DS1305EN/R datasheet, PDF - EEWORLD Datasheet

DS1305

Serial Alarm Real-Time Clock

www.maxim-ic.com

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:

-40°C to +85°C

Available in Space-Efficient, 20-Pin TSSOP

Package

Underwriters Laboratory (UL) Recognized

PIN CONFIGURATIONS

TOP VIEW

V

CC2

V

BAT

X1

N.C.

X2

N.C.

INT0

N.C.

INT1

GND

1

2

3

4

5

6

7

8

9

10

20

V

CC1

N.C.

PF

V

CCIF

SD0

SDI

SCLK

N.C.

CE

SERMODE

§

DS1305

19

18

17

16

15

14

13

12

11

TSSOP (4.4mm)

V

CC2

V

BAT

X1

X2

N.C.

INT0

INT1

GND

1

2

3

4

5

6

7

8

16

15

V

CC1

PF

V

CCIF

SDO

SDI

SCLK

CE

SERMODE

DS1305

14

13

12

11

10

9

DIP (300 mils)

SPI is a trademark of Motorola, Inc.

TYPICAL OPERATING CIRCUIT

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REV: 070705

DS1305

ORDERING INFORMATION

PART

DS1305

DS1305E+

DS1305EN+

DS1305EN+T&R

DS1305E+T&R

DS1305E

DS1305EN

DS1305EN/T&R

DS1305E/T&R

DS1305N

TEMP RANGE

0°C to +70°C

-40°C to +85°C

0°C to +70°C

-40°C to +85°C

0°C to +70°C

-40°C to +85°C

PIN-PACKAGE

16 DIP (300 mils)

20 TSSOP (173 mils)

20 TSSOP (173), Tape/Reel

20 TSSOP (173 mils), Tape/Reel

20 TSSOP (173)

20 TSSOP (173 mils)

20 TSSOP (173 mils), Tape/Reel

16 DIP (300 mils)

TOP MARK*

DS1305

DS1305N

DS1305

DS1305N

+

Denotes a lead-free/RoHS-compliant device.

*

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 (V

CCIF

) 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 V

BAT

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 V

CC1

, V

CC2

, or V

BAT

.

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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DS1305

PIN DESCRIPTION

DIP

TSSOP

1

NAME

V

CC2

FUNCTION

2

V

BAT

3

X1

4

5

4, 6, 8,

13, 19

X2

N.C.

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.

Battery Input for Standard +3V Lithium Cell or Other Energy Source. If not

used, V

BAT

must be connect to ground. Diodes must not be placed in series

between V

BAT

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.

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.

No Connection

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

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 V

CC1

,

V

CC2

, or V

BAT

. The

INT0

pin is an open-drain output and requires an external

pullup resistor.

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

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 V

CC1

, V

CC2

, or V

BAT

. 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 V

CC

(as long as a power source is present).

Ground

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 V

CC

, SPI communication is

selected.

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 55kW

pulldown resistor (typical).

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

interface for either the SPI or 3-wire interface.

6

7

INT0

7

9

INT1

8

9

10

11

GND

SERMODE

10

11

12

14

CE

SCLK

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DS1305

PIN DESCRIPTIONS (continued)

DIP

TSSOP

12

15

NAME

FUNCTION

SDI

13

16

SDO

14

17

V

CCIF

15

16

18

20

PF

V

CC1

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).

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).

Interface Logic Power-Supply Input. The V

CCIF

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.

Active-Low Power-Fail Output. The

PF

pin is used to indicate loss of the

primary power supply (V

CC1

). When V

CC1

is less than V

CC2

or is less than V

BAT

,

the

PF

pin is driven low.

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

OSCILLATOR AND

COUNTDOWN CHAIN

1Hz

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DS1305

RECOMMENDED LAYOUT FOR CRYSTAL

Local ground plane (Layer 2)

X1

crystal

X2

GND

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.

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.

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.

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DS1305EN/R

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