DS1306+ - MAXIM INTEGRATED PRODUCTS

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FEATURES

 Real-Time Clock (RTC) Counts Seconds,

Minutes, Hours, Date of the Month, Month,

Day of the Week, and Year with Leap-Year

Compensation Valid Up to 2100

 96-Byte, Battery-Backed NV RAM for Data

Storage

 Two Time-of-Day Alarms, Programmable on

Combination of Seconds, Minutes, Hours,

and Day of the Week

 1Hz and 32.768kHz Clock Outputs

 Supports Motorola SPI™ (Serial Peripheral

Interface) Modes 1 and 3 or Standard 3-Wire

Interface

 Burst Mode for Reading/Writing Successive

Addresses in Clock/RAM

 Dual-Power Supply Pins for Primary and

Backup Power Supplies

 Optional Trickle Charge Output to Backup

Supply

 2.0V to 5.5V Operation

 Optional Industrial Temperature Range:

-40°C to +85°C

 Available in Space-Efficient, 20-Pin TSSOP

Package

 Underwriters Laboratory (UL) Recognized

PIN CONFIGURATIONS

www.maxim-ic.com

DS1306

Serial Alarm Real-Time Clock

SPI is a trademark of Motorola, Inc.

TSSOP (4.4mm)

VCC2

VBAT

N.C.

NT0

INT1

1Hz

GND

VCC1

N.C.

32kHz

VCCIF

SDO

SDI

SCLK

SERMODE

N.C.

VCC2

DIP (300 mils)

NT0

1Hz

GND

VCC1

SDO

SDI

SCLK

SERMODE

VBAT

INT1

32kHz

VCCIF

19-5056; Rev 12/09

DS1306

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ORDERING INFORMATION

PART TEMP RANGE PIN-PACKAGE TOP MARK*

DS1306 0°C to +70°C 16 DIP (300 mils) DS1306

DS1306+ 0°C to +70°C 16 DIP (300 mils) DS1306 +

DS1306N -40°C to +85°C 16 DIP (300 mils) DS1306N

DS1306N+ 0°C to +70°C 16 DIP (300 mils) DS1306N +

DS1306E 0°C to +70°C 20 TSSOP (173 mils) DS1306

DS1306E+ 0°C to +70°C 20 TSSOP (173 mils) DS1306 +

DS1306EN -40°C to +85°C 20 TSSOP (173 mils) DS1306N

DS1306EN+ -40°C to +85°C 20 TSSOP (173 mils) DS1306N +

DS1306EN/T&R -40°C to +85°C 20 TSSOP (173 mils) DS1306N

DS1306EN+T&R -40°C to +85°C 20 TSSOP (173 mils) DS1306N +

DS1306E/T&R 0°C to +70°C 20 TSSOP (173 mils) DS1306

DS1306E+T&R 0°C to +70°C 20 TSSOP (173 mils) DS1306 +

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

T&R = Tape and reel.

*An “N” on the top mark indicates an industrial device.

PIN DESCRIPTION

TSSOP DIP NAME FUNCTION

1 1 VCC2

Backup Power Supply. This is the secondary power supply pin. In systems

using the trickle charger, the rechargeable energy source is connected to this

pin.

2 2 VBAT

Battery Input for Any Standard +3V Lithium Cell or Other Energy

Source. If not used, VBAT must be connected to ground. Diodes must not be

placed in series between VBAT and the battery, or improper operation will

result. UL recognized to ensure against reverse charging current when used

in conjunction with a lithium battery. See “Conditions of Acceptability” at

www.maxim-ic.com/TechSupport/QA/ntrl.htm.

3 3 X1

5 4 X2

Connections for Standard 32.768kHz Quartz Crystal. The internal

oscillator is designed for operation with a crystal having a specified load

capacitance of 6pF. For more information on crystal selection and crystal

layout considerations, refer to Application Note 58, “Crystal Considerations

with Dallas Real-Time Clocks.” The DS1306 can also be driven by an

external 32.768kHz oscillator. In this configuration, the X1 pin is connected

to the external oscillator signal and the X2 pin is floated.

7 5

INT0

Active-Low Interrupt 0 Output. The INT0 pin is an active-low output of

the DS1306 that can be used as an interrupt input to a processor. The INT0

pin can be programmed to be asserted by Alarm 0. The INT0 pin remains

low as long as the status bit causing the interrupt is present and the

corresponding interrupt enable bit is set. The INT0 pin operates when the

DS1306 is powered by VCC1, VCC2, or VBAT. The INT0 pin is an open-drain

output and requires an external pullup resistor.

8 6 INT1

Interrupt 1 Output. The INT1 pin is an active-high output of the DS1306

that can be used as an interrupt input to a processor. The INT1 pin can be

programmed to be asserted by Alarm 1. When an alarm condition is present,

the INT1 pin generates a 62.5ms active-high pulse. The INT1 pin operates

only when the DS1306 is powered by VCC2 or VBAT. When active, the INT1

pin is internally pulled up to VCC2 or VBAT. When inactive, the INT1 pin is

internally pulled low.

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PIN DESCRIPTION (continued)

TSSOP DIP NAME FUNCTION

9 7 1Hz

1Hz Output. The 1Hz pin provides a 1Hz square wave output. This output

is active when the 1 Hz bit in the control register is a logic 1. Both INT0 and

1Hz pins are open-drain outputs. The interrupt, 1Hz signal, and the internal

clock continue to run regardless of the level of VCC (as long as a power

source is present).

10 8 GND

Ground

11 9 SERMODE

Serial Interface Mode. The SERMODE pin offers the flexibility to choose

between two serial interface modes. When connected to GND, standard

3-wire communication is selected. When connected to VCC, SPI

communication is selected.

12 10 CE

Chip Enable. The chip enable signal must be asserted high during a read or

a write for both 3-wire and SPI communication. This pin has an internal

55k pulldown resistor (typical).

14 11 SCLK

Serial Clock. SCLK is used to synchronize data movement on the serial

interface for either the SPI or 3-wire interface.

15 12 SDI

Serial Data In. When SPI communication is selected, the SDI pin is the

serial data input for the SPI bus. When 3-wire communication is selected,

this pin must be tied to the SDO pin (the SDI and SDO pins function as a

single I/O pin when tied together).

16 13 SDO

Serial Data Out. When SPI communication is selected, the SDO pin is the

serial data output for the SPI bus. When 3-wire communication is selected,

this pin must be tied to the SDI pin (the SDI and SDO pins function as a

single I/O pin when tied together). VCCIF provides the logic-high level.

17 14 VCCIF

Interface Logic Power-Supply Input. The VCCIF pin allows the DS1306 to

drive SDO and 32kHz output pins to a level that is compatible with the

interface logic, thus allowing an easy interface to 3V logic in mixed supply

systems. This pin is physically connected to the source connection of the

p-channel transistors in the output buffers of the SDO and 32kHz pins.

18 15 32kHz

32.768kHz Output. The 32kHz pin provides a 32.768kHz output. This

signal is always present. VCCIF provides the logic-high level.

20 16 VCC1 Primary Power Supply. DC power is provided to the device on this pin.

VCC1 is the primary power supply.

4, 6, 13,

19 — N.C.

No Connection

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DESCRIPTION

The DS1306 serial alarm real-time clock (RTC) provides a full binary coded decimal (BCD) clock

calendar that is accessed by a simple serial interface. The clock/calendar provides seconds, minutes,

hours, day, date, month, and year information. The end of the month date 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. In addition, 96 bytes of NV RAM are provided for data

storage.

An interface logic power-supply input pin (VCCIF) allows the DS1306 to drive SDO and 32kHz pins to a

level that is compatible with the interface logic. This allows an easy interface to 3V logic in mixed supply

systems. The DS1306 offers dual-power supplies as well as a battery-input pin. The dual-power supplies

support a programmable trickle charge circuit that allows a rechargeable energy source (such as a super

cap or rechargeable battery) to be used for a backup supply. The VBAT pin allows the device to be backed

up by a non-rechargeable battery. The DS1306 is fully operational from 2.0V to 5.5V.

Two programmable time-of-day alarms are provided by the DS1306. Each alarm can generate an

interrupt on a programmable combination of seconds, minutes, hours, and day. “Don’t care” states can be

inserted into one or more fields if it is desired for them to be ignored for the alarm condition. A 1Hz and a

32kHz clock output are also available.

The DS1306 supports a direct interface to SPI serial data ports or standard 3-wire interface. An easy-to-

use address and data format is implemented in which data transfers can occur 1 byte at a time or in

multiple-byte burst mode.

OPERATION

The block diagram in Figure 1 shows the main elements of the serial alarm RTC. The following

paragraphs describe the function of each pin.

Figure 1. BLOCK DIAGRAM

1Hz

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RECOMMENDED LAYOUT FOR CRYSTAL

CLOCK ACCURACY

The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match

between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was

trimmed. Additional error is added by crystal frequency drift caused by temperature shifts. External

circuit noise coupled into the oscillator circuit can result in the clock running fast. Refer to Application

Note 58: Crystal Considerations with Dallas Real-Time Clocks for detailed information.

Table 1. Crystal Specifications

PARAMETER SYMBOL MIN TYP MAX UNITS

Nominal Frequency fO 32.768 kHz

Series Resistance ESR 45 k

Load Capacitance CL 6 pF

*The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to

Application Note 58: Crystal Considerations for Dallas Real-Time Clocks for additional specifications.

CLOCK, CALENDAR, AND ALARM

The time and calendar information is obtained by reading the appropriate register bytes. The RTC

registers are illustrated in Figure 2. The time, calendar, and alarm are set or initialized by writing the

appropriate register bytes. Note that some bits are set to 0. These bits always read 0 regardless of how

they are written. Also note that registers 12h to 1Fh (read) and registers 92h to 9Fh are reserved. These

registers always read 0 regardless of how they are written. The contents of the time, calendar, and alarm

registers are in the BCD format.. Values in the day register that correspond to the day of the week are

user-defined, but must be sequential (e.g. if 1 equals Sunday, 2 equals Monday and so on). The day

WRITING TO THE CLOCK REGISTERS

The internal time and date registers continue to increment during write operations. However, the

countdown chain is reset when the seconds register is written. Writing the time and date registers within

one second after writing the seconds register ensures consistent data.

Terminating a write before the last bit is sent aborts the write for that byte.

READING FROM THE CLOCK REGISTERS

Buffers are used to copy the time and date register at the beginning of a read. When reading in burst

mode, the user copy is static while the internal registers continue to increment.

Local ground plane (Layer 2)

crystal

GND

DS1306

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Figure 2. RTC REGISTERS AND ADDRESS MAP

HEX ADDRESS

READ WRITE Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 RANGE

00h 80h 0 10 SEC SEC 00–59

01h 81h 0 10 MIN MIN 00–59

12 A 01–12 + P/A

02h 82h 0

24 10

10-HR HOURS

00–23

03h 83h 0 0 0 0 0 DAY 01–07

04h 84h 0 0 10-DATE DATE 1–31

05h 85h 0 0 10-MONTH MONTH 01–12

06h 86h 10-YEAR YEAR 00–99

07h 87h M 10-SEC ALARM 0 SEC ALARM 0 00–59

08h 88h M 10-MIN ALARM 0 MIN ALARM 0 00–59

12 A 01–12 + P/A

09h 89h M

24 10

10-HR HOUR ALARM 0

00–23

0Ah 8Ah M 0 0 0 0 DAY ALARM 0 01–07

0Bh 8Bh M 10 SEC ALARM 1 SEC ALARM 1 00–59

0Ch 8Ch M 10 MIN ALARM 1 MIN ALARM 1 00–59

12 A 01–12 + P/A

0Dh 8Dh M

24 10

10-HR HOUR ALARM 1

00–23

0Eh 8Eh M 0 0 0 0 DAY ALARM 1 01–07

—

0Fh 8Fh CONTROL REGISTER —

10h 90h STATUS REGISTER —

11h 91h TRICKLE CHARGER REGISTER —

12h–1Fh 92h–

9Fh RESERVED —

20h–7Fh A0h–

FFh 96-BYTES USER RAM —

Note: Range for alarm registers does not include mask’m’ bits.

The DS1306 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the

12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the

AM/PM bit with logic-high being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20 to 23

hours).

The DS1306 contains two time-of-day alarms. Time-of-day alarm 0 can be set by writing to registers 87h

to 8Ah. Time-of-day Alarm 1 can be set by writing to registers 8Bh to 8Eh. Bit 7 of each of the time-of-

day alarm registers are mask bits (Table 2). When all of the mask bits are logic 0, a time-of-day alarm

only occurs once per week when the values stored in timekeeping registers 00h to 03h match the values

stored in the time-of-day alarm registers. An alarm is generated every day when bit 7 of the day alarm

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registers is set to a logic 1. Similarly, an alarm is generated every minute when bit 7 of the day, hour, and

minute alarm registers is set to a logic 1. When bit 7 of the day, hour, minute, and seconds alarm registers

is set to a logic 1, an alarm occurs every second.

During each clock update, the RTC compares the Alarm 0 and Alarm 1 registers with the corresponding

clock registers. When a match occurs, the corresponding alarm flag bit in the status register is set to a 1. If

the corresponding alarm interrupt enable bit is enabled, an interrupt output is activated.

Table 2. TIME-OF-DAY ALARM MASK BITS

ALARM REGISTER MASK BI TS (BIT 7)

SECONDS MINUTES HOURS DAYS FUNCTION

1 1 1 1 Alarm once per second

0 1 1 1 Alarm when seconds match

0 0 1 1 Alarm when minutes and seconds match

0 0 0 1 Alarm hours, minutes, and seconds match

0 0 0 0 Alarm day, hours, minutes and seconds match

SPECIAL PURPOSE REGISTERS

The DS1306 has three additional registers (control register, status register, and trickle charger register)

that control the real-time clock, interrupts, and trickle charger.

CONTROL REGISTER (READ 0Fh, WRITE 8Fh)

BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0

0 WP 0 0 0 1Hz AIE1 AIE0

WP (Write Protect) – Before any write operation to the clock or RAM, this bit must be logic 0. When

high, the write protect bit prevents a write operation to any register, including bits 0, 1, and 2 of the

control register. Upon initial power-up, the state of the WP bit is undefined. Therefore, the WP bit should

be cleared before attempting to write to the device. When WP is set, it must be cleared before any other

control register bit can be written.

1Hz (1Hz Output Enable) – This bit controls the 1Hz output. When this bit is a logic 1, the 1Hz output

is enabled. When this bit is a logic 0, the 1Hz output is high-Z.

AIE0 (Alarm Interrupt Enable 0) – When set to a logic 1, this bit permits the interrupt 0 request flag

(IRQF0) bit in the status register to assert INT0 . When the AIE0 bit is set to logic 0, the IRQF0 bit does

not initiate the INT0 signal.

AIE1 (Alarm Interrupt Enable 1) – When set to a logic 1, this bit permits the interrupt 1 request flag

(IRQF1) bit in the status register to assert INT1. When the AIE1 bit is set to logic 0, the IRQF1 bit does

not initiate an interrupt signal, and the INT1 pin is set to a logic 0 state.

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STATUS REGISTER (READ 10H)

BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0

0 0 0 0 0 0 IRQF1 IRQF0

IRQF0 (Interrupt 0 Request Flag) – A logic 1 in the interrupt request flag bit indicates that the current

time has matched the Alarm 0 registers. If the AIE0 bit is also a logic 1, the INT0 pin goes low. IRQF0 is

cleared when the address pointer goes to any of the Alarm 0 registers during a read or write. IRQF0 is

activated when the device is powered by VCC1, VCC2, or VBAT.

IRQF1 (Interrupt 1 Request Flag) – A logic 1 in the interrupt request flag bit indicates that the current

time has matched the Alarm 1 registers. If the AIE1 bit is also a logic 1, the INT1 pin generates a 62.5ms

active-high pulse. IRQF1 is cleared when the address pointer goes to any of the alarm 1 registers during a

read or write. IRQF1 is activated only when the device is powered by VCC2 or VBAT.

TRICKLE CHARGE REGISTER (READ 11H, WRITE 91H)

This register controls the trickle charge characteristics of the DS1306. The simplified schematic of Figure

3 shows the basic components of the trickle charger. The trickle charge select (TCS) bits (bits 4–7)

control the selection of the trickle charger. In order to prevent accidental enabling, only a pattern of 1010

enables the trickle charger. All other patterns disable the trickle charger. The DS1306 powers up with the

trickle charger disabled. The diode select (DS) bits (bits 2–3) select whether one diode or two diodes are

connected between VCC1 and VCC2. The diode select (DS) bits (bits 2–3) select whether one diode or two

diodes are connected between VCC1 and VCC2. The resistor select (RS) bits select the resistor that is

connected between VCC1 and VCC2. The resistor and diodes are selected by the RS and DS bits as shown

in Table 3.

Figure 3. PROGRAMMABLE TRICKLE CHARGER

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Table 3. TRICKLE CHARGER RESISTOR AND DIODE SELECT

TCS

Bit 7 TCS

Bit 6 TCS

Bit 5 TCS

Bit 4 DS

Bit 3 DS

Bit 2 RS

Bit 1 RS

Bit 0 FUNCTION

X X X X X X 0 0 Disabled

X X X X 0 0 X X Disabled

X X X X 1 1 X X Disabled

1 0 1 0 0 1 0 1 1 Diode, 2k

1 0 1 0 0 1 1 0 1 Diode, 4k

1 0 1 0 0 1 1 1 1 Diode, 8k

1 0 1 0 1 0 0 1 2 Diodes, 2k

1 0 1 0 1 0 1 0 2 Diodes, 4k

1 0 1 0 1 0 1 1 2 Diodes, 8k

0 1 0 1 1 1 0 0 Initial power-on state

If RS is 00, the trickle charger is disabled independently of TCS.

Diode and resistor selection is determined by the user according to the maximum current desired for

battery or super cap charging. The maximum charging current can be calculated as illustrated in the

following example. Assume that a system power supply of 5V is applied to VCC1 and a super cap is

connected to VCC2. Also assume that the trickle charger has been enabled with one diode and resister R1

between VCC1 and VCC2. The maximum current IMAX would, therefore, be calculated as follows:

IMAX = (5.0V - diode drop) / R1  (5.0V - 0.7V) / 2k  2.2mA

As the super cap charges, the voltage drop between VCC1 and VCC2 decreases and, therefore, the charge

current decreases.

POWER CONTROL

Power is provided through the VCC1, VCC2, and VBAT pins. Three different power supply configurations

are illustrated in Figure 4. Configuration 1 shows the DS1306 being backed up by a non-rechargeable

energy source such as a lithium battery. In this configuration, the system power supply is connected to

VCC1 and VCC2 is grounded. When VCC falls below VBAT the device switches into a low-current battery

backup mode. Upon power-up, the device switches from VBAT to VCC when VCC is greater than

VBAT + 0.2V. The device is write-protected whenever it is switched to VBAT.

Configuration 2 illustrates the DS1306 being backed up by a rechargeable energy source. In this case, the

VBAT pin is grounded, VCC1 is connected to the primary power supply, and VCC2 is connected to the

secondary supply (the rechargeable energy source). The DS1306 operates from the larger of VCC1 or

VCC2. When VCC1 is greater than VCC2 + 0.2V (typical), VCC1 powers the DS1306. When VCC1 is less than

VCC2, VCC2 powers the DS1306. The DS1306 does not write-protect itself in this configuration.

Configuration 3 shows the DS1306 in battery-operate mode, where the device is powered only by a single

battery. In this case, the VCC1 and VBAT pins are grounded and the battery is connected to the VCC2 pin.

Only these three configurations are allowed. Unused supply pins must be grounded.

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Figure 4. POWER-SUPPLY CONFIGURATIONS

NOTE: DEVICE DOES NOT PROVIDE AUTOMATIC WRITE PROTECTION.

NOTE: DEVICE IS WRITE-PROTECTED IF VCC < VCCTP.

CONFIGURATION 1 : BACKUP SUPPLY IS

NONRECHARGEABLE LITHIUM BATTERY

CONFIGURATION 2 : BACKUP SUPPLY IS A

RECHARGEABLE BATTERY OR SUPER

CAPACITOR

CONFIGURATION 3: BATTERY OPERATE

MODE

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SERIAL INTERFACE

The DS1306 offers the flexibility to choose between two serial interface modes. The DS1306 can

communicate with the SPI interface or with a standard 3-wire interface. The interface method used is

determined by the SERMODE pin. When this pin is connected to VCC, SPI communication is selected.

When this pin is connected to ground, standard 3-wire communication is selected.

SERIAL PERIPHERAL INTERFACE (SPI)

The serial peripheral interface (SPI) is a synchronous bus for address and data transfer and is used when

interfacing with the SPI bus on specific Motorola microcontrollers such as the 68HC05C4 and the

68HC11A8. The SPI mode of serial communication is selected by tying the SERMODE pin to VCC.

Four pins are used for the SPI. The four pins are the SDO (serial data out), SDI (serial data in), CE (chip

enable), and SCLK (serial clock). The DS1306 is the slave device in an SPI application, with the

microcontroller being the master.

The SDI and SDO pins are the serial data input and output pins for the DS1306, respectively. The CE

input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data

movement between the master (microcontroller) and the slave (DS1306) devices.

The shift clock (SCLK), which is generated by the microcontroller, is active only during address and data

transfer to any device on the SPI bus. The inactive clock polarity is programmable in some

microcontrollers. The DS1306 determines on the clock polarity by sampling SCLK when CE becomes

active. Therefore either SCLK polarity can be accommodated. Input data (SDI) is latched on the internal

strobe edge and output data (SDO) is shifted out on the shift edge (Figure 5). There is one clock for each

bit transferred. Address and data bits are transferred in groups of eight, MSB first.

Figure 5. SERIAL CLOCK AS A FUNCTION OF MICROCONTROLLER

CLOCK POLARITY (CPOL)

CPOL = 1 SCLK DATA LATCH (WRITE)

SHIFT DATA OUT (READ)

CPOL = 0 SCLK DATA LATCH (WRITE)

SHIFT DATA OUT (READ)

NOTE 1: CPHA BIT POLARITY (IF APPLICABLE) MAY NEED TO BE SET ACCORDINGLY.

NOTE 2: CPOL IS A BIT THAT IS SET IN THE MICROCONTROLLER’S CONTROL REGISTER.

NOTE 3: SDO REMAINS AT HIGH-Z UNTIL 8 BITS OF DATA ARE READY TO BE SHIFTED OUT DURING A READ.

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ADDRESS AND DATA BYTES

Address and data bytes are shifted MSB first into the serial data input (SDI) and out of the serial data

output (SDO). Any transfer requires the address of the byte to specify a write or read to either a RTC or

RAM location, followed by one or more bytes of data. Data is transferred out of the SDO for a read

operation and into the SDI for a write operation (Figures 6 and 7).

Figure 6. SPI SINGLE-BYTE WRITE

Figure 7. SPI SINGLE-BYTE READ

The address byte is always the first byte entered after CE is driven high. The most significant bit (A7) of

this byte determines if a read or write takes place. If A7 is 0, one or more read cycles occur. If A7 is 1,

one or more write cycles occur.

Data transfers can occur one byte at a time or in multiple-byte burst mode. After CE is driven high an

address is written to the DS1306. After the address, 1 or more data bytes can be written or read. For a

single-byte transfer, one byte is read or written and then CE is driven low. For a multiple-byte transfer,

however, multiple bytes can be read or written to the DS1306 after the address has been written. Each

read or write cycle causes the RTC register or RAM address to automatically increment. Incrementing

continues until the device is disabled. When the RTC is selected, the address wraps to 00h after

incrementing to 1Fh (during a read) and wraps to 80h after incrementing to 9Fh (during a write). When

the RAM is selected, the address wraps to 20h after incrementing to 7Fh (during a read) and wraps to

A0h after incrementing to FFh (during a write).

* SCLK CAN BE EITHER POLARITY.

* SCLK CAN BE EITHER POLARITY. SERMODE = VCC

SERMODE = VCC

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Figure 8. SPI MULTIPLE-BYTE BURST TRANSFER

READING AND WRITING IN BURST MODE

Burst mode is similar to a single-byte read or write, except that CE is kept high and additional SCLK

cycles are sent until the end of the burst. The clock registers and the user RAM may be read or written in

burst mode. When accessing the clock registers in burst mode, the address pointer will wrap around after

reaching 1Fh (9Fh for writes). When accessing the user RAM in burst mode, the address pointer wraps

around after reaching 7Fh (FFh for writes).

3-WIRE INTERFACE

The 3-wire interface mode operates similar to the SPI mode. However, in 3-wire mode there is one I/O

instead of separate data in and data out signals. The 3-wire interface consists of the I/O (SDI and SDO

pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first, unlike SPI

mode, where each byte is shifted in MSB first.

As is the case with the SPI mode, an address byte is written to the device followed by a single data byte

or multiple data bytes. Figure 9 illustrates a read and write cycle. In 3-wire mode, data is input on the

rising edge of SCLK and output on the falling edge of SCLK.

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Figure 9. 3-WIRE SINGLE BYTE TRANSFER

NOTE: IN BURST MODE, CE IS KEPT HIGH AND ADDITIONAL SCLK CYCLES ARE SENT UNTIL THE END OF THE BURST.

*I/O IS SDI AND SDO TIED TOGETHER.

A0 A1 A2 A3 A4 A5 A6 1

SCLK

I/O*

D0 D1 D2 D3 D4 D5 D6 D7

SINGLE-BYTE WRITE

D0 D1 D2 D3 D4 D5 D6 D7

A0 A1 A2 A3 A4 A5 A6 0

I/O*

SCLK

SINGLE-BYTE READ

SERMODE = GND

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ABSOLUTE MAXIMUM RATINGS

Voltage Range on Any Pin Relative to Ground……………………………………………..-0.5V to +7.0V

Storage Temperature Range……………………………………………………………….-55C to +125C

Soldering Temperature.……………………………….Refer to the IPC/JEDEC Standard J-STD-020

Specification

This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operation

sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time can affect

reliability.

OPERATING RANGE

RANGE TEMP RANGE VCC (V)

Commercial 0°C to +70°C 2.0 to 5.5 VCC1 or VCC2

Industrial -40°C to +85°C 2.0 to 5.5 VCC1 or VCC2

RECOMMENDED DC OPERATING CONDITIONS

(TA = Over the operating range, unless otherwise specified.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Supply Voltage

VCC1, VCC2 VCC1, VCC2 2.0 5.5 V 1, 8

Logic 1 Input VIH 2.0 VCC + 0.3 V

VCC = 2.0V +0.3

Logic 0 Input VIL VCC = 5V -0.3 +0.8 V

VBAT Battery Voltage VBAT 2.0 5.5 V

VCCIF Supply Voltage VCCIF 2.0 5.5 V 10

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DC ELECTRICAL CHARACTERISTICS

(TA = Over the operating range, unless otherwise specified.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Leakage ILI -100 +500

A

Output Leakage ILO -1 +1

A

IOL = 1.5mA VCC = 2.0 0.4

Logic 0 Output IOL = 4.0mA VOL VCC = 5V 0.4 V

IOH = -0.4mA VCCIF = 2.0V 1.6

Logic 1 Output IOH = -1.0mA VOH VCCIF = 5V 2.4 V

Logic 1 Output Current

(INT1 pin)

IOH,

INT1

(VCC2, VBAT)

-0.3V -100 A

VCC1 = 2.0V 0.425

VCC1 Active Supply Current ICC1A VCC1 = 5V 1.28 mA 2, 7

VCC1 = 2.0V 25.3

VCC1 Timekeeping Current ICC1T VCC1 = 5V 81 A 1, 7

VCC2 = 2.0V 0.4

VCC2 Active Supply Current ICC2A VCC2 = 5V 1.2 mA 2, 8

VCC2 = 2.0V 0.4

VCC2 Timekeeping Current ICC2T VCC2 = 5V 1 A 1, 8

Battery Timekeeping Current IBAT V

BAT = 3V 550 nA 9

Battery Timekeeping Current

(IND) IBAT V

BAT = 3V 800 nA 9

VCC Trip Point VCCTP VBAT -

50 VBAT +

200 mV

R1 2

R2 4

Trickle Charge Resistors

R3 8

k

Trickle Charger Diode Voltage

Drop VTD 0.7 V

CAPACITANCE

(TA = +25C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CI 10 pF

Output Capacitance CO 15 pF

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3-WIRE AC ELECTRICAL CHARACTERISTICS

(TA = Over the operating range, unless otherwise specified.) (Figure 10 and Figure 11)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

VCC = 2.0V 200

Data to CLK Setup tDC VCC = 5V 50 ns 3, 4

VCC = 2.0V 280

CLK to Data Hold tCDH VCC = 5V 70 ns 3, 4

VCC = 2.0V 800

CLK to Data Delay tCDD VCC = 5V 200 ns 3, 4, 5

VCC = 2.0V 1000

CLK Low Time tCL VCC = 5V 250 ns 4

VCC = 2.0V 1000

CLK High Time tCH VCC = 5V 250 ns 4

VCC = 2.0V 0.6

CLK Frequency tCLK VCC = 5V DC 2.0 MHz 4

VCC = 2.0V 2000

CLK Rise and Fall tR, tF VCC = 5V 500 ns

VCC = 2.0V 4

CE to CLK Setup tCC VCC = 5V 1 s 4

VCC = 2.0V 240

CLK to CE Hold tCCH VCC = 5V 60 ns 4

VCC = 2.0V 4

CE Inactive Time tCWH VCC = 5V 1 s 4

VCC = 2.0V 280

CE to Output High-Z tCDZ VCC = 5V 70 ns 3, 4

VCC = 2.0V 280

SCLK to Output High-Z tCCZ VCC = 5V 70 ns 3, 4

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Figure 10. TIMING DIAGRAM: 3-WIRE READ DATA TRANSFER

Figure 11. TIMING DIAGRAM: 3-WIRE WRITE DATA TRANSFER

* I/O IS SDI AND SDO TIED TOGETHER.

SERMODE = GND

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SPI AC ELECTRICAL CHARACTERISTICS

(TA = Over the operating range, unless otherwise specified.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

VCC = 2.0V 200

Data to CLK Setup tDC VCC = 5V 50 ns 3, 4

VCC = 2.0V 280

CLK to Data Hold tCDH VCC = 5V 70 ns 3, 4

VCC = 2.0V 800

CLK to Data Delay tCDD VCC = 5V 200 ns 3, 4, 5

VCC = 2.0V 1000

CLK Low Time tCL VCC = 5V 250 ns 4

VCC = 2.0V 1000

CLK High Time tCH VCC = 5V 250 ns 4

VCC = 2.0V 0.6

CLK Frequency tCLK VCC = 5V DC 2.0 MHz 4

VCC = 2.0V 2000

CLK Rise and Fall tR, tF VCC = 5V 500 ns

VCC = 2.0V 4

CE to CLK Setup tCC VCC = 5V 1 s 4

VCC = 2.0V 240

CLK to CE Hold tCCH VCC = 5V 60 ns 4

VCC = 2.0V 4

CE Inactive Time tCWH VCC = 5V 1 s 4

VCC = 2.0V 280

CE to Output High-Z tCDZ VCC = 5V 70 ns 3, 4

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Figure 12. TIMING DIAGRAM: SPI READ DATA TRANSFER

Figure 13. TIMING DIAGRAM: SPI WRITE DATA TRANSFER

* SCLK CAN BE EITHER POLARITY, TIMING SHOWN FOR CPOL = 1.

SERMODE = VCC

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NOTES:

1) ICC1T and ICC2T are specified with CE set to a logic 0.

2) ICC1A and ICC2A are specified with CE = VCC, SCLK = 2MHz at VCC = 5V; SCLK = 500kHz at VCC =

2.0V, VIL = 0V, VIH = VCC.

3) Measured at VIH = 2.0V or VIL = 0.8V and 10ms maximum rise and fall time.

4) Measured with 50pF load.

5) Measured at VOH = 2.4V or VOL = 0.4V.

6) VCC = VCC1, when VCC1 > VCC2 + 0.2V (typical); VCC = VCC2, when VCC2 > VCC1.

7) VCC2 = 0V.

8) VCC1 = 0V.

9) VCC1 < VBAT.

10) VCCIF must be less than or equal to the largest of VCC1, VCC2, and VBAT.

PACKAGE INFORMATION

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

16 PDIP P16+1 21-0043

20 TSSOP U20+1 21-0066

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Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim

reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

REVISION HISTORY

REVISION

DATE DESCRIPTION PAGES

CHANGED

Added Table 1. Crystal Specifications to the Clock Accuracy section. 5

Added “SERMODE = VCC” to Figures 6, 7, 12, and 13. 12, 20

Added “SERMODE = GND” to Figures 9, 10, and 11. 14, 18

12/09

Removed the “Crystal Capacitance” parameter from the Capacitance

table. 16