DS1305EN+ - Maxim Integrated Products, Inc.

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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

 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:

-C to +85C

 Available in Space-Efficient, 20-Pin TSSOP

Package

 Underwriters Laboratory (UL) Recognized

PIN CONFIGURATIONS

TYPICAL OPERATING CIRCUIT

www.maxim-ic.com

DS1305

Serial Alarm Real-Time Clock

SPI is a trademark of Motorola, Inc.

VCC2 1 16 VCC1

VBAT 2 15 PF

X1 3 14 VCCIF

X2 4 13 SDO

N.C. 5 12 SDI

INT0 6 11 SCLK

INT1 7 10 CE

GND 8 9 SERMODE

DIP

(

300 mils

)

DS1305

VCC2 1 20 VCC1

VBAT 2 19 N.C.

X1 3 18 PF

N.C. 4 17 VCCIF

X2 5 16 SD0

N.C. 6 15 SDI

INT0 7 14 SCLK

N.C. 8 13 N.C.

INT1 9 12 CE

GND 10 11 SERMODE

DS1305

TSSOP (4.4mm)

TOP VIEW

19-5055; Rev 12/09

DS1305

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ORDERING INFORMATION

PART TEMP RANGE PIN-PACKAGE TOP MARK*

DS1305 0°C to +70°C 16 DIP (300 mils) DS1305

DS1305N -40°C to +85°C 16 DIP (300 mils) DS1305N

DS1305E 0°C to +70°C 20 TSSOP (173 mils) DS1305

DS1305E+ 0°C to +70°C 20 TSSOP (173 mils) DS1305

DS1305E/T&R 0°C to +70°C 20 TSSOP (173 mils) DS1305

DS1305E+T&R 0°C to +70°C 20 TSSOP (173 mils) DS1305

DS1305EN -40°C to +85°C 20 TSSOP (173 mils) DS1305

DS1305EN+ -40°C to +85°C 20 TSSOP (173 mils) DS1305N

DS1305EN/T&R -40°C to +85°C 20 TSSOP (173 mils) DS1305

DS1305EN+T&R -40°C to +85°C 20 TSSOP (173 mils) DS1305

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

T&R = Tape and reel.

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

DESCRIPTION

The DS1305 serial alarm real-time clock 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. The

DS1305 will maintain the time and date, provided the oscillator is enabled, as long as at least one supply

is at a valid level.

An interface logic power-supply input pin (VCCIF) allows the DS1305 to drive SDO and PF pins to a level

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

systems.

The DS1305 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 DS1305 is fully operational from 2.0V to 5.5V.

Two programmable time-of-day alarms are provided by the DS1305. 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. The time-of-

day alarms can be programmed to assert two different interrupt outputs or to assert one common interrupt

output. Both interrupt outputs operate when the device is powered by VCC1, VCC2, or VBAT.

The DS1305 supports a direct interface to SPI serial data ports or standard 3-wire interface. A

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

or in multiple-byte-burst mode.

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PIN DESCRIPTION

DIP TSSOP 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 Standard +3V Lithium Cell or Other Energy Source. If not

used, VBAT must be connect 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

4 5 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 DS1305 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.

5 4, 6, 8,

13, 19 N.C. No Connection

6 7 INT0

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

DS1305 that can be used as an interrupt input to a processor. The INT0 pin

can be programmed to be asserted by only Alarm 0 or can be programmed to

be asserted by either Alarm 0 or Alarm 1. 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 DS1305 is powered by VCC1,

VCC2, or VBAT. The INT0 pin is an open-drain output and requires an external

pullup resistor.

7 9 INT1

Active-Low Interrupt 1 Output. The INT1 pin is an active-low output of the

DS1305 that can be used as an interrupt input to a processor. The INT1 pin

can be programmed to be asserted by Alarm 1 only. The INT1 pin remains

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

corresponding interrupt enable bit is set. The INT1 pin operates when the

DS1305 is powered by VCC1, VCC2, or VBAT. The INT1 pin is an open-drain

output and requires an external pullup resistor. Both INT0 and INT1 are open-

drain outputs. The two interrupts and the internal clock continue to run

regardless of the level of VCC (as long as a power source is present).

8 10 GND Ground

9 11 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.

10 12 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).

11 14 SCLK

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

interface for either the SPI or 3-wire interface.

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PIN DESCRIPTION (continued)

DIP TSSOP NAME FUNCTION

12 15 SDI

Serial Data Input. 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).

13 16 SDO

Serial Data Output. 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).

14 17 VCCIF

Interface Logic Power-Supply Input. The VCCIF pin allows the DS1305 to drive

SDO and PF 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 PF pins.

15 18 PF

Active-Low Power-Fail Output. The PF pin is used to indicate loss of the

primary power supply (VCC1). When VCC1 is less than VCC2 or is less than VBAT,

the PF pin is driven low.

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

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

OSCILLATOR AND

COUNTDOWN CHAIN

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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

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

Applications 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 and user RAM 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. The day register increments at midnight. Values that correspond to

the day of week are user-defined but must be sequential (e.g., if 1 equals Sunday, 2 equals Monday and so

on). Illogical time and date entries result in undefined operation.

Except where otherwise noted, the initial power on state of all registers is not defined. Therefore, it is

important to enable the oscillator (EOSC = 0) and disable write protect (WP = 0) during initial

configuration.

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.

Local ground plane (Layer 2)

crystal

GND

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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.

Figure 2. RTC REGISTERS AND ADDRESS MAP

HEX ADDRESS

READ WRITE

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 RANGE

00h 80h 0 10 Seconds Seconds 00–59

01h 81h 0 10 Minutes Minutes 00–59

P 01–12 + P/A

12 A

02h 82h 0

24 10

10 Hour Hours 00–23

03h 83h 0 0 0 0 Day 1–7

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

— — Alarm 0 —

07h 87h M 10 Seconds Alarm Seconds Alarm 00–59

08h 88h M 10 Minutes Alarm Minutes Alarm 00–59

12 A 01–12 + P/A

09h 89h M

24 10

10 Hour Hour Alarm 00–23

0Ah 8Ah M 0 0 0 Day Alarm 01–07

— — Alarm 1 —

0Bh 8Bh M 10 Seconds Alarm Seconds Alarm 00–59

0Ch 8Ch M 10 Minutes Alarm Minutes Alarm 00–5 9

12 A 01–12 + P/A

0Dh 8Dh M

24 10

10 Hour Hour Alarm 00–23

0Eh 8Eh M 0 0 0 Day Alarm 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 00–FF

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

The DS1305 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 DS1305 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. The alarms can be

programmed (by the INTCN bit of the control register) to operate in two different modes; each alarm can

drive its own separate interrupt output or both alarms can drive a common interrupt output. 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 register is set to a logic 1. An alarm is generated every hour when bit 7 of the day and hour

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

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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, 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 BITS (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 DS1305 has three additional registers (control register, status register, and trickle charger register)

that control the RTC, interrupts, and trickle charger.

CONTROL REGISTER (READ 0Fh, WRITE 8Fh)

BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0

EOSC WP 0 0 0 INTCN AIE1 AIEO

EOSC (Enable Oscillator) – This bit when set to logic 0 starts the oscillator. When this bit is set to a

logic 1, the oscillator is stopped and the DS1305 is placed into a low-power standby mode with a current

drain of less than 100nA when power is supplied by VBAT or VCC2. On initial application of power, this bit

will be set to a logic 1.

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, 2, and 7 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.

INTCN (Interrupt Control) – This bit controls the relationship between the two time-of-day alarms and

the interrupt output pins. When the INTCN bit is set to a logic 1, a match between the timekeeping

registers and the Alarm 0 registers activates the INT0 pin (provided that the alarm is enabled) and a

match between the timekeeping registers and the Alarm 1 registers activate the INT1 pin (provided that

the alarm is enabled). When the INTCN bit is set to a logic 0, a match between the timekeeping registers

and either Alarm 0 or Alarm 1 activate the INT0 pin (provided that the alarms are enabled). INT1 has no

function when INTCN is set to a logic 0.

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.

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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 INTCN = 1) or to assert INT0 (when INTCN = 0).

When the AIE1 bit is set to logic 0, the IRQF1 bit does not initiate an interrupt signal.

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.

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. This flag can be used to generate an interrupt on either INT0 or

INT1 depending on the status of the INTCN bit in the control register. If the INTCN bit is set to a logic 1

and IRQF1 is at a logic 1 (and AIE1 bit is also a logic 1), the INT1 pin goes low. If the INTCN bit is set

to a logic 0 and IRQF1 is at a logic 1 (and AIE1 bit is also a logic 1), the INT0 pin goes low. IRQF1 is

cleared when the address pointer goes to any of the Alarm 1 registers during a read or write.

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

This register controls the trickle charge characteristics of the DS1305. 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. To prevent accidental enabling, only a pattern of 1010 enables

the trickle charger. All other patterns disable the trickle charger. On the initial application of power, the

DS1305 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 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

Bit 2

Bit 1

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

The user determines diode and resistor selection 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 1 diode and resister R1 between VCC1

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

MAX = (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 DS1305 being backed up by a nonrechargeable

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

VCC1 and VCC2 is grounded. The DS1305 is write-protected if VCC1 is less than VBAT. The DS1305 is fully

accessible when VCC1 is greater than VBAT + 0.2V.

Configuration 2 illustrates the DS1305 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 DS1305 operates from the larger of VCC1 or

VCC2. When VCC1 is greater than VCC2 + 0.2V (typical), VCC1 powers the DS1305. When VCC1 is less than

VCC2, VCC2 powers the DS1305. The DS1305 does not write-protect itself in this configuration.

Configuration 3 shows the DS1305 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 DS1305 offers the flexibility to choose between two serial interface modes. The DS1305 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 DS1305 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 DS1305, 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 (DS1305) 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 DS1305 determines 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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* SCLK CAN BE EITHER POLARITY.

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 DS1305. After the address, one 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 DS1305 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. 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 can be read or written in

burst mode. When accessing the clock registers in burst mode, the address pointer wraps 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).

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3-WIRE INTERFACE

The 3-wire interface mode operates similarly 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.

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………………………………………….See IPC/JEDEC 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

(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 7

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 11

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DC ELECTRICAL CHARACTERISTICS

(Over the operating range, unless otherwise specified.)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Leakage ILI -100 +500 µA

Output Leakage ILO -1 1 µA

IOL= 1.5mA VCC = 2.0V 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

VCC1 = 2.0V 0.425

VCC1 Active Supply Current ICC1A VCC1 = 5V 1.28 mA 2, 8

VCC1 = 2.0V 25.3

VCC1 Timekeeping Current

(Osc on) ICC1T VCC1 = 5V 81 A 1, 8, 12

VCC1 = 2.0V 25

VCC1 Standby Current

(Osc off) ICC1S VCC1 = 5V 80 A 6, 8, 12

VCC2 = 2.0V 0.4

VCC2 Active Supply Current ICC2A VCC2 = 5V 1.2 mA 2, 9

VCC2 = 2.0V 0.3

VCC2 Timekeeping Current

(Osc on) ICC2T VCC2 = 5V 1 µA 1, 9, 12

VCC2 = 2.0V 200

VCC2 Standby Current

(Osc off) ICC2S VCC2 = 5V 200 nA 6, 9, 12

Battery Timekeeping Current IBAT V

BAT = 3V 400 nA 10, 12

Battery Standby Current IBATS V

BAT = 3V 200 nA 10, 12

VCC Trip Point VCCTP V

BAT - 50 VBAT +

200 mV

R1 2

Trickle Charge Resistors

k

Trickle Charge 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

(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

(Over the operating range, unless otherwise specified.) (Figure 12 and Figure 13)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

VCC = 2.0V 200

Data to CLK Setup tDC VCC = 5V 50 ns 5,6

VCC = 2.0V 280

CLK to Data Hold tCDH VCC = 5V 70 ns 5,6

VCC = 2.0V 800

CLK to Data Delay tCDD VCC = 5V 200 ns 5,6,7

VCC = 2.0V 1000

CLK Low Time tCL VCC = 5V 250 ns 6

VCC = 2.0V 1000

CLK High Time tCH VCC = 5V 250 ns 6

VCC = 2.0V 0.6

CLK Frequency tCLK VCC = 5V DC 2.0 MHz 6

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 6

VCC = 2.0V 240

CLK to CE Hold tCCH VCC = 5V 60 ns 6

VCC = 2.0V 4

CE Inactive Time tCWH VCC = 5V 1 s 6

VCC = 2.0V 280

CE to Output High-Z tCDZ VCC = 5V 70 ns 5,6

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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 and EOSC bit = 0 (oscillator enabled).

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

at VCC = 2.0V, VIL = 0V, VIH = VCC, and EOSC bit = 0 (oscillator enabled).

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) ICC1S and ICC2S are specified with CE set to a logic 0. The EOSC bit must be set to logic 1

(oscillator disabled).

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

8) VCC2 = 0V.

9) VCC1 = 0V.

10) VCC1 < VBAT.

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

12) Using a crystal on X1 and X2, rated for 6pF load.

DS1305

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 no tice at any time.

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

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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