Datasheet

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Low-Current I

C RTCs for High-ESR Crystals

DS1341/DS1342

General Description

The DS1341/DS1342 low-current real-time clocks (RTCs)

are timekeeping devices that provide an extremely low

standby current, which permits longer life from a power

supply. The DS1341/DS1342 support high-ESR crystals,

which broaden the pool of usable crystals for the devices.

The DS1341 uses a 6pF crystal, while the DS1342 uses a

12.5pF crystal. These devices are accessed through an

C serial interface. Other features include two time-of-day

alarms, two interrupt outputs, a programmable square-

wave output, and a serial bus timeout mechanism.

The clock/calendar provides 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 24hr or 12hr format

with an AM/PM indicator.

The DS1341/DS1342 also include an input for synchroni-

zation. When a reference clock (e.g., 60Hz power line or

GPS 1PPS) is present at the CLKIN pin and the enable

external clock input bit (ECLK) is set to 1, the DS1341/

DS1342 RTCs are frequency-locked to the external clock

and the clock accuracy is determined by the external

source. In case of external clock failure, the clock is

switched to the crystal oscillator.

The devices are available in lead(Pb)-free/RoHS-

compliant, 8-pin FSOP or TDFN packages. The devices

support a -40NC to +85NC extended temperature range.

Features

S Low Timekeeping Current of 250nA (typ)

S Compatible with Crystal ESR Up to 100kI

S Use Crystals with C

= 6pF (DS1341) or

= 12.5pF (DS1342)

S +1.8V to +5.5V Operating Voltage Range

S Maintain Time Down to +1.15V (typ)

S Fast (400kHz) I

C Interface

S Bus Timeout for Lockup-Free Operation

S RTC Counts Seconds, Minutes, Hours, Day, Date,

Month, and Year with Leap Year Compensation

Valid Through 2099

S External Clock Source for Synchronization Clock

Reference (e.g., 32kHz, 50Hz/60Hz Power Line,

GPS 1PPS)

S Two Time-of-Day Alarms with Two Interrupt

Outputs

S Programmable Square-Wave Output

S Industrial Temperature Range

S Small, 8-Pin µSOP or TDFN Packages

Applications

19-4998; Rev 2; 1/12

Typical Operating Circuit

Ordering Information

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

T&R = Tape and reel.

*EP = Exposed pad.

Medical

Point of Sale (POS)

Telematics

Portable Instruments

Portable Audio

Automotive

DS1341/DS1342

SCL

SDA

CLKIN/INTA

SQW/INTB

GND

CPU

PART TEMP RANGE

PIN-

PACKAGE

OSC

(pF)

DS1341U+

-40NC to +85NC 8 FSOP

DS1341U+T&R

-40NC to +85NC 8 FSOP

DS1341T+

-40NC to +85NC

8 TDFN-EP* 6

DS1341T+T&R

-40NC to +85NC

8 TDFN-EP* 6

DS1342U+

-40NC to +85NC 8 FSOP

12.5

DS1342U+T&R

-40NC to +85NC 8 FSOP

12.5

DS1342T+

-40NC to +85NC

8 TDFN-EP* 12.5

DS1342T+T&R

-40NC to +85NC

8 TDFN-EP* 12.5

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Summary of content (16 pages)

PAGE 1
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals General Description The DS1341/DS1342 low-current real-time clocks (RTCs) are timekeeping devices that provide an extremely low standby current, which permits longer life from a power supply. The DS1341/DS1342 support high-ESR crystals, which broaden the pool of usable crystals for the devices. The DS1341 uses a 6pF crystal, while the DS1342 uses a 12.5pF crystal. These devices are accessed through an I2C serial interface.
PAGE 2
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground.....-0.3V to +6.0V Operating Temperature Range........................... -40NC to +85NC Junction Temperature Maximum......................................+150NC Storage Temperature Range............................. -55NC to +125NC Lead Temperature (soldering, 10s).................................+300NC Soldering Temperature (reflow).......................................
PAGE 3
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals AC ELECTRICAL CHARACTERISTICS (VCC = +1.8V to +5.5V, TA = -40NC to +85NC, unless otherwise noted.) (Note 2, Figure 1) PARAMETER SYMBOL SCL Clock Frequency fSCL Bus Free Time Between a STOP and START Condition tBUF Hold Time (Repeated) START Condition tHD:STA CONDITIONS MIN TYP (Note 6) (Note 7) 0.6 Fs Fs tLOW 1.3 tHIGH 0.
PAGE 4
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals Note 11: CB is the total capacitance of one bus line, including all connected devices, in pF. Note 12: Guaranteed by design; not 100% production tested. Note 13: The parameter tOSF is the period of time the oscillator must be stopped for the OSF flag to be set over the voltage range of 2.4V P VCC P VCCMAX. Note 14: The DS1341/DS1342 can detect any single SCL clock held low longer than tTIMEOUTMIN.
PAGE 5
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) CLKIN = GND, IOUT = 0mA 350 300 +85°C +25°C 250 CLKIN = GND, IOUT = 0mA 500 SUPPLY CURRENT (nA) 400 SUPPLY CURRENT (nA) 550 DS1341/2 toc01 450 DS1341 ICCT SUPPLY CURRENT vs. SUPPLY VOLTAGE (EGFIL = 1, DOSF = 0) 200 150 450 +85°C 400 350 +25°C 300 250 -40°C 100 2 1 3 -40°C 200 4 5 2 1 4 5 DS1342 ICCT SUPPLY CURRENT vs.
PAGE 6
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals 2 CLKIN/INTA 3 GND 4 DS1341 DS1342 µSOP 8 VCC 7 SQW/INTB 6 SCL 5 SDA SQW/ INTB SCL SDA 5 DS1341 DS1342 EP + 1 2 3 4 GND X2 + 6 CLKIN/ INTA 1 7 X2 X1 8 X1 TOP VIEW VCC Pin Configurations TDFN Pin Description 6 PIN NAME FUNCTION 1 X1 2 X2 Connections for a Standard 32.768kHz Quartz Crystal.
PAGE 7
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals Detailed Description The DS1341/DS1342 low-current RTCs are timekeeping devices that consume an extremely low timekeeping current, which permits longer life from a power supply. The clock/calendar provides 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 through 2099.
PAGE 8
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals External Synchronization When an external clock reference is used, the input from CLKIN/INTA is divided down to 1Hz by the divisor selected by the CLKSEL[2:1] bits. The 1Hz from the divider (Ext-1Hz, see the Functional Diagram) is used to correct the 1Hz that is derived from the 32.768kHz oscillator (Osc-1Hz). As Osc-1Hz drifts in relation to Ext-1Hz, Osc-1Hz is digitally adjusted.
PAGE 9
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals the ECLK bit is set. The external clock reference must be within the defined frequency tolerance prior to initializing the LOS flag. Register Map Table 1 shows the map for the DS1341/DS1342 registers. During a multibyte access, if the address pointer reaches the end of the register space (0Fh), it wraps around to location 00h.
PAGE 10
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals when the interface timeout is exceeded, prior to the acknowledge, the incomplete byte of data is not written. Clock and Calendar (00h–06h) The time and calendar information is obtained by reading the appropriate register bytes. The RTC registers are illustrated in Table 1. The time and calendar are set or initialized by writing the appropriate register bytes.
PAGE 11
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals When the RTC register values match alarm register settings, the corresponding alarm flag bit (A1F or A2F) is set to 1 in the Control/Status register. If the corresponding alarm interrupt enable bit (A1IE or A2IE) is also set to 1 in the Control register, the alarm condition activates the output(s) defined by the ECLK and INTCN bits (see Table 5). Control Register (0Eh) Bit 7: Enable Oscillator (EOSC).
PAGE 12
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals Control/Status Register Bitmap (0Fh) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 OSF DOSF LOS CLKSEL2 CLKSEL1 ECLK A2F A1F 1 0 1 0 0 0 X X Control/Status Register (0Fh) Bit 7: Oscillator Stop Flag (OSF). If the OSF bit is a 1, that indicates the oscillator has stopped or was stopped for some period of time, and could be used to judge the validity of the clock and calendar data.
PAGE 13
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals I2C Serial Port Operation I2C Slave Address The DS1341/DS1342s’ slave address byte is D0h. The first byte sent to the device includes the device identifier and the R/W bit (Figure 5). The device address sent by the I2C master must match the address assigned to the device. I2C Definitions The following terminology is commonly used to describe I2C data transfers. Master Device: The master device controls the slave devices on the bus.
PAGE 14
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals TYPICAL I2C WRITE TRANSACTION MSB START 1 LSB 1 0 1 0 0 0 R/W MSB SLAVE ACK b7 LSB b6 READ/ WRITE SLAVE ADDRESS b5 b4 b3 b2 b1 b0 MSB SLAVE ACK b7 LSB b6 b5 b4 REGISTER ADDRESS b3 b2 b1 b0 SLAVE ACK STOP DATA EXAMPLE I2C TRANSACTIONS D0h A) SINGLE BYTE WRITE -WRITE CONTROL REGISTER TO 18h START B) SINGLE BYTE READ -READ CONTROL REGISTER START 1 1 0 1 0 0 0 0 11010000 D0h 0Eh SLAVE 00001110 ACK 0Eh SLAVE SLAVE 000
PAGE 15
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals reads data with ACK or NACK as applicable, and generates a STOP condition. See Figure 6 for a read example using the repeated START condition to specify the starting memory location. Reading Multiple Bytes from a Slave: The read operation can be used to read multiple bytes with a single transfer. When reading bytes from the slave, the master simply ACKs the data byte if it desires to read another byte before terminating the transaction.
PAGE 16
DS1341/DS1342 Low-Current I2C RTCs for High-ESR Crystals Revision History REVISION NUMBER REVISION DATE 0 10/09 Initial release 12/10 Removed future status from the DS1342 in the Ordering Information table; added the Package Thermal Characteristics section; added the DS1342 ICCT parameter to the DC Electrical Characteristics table; changed the ESR specification in the Crystal Parameters table from 80kW (max) to 100kW (max) and removed 35kW typ; added the TDFN package to the Ordering Information, Pin C