Connects to Most

Microcontrollers

• 4MHz SPI Bus Supports Modes 1 and 3

• Battery-Backup Input for Continuous Timekeeping

• Low Power Operation Extends Battery Backup Run

Time

• Operating Temperature Ranges: Commercial: 0°C to

+70°C, Industrial: -40°C to +85°C

• 300-Mil, 20-Pin SO Package

• Underwriters Laboratories

®

(UL) Recognized

19-5339; Rev 4; 3/15

Ordering Information

Typical Operating Circuit

#

Denotes an RoHS-compliant device that may include lead(Pb)
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 an RoHS-compliant device.

Underwriters Laboratories Inc. is a registered certification mark
of Underwriters Laboratories Inc.

PART TEMP RANGE

DS3234S# 0°C to +70°C 20 SO DS3234S

DS3234SN# -40°C to +85°C 20 SO DS3234SN

PIN­PACKAGE

TOP

MARK

V

V

µP

CC

SCLK
MOSI
MISO

SS

RST

PUSH-

BUTTON

RESET

CS
SCLK
DIN

DOUT
RST

N.C.
N.C.
N.C.
N.C.
N.C.

CC

V

CC

DS3234

GND

INT/SQW

32kHz

V

BAT

N.C.
N.C.
N.C.
N.C.

V

PU

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

Maxim Integrated | 2www.maximintegrated.com

Absolute Maximum Ratings

Recommended Operating Conditions

(TA= -40°C to +85°C, unless otherwise noted.) (Notes 2, 3)

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.

Voltage Range on Any Pin Relative to Ground......-0.3V to +6.0V

Junction-to-Ambient Thermal Resistance (θ

JA

) (Note 1) ...55°C/W

Junction-to-Case Thermal Resistance (θ

JC

) (Note 1) ........24°C/W

Operating Temperature Range

(noncondensing) .............................................-40°C to +85°C

Junction Temperature......................................................+125°C

Storage Temperature Range ...............................-40°C to +85°C

Lead Temperature (soldering, 10s) .................................+260°C

Soldering Temperature (reflow, 2 times max) ....................+260°C

(See the

Handling, PC Board Layout, and Assembly

section.)

Electrical Characteristics

(VCC= 2.0V to 5.5V, VCC= active supply (see Table 1), TA= -40°C to +85°C, unless otherwise noted.) (Typical values are at VCC=

3.3V, V

BAT

= 3.0V, and TA= +25°C, unless otherwise noted. TCXO operation guaranteed from 2.3V to 5.5V on VCCand 2.3V to 3.8V on

V

BAT

.) (Notes 2, 3)

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer

board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial

.

Supply Voltage

Logic 1 Input CS, SCLK, DIN V

Logic 0 Input CS, SCLK, DIN,

RST

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

VCC 2.0 3.3 5.5

2.0 3.0 3.8

V

BAT

IH

V

2.0V  VCC 3.63V -0.3

IL

3.63V < VCC 5.5V -0.3 +0.7

V

0.7 x
V

CC

VCC +

0.3

+0.2 x

V

CC

V

V

Active Supply Current I

Standby Supply Current I

Temperature Conversion Current I

Power-Fail Voltage V

V

(VCC = 2.0V to 5.5V, TA = -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)

Logic 1 Output, 32kHz
I

OH

I

OH

I

OH

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

VCC = 3.63V 400

V

= 5.5V 700

CC

VCC = 3.63V 120

V

= 5.5V 160

CC

VCC = 3.63V 500

V

= 5.5V 600

CC

2.45 2.575 2.70 V

25 100 nA

0.85 x V

CC

Leakage Current I

BAT

= -500µA
= -250µA
= -125µA

CCA

CCS

CCSCONV

PF

BATLKG

V

OH

SCLK = 4MHz, BSY = 0
(Notes 4, 5)

CS = VIH, 32kHz output off,
SQW output off
(Note 5)

SPI bus inactive, 32kHz
output off, SQW output off

VCC > 3.63V,

3.63V > V

2.7V > (V
(BB32kHz = 1)

CC

CC

> 2.7V,

or V

BAT

) > 2.0V

µA

µA

µA

V

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

Maxim Integrated | 3www.maximintegrated.com

Electrical Characteristics (continued)

(VCC= 2.0V to 5.5V, VCC= active supply (see Table 1), TA= -40°C to +85°C, unless otherwise noted.) (Typical values are at VCC=

3.3V, V

BAT

= 3.0V, and TA= +25°C, unless otherwise noted. TCXO operation guaranteed from 2.3V to 5.5V on VCCand 2.3V to 3.8V on

V

BAT

.) (Notes 2, 3)

Electrical Characteristics

(VCC= 0V, V

BAT

= 2.0V to 3.8V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

Logic 0 Output, 32kHz V
Logic 1 Output, DOUT V
Logic 0 Output, DOUT, INT/SQW V
Logic 0 Output, RST V

Output Leakage Current 32kHz,

INT/SQW, DOUT

Input Leakage DIN, CS, SCLK I
RST Pin I/O Leakage I
TCXO (V
Output Frequency f

Frequency Stability vs.

Temperature

Frequency Stability vs. Voltage Δf/V 1 ppm/V

Trim Register Frequency

Sensitivity per LSB

Temperature Accuracy Temp -3 +3 °C

Crystal Aging Δf/f

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

I

= 1mA 0.4 V

OL

I

= -1.0mA 0.85 x V

OH

I

= 3mA 0.4 V

OL

I

= 1.0mA 0.4 V

OL

CC

Output high impedance -1 0 +1 µA

-1 +1 µA
RST high impedance (Note 6) -200 +10 µA

V

= 3.3V or V

CC

BAT

= 3.3V

32.768 kHz

= 2.3V to 5.5V, V

CC

OL

OH

OL

OL

I

LO

LI

OL

= 2.3V to 3.8V, TA = -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)

BAT

OUT

0°C to +40°C -2 +2

V

= 3.3V or

Δf/f

OUT

CC

= 3.3V

V

BAT

-40°C to 0°C and

+40°C to +85°C

-3.5 +3.5

-40°C 0.7

Δf/LSB Specified at:

+25°C 0.1
+70°C 0.4
+85°C 0.8

After reflow,

OUT

not production tested

First year ±1.0

0–10 years ±5.0

V

ppm

ppm

ppm

Timekeeping Battery Current
(Note 5)

Temperature Conversion Current I

Data-Retention Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

I

BATTC

BATTDR

BATT

V

= 3.4V 1.5 2.3

EOSC = 0, BBSQW = 0,
CRATE1 = CRATE0 = 0

EOSC = 0, BBSQW = 0 400 µA
EOSC = 1 100 nA

BAT

V

= 3.8V 1.5 2.5

BAT

µA

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

Maxim Integrated | 4www.maximintegrated.com

Electrical Characteristics

(VCC= 2.0V to 5.5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

Power-Switch Characteristics

5(TA= -40°C to +85°C)

Capacitance

(TA= +25°C)

SCLK Clock Frequency f

Data to SCLK Setup t

SCLK to Data Hold t
SCLK to CS Setup t

SCLK to Data Valid (Note 7) t

SCLK Low Time t

SCLK High Time t

SCLK Rise and Fall tR, t
CS to SCLK Setup t

SCLK to CS Hold t

CS Inactive Time t
CS to Output High Impedance t

Pushbutton Debounce PBDB 250 ms

Reset Active Time t

Oscillator Stop Flag (OSF) Delay t

Temperature Conversion Time t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SCL

DC

CDH

CCS

CDD

CL

CH

CC

CCH

CWH

CDZ

RST

OSF

CONV

2.7V ≤ VCC ≤ 5.5V 4

2.0V ≤ V

< 2.7V 2

CC

30 ns

30 ns

30 ns

2.7V ≤ VCC ≤ 5.5V 80

2.0V ≤ V

< 2.7V 160

CC

2.7V ≤ VCC ≤ 5.5V 110

2.0V ≤ V

< 2.7V 220

CC

2.7V ≤ VCC ≤ 5.5V 110

2.0V ≤ V

F

< 2.7V 220

CC

400 ns

2.7V ≤ VCC ≤ 5.5V 100

2.0V ≤ V

< 2.7V 200

CC

400 ns

(Note 8) 40 ns

250 ms

(Note 9) 100 ms

125 200 ms

200 ns

MHz

ns

ns

ns

ns

VCC Fall Time; V
V

PF(MIN)

VCC Rise Time; V
V

PF(MAX)

Recovery at Power-Up t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

to

PF(MAX)

PF(MIN)

to

t

t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Capacitance on All Input Pins C

Capacitance on All Output Pins C

VCCF

VCCR

REC

IN

IO

300 µs

0µs

(Note 10) 125 300 ms

(Note 11) 10 pF

Outputs high impedance (Note 11) 10 pF

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

Maxim Integrated | 5www.maximintegrated.com

Pushbutton Reset Timing

Power-Switch Timing

Note 2: Limits at -40°C are guaranteed by design and not production tested.
Note 3: All voltages are referenced to ground.
Note 4: Measured at V

IH

= 0.8 x VCCor VIL= 0.2 x VCC, 10ns rise/fall time, DOUT = no load.

Note 5: Current is the averaged input current, which includes the temperature conversion current. CRATE1 = CRATE0 = 0.
Note 6: The RST pin has an internal 50kΩ (nominal) pullup resistor to V

CC

.

Note 7: Measured at V

OH

= 0.8 x VCCor VOL= 0.2 x VCC. Measured from the 50% point of SCLK to the VOHminimum of DOUT.

Note 8: With 50pF load.
Note 9: 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 10: 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 11: Guaranteed by design and not production tested.

WARNING: Negative undershoots below -0.3V while the part is in battery-backed mode may
cause loss of data.

RST

V

CC

V

PF(MAX)

V

PF(MIN)

t

VCCF

RST

PB

DB

V

PF

t

RST

V

PF

t

VCCR

t

REC

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

Maxim Integrated | 6www.maximintegrated.com

Timing Diagram—SPI Read Transfer

Timing Diagram—SPI Write Transfer

t

CS

CCS

t

SCLK

DIN

DOUT

NOTE: SCLK CAN BE EITHER POLARITY, SHOWN FOR CPOL = 1.

CC

t

DC

W/R

t

t

CL

t

CDH

WRITE ADDRESS BYTE

R

A6

HIGH IMPEDANCE

t

CH

CS

SCLK

t

CC

t

R

t

F

t

F

t

CDZ

t

CDD

A0

D7

READ DATA BYTE

t

CWH

t

D0

CCH

t

CL

t

CDH

WRITE ADDRESS BYTE

DOUT

DIN

t

DC

W/R

t

CH

A6

A0

HIGH IMPEDANCE

D7 D0

WRITE DATA BYTE

Maxim Integrated | 7www.maximintegrated.com

DS3234

Extremely Accurate SPI Bus RTC

with Integrated Crystal and SRAM

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

DS3234 toc01

VCC (V)

SUPPLY CURRENT (μA)

5.3

4.8

4.32.8

3.3 3.8

50

100

150

125

75

25

0

2.3

RST ACTIVE

INPUTS = GND

BATTERY CURRENT

vs. SUPPLY VOLTAGE

DS3234 toc02

SUPPLY VOLTAGE (V

BAT

)

SUPPLY CURRENT (nA)

3.8

3.3

2.8

1100

2100

1850

2600

2350

1600

1350

850

600

2.3

VCC = 0V
BB32kHz = 0

BBSQW = 1

BBSQW = 0

BATTERY CURRENT

vs. TEMPERATURE

DS3234 toc03

TEMPERATURE (°C)

SUPPLY CURRENT (nA)

80

6040

-20

0

20

700

650

750

800

850

600

-40

V

BAT

= 3.4V

V

BAT

= 3.0V

VCC = 0V
BB32kHz = 0
BBSQW = 0

FREQUENCY DEVIATION

vs. TEMPERATURE vs. AGING VALUE

DS3234 toc04

TEMPERATURE (°C)

FREQUENCY DEVIATION (ppm)

80

60

40

-20

020

25

15

5

-5

-15

-25

-35

65

55

45

35

-45

-40

AGING = -128

AGING = -33

AGING = 127

AGING = 0

AGING = 32

I

CCA

vs. DOUT LOAD

DS3234 toc05

CAPACITANCE (pF)

SUPPLY CURRENT (μA)

40

30

20

10

250

350

300

400

450

500

200

0

SCLK = 4MHz

DELTA TIME AND FREQUENCY

vs. TEMPERATURE

TEMPERATURE (°C)

DELTA FREQUENCY (ppm)

DELTA TIME (MIN/YEAR)

807050 60-10 0 10 20 30 40-30 -20

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

-200

-80

-60

-40

-20

0

-100

-40

DS3234 toc06

CRYSTAL

+20ppm

CRYSTAL

-20ppm

TYPICAL CRYSTAL,
UNCOMPENSATED

DS3234

ACCURACY

BAND

Typical Operating Characteristics

(VCC= +3.3V, TA = +25°C, unless otherwise noted.)