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DS1339
I2C Serial Real-Time Clock
GENERAL DESCRIPTION
The DS1339 serial real-time clock (RTC) is a low-
power clock/date device with two programmable time-
of-day alarms and a programmable square-wave
output. Address and data are transferred serially
through an I2C bus. The clock/date 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 the 24-hour or 12-hour format with
AM/PM indicator. The DS1339 has a built-in power-
sense circuit that detects power failures and
automatically switches to the backup supply,
maintaining time, date, and alarm operation.
APPLICATIONS
Handhelds (GPS, POS Terminals)
Consumer Electronics (Set-Top Box, Digital
Recording, Network Appliance)
Office Equipment (Fax/Printers, Copier)
Medical (Glucometer, Medicine Dispenser)
Telecommunications (Routers, Switches, Servers)
Other (Utility Meter, Vending Machine, Thermostat,
Modem)
FEATURES
Real-Time Clock (RTC) Counts Seconds, Minutes,
Hours, Day, Date, Month, and Year with Leap-
Year Compensation Valid Up to 2100
Available in a Surface-Mount Package with an
Integrated Crystal (DS1339C)
I2C Serial Interface
Two Time-of-Day Alarms
Programmable Square-Wave Output
Oscillator Stop Flag
Automatic Power-Fail Detect and Switch Circuitry
Trickle-Charge Capability
Underwriters Laboratory (UL) Recognized
Pin Configurations appear at end of data sheet.
ORDERING INFORMATION
PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK†
DS1339C-2 -40°C to +85°C 2.0 16 SO (300 mils) DS1339C-2
DS1339C-2# -40°C to +85°C 2.0 16 SO (300 mils) DS1339C-2
DS1339C-3 -40°C to +85°C 3.0 16 SO (300 mils) DS1339C-3
DS1339C-3# -40°C to +85°C 3.0 16 SO (300 mils) DS1339C-3
DS1339C-33 -40°C to +85°C 3.3 16 SO (300 mils) DS1339C-33
DS1339C-33# -40°C to +85°C 3.3 16 SO (300 mils) DS1339C-33
DS1339U-2 -40°C to +85°C 2.0 8 µSOP 1339 rr-2
DS1339U-2+ -40°C to +85°C 2.0 8 µSOP 1339 rr-2
DS1339U-3 -40°C to +85°C 3.0 8 µSOP 1339 rr-3
DS1339U-3+ -40°C to +85°C 3.0 8 µSOP 1339 rr-3
DS1339U-33 -40°C to +85°C 3.3 8 µSOP 1339 rr-33
DS1339U-33+ -40°C to +85°C 3.3 8 µSOP 1339 rr-33
+ Denotes a lead-free/RoHS-compliant device.
# Denotes a RoHS-compliant device that may include lead that is exempt under the RoHS requirements. The lead finish is JESD97 category
e3, and is compatible with both lead-based and lead-free soldering processes.
† A “+” anywhere on the top mark indicates a lead-free device. A “#” denotes a RoHS-compliant device. rr = second line, revision code
www.maxim-ic.com
DS1339 I2C Serial Real-Time Clock
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ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground………………………………………………………………-0.3V to +6.0V
Operating Temperature Range (Noncondensing)………………………………………………………….-40°C to +85°C
Storage Temperature Range………………………………………………………………………………..-55°C to +125°C
Soldering Temperature Range………….See precautions in the Handling, PC Bo ard Layout, and Assembly section.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. The se are stress ratings only,
and functional operation of the device at these or any other c onditions beyond those indicated in the o perational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS
(TA = -40°C to +85°C) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DS1339-2 1.8 2.0 2.2
DS1339-3 2.7 3.0 3.3
Supply Voltage VCC
DS1339-33 2.97 3.3 5.5
V
Backup Supply Voltage VBACKUP 1.3 3.0 3.7 V
Pullup Resistor Voltage (SQW/INT,
SDA, SCL), VCC = 0V VPU 5.5 V
Logic 1 VIH 0.7 x
VCC
VCC +
0.3 V
Logic 0 VIL -0.3
+0.3 x
VCC
V
DS1339-2 1.58 1.70 1.80
DS1339-3 2.45 2.59 2.70
Power-Fail Voltage VPF
DS1339-33 2.70 2.85 2.97
V
DC ELECTRICAL CHARACTERISTICS
(VCC = MIN to MAX, TA = -40°C to +85°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Leakage ILI (Note 2) 1 µA
I/O Leakage ILO (Note 3) 1 µA
Logic 0 Out
VOL = 0.4V; VCC > VCC MIN (-3, -33);
VCC ≥ 2.0V (-2)
IOL (Note 3) 3 mA
Logic 0 Out
VOL = 0.2 (VCC);
1.8V < VCC < 2.0V (DS1339-2)
IOL (Note 3) 3 mA
Logic 0 Out
VOL = 0.2 (VCC);
1.3V < VCC < 1.8V (DS1339-2)
IOL (Note 3) 250 µA
VCC Active Current ICCA (Note 4) 450 µA
VCC ≤ 3.63V 80 150
VCC Standby Current (Note 5) ICCS 3.63V < VCC ≤ 5.5V 200 µA
DS1339 I2C Serial Real-Time Clock
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = MIN to MAX, TA = -40°C to +85°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Trickle-Charger Resistor Register
10h = A5h, VCC = Typ, VBACKUP = 0V R1 (Note 6) 250 Ω
Trickle-Charger Resistor Register
10h = A6h, VCC = Typ, VBACKUP = 0V R2 2000 Ω
Trickle-Charger Resistor Register
10h = A7h, VCC = Typ, VBACKUP = 0V R3 4000 Ω
VBACKUP Leakage Current IBKLKG 25 100 nA
DC ELECTRICAL CHARACTERISTICS
(VCC = 0V, TA = -40°C to +85°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VBACKUP Current EOSC = 0, SQW Off IBKOSC (Note 7) 400 700 nA
VBACKUP Current EOSC = 0, SQW On IBKSQW (Note 7) 600 1000 nA
VBACKUP Current EOSC = 1 IBKDR (Note 7) 10 100 nA
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DS1339 I2C Serial Real-Time Clock
AC ELECTRICAL CHARACTERISTICS
(VCC = MIN to MAX, TA = -40°C to +85°C.) (Note 13)
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS
Fast mode 100 400
SCL Clock Frequency fSCL Standard mode 100
kHz
Fast mode 1.3
Bus Free Time Between a STOP
and START Condition tBUF Standard mode 4.7 µs
Fast mode 0.6
Hold Time (Repeated) START
Condition (Note 8) tHD:STA Standard mode 4.0 µs
Fast mode 1.3
LOW Period of SCL Clock tLOW Standard mode 4.7 µs
Fast mode 0.6
HIGH Period of SCL Clock tHIGH Standard mode 4.0 µs
Fast mode 0.6
Setup Time for a Repeated
START Condition tSU:STA Standard mode 4.7 µs
Fast mode 0 0.9
Data Hold Time (Notes 9, 10) tHD:DAT Standard mode 0 µs
Fast mode 100
Data Setup Time (Note 11) tSU:DAT Standard mode 250 ns
Fast mode 20 + 0.1CB300
Rise Time of Both SDA and SCL
Signals (Note 12) tRStandard mode 20 + 0.1CB1000 ns
Fast mode 20 + 0.1CB300
Fall Time of Both SDA and SCL
Signals (Note 12) tFStandard mode 20 + 0.1CB300 ns
Fast mode 0.6
Setup Time for STOP Condition tSU:STO Standard mode 4.0 µs
Capacitive Load for Each Bus
Line (Note 12) CB 400 pF
I/O Capacitance (SDA, SCL) CI/O (Note 13) 10 pF
Oscillator Stop Flag (OSF) Delay tOSF (Note 14) 100 ms
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DS1339 I2C Serial Real-Time Clock
POWER-UP/DOWN CHARACTERISTICS
(TA = -40°C to +85°C) (Note 1, Figure 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Recovery at Power-Up tREC (Note 15) 2 ms
VCC Fall Time; VPF(MAX) to VPF(MIN) tVCCF 300
µs
VCC Rise Time; VPF(MIN) to VPF(MAX) tVCCR 0
µs
WARNING: Under no circumstances are negative undershoots, of any amplitude, allowed when device is in
battery-backup mode.
Note 1: Limits at -40°C are guaranteed by design and are not production tested.
Note 2: SCL only.
Note 3: SDA and SQW/INT.
Note 4: I
CCA—SCL at fSC max, VIL = 0.0V, VIH = VCC, trickle charger disabled.
Note 5: Specified with the I2C bus inactive, VIL = 0.0V, VIH = VCC, trickle charger disabled.
Note 6: VCC must be less than 3.63V if the 250Ω resistor is selected.
Note 7: Using recommended crystal on X1 and X2.
Note 8: After this period, the first clock pulse is generated.
Note 9: A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the VIHMIN of the SCL signal) to bridge
the undefined region of the falling edge of SCL.
Note 10: The maximum tHD:DAT need only be met if the device does not stretch the LOW period (tLOW) of the SCL signal.
Note 11: A fast-mode device can be used in a standard-mode system, but the requirement tSU:DAT ≥ to 250ns must then be met. This is
automatically the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW
period of the SCL signal, it must output the next data bit to the SDA line tR(MAX) + tSU:DAT = 1000 + 250 = 1250ns before the SCL line
is released.
Note 12: C
B—total capacitance of one bus line in pF.
Note 13: Guaranteed by design. Not production tested.
Note 14: 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 0.0V ≤
VCC ≤ VCCMAX and 1.3V ≤ VBACKUP ≤ 3.7V.
Note 15: This delay applies only if the oscillator is running. If the oscillator is disabled or stopped, no power-up delay occurs.
Figure 1. Power-Up/Down Timing
OUTPUTS
VCC
V
PF(MAX)
V
PF(MIN)
INPUTS
HIGH-Z
DON'T CARE
VALID
RECOGNIZED RECOGNIZED
VALID
t
VCCF
t
VCCR
tREC
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DS1339 I2C Serial Real-Time Clock
Figure 2. Timing Diagram
Figure 3. Block Diagram
A
LARM,
TRICKLE CHARGE,
AND CONTROL
REGISTERS
SERIAL BUS
INTERFACE AND
ADDRESS
REGISTER
CONTROL
LOGIC
1Hz
1Hz/4.096kHz/8.192kHz/32.768kHz
MUX/
BUFFER
USER BUFFER
(7 BYTES)
CLOCK AND
CALENDAR
REGISTERS
POWER
CONTROL
X1
C
L
C
L
X2
Dallas
Semiconductor
DS1339
SQW/
I
NT
V
CC
V
BACKUP
SCL
SDA
GND
OSCILLATOR
AND DIVIDER
"C" VERSION ONLY
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DS1339 I2C Serial Real-Time Clock
TYPICAL OPERATING CHARACTERISTICS
(VCC = 3.3v, TA = +25°C, unless otherwise noted.)
IBACKUP vs. VBACKUP
300
350
400
450
500
550
600
650
700
750
800
850
900
1.3 1.8 2.3 2.8 3.3 3.8 4.3 4.8 5.3
VBACKUP (V)
SUPPLY CURRENT (nA
)
VCC=0V
RS1=RS0=1
IBATOSC2
(SQWE = 1)
IBAT OSC1
(SQWE = 0)
IBACKUP vs. Tem perature
VBACKUP = 3.0V
300
350
400
450
500
550
600
650
-40-20020406080
TEMPERATURE (°C)
SUPPLY CURRENT (nA
)
VCC=0V
INTCN = 0
RS2 = RS1 = 1
INTCN = 0
ICC vs. VCC
50
100
150
200
250
1.8 2.3 2.8 3.3 3.8 4.3 4.8 5.3
VCC (V )
SUPPLY CURRENT (uA
)
SCL=400kHz
ICCA
SCL=SDA =0Hz
ICCS
Oscillator Frequency vs. Supply Voltage
32768.0
32768.1
32768.2
32768.3
32768.4
1.3 1.8 2.3 2.8 3.3 3.8 4.3 4.8
Oscillator Supply Vo ltage (V)
FREQUENCY (Hz)
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DS1339 I2C Serial Real-Time Clock
PIN DESCRIPTION
PIN
µSOP SO NAME FUNCTION
1 — X1
2 — X2
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator
circuitry is designed for operation with a crystal having a specified load
capacitance (CL) of 6pF. An external 32.768kHz oscillator can also drive the
DS1339. In this configuration, the X1 pin is connected to the external oscillator
signal and the X2 pin is floated.
For more information about crystal selection and crystal layout considerations,
refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks.
3 14 VBACKUP
Secondary Power Supply. Supply voltage must be held between 1.3V and 3.7V
for proper operation. This pin can be connected to a primary cell, such as a
lithium button cell. Additionally, this pin can be connected to a rechargeable cell
or a super cap when used in conjunction with the trickle-charge feature. Diodes
should not be placed in series between the backup source and the VBACKUP input,
or improper operation will result. UL recognized to ensure against reverse
charging current when used with a lithium cell. If a backup supply is not required,
VBACKUP must be grounded.
4 15 GND Ground. DC power is provided to the device on these pins.
5 16 SDA
Serial Data Input/Output. SDA is the input/output pin for the I2C serial interface.
The SDA pin is an open-drain output and requires an external pullup resistor.
6 1 SCL
Serial Clock Input. SCL is used to synchronize data movement on the serial
interface.
7 2
SQW/INT
Square-Wave/Interrupt Output. Programmable square-wave or interrupt output
signal. The SQW/INT pin is an open-drain output and requires an external pullup
resistor.
8 3 VCC
Primary Power Supply. When voltage is applied within normal limits, the device
is fully accessible and data can be written and read. When a backup supply is
connected and VCC is below VPF, reads and writes are inhibited. The timekeeping
and alarm functions operate when the device is powered by VCC or VBACKUP.
— 4–13 N.C. No Connection. These pins are unused and must be connected to ground.
TYPICAL OPERATING CIRCUIT
DS1339
4
CPU
VCC
VCC
VCC
5
6
8
12
SDA
SCL
GND
X2X1
VCC
RPU RPU
CRYSTAL
SQW/INT
VBACKUP
3
7
i
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DS1339 I2C Serial Real-Time Clock
DETAILED DESCRIPTION
The DS1339 serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day
alarms and a programmable square-wave output. Address and data are transferred serially through an I2C bus.
The clock/date 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 the 24-hour or 12-hour format with AM/PM indicator. The DS1339 has a built-in power-
sense circuit that detects power failures and automatically switches to the backup supply, maintaining time, date,
and alarm operation.
OPERATION
The DS1339 operates as a slave device on the serial bus. Access is obtained by implementing a START condition
and providing a device identification code followed by data. Subsequent registers can be accessed sequentially
until a STOP condition is executed. 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. If
VPF is less than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VPF. If VPF is
greater than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VBACKUP. The
registers are maintained from the VBACKUP source until VCC is returned to nominal levels. The block diagram in
Figure 3 shows the main elements of the serial real-time clock.
OSCILLATOR CIRCUIT
The DS1339 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or
capacitors to operate. Table 1 specifies several crystal parameters for the external crystal. Figure 4 shows a
functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a crystal
with the specified characteristics.
POWER CONTROL
The power-control function is provided by a precise, temperature-compensated voltage reference and a
comparator circuit that monitors the VCC 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. If VPF is less than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VPF. If
VPF is greater than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VBACKUP. The
registers are maintained from the VBACKUP source until VCC is returned to nominal levels (Table 1). After VCC returns
above VPF, read and write access is allowed after tREC (Figure 1).
Table 1. Power Control
SUPPLY CONDITION READ/WRITE
ACCESS
POWERED
BY
VCC < VPF, VCC < VBACKUP No VBACKUP
VCC < VPF, VCC > VBACKUP No VCC
VCC > VPF, VCC < VBACKUP Yes VCC
VCC > VPF, VCC > VBACKUP Yes VCC
OSCILLATOR CIRCUIT
The DS1339 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or
capacitors to operate. Table 2 specifies several crystal parameters for the external crystal. Figure 3 shows a
functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a crystal
with the specified characteristics.
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DS1339 I2C Serial Real-Time Clock
Table 2. Crystal Specifications*
PARAMETER SYMBOL MIN TYP MAX UNITS
Nominal Frequency fO 32.768 kHz
Series Resistance ESR 45 kΩ
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 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 may result in the clock running fast. Figure 4 shows a typical PC board layout for isolating the
crystal and oscillator from noise. Refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks for detailed information
DS1339C ONLY
The DS1339C integrates a standard 32,768Hz crystal in the package. Typical accuracy at nominal VCC and +25°C
is approximately 10ppm. Refer to Application Note 58 for information about crystal accuracy vs. temperature.
Figure 4. Typical PC Board Layout for Crystal
LOCAL GROUND PLANE (LAYER 2)
CRYSTAL
X1
X2
GND
NOTE:
A
VOID ROUTING SIGNALS IN
THE CROSSHATCHED AREA (UPPER
LEFT-HAND QUADRANT) OF THE
PACKAGE UNLESS THERE IS A
GROUND PLANE BETWEEN THE
SIGNAL LINE AND THE PACKAGE.
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DS1339 I2C Serial Real-Time Clock
ADDRESS MAP
Table 3 shows the address map for the DS1339 registers. During a multibyte access, when the address pointer
reaches the end of the register space (10h), it wraps around to location 00h. On an I2C START, STOP, or address
pointer incrementing to location 00h, the current time is transferred to a second set of registers. The time
information is read from these secondary registers, while the clock may continue to run. This eliminates the need
to re-read the registers in case of an update of the main registers during a read.
Table 3. Timekeeper Registers
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00H 0 10 Seconds Seconds Seconds 00–59
01H 0 10 Minutes Minutes Minutes 00–59
AM/PM
02H 0
12/24 10 Hour 10 Hour Hour Hours
1–12
+AM/PM
00–23
03H 0 0 0 0 0 Day Day 1–7
04H 0 0 10 Date Date Date 01–31
05H Century 0 0 10
Month Month Month/
Century
01–12 +
Century
06H 10 Year Year Year 00–99
07H A1M1 10 Seconds Seconds Alarm 1
Seconds 00–59
08H A1M2 10 Minutes Minutes Alarm 1
Minutes 00–59
AM/PM
09H A1M3
12/24 10 Hour 10 Hour Hour Alarm 1
Hours
1–12 +
AM/PM
00–23
0AH A1M4 DY/DT 10 Date Day, Date
Alarm 1
Day,
Alarm 1
Date
1-7, 1-31
0BH A2M2 10 Minutes Minutes Alarm 2
Minutes 00–59
AM/PM
0CH A2M3
12/24 10 Hour 10 Hour Hour Alarm 2
Hours
1–12 +
AM/PM
00–23
0DH A2M4
DY/DT 10 Date Day, Date
Alarm 2
Day,
Alarm 2
Date
1–7, 1–31
0EH EOSC 0 BBSQI RS2 RS1 INTCN A2IE A1IE Control
0FH OSF 0 0 0 0 0 A2F A1F Status
10H TCS3 TCS2 TCS1 TCS0 DS1 DS0
ROUT1 ROUT0 Trickle
Charger
Note: Unless otherwise specified, the state of the registers are not defined when power is first applied or when VCC and VBACKUP falls below the
VBACKUP(MIN).
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DS1339 I2C Serial Real-Time Clock
TIME AND DATE OPERATION
The time and date information is obtained by reading the appropriate register bytes. Table 3 shows the RTC
registers. The time and date are set or initialized by writing the appropriate register bytes. The contents of the time
and date registers are in the BCD format. The DS1339 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). All hours values, including the alarms, must be re-entered whenever the 12/24-hour mode bit is
changed. The century bit (bit 7 of the month register) is toggled when the years register overflows from 99 to 00.
The day-of-week register increments at midnight. Values that correspond to the day of week are user-defined, but
must be sequential (i.e., if 1 equals Sunday, then 2 equals Monday and so on). Illogical time and date entries result
in undefined operation.
When reading or writing the time and date registers, secondary (user) buffers are used to prevent errors when the
internal registers update. When reading the time and date registers, the user buffers are synchronized to the
internal registers on any start or stop, and when the address pointer rolls over to zero. The countdown chain is
reset whenever the seconds register is written. Write transfers occurs on the acknowledge pulse from the device.
To avoid rollover issues, once the countdown chain is reset, the remaining time and date registers must be written
within one second. If enabled, the 1Hz square-wave output transitions high 500ms after the seconds data transfer,
provided the oscillator is already running.
ALARMS
The DS1339 contains two time of day/date alarms. Alarm 1 can be set by writing to registers 07h to 0Ah. Alarm 2
can be set by writing to registers 0Bh to 0Dh. The alarms can be programmed (by the Alarm Enable and INTCN
bits of the Control Register) to activate the SQW/INT output on an alarm match condition. Bit 7 of each of the time
of day/date alarm registers are mask bits (Table 4). When all the mask bits for each alarm are logic 0, an alarm
only occurs when the values in the timekeeping registers 00h to 06h match the values stored in the time of
day/date alarm registers. The alarms can also be programmed to repeat every second, minute, hour, day, or date.
Table 4 shows the possible settings. Configurations not listed in the table result in illogical operation.
The DY/DT bits (bit 6 of the alarm day/date registers) control whether the alarm value stored in bits 0 to 5 of that
register reflects the day of the week or the date of the month. If DY/DT is written to a logic 0, the alarm is the result
of a match with date of the month. If DY/DT is written to a logic 1, the alarm is the result of a match with day of the
week.
The device checks for an alarm match once per second. When the RTC register values match alarm register
settings, the corresponding Alarm Flag ‘A1F’ or ‘A2F’ bit is set to logic 1. If the corresponding Alarm Interrupt
Enable ‘A1IE’ or ‘A2IE’ is also set to logic 1 and the INTCN bit is set to logic 1, the alarm condition activates the
SQW/INT) signal. If the BBSQI bit is set to 1, the INT output activates while the part is being powered by VBACKUP.
The alarm output remains active until the alarm flag is cleared by the user.
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DS1339 I2C Serial Real-Time Clock
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Table 4. Alarm Mask Bits
ALARM 1 REGISTER MASK BITS
(Bit 7)
DY/DT A1M4 A1M3 A1M2 A1M1 ALARM RATE
X 1 1 1 1 Alarm once per second
X 1 1 1 0 Alarm when seconds match
X 1 1 0 0 Alarm when minutes and seconds match
X 1 0 0 0 Alarm when hours, minutes, and seconds match
0 0 0 0 0
Alarm when date, hours, minutes, and seconds
match
1 0 0 0 0 Alarm when day, hours, minutes, and seconds match
ALARM 2 REGISTER MASK BITS
(Bit 7)
DY/DT A2M4 A2M3 A2M2 ALARM RATE
X 1 1 1 Alarm once per minute (00 sec. of every min.)
X 1 1 0 Alarm when minutes match
X 1 0 0 Alarm when hours and minutes match
0 0 0 0 Alarm when date, hours, and minutes match
1 0 0 0 Alarm when day, hours, and minutes match
SPECIAL-PURPOSE REGISTERS
The DS1339 has two additional registers (control and status) that control the RTC, alarms, and square-wave
output.
CONTROL REGISTER (0Eh)
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
EOSC 0 BBSQI RS2 RS1 INTCN A2IE A1IE
Bit 7: Enable Oscillator (EOSC). This bit when set to logic 0 starts the oscillator. When this bit is set to a logic 1,
the oscillator is stopped. This bit is enabled (logic 0) when power is first applied.
Bit 5: Battery-Backed Square-Wave and Interrupt Enable (BBSQI). This bit when set to a logic 1 enables the
square wave or interrupt output when VCC is absent and the DS1339 is being powered by the VBACKUP pin. When
BBSQI is a logic 0, the SQW/INT pin goes high impedance when VCC falls below the power-fail trip point. This bit is
disabled (logic 0) when power is first applied.
Bits 4 and 3: Rate Select (RS2 and RS1). These bits control the frequency of the square-wave output when the
square wave has been enabled. Table 5 shows the square-wave frequencies that can be selected with the RS bits.
These bits are both set to logic 1 (32kHz) when power is first applied.
Table 5. SQW/INT Output
INTCN RS2 RS1 SQW/INT
OUTPUT A2IE A1IE
0 0 0 1Hz X X
0 0 1 4.096kHz X X
0 1 0 8.192kHz X X
0 1 1 32.768kHz X X
1 X X A1F 0 1
1 X X A2F 1 0
1 X X A2F + A1F 1 1
DS1339 I2C Serial Real-Time Clock
14 of 19
Bit 2: Interrupt Control (INTCN). This bit controls the relationship between the two alarms and the interrupt output
pins. When the INTCN bit is set to logic 1, a match between the timekeeping registers and the alarm 1 or alarm 2
registers activate the SQW/INT pin (provided that the alarm is enabled). When the INTCN bit is set to logic 0, a
square wave is output on the SQW/INT pin. This bit is set to logic 0 when power is first applied.
Bit 1: Alarm 2 Interrupt Enable (A2IE). When set to a logic 1, this bit permits the Alarm 2 Flag (A2F) bit in the
status register to assert SQW/INT (when INTCN = 1). When the A2IE bit is set to logic 0 or INTCN is set to logic 0,
the A2F bit does not initiate an interrupt signal. The A2IE bit is disabled (logic 0) when power is first applied.
Bit 0: Alarm 1 Interrupt Enable (A1IE). When set to logic 1, this bit permits the Alarm 1 Flag (A1F) bit in the
status register to assert SQW/INT (when INTCN = 1). When the A1IE bit is set to logic 0 or INTCN is set to logic 0,
the A1F bit does not initiate an interrupt signal. The A1IE bit is disabled (logic 0) when power is first applied.
STATUS REGISTER (0Fh)
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
OSF 0 0 0 0 0 A2F A1F
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 may be used to judge the validity of the clock and date data. This bit is edge triggered
and is set to logic 1 when the oscillator stops. The following are examples of conditions that can cause the OSF bit
to be set:
1) The first time power is applied.
2) The voltage on both VCC and VBACKUP are insufficient to support oscillation.
3) The EOSC bit is turned off.
4) External influences on the crystal (e.g., noise, leakage, etc.).
This bit remains at logic 1 until written to logic 0. This bit can only be written to a logic 0.
Bit 1: Alarm 2 Flag (A2F). A logic 1 in the Alarm 2 Flag bit indicates that the time matched the alarm 2 registers. If
the A2IE bit is a logic 1 and the INTCN bit is set to a logic 1, the SQW/INT pin is also asserted. A2F is cleared
when written to logic 0. This bit can only be written to logic 0. Attempting to write to logic 1 leaves the value
unchanged.
Bit 0: Alarm 1 Flag (A1F). A logic 1 in the Alarm 1 Flag bit indicates that the time matched the alarm 1 registers. If
the A1IE bit is a logic 1 and the INTCN bit is set to a logic 1, the SQW/INT pin is also asserted. A1F is cleared
when written to logic 0. This bit can only be written to logic 0. Attempting to write to logic 1 leaves the value
unchanged.
DS1339 I2C Serial Real-Time Clock
15 of 19
TRICKLE CHARGER REGISTER (10h)
The simplified schematic in Figure 5 shows the basic components of the trickle charger. The trickle-charge select
(TCS) bits (bits 4 to 7) control the selection of the trickle charger. To prevent accidental enabling, only a pattern on
1010 enables the trickle charger. All other patterns disable the trickle charger. The trickle charger is disabled when
power is first applied. The diode-select (DS) bits (bits 2 and 3) select whether or not a diode is connected between
VCC and VBACKUP. The ROUT bits (bits 0 and 1) select the value of the resistor connected between VCC and VBACKUP.
Table 6 shows the bit values.
Table 6. Trickle Charger Register (10h)
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0 FUNCTION
X X X X 0 0 X X Disabled
X X X X 1 1 X X Disabled
X X X X X X 0 0 Disabled
1 0 1 0 0 1 0 1
No diode, 250Ω resistor
1 0 1 0 1 0 0 1
One diode, 250Ω resistor
1 0 1 0 0 1 1 0
No diode, 2kΩ resistor
1 0 1 0 1 0 1 0
One diode, 2kΩ resistor
1 0 1 0 0 1 1 1
No diode, 4kΩ resistor
1 0 1 0 1 0 1 1
One diode, 4kΩ resistor
0 0 0 0 0 0 0 0 Initial power-up values
Warning: The ROUT value of 250Ω must not be selected whenever VCC is greater than 3.63V.
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 3.3V system power supply is applied to VCC and a super cap is connected to VBACKUP. Also assume that the
trickle charger has been enabled with a diode and resistor R2 between VCC and VBACKUP. The maximum current IMAX
would therefore be calculated as follows:
IMAX = (3.3V - diode drop) / R2 ≈ (3.3V - 0.7V) / 2kΩ ≈ 1.3mA
As the super cap or battery charges, the voltage drop between VCC and VBACKUP decreases and therefore the
charge current decreases.
DS1339 I2C Serial Real-Time Clock
16 of 19
Figure 5. Programmable Trickle Charger
1 OF 16 SELECT
NOTE: ONLY 1010 ENABLES CHARGER
1 OF 2
SELECT
1 OF 3
SELECT
TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
250Ω
2kΩ
4kΩ
R1
R3
R2
TRICKLE CHARGE REGISTER
TCS0-3 = TRICKLE CHARGER SELECT
DS0-1 = DIODE SELECT
ROUT0-1 = RESISTOR SELECT
VCC VBACKUP
I2C SERIAL DATA BUS
The DS1339 supports the I2C bus protocol. A device that sends data onto the bus is defined as a transmitter and a
device receiving data as a receiver. The device that controls the message is called a master. The devices that are
controlled by the master are referred to as slaves. The bus must be controlled by a master device that generates
the serial clock (SCL), controls the bus access, and generates the START and STOP conditions. The DS1339
operates as a slave on the I2C bus. Within the bus specifications, a standard mode (100kHz cycle rate) and a fast
mode (400kHz cycle rate) are defined. The DS1339 works in both modes. Connections to the bus are made via the
open-drain I/O lines SDA and SCL.
The following bus protocol has been defined (Figure 6):
Data transfer may be initiated only when the bus is not busy.
During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the
data line while the clock line is HIGH are interpreted as control signals.
Accordingly, the following bus conditions have been defined:
Bus not busy: Both data and clock lines remain HIGH.
Start data transfer: A change in the state of the data line, from HIGH to LOW, while the clock is HIGH,
defines a START condition.
Stop data transfer: A change in the state of the data line, from LOW to HIGH, while the clock line is
HIGH, defines the STOP condition.
Data valid: The state of the data line represents valid data when, after a START condition, the data line is
stable for the duration of the HIGH period of the clock signal. The data on the line must be changed during
the LOW period of the clock signal. There is one clock pulse per bit of data.
DS1339 I2C Serial Real-Time Clock
17 of 19
Each data transfer is initiated with a START condition and terminated with a STOP condition. The number
of data bytes transferred between START and STOP conditions is not limited, and is determined by the
master device. The information is transferred byte-wise and each receiver acknowledges with a ninth bit.
Acknowledge: Each receiving device, when addressed, is obliged to generate an acknowledge after the
reception of each byte. The master device must generate an extra clock pulse that is associated with this
acknowledge bit.
A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a
way that the SDA line is stable LOW during the HIGH period of the acknowledge related clock pulse. Of
course, setup and hold times must be taken into account. A master must signal an end of data to the slave
by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case,
the slave must leave the data line HIGH to enable the master to generate the STOP condition.
Figure 6. Data Transfer on I2C Serial Bus
Depending upon the state of the R/W bit, two types of data transfer are possible:
1) Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master is
the slave address. Next follows a number of data bytes. The slave returns an acknowledge bit after each
received byte. Data is transferred with the most significant bit (MSB) first.
2) Data transfer from a slave transmitter to a master receiver. The first byte (the slave address) is
transmitted by the master. The slave then returns an acknowledge bit. This is followed by the slave
transmitting a number of data bytes. The master returns an acknowledge bit after all received bytes other
than the last byte. At the end of the last received byte, a “not acknowledge” is returned. The master device
generates all of the serial clock pulses and the START and STOP conditions. A transfer is ended with a
STOP condition or with a repeated START condition. Since a repeated START condition is also the
beginning of the next serial transfer, the bus is not released. Data is transferred with the most significant bit
(MSB) first.
The DS1339 can operate in the following two modes:
1) Slave Receiver Mode (Write Mode): Serial data and clock are received through SDA and SCL. After each
byte is received an acknowledge bit is transmitted. START and STOP conditions are recognized as the
beginning and end of a serial transfer. Address recognition is performed by hardware after reception of the
slave address and direction bit (Figure 7). The slave address byte is the first byte received after the
START condition is generated by the master. The slave address byte contains the 7-bit DS1339 address,
which is 1101000, followed by the direction bit (R/W), which is 0 for a write. After receiving and decoding
the slave address byte the slave outputs an acknowledge on the SDA line. After the DS1339
acknowledges the slave address + write bit, the master transmits a register address to the DS1339. This
DS1339 I2C Serial Real-Time Clock
18 of 19
sets the register pointer on the DS1339, with the DS1339 acknowledging the transfer. The master may
then transmit zero or more bytes of data, with the DS1339 acknowledging each byte received. The
address pointer increments after each data byte is transferred. The master generates a STOP condition to
terminate the data write.
2) Slave Transmitter Mode (Read Mode): The first byte is received and handled as in the slave receiver
mode. However, in this mode, the direction bit indicates that the transfer direction is reversed. Serial data
is transmitted on SDA by the DS1339 while the serial clock is input on SCL. START and STOP conditions
are recognized as the beginning and end of a serial transfer (Figure 8). The slave address byte is the first
byte received after the START condition is generated by the master. The slave address byte contains the
7-bit DS1339 address, which is 1101000, followed by the direction bit (R/W), which is 1 for a read. After
receiving and decoding the slave address byte the slave outputs an acknowledge on the SDA line. The
DS1339 then begins to transmit data starting with the register address pointed to by the register pointer. If
the register pointer is not written to before the initiation of a read mode the first address that is read is the
last one stored in the register pointer. The address pointer is incremented after each byte is transferred.
The DS1339 must receive a “not acknowledge” to end a read.
Figure 7. Data Write—Slave Receiver Mode
...AXXXXXXXXAS 0 XXXXXXXX AXXXXXXXX AXXXXXXXX A P
S - Start
A - Acknowledge (ACK)
P - Stop
<R/W>
DATA TRANSFERRED
(X+1 BYTES + ACKNOWLEDGE)
1101000
<Slave Address> <Word Address (n)> <Data(n)> <Data(n+1)> <Data(n+X)>
Master to slave
Slave to master
Figure 8. Data Read (from Current Pointer Location)—Slave Transmitter Mode
...AXXXXXXXXA1101000S 1 XXXXXXXX AXXXXXXXX XXXXXXXX AP
<Data(n+2)> <Data(n+X)>
A
S - Start
A - Acknowledge (ACK)
P - Stop
A - Not Acknowledge (NACK)
<RW>
DATA TRANSFERRED
(X+1 BYTES + ACKNOWLEDGE)
NOTE: LAST DATA BYTE IS FOLLOWED BY A NACK
<Slave Address> <Data(n)> <Data(n+1)>
Master to slave
Slave to master
Figure 9. Data Read (Write Pointer, Then Read)—Slave Receive and Transmit
...AXXXXXXXX XXXXXXXX AXXXXXXXX AXXXXXXXX AP
S - Start
Sr - Repeated Start
A - Acknowledge (ACK)
P - Stop
A - Not Acknowledge (NACK)
DATA TRANSFERRED
(X+1 BYTES + ACKNOWLEDGE)
NOTE: LAST DATA BYTE IS FOLLOWED BY A NACK
AXXXXXXXXA1101000S 0
<RW>
<Word Address (n)>
A1101000Sr 1
<RW>
<Slave Address>
<Data(n)> <Data(n+1)> <Data(n+2)> <Data(n+X)>
Master to slave
Slave to master
DS1339 I2C Serial Real-Time Clock
19 of 19
Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.
No circuit patent licenses are implied. Maxim/Dallas Semiconductor 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
© 2006 Maxim Integrated Products
The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor.
HANDLING, PC BOARD LAYOUT, AND ASSEMBLY
The DS1339C package contains a quartz tuning-fork crystal. Pick-and-place equipment may be used, but
precautions should be taken to ensure that excessive shocks are avoided. Ultrasonic cleaning should be avoided
to prevent damage to the crystal.
Avoid running signal traces under the package, unless a ground plane is placed between the package and the
signal line. All N.C. (no connect) pins must be connected to ground.
The leaded SO package may be reflowed as long as the peak temperature does not exceed 240°C. Peak reflow
temperature (≥ 230°C) duration should not exceed 10 seconds, and the total time above 200°C should not exceed
40 seconds (30 seconds nominal). Exposure to reflow is limited to 2 times maximum.
The RoHS SO package may be reflowed using a reflow profile that complies with JEDEC J-STD-020 lead-free
assembly.
Moisture-sensitive packages are shipped from the factory dry-packed. Handling instructions listed on the package
label must be followed to prevent damage during reflow. Refer to the IPC/JEDEC J-STD-020B standard for
moisture-sensitive device (MSD) classifications.
PIN CONFIGURATIONS
SQW/
I
N
T
SCL SDA
GND
V
BAC UP K
N.C.
VCC
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
DS1339
C
SO
(
300 mils
)
TOP VIEW
µ
SOP
SQW/
I
NT
X1
X2
GND
VCC
SCL
SDA
VBACKUP
DS133
9
TOP VIEW
CHIP INFORMATION
TRANSISTOR COUNT: 11,325
PROCESS: CMOS
THERMAL AND PACKAGE INFORMATION
PART THETA-JA
(°C/W) THETA-JC
(°C/W) CONDITIONS PACKAGE OUTLINE
µSOP 229 39 21-0036
SO 73 23
Typical 56-G4009-001
For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.
