MAXIM DS3234 User Manual

General Description

The DS3234 is a low-cost, extremely accurate SPI™ bus
real-time clock (RTC) with an integrated temperature­compensated crystal oscillator (TCXO) and crystal. The
DS3234 incorporates a precision, temperature-compen­sated voltage reference and comparator circuit to moni­tor V

CC

. When VCCdrops below the power-fail voltage

(V

PF

), the device asserts the RST output and also dis-

ables 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 reset externally. 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

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 Laboratory (UL) Recognized

DS3234

Extremely Accurate SPI Bus RTC with

Integrated Crystal and SRAM

______________________________________________

Maxim Integrated Products

1

Rev 1; 7/07

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.

Ordering Information

SPI is a trademark of Motorola, Inc.

Typical Operating Circuit

#

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.

TOP VIEW

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

SCLK

DOUT

SCLK

DINV

CC

32kHz

N.C.

CS

V

BAT

GND

N.C.

N.C.N.C.

N.C.

RST

INT/SQW

12

11

9

10

N.C.

N.C.N.C.

N.C.

SO

DS3234

Pin Configuration

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

CC

SS
SCLK
MOSI
MISO

RST

CPU

PUSH-

BUTTON

RESET

CS
SCLK
DIN

DOUT
RST

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

CC

V

CC

INT/SQW

DS3234

GND

32kHz

V

BAT

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

V

PU

DS3234

Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED DC OPERATING CONDITIONS

(TA= -40°C to +85°C, unless otherwise noted.) (Notes 1, 2)

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

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

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 1, 2)

Supply Voltage

Logic 1 Input CS, SCLK, DIN V

Logic 0 Input CS, SCLK, DIN,

RST

Pullup Voltage INT/SQW V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

CC

V

BAT

IH

V

PU

2.0V ≤ VCC ≤ 3.63V -0.3

IL

3.63V < VCC ≤ 5.5V -0.3 +0.7

VCC = 0V 5.5 V

2.0 3.3 5.5

2.0 3.0 3.8

0.7 x
V

CC

VCC +

0.3

+0.2 x

V

CC

V

V

V

Active Supply Current I

Standby Supply Current I

Temperature Conversion Current I

Power-Fail Voltage V

V

BAT

(VCC = 2.0V to 5.5V, TA = -40°C to +85°C, unless otherwise noted.) (Notes 1 and 2)

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

= -500µA
= -250µA
= -125µA

CCA

CCS

CCSCONV

PF

BATLKG

V

OH

SCLK = 4MHz, BSY = 0
(Notes 3, 4)

CS = VIH, 32kHz output off,
SQW output off
(Note 4)

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

_____________________________________________________________________ 3

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 1, 2)

ELECTRICAL CHARACTERISTICS

(VCC= 0V, V

BAT

= 2.0V to 3.8V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

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

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 5) -200 +10 µA

V

= 3.3V or V

CC

= 3.3V 32.768 kHz

BAT

= 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 1 and 2)

BAT

OUT

V

0°C to +40°C -2 +2

Frequency Stability vs.

Temperature

Δf/f

OUT

V

V

CC

BAT

= 3.3V or

= 3.3V

-40°C to 0°C and

+40°C to +85°C

-3.5 +3.5

ppm

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

-40°C 0.7

Trim Register Frequency

Sensitivity per LSB

Δf/LSB Specified at:

+25°C 0.1
+70°C 0.4

ppm

+85°C 0.8

Temperature Accuracy Temp -3 +3 °C

Crystal Aging Δf/f

OUT

After reflow,
not production tested

First year ±1.0

0–10 years ±5.0

ppm

Battery Current
(Note 4)

Temperature Conversion Current I

Data-Retention Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

I

BAT

TC

BATTC

V

= 3.4V 1.5 2.3

EOSC = 0, BBSQW = 0

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

BAT

= 3.8V 1.5 2.5

V

BAT

µA

DS3234

Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM

4 _____________________________________________________________________

AC ELECTRICAL CHARACTERISTICS

(VCC= 2.0V to 5.5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

POWER-SWITCH CHARACTERISTICS

(TA= -40°C to +85°C)

CAPACITANCE

(TA= +25°C)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SCLK Clock Frequency f

Data to SCLK Setup t

SCLK to Data Hold t
SCLK to CS Setup t

SCLK to Data Valid (Note 6) 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

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 ≤ VCC ≤ 5.5V 80

2.0V ≤ V

2.7V ≤ VCC ≤ 5.5V 110

2.0V ≤ V

2.7V ≤ VCC ≤ 5.5V 110

2.0V ≤ V

F

2.7V ≤ VCC ≤ 5.5V 100

2.0V ≤ V

(Note 7) 40 ns

(Note 8) 100 ms

< 2.7V 2

CC

30 ns

30 ns

30 ns

< 2.7V 160

CC

< 2.7V 220

CC

< 2.7V 220

CC

400 ns

< 2.7V 200

CC

250 ms

125 200 ms

MHz

ns

ns

ns

200 ns

ns

400 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

VCCF

t

VCCR

REC

(Note 9) 125 300 ms

Capacitance on All Input Pins C

Capacitance on All Output Pins C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

(Note 10) 10 pF

IN

Outputs high impedance (Note 10) 10 pF

IO

300 µs

0µs

DS3234

Extremely Accurate SPI Bus RTC with

Integrated Crystal and SRAM

_____________________________________________________________________ 5

Pushbutton Reset Timing

Power-Switch Timing

Note 1: Limits at -40°C are guaranteed by design and not production tested.
Note 2: All voltages are referenced to ground.
Note 3: Measured at V

IH

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

Note 4: Current is the averaged input current, which includes the temperature conversion current. CRATE1 = CRATE0 = 0.
Note 5: The RST pin has an internal 50kΩ (nominal) pullup resistor to V

CC

.

Note 6: 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 7: With 50pF load.
Note 8: 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.

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

V

PF(MAX)

V

PF(MIN)

RST

PB

DB

t

RST

V

CC

t

VCCF

V

PF

V

PF

t

VCCR

t

REC

RST

DS3234

Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM

6 _____________________________________________________________________

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.

SCLK

CC

t

DC

W/R

CS

t

CC

t

t

CL

t

CDH

WRITE ADDRESS BYTE

t

R

A6

HIGH IMPEDANCE

R

t

F

t

t

CH

t

CDD

A0

D7

READ DATA BYTE

D0

CDZ

t

CWH

t

t

F

CCH

t

DOUT

DIN

CL

t

t

DC

W/R

CDH

WRITE ADDRESS BYTE

t

CH

A6

A0

HIGH IMPEDANCE

D7 D0

WRITE DATA BYTE