Rainbow Electronics DS1374 User Manual

General Description

The DS1374 is a 32-bit binary counter designed to continuously count time in seconds. An additional counter generates a periodic alarm or serves as a watchdog timer. If disabled, this counter can be used as 3 bytes of nonvolatile (NV) RAM. Separate output pins are provided for an interrupt and a square wave at one of four selectable frequencies. A precision temperature-compensated reference and comparator circuit monitor the status of VCCto detect power failures, provide a reset output, and automatically switch to the backup supply when necessary. Additionally, the reset pin is monitored as a pushbutton input for externally generating a reset. The device is programmed serially through an I2C™ serial interface.

Applications

Portable Instruments

Point-of-Sale Equipment

Medical Equipment

Telecommunications

Features

♦ 32-Bit Binary Counter

♦ Second Binary Counter Provides Time-of-Day

Alarm, Watchdog Timer, or NV RAM

♦ Separate Square-Wave and Interrupt Output Pins

♦ I2C Serial Interface

♦ Automatic Power-Fail Detect and Switch Circuitry

♦ Single-Pin Pushbutton Reset Input/Open-Drain

Reset Output

♦ Low-Voltage Operation

♦ Trickle-Charge Capability

♦ -40°C to +85°C Operating Temperature Range

♦ 10-Pin µSOP, 16-Pin SO

♦ Available in a Surface-Mount Package with an

Integrated Crystal (DS1374C)

♦ Underwriters Laboratory (UL) Recognized

DS1374

I2C, 32-Bit Binary Counter Watchdog RTC with

Trickle Charger and Reset Input/Output

______________________________________________ Maxim Integrated Products 1

Ordering Information

DS1374

X1 X2

CRYSTAL

SQW

SCL

SDA

INT

RST

INT

RST

GND

BACKUP

N.O.

PUSHBUTTON

RESET

PRIMARY BATTERY, RECHARGEABLE BATTERY, OR SUPER CAPACITOR

CPU

RPU

RPU = t

r/CB

RPU

Typical Operating Circuit

Rev 1; 9/04

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.

PART

TEMP RANGE

PINPACKAGE

TOP MARK

DS1374U-18

10 µSOP DS1374-18

DS1374U-3

10 µSOP DS1374-3

DS1374U-33

10 µSOP DS1374-33

DS1374C-18

DS1374C-3

DS1374C-33

I2C is a trademark of Philips Corp. Purchase of I2C components of Maxim Integrated Products, Inc., or one of its sublicensed Associated Companies, conveys a license under the Philips I

C Patent Rights to use these components in an I2C

system, provided that the system conforms to the I

C Standard

Specification as defined by Philips.

Pin Configurations appear at the end of the data sheet.

-40°C to +85°C

-40°C to +85°C 16 SO, 0.300"

DS1374

I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED DC OPERATING CONDITIONS

(VCC= V

CC MIN

to V

CC MAX

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

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 VCCPin Relative to Ground .....-0.3V to +6.0V

Voltage Range on SDA, SCL, and WDS

Relative to Ground....................................-0.3V to V

+ 0.3V

Operating Temperature Range ...........................-40

°C to +85°C

Storage Temperature Range .............................-55°C to +125°C

Soldering Temperature Range ........................See the Handling,

PC Board Layout, and Assembly section.

PARAMETER

CONDITIONS

UNITS

DS1374-33

3.3

DS1374-3 2.7 3.0 3.3

Supply Voltage (Notes 2, 3)

DS1374-18

1.8

Input Logic 1 V

(Note 2)

Input Logic 0 V

(Note 2)

+0.3 x

Pullup Resistor Voltage (INT, SQW, SDA, SCL), V

= 0V

(Note 2) 5.5 V

DS1374-33

DS1374-3

2.6 2.7

Power-Fail Voltage (Note 2)

DS1374-18

1.6

DS1374-33 1.3 3.0

DS1374-3 1.3 3.0 3.7

Backup Supply Voltage (Notes 2, 3, 4)

SYMBOL

BACKUP

MIN TYP MAX

2.97

1.71

0.7 x V

-0.3

2.70 2.88 2.97

2.45

1.51

5.50

1.89

+ 0.3

1.71

MAX

DS1374

I2C, 32-Bit Binary Counter Watchdog RTC with

Trickle Charger and Reset Input/Output

_____________________________________________________________________ 3

DC ELECTRICAL CHARACTERISTICS

(VCC= V

CC MIN

to V

CC MAX

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

PARAMETER

CONDITIONS

UNITS

R1 (Note 5)

R2 (Note 6)

Trickle-Charge Current-Limiting Resistors

R3 (Note 7)

Ω

Input Leakage I

(Note 8) -1 +1

I/O Leakage I

(Note 9) -1 +1

RST Pin I/O Leakage I

LORST

(Note 10)

µA

SDA Logic 0 Output (V

= 0.4V)

OLSDA

3.0 mA

VCC > 2V; VOL = 0.4V 3.0

1.71V < VCC < 2V; VOL = 0.2 V

3.0

RST, SQW, and INT Logic 0 Outputs (Note 11)

OL1

1.3V < VCC < 1.71V; VOL = 0.2 V

250 µA

DS1374-18 75 150

DS1374-3

200

Active Supply Current (Notes 11, 12)

CCA

DS1374-33

300

µA

DS1374-18 60 100

DS1374-3 80 125

Standby Current (Notes 11, 13) I

CCS

DS1374-33

175

µA

BACKUP

Leakage Current

BACKUP

= 3.7V)

100 nA

DC ELECTRICAL CHARACTERISTICS

(VCC= 0V, V

BACKUP

= 3.7V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

PARAMETER

CONDITIONS

UNITS

BACKUP

Current (OSC ON);

SQW OFF

(Note 14)

700 nA

BACKUP

Current (OSC ON);

SQW ON (32kHz)

(Notes 14, 15)

BACKUP

Data-Retention Current

(OSC OFF)

25 100 nA

SYMBOL

BACKUPLKG

MIN TYP MAX

250

2000

4000

-200

110

180

115

SYMBOL

BKOSC1

BKOSC2

BACKUPDR

MAX TYP MAX

400

600 1000

DS1374

I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output

4 _____________________________________________________________________

AC ELECTRICAL CHARACTERISTICS

(VCC= V

CC MIN

to V

CC MAX

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

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Fast mode

400

SCL Clock Frequency (Note 16) f

SCL

Standard mode 0 100

kHz

Fast mode 1.3

Bus Free Time Between STOP and START Conditions

BUF

Standard mode 4.7

µs

Fast mode 0.6

Hold Time (Repeated) START Condition (Note 17)

Standard mode 4.0

µs

Fast mode 1.3

Low Period of SCL Clock t

LOW

Standard mode 4.7

µs

Fast mode 0.6

High Period of SCL Clock t

HIGH

Standard mode 4.0

µs

Fast mode 0 0.9

Data Hold Time (Notes 18, 19)

Standard mode 0 0.9

µs

Fast mode

Data Setup Time (Note 20)

Standard mode

Fast mode 0.6

Start Setup Time t

SU:STA

Standard mode 4.7

µs

Fast mode 300

Rise Time of Both SDA and SCL Signals (Note 16)

Standard mode

20 +

Fast mode 300

Fall Time of Both SDA and SCL Signals (Note 16)

Standard mode

20 +

300

Fast mode 0.6

Setup Time for STOP Condition

Standard mode 4.7

µs

C ap aci ti ve Load for E ach Bus Li ne

(Note 16) 400 pF

I/O C ap aci tance ( S D A, S C L) C

I/O

(Note 21) 10 pF

Pulse Width of Spikes That Must

be Suppressed by the Input Filter

Fast mode 30 ns

Pushbutton Debounce PB

(Figure 2)

Reset Active Time t

RST

(Figure 2)

Oscillator Stop Flag (OSF) Delay

OSF

(Note 22)

100

HD:STA

HD:DAT

SU:DAT

SU:STO

100

250

0.1C

B 1000

0.1C

250

100

DS1374

I2C, 32-Bit Binary Counter Watchdog RTC with

Trickle Charger and Reset Input/Output

_____________________________________________________________________ 5

POWER-UP/POWER-DOWN CHARACTERISTICS

(TA= -40°C to +85°C) (Figure 3)

PARAMETER

CONDITIONS

UNITS

VCC Detect to Recognize Inputs (V

Rising)

RPU

(Note 23)

VCC Fall Time; V

PF(MAX)

PF(MIN)

µs

VCC Rise Time; V

PF(MIN)

PF(MAX)

0µs

WARNING: Under no circumstances are negative undershoots, of any amplitude, allowed when the device is in write protection.

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

BACKUP

should not exceed V

MAX

or 3.7V, whichever is greater.

Note 4: The use of the 250Ω trickle-charge resistor is not allowed at V

> 3.63V and should not be enabled.

Note 5: Measured at V

= typ, V

BACKUP

= 0V, register 09h = A5h.

Note 6: Measured at V

= typ, V

BACKUP

= 0V, register 09h = A6h.

Note 7: Measured at V

= typ, V

BACKUP

= 0V, register 09h = A7h.

Note 8: SCL only. Note 9: SDA and SQW and INT. Note 10: The RST pin has an internal 50kΩ pullup resistor to V

Note 11: Trickle charger disabled. Note 12: I

CCA

—SCL clocking at max frequency = 400kHz.

Note 13: Specified with I

C bus inactive.

Note 14: Measured with a 32.768kHz crystal attached to the X1 and X2 pins. Note 15: WDSTR = 1. BBSQW = 1 is required for operation when V

is below the power-fail trip point (or absent).

Note 16: C

—total capacitance of one bus line in pF.

Note 17: After this period, the first clock pulse is generated. Note 18: The maximum t

HD:DAT

only has to be met if the device does not stretch the low period (t

LOW

) of the SCL signal.

Note 19: A device must internally provide a hold time of at least 300ns for the SDA signal (referred to as the V

IHMIN

of the SCL sig-

nal) to bridge the undefined region of the falling edge of SCL.

Note 20: A fast-mode device can be used in a standard-mode system, but the requirement t

SU:DAT

≥ to 250ns must be met. This is automatically the case if the device does not stretch the low period of the SCL signal. If such a device does stretch the low period of the SCL signal, it must output the next data bit to the SDA line t

max +

SU:DAT

= 1000 + 250 = 1250ns before

the SCL line is released.

Note 21: Guaranteed by design. Not production tested. Note 22: 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

≤ V

CC MAX

and 1.3V ≤ V

BACKUP

≤ 3.7V.

Note 23: This delay applies only if the oscillator is enabled and running. If the EOSC bit is 1, the startup time of the oscillator is

added to this delay.

SYMBOL

MIN TYP MAX

300

250

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