Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsIntegrated Circuits (ICs)Timer IC t- real time clock Binary counter µSOP-10

General Description

The DS1374 is a 32-bit binary counter designed to contin-

uously count time in seconds. An additional counter gen-

erates a periodic alarm or serves as a watchdog timer. If

disabled, this counter can be used as 3 bytes of non-

volatile (NV) RAM. Separate output pins are provided for

an interrupt and a square wave at one of four selectable

frequencies. A precision temperature-compensated refer-

ence and comparator circuit monitor the status of V

detect power failures, provide a reset output, and auto-

matically 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 pro-

grammed serially through an I

C 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

♦ I

C 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 Laboratories (UL) Recognized

DS1374

C, 32-Bit Binary Counter Watchdog RTC with

Trickle Charger and Reset Input/Output

______________________________________________

Maxim Integrated Products

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

RPU

Typical Operating Circuit

19-5484; Rev 4; 8/10

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.

PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK**

DS1374C-18# -40°C to +85°C 1.8 16 SO (300 mils) DS1374C-18

DS1374C-3# -40°C to +85°C 3.0 16 SO (300 mils) DS1374C-3

DS1374C-33# -40°C to +85°C 3.3 16 SO (300 mils) DS1374C-33

DS1374U-18+ -40°C to +85°C 1.8 10 μSOP DS1374-18

DS1374U-3+ -40°C to +85°C 3.0 10 μSOP DS1374-3

DS1374U-33+ -40°C to +85°C 3.3 10 μSOP DS1374-33

Pin Configurations appear at the end of the data sheet.

Denotes a RoHS-compliant device that may include lead that is exempt under RoHS requirements. The lead finish is JESD97 category

e3, and is compatible with both lead-based and lead-free soldering processes.

Denotes a lead(Pb)-free/RoHS-compliant package.

A "#" anywhere on the top mark denotes a RoHS-compliant package. A “+” anywhere on the top mark denotes a lead(Pb)-free

package.

Summary of content (18 pages)

PAGE 1
9-5484; Rev 4; 8/10 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Features 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.
PAGE 2
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output ABSOLUTE MAXIMUM RATINGS Voltage Range on VCC Pin Relative to Ground .....-0.3V to +6.0V Voltage Range on SDA or SCL Relative to Ground ....................................-0.3V to VCC + 0.3V Junction-to-Ambient Thermal Resistance (θJA) (Note 1) 16-Pin SO .....................................................................73°C/W 10-Pin µSOP ...............................................................
PAGE 3
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output DS1374 DC ELECTRICAL CHARACTERISTICS (VCC = VCC(MIN) to VCC(MAX) , TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER Trickle-Charge Current-Limiting Resistors SYMBOL CONDITIONS MIN TYP R1 (Note 6) 250 R2 (Note 7) 2000 MAX R3 (Note 8) Input Leakage ILI (Note 9) -1 +1 I/O Leakage ILO (Note 10) -1 +1 RST Pin I/O Leakage ILORST (Note 11) -200 SDA Logic 0 Output (VOL = 0.
PAGE 4
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output AC ELECTRICAL CHARACTERISTICS (VCC = VCC(MIN) to VCC(MAX), TA = -40°C to +85°C, unless otherwise noted.
PAGE 5
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output (TA = -40°C to +85°C) (Figure 3) PARAMETER VCC Detect to Recognize Inputs (VCC Rising) SYMBOL tRPU CONDITIONS MIN (Note 24) TYP 250 MAX UNITS ms VCC Fall Time; VPF(MAX) to VPF(MIN) tF 300 μs VCC Rise Time; V PF(MIN) to VPF(MAX) tR 0 μs WARNING: Under no circumstances are negative undershoots, of any amplitude, allowed when the device is in write protection.
PAGE 6
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output SDA tBUF tSP tHD:STA tLOW tR tF SCL tHD:STA STOP tSU:STA tHIGH tSU:DAT START tSU:STO REPEATED START tHD:DAT Figure 1. Data Transfer on I2C Serial Bus RST PBDB tRST Figure 2. Pushbutton Reset Timing VCC VPF(MAX) VPF VPF VPF(MIN) tF tR tRPU tRST RST INPUTS RECOGNIZED DON'T CARE RECOGNIZED HIGH-Z OUTPUTS VALID Figure 3.
PAGE 7
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output IBAT0SC2 vs. VBAT SQUARE-WAVE ON VCC = 0V SUPPLY CURRENT (nA) 750 450 400 475 VCC = 0V 700 650 600 550 500 450 425 400 450 350 400 350 2.8 3.3 3.8 4.3 4.8 5.3 375 1.3 1.8 2.3 2.8 VBAT (V) 3.3 3.8 4.3 4.8 5.3 -20 -40 VBAT (V) 0 20 40 60 80 TEMPERATURE (°C) ICCA vs. VCC (SQUARE-WAVE ON) OSCILLATOR FREQUENCY vs. VBACKUP 275 32768.8 250 VCC = 0V 32768.7 225 FREQUENCY (Hz) 32768.
PAGE 8
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Pin Description PIN μSOP 1, 2 3 SO — 13 NAME FUNCTION X1, X2 Connections for a Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 6pF. Pin X1 is the input to the oscillator and can optionally be connected to an external 32.768kHz oscillator.
PAGE 9
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output PARAMETER SYMBOL Nominal Frequency fO Series Resistance ESR MIN TYP DS1374 Table 1. Crystal Specifications* LOCAL GROUND PLANE (LAYER 2) MAX UNITS 32.768 X1 kHz CRYSTAL Load Capacitance 45 CL 6 kΩ X2 pF *The crystal, traces, and crystal input pins should be isolated from RF generating signals.
PAGE 10
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Power Control Address Map The power-control function is provided by a precise, temperature-compensated voltage reference and a comparator circuit that monitors the V CC level. The device is fully accessible and data can be written and read when VCC is greater than VPF. However, when VCC falls below VPF, the internal clock registers are blocked from any access.
PAGE 11
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output The contents of the watchdog/alarm counter, which is a separate 24-bit down counter, are accessed in the address range 04h–06h. When this counter is written, the counter and a seed register are loaded with the desired value. When the counter is to be reloaded, it uses the value in the seed register.
PAGE 12
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Bit 7 EOSC Bit 6 WACE Bit 5 WD/ALM Bit 4 BBSQW Special Purpose Registers The DS1374 has two additional registers (07h–08h) that control the WD/ALM counter and the square-wave, interrupt, and reset outputs. Control Register (07h) Bit 7/Enable Oscillator (EOSC). When set to logic 0, the oscillator is started. When set to logic 1, the oscillator is stopped.
PAGE 13
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 OSF 0 0 0 0 0 0 AF Status Register (08h) Bit 7/Oscillator Stop Flag (OSF). A logic 1 in this bit indicates that the oscillator either is stopped or was stopped for some period of time and can be used to judge the validity of the timekeeping data. This bit is set to logic 1 any time the oscillator stops.
PAGE 14
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output BIT 7 TCS3 BIT 6 TCS2 BIT 5 TCS1 BIT 4 TCS0 BIT 3 DS1 BIT 2 DS0 BIT 1 BIT 0 ROUT1 ROUT0 TCS0-3 = TRICKLE CHARGER SELECT DS0-1 = DIODE SELECT TOUT0-1 = RESISTOR SELECT 1 OF 16 SELECT NOTE: ONLY 1010b ENABLES CHARGER 1 OF 2 SELECT 1 OF 3 SELECT R1 250Ω R2 2kΩ VCC VBACKUP R3 4kΩ Figure 7.
PAGE 15
S 1101000 0 A XXXXXXXX A S - START A - ACKNOWLEDGE P - STOP R/W - READ/WRITE OR DIRECTION BIT DATA (n) XXXXXXXX DATA (n + 1) A SLAVE ADDRESS DATA (n + x) XXXXXXXX A XXXXXXXX P DATA TRANSFERRED (X+1 Bytes + Acknowledge) S 1101000 R/W REGISTER ADDRESS (n) DATA (n) DATA (n + 1) 1 A XXXXXXXX A S - START A - ACKNOWLEDGE P - STOP /A - NOT ACKNOWLEDGE R/W - READ/WRITE OR DIRECTION BIT XXXXXXXX DATA (n + 2) A DS1374 SLAVE ADDRESS R/W I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger
PAGE 16
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output DS1374 After the DS1374 acknowledges the slave address + write bit, the master transmits a register address to the DS1374. This sets the register pointer on the DS1374, with the DS1374 acknowledging the transfer. The master can then transmit zero or more bytes of data, with the DS1374 acknowledging each byte received. The register pointer increments after each data byte is transferred.
PAGE 17
I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output TOP VIEW SCL 1 16 SDA INT 2 15 GND SQW 3 14 RST SCL VCC 4 13 VBACKUP SDA N.C. 5 12 N.C. N.C. 6 11 N.C. N.C. 7 10 N.C. N.C. 8 9 N.C. X1 1 10 VCC X2 2 9 SQW VBACKUP 3 8 INT RST 4 7 GND 5 6 DS1374 μSOP DS1374C SO (0.300") Chip Information PROCESS: CMOS SUBSTRATE CONNECTED TO GROUND Package Information For the latest package outline information and land patterns, go to www.
PAGE 18
DS1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output Revision History REVISION NUMBER 3 REVISION DATE DESCRIPTION PAGES CHANGED 8/10 Removed leaded parts from the Ordering Information table; in the Absolute Maximum Ratings section, added the thermal information, lead information, and new Note 1, and updated the soldering information; in the Control Register (07h) section, corrected the references of INTCN to WDSTR in the AIE bit description; removed the section a