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19-5801; Rev 0; 3/11
Low-Current SPI/3-Wire RTCs
General Description
The DS1343/DS1344 low-current real-time clocks (RTCs) are timekeeping devices that provide an extremely low standby current, permitting longer life from a backup supply source. The devices also support high-ESR crystals, broadening the pool of usable crystals for the devices. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either 24-hour or 12-hour format with an AM/PM indicator. Address and data are transferred serially through an SPITM or 3-wire interface. Two programmable time-of-day alarms are provided. Each alarm can generate an interrupt on a 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 they can be combined to assert one common interrupt output. Both interrupt outputs operate when the device is powered by either VCC or VBAT. The devices are available in a lead-free/RoHS-compliant, 20-pin TSSOP or 14-pin TDFN package, and support a -40C to +85C extended industrial temperature range.
Features
S Low Timekeeping Current of 250nA (typ) S Compatible with Crystal ESR Up to 100kI S Versions Available to Support Either 6pF or 12.5pF Crystals S RTC Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap Year Compensation Valid Through 2099 S Power-Fail and Switch Circuitry S Three Operating Voltages 1.8V 5% 3.0V10% 3.3V 10% S Trickle-Charge Capability S Maintain Time Down to 1.15V (typ) S Support Motorola SPI Modes 1 and 3, or Standard 3-Wire Interface S Burst Mode for Reading/Writing Successive Addresses in Clock/RAM S 96-Byte Battery-Backed NV RAM for Data Storage S Two Time-of-Day Alarms with Two Interrupt Outputs S Industrial Temperature Range S 20-Pin TSSOP or 14-Pin TDFN Package
DS1343/DS1344
Applications
Medical Handheld Devices
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Typical Operating Circuit
VCC
Telematics Embedded Timestamping
RPU
VCC INT0 PF INT1 CE SCLK SDI SDO X1 DS1343 DS1344
INT RST P 3-WIRE PORT
X2 VBAT
Ordering Information appears at end of data sheet.
SERMODE GND
NOTE: SHOWN IN 3-WIRE I/O CONFIGURATION.
SPI is a trademark of Motorola, Inc.
_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Low-Current SPI/3-Wire RTCs DS1343/DS1344
ABSOLUTE MAXIMUM RATINGS
Voltage Range on VCC or VBAT Relative to Ground............................................-0.3V to +6.0V Voltage Range on Any Nonpower Pin Relative to Ground................................ -0.3V to (VCC + 0.3V) Operating Temperature Range .......................... -40NC to +85NC Junction Temperature Maximum.....................................+150NC Storage Temperature Range............................ -55NC to +125NC Lead Temperature (soldering, 10s) ................................+260NC Soldering Temperature (reflow) ......................................+260NC
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TSSOP Junction-to-Ambient Thermal Resistance (BJA) ..........91NC/W Junction-to-Case Thermal Resistance (BJC) ...............20NC/W TDFN Junction-to-Ambient Thermal Resistance (BJA) ..........54NC/W Junction-to-Case Thermal Resistance (BJC) .................8NC/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
RECOMMENDED OPERATING CONDITIONS
(TA = -40C to +85C, unless otherwise noted.) (Note 2) PARAMETER Operating Voltage Range Minimum Timekeeping Voltage Backup Voltage Logic 1 Input Logic 0 Input SYMBOL DS134_-18 VCC VBATTMIN VBAT VIH VIL DS134_-3 DS134_-33 TA = +25NC 1.3 0.7 x VCC -0.3 CONDITIONS MIN 1.71 2.7 3.0 TYP 1.8 3.0 3.3 1.15 MAX 5.5 5.5 5.5 1.3 5.5 VCC + 0.3 0.3 x VCC V V V V V UNITS
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DC ELECTRICAL CHARACTERISTICS
(VCC = VCC(MIN) to +5.5V, VBAT = +1.3V to +5.5V, TA = -40C to +85C, unless otherwise noted.) (Notes 2, 3) PARAMETER Power-Supply Active Current Power-Supply Standby Current (Note 5) Backup Current (Oscillator Off) Backup Current DS1343 (Note 6) Backup Current DS1343 (Note 7) SYMBOL ICCA ICCS IBAT IBAT1 IBAT2 CONDITIONS -3 or -33: fSCLK = 4MHz (Note 4) -33: VCC = 3.63V VCC = VCC(MAX) TA = +25NC, VCC = 0V, EOSC = 1 VBAT = 3V VBAT = VBAT(MAX) VBAT = 3V VBAT = VBAT(MAX) 250 500 300 600 MIN TYP MAX 600 120 160 100 UNITS FA FA nA nA nA
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Low-Current SPI/3-Wire RTCs
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = VCC(MIN) to +5.5V, VBAT = +1.3V to +5.5V, TA = -40C to +85C, unless otherwise noted.) (Notes 2, 3) PARAMETER Input Leakage (CE, SERMODE, SCLK, SDI) Output Leakage (INT0, INT1, PF, SDO) Output Logic 1 (PF, SDO) Output Logic 0 VOL = 0.4V (INT0, INT1, PF, SDO) Power-Fail Trip Point SYMBOL II IO IOH IOL CONDITIONS VIN = 0V to VCC CE = VIL, no alarms -3 or -33: VOH = 2.4V VCC R VCC(MIN) VBAT R 1.3V R VCC + 0.2V (Note 8) -18 VPF -3 -33 Switchover Voltage VSW R1 Trickle-Charger Resistors R2 R3 VBAT > VPF VBAT < VPF MIN -0.1 -0.1 -1 3.0 250 1.51 2.45 2.70 1.6 2.6 2.88 VPF VBAT > VCC 1 2 4 kI 1.71 2.70 3.0 V V TYP MAX +0.1 +0.1 UNITS FA FA mA mA FA
DS1343/DS1344
AC ELECTRICAL CHARACTERISTICS
(VCC = VCC(MIN) to VCC(MAX), TA = -40C to +85C, unless otherwise noted.) (Notes 2, 3) PARAMETER SCLK Frequency Data to SCLK Setup
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SYMBOL fSCLK tDC tCDH tCDD tCL tCH tR, tF tCC tCCH tCWH tCDZ tOSF (Note 9) -18 -3 or -33 -18 -3 or -33 -18 -3 or -33 -18 -3 or -33 -18 -3 or -33
CONDITIONS
MIN DC DC 30 30
TYP
MAX 1 4
UNITS MHz ns ns
SCLK to Data Hold SCLK to Data Delay SCLK Low Time SCLK High Time SCLK Rise and Fall CE to SCLK Setup SCLK to CE Hold CE Inactive Time CE to Output High-Z Oscillator Stop Flag (OSF) Delay
160 80 400 110 400 110 200 400 100 500 400 40 25 100
ns ns ns ns ns ns ns ns ms
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
POWER-UP/DOWN CHARACTERISTICS
(TA = -40C to +85C, unless otherwise noted.) PARAMETER Recovery at Power-Up VCC Fall Time (VPF to 0V) VCC Rise Time (0V to VPF) SYMBOL tREC tVCCF tVCCR 150 0 CONDITIONS MIN TYP 20 MAX 40 UNITS ms Fs Fs
CAPACITANCE
(TA = +25C, unless otherwise noted.) PARAMETER Input Capacitance Output Capacitance SYMBOL CI CO (Note 10) (Note 10) CONDITIONS MIN TYP 10 15 MAX UNITS pF pF
CRYSTAL PARAMETERS
PARAMETER Nominal Frequency Series Resistance Load Capacitance Note Note Note Note Note Note Note Note Note SYMBOL fO ESR CL DS1343 DS1344 6 12.5 CONDITIONS MIN TYP 32.768 100 MAX UNITS kHz kI pF
2: Voltage referenced to ground. 3: Limits at TA = -40C are guaranteed by design and not production tested. 4: CE = VCC, VSCLK = VCC to GND, IOUT = 0mA, trickle charger disabled. 5: CE = GND, IOUT = 0mA, EOSC = EGFIL = DOSF = 0, trickle charger disabled. 6: VCC = 0V, EGFIL = 0, DOSF = 1. 7: VCC = 0V, EGFIL = 1, DOSF = 0. 8: Applies to INT0 and INT1. 9: The parameter tOSF is the period of time the oscillator must be stopped for the OSF flag to be set. 10: Guaranteed by design; not 100% production tested.
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Low-Current SPI/3-Wire RTCs
SPI Write Timing
tCWH
DS1343/DS1344
CE tCC tCL SCLK* tCDH tCH tF tR tCCH
tDC
tCDH
SDI
R/W = 1
A6
A0
D7
D0
WRITE ADDRESS BYTE *SCLK CAN BE EITHER POLARITY. TIMING SHOWN FOR CPOL = 1. SERMODE = VCC.
WRITE DATA BYTE
SPI Read Timing
tCWH
CE tCC
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tCL
tCH
SCLK* tCDH tDC SDI
tCDD
tCDZ
R/W = 0
A6
A0
SDO
D7
D0
WRITE ADDRESS BYTE *SCLK CAN BE EITHER POLARITY. TIMING SHOWN FOR CPOL = 1. SERMODE = VCC.
READ DATA BYTE
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
3-Wire Write Timing
tCWH
CE tCCH tCL tR tF
tCC
SCLK tCDH tCH
tDC
I/O*
A0
A1
R/W = 1
D0
D7
WRITE ADDRESS BYTE *I/O IS SDI AND SDO CONNECTED TOGETHER. SERMODE = GND.
WRITE DATA BYTE
3-Wire Read Timing
tCWH
CE
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tCC
tCL
tCDD
tCDZ
SCLK tCDH tCH
tDC A0
I/O*
A1
R/W = 0
D0
D7
WRITE ADDRESS BYTE *I/O IS SDI AND SDO CONNECTED TOGETHER. SERMODE = GND.
READ DATA BYTE
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Low-Current SPI/3-Wire RTCs
Typical Operating Characteristics
(VCC = +3.3V, TA = +25C, unless otherwise noted.)
POWER-SUPPLY CURRENT vs. POWER-SUPPLY VOLTAGE
DS1343/4 toc01
DS1343/DS1344
POWER-SUPPLY CURRENT vs. POWER-SUPPLY VOLTAGE
130 SUPPLY CURRENT (A) 120 110 100 90 80 70 60
500 SUPPLY CURRENT (A) 400 300 200 100 0 3.0
TA = +25C CE = VIH IOUT = 0mA
CE = VIL IOUT = 0mA TA = +85C TA = +25C
fSCLK = 4MHz
fSCLK = 1MHz
TA = -40C
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
BATTERY CURRENT1 vs. BATTERY VOLTAGE
DS1343/4 toc03
BATTERY CURRENT2 vs. BATTERY VOLTAGE
320 BATTERY CURRENT (nA) 300 280 260 240 220 200
260 BATTERY CURRENT (nA) 240 220 200 180 160
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EGFIL = 0 DOSF = 1 IOUT = 0mA TA = +85C TA = +25C TA = -40C
EGFIL = 1 DOSF = 0 IOUT = 0mA TA = +85C TA = +25C TA = -40C
140 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 BATTERY VOLTAGE (V)
180 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 BATTERY VOLTAGE (V)
DS1343/4 toc04
280
340
DS1343/4 toc02
600
140
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
Pin Configurations
SERMODE
TOP VIEW TOP VIEW
VCC
SCLK 9 EP 6 INT1
SDO
SDI
VBAT N.C. X1 N.C. X2 N.C. INT0 N.C. INT1 GND
1 2 3 4 5 6 7 8 9 10
20 19 18
VCC N.C. PF N.C. SDO SDI SCLK N.C. CE SERMODE
14
13
12
11
10
DS1343 DS1344
17 16 15 14 13 12 11
DS1343 DS1344
+
1 VBAT 2 X1 3 X2 4 N.C. 5 INT0
TSSOP
TDFN (3mm x 3mm)
Pin Descriptions
PIN TSSOP 1 2, 4, 6, 8, 13, 17, 19
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TDFN-EP 1
NAME
FUNCTION Battery Input for Standard +3V Lithium Cell or Other Energy Source. UL recognized to ensure against reverse charging current when used in conjunction with a primary lithium battery. No Connection. N.C. pins can be connected to GND to reduce noise around the crystal inputs. Connections for Standard 32.768kHz Quartz Crystal (see the Crystal Characteristics table). The devices can also be driven by an external 32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator and the X2 pin is left unconnected. Active-Low Interrupt 0 Output. INT0 is an active-low output that can be used as an interrupt output to a processor. 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. INT0 remains low as long as the status bit causing the interrupt is present and the corresponding interrupt enable bit is set. INT0 operates when the component is powered by VCC or VBAT. INT0 is an open-drain output and requires an external pullup resistor. Active-Low Interrupt 1 Output. INT1 is an active-low output that can be used either as an interrupt output to a processor or a 32kHz square-wave output. INT1 can be programmed to be asserted by Alarm 1 only. INT1 remains low as long as the status bit causing the interrupt is present and the corresponding interrupt enable bit is set. INT1 operates when the component is powered by VCC or VBAT. INT1 is an opendrain output and requires an external pullup resistor.
VBAT
4 2 3
N.C. X1 X2
3 5
7
5
INT0
9
6
INT1
8
GND
CE 8 7
PF
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Low-Current SPI/3-Wire RTCs
Pin Descriptions (continued)
PIN TSSOP 10 11 12 14 TDFN-EP 7 13 8 9 NAME GND SERMODE CE SCLK Ground Serial-Interface Mode Input. When connected to GND, standard 3-wire communication is selected. When connected to VCC, SPI communication is selected. Chip Enable. The chip-enable signal must be asserted high during a read or a write for either 3-wire or SPI communications. Serial-Clock Input. SCLK is used to synchronize data movement on the serial interface for either 3-wire or SPI communications. Serial-Data Input. When SPI communication is selected, SDI is the serial-data input for the SPI bus. When 3-wire communication is selected, this pin must be connected to SDO (SDI and SDO function as a single I/O pin when connected together). Serial-Data Output. When SPI communication is selected, SDO is the serial-data output for the SPI bus. When 3-wire communication is selected, this pin must be connected to SDI (SDI and SDO function as a single I/O pin when connected together). Active-Low Power-Fail Output. The PF pin is used to indicate loss of the primary power supply (VCC). When VCC is less than VPF, the PF pin is driven low. Power-Supply Input Exposed Pad (TDFN Only). Connect to GND or leave unconnected. FUNCTION
DS1343/DS1344
15
10
SDI
16
11
SDO
18 20 --
12 14 --
PF VCC EP
Functional Diagram
32.768kHz
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X1
X2
VCC PF VBAT GND
POWER CONTROL AND TRICKLE CHARGER
OSCILLATOR AND COUNTDOWN CHAIN
1Hz INT0 CLOCK, CALENDAR, AND ALARM REGISTERS
N
ON_VCC
DS1343 DS1344
CONTROL REGISTERS
INT1
CE SCLK SDI SDO SERMODE SERIAL INTERFACE INPUT SHIFT REGISTER USER RAM
N
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
Detailed Description
The DS1343/DS1344 low-current real-time clocks (RTCs) are timekeeping devices that consume an extremely low timekeeping current and also support high-ESR crystals, broadening the pool of usable crystals for the device. The devices provide 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 date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year through 2099. The clock operates in either a 24-hour or 12-hour format with an AM/PM indicator. In addition, 96 bytes of NV RAM are provided for data storage. The devices maintain the time and date, provided that the oscillator is enabled, as long as at least one supply is at a valid level. Both devices provide two programmable time-of-day alarms. 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 VCC or VBAT. The devices support a direct interface to SPI serial-data ports or standard 3-wire interface. A straight-forward address and data format is implemented in which data transfers can occur one byte at a time or in multiple-byte burst mode.
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when VCC falls below VPF, the internal clock registers are blocked from any access, and the device power is switched from VCC to VBAT. If VPF is less than the voltage on the backup supply, the device power is switched from VCC to the backup supply when VCC drops below VPF. If VPF is greater than the backup supply, the device power is switched from VCC to the backup supply when VCC drops below the backup supply. The registers are maintained from the backup supply source until VCC is returned to nominal levels. The Functional Diagram illustrates the main elements. When a battery is first attached to the device, the device does not immediately provide battery-backup power to the RTC or internal circuitry. After VCC exceeds VPF, the devices leave the freshness seal mode and provide battery-backup power whenever VCC subsequently falls below VBAT. This mode allows attachment of the battery during product manufacturing, but no battery capacity is consumed until after the system has been activated for the first time. As a result, minimum battery energy is used during storage and shipping. The devices use an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate. The DS1343 includes integrated capacitive loading for a 6pF CL crystal, and the DS1344 includes integrated capacitive loading for a 12.5pF CL crystal. See the Crystal Parameters table for the external crystal parameters. The Functional Diagram shows a simplified schematic of the oscillator circuit. The startup time is usually less than one second when using a crystal with the specified characteristics. When running from the internal oscillator, 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. Figure 1 shows a typical PCB layout for isolation of the crystal and oscillator from noise. Refer to Application Note 58: Crystal Considerations with Dallas Real-Time Clocks for detailed information.
Freshness Seal Mode
Oscillator Circuit
The devices have a built-in temperature-compensated power-sense circuit that detects power failures and automatically switches to the backup supply. The VBAT pin can be configured to provide trickle charging of a rechargeable voltage source, with selectable charging resistance and diode-voltage drops. The devices operate as slave devices on a 3-wire or SPI serial bus. Access is obtained by selecting the part by the CE pin and clocking data into/out of the part using the SCLK and SDI/SDO pins. Multiple byte transfers are supported within one CE high period; see the Serial Peripheral Interface (SPI) section for more information. The devices are fully accessible and data can be written and read when VCC is greater than VPF. However,
Clock Accuracy
I/O and Power-Switching Operation
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
LOCAL GROUND PLANE (LAYER 2)
X1 CRYSTAL X2
NOTE: AVOID ROUTING SIGNAL LINES IN THE CROSSHATCHED AREA (UPPER LEFT QUADRANT) OF THE PACKAGE UNLESS THERE IS A GROUND PLANE BETWEEN THE SIGNAL LINE AND THE DEVICE PACKAGE.
GND
Figure 1. Layout Example
Register Map
Table 1 shows the devices' register map. During a multibyte RTC access, if the address pointer reaches the end of the register space (1Fh), it wraps around to location 00h. During a multibyte RAM access, if the address pointer reaches the end of the register space (7Fh), it wraps around to location 20h. On either the rising edge of CE or an RTC address pointer wrap around, the current time is transferred to a secondary set of registers. The time information is read from these secondary registers, while the clock continues to run. This eliminates the need to reread the registers in case the main registers update during a read.
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7 of Month) is toggled when the Years register rolls over from 99 to 00. On a power-on reset (POR), the time and date are set to 00:00:00 01/01/00 (hh:mm:ss MM/DD/YY), and the Day register is set to 01. The devices contains two time-of-day/date alarms. Alarm 0 can be set by writing to registers 07h-0Ah. Alarm 1 can be set by writing to registers 0Bh-0Eh. The alarms can be programmed to activate the INT0 or INT1 outputs on an alarm match condition (see Table 2). Bit 7 of each of the time of day/date alarm registers are mask bits. When all the mask bits for each alarm are 0, an alarm only occurs when the values in the timekeeping registers 00h-06h match the values stored in the alarm registers. The alarms can also be programmed to repeat every second, minute, hour, or day. Configurations not listed in the table result in illogical operation. POR values are undefined. When the RTC register values match alarm register settings, the corresponding alarm flag bit (IRQF0 or IRQF1) is set to 1 in the Status register. If the corresponding alarm interrupt enable bit (A0IE or A1IE) is also set to 1 in the Control register, the alarm condition activates the output(s) defined by the INTCN bit. Upon an active alarm, clearing the associated IRQF[1:0] bit deasserts the selected interrupt output while leaving the alarm enabled for the next occurrence of a match. Alternatively, clearing the A_IE bit deasserts the output and inhibits further output activations. The alarm flags are always active, fully independent of the A_IE bit states. All alarm registers should be written to logic zero to disable the alarm matching.
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Alarms (07h-0Eh)
The time and calendar information is obtained by reading the appropriate register bytes. Table 1 shows the RTC registers. The time and calendar are set or initialized by writing the appropriate register bytes. The contents of the time and calendar registers are in the BCD format. The Day register increments at midnight and rolls over from 7 to 1. 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. The devices 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 a content of 1 being PM. In the 24-hour mode, bit 5 is the 20-hour field. Changing the 12/24 mode-select bit requires that the Hours data subsequently be reentered, including the Alarm register (if used). The Century bit (bit
Clock and Calendar (00h-06h)
Low-Current SPI/3-Wire RTCs DS1343/DS1344
Table 1. Register Map
ADDRESS 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch 0Dh 0Eh
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BIT 7 MSB 0 0 0 0 0 Century
BIT 6
BIT 5 10 Seconds 10 Minutes AM/PM 20 Hours 0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0 LSB
FUNCTION Seconds Minutes Hours
RANGE 00-59 00-59 1-12 + AM/PM 00-23 1-7 01-31 01-12 + Century 00-99 00-59 00-59 1-12 + AM/PM 00-23 1-7 00-59 00-59 1-12 + AM/PM 00-23 1-7 -- -- -- -- 00h-FFh
Seconds Minutes 10 Hours 0 0 Date Month Year Seconds Minutes 10 Hours 0 Hour Day Seconds Minutes 10 Hours 0 EGFIL 0 TCS0 SQW 0 DS1 0 DS0 Hour Day INTCN A1IE IRQF1 RS1 A0IE IRQF0 RS0 Hour Day
12/24 0 0 0
Day Date Month/ Century Year Alarm 0 Seconds Alarm 0 Minutes Alarm 0 Hours Alarm 0 Day Alarm 1 Seconds Alarm 1 Minutes Alarm 1 Hours Alarm 1 Day Control Status Trickle Charger Reserved User RAM
10 Date 0 10 Year 10 Month
A0M1 A0M2 A0M3 A0M4 A1M1 A1M2 A1M3 A1M4 EOSC OSF TCS3
10 Seconds 10 Minutes AM/PM 20 Hours 0 10 Seconds 10 Minutes AM/PM 20 Hours 0 DOSF 0 TCS1
12/24 0
12/24 0 X 0 TCS2
0Fh 10h 11h
12h-1Fh 20h-7Fh
Reserved User RAM
Note: Bits listed as 0 always read back as 0 and cannot be written to 1.
Table 2. Alarm Mask Bits
ALARM REGISTER MASK BITS (BIT 7) A_M4 1 1 1 1 0 A_M3 1 1 1 0 0 A_M2 1 1 0 0 0 A_M1 1 0 0 0 0 Alarm once a second Alarm when seconds match Alarm when minutes and seconds match Alarm when hours, minutes, and seconds match Alarm when day, hours, minutes, and seconds match ALARM RATE
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Low-Current SPI/3-Wire RTCs
Control Register (0Fh)
BIT 7 EOSC 1 BIT 6 X 0 BIT 5 DOSF 0 BIT 4 EGFIL 0 BIT 3 SQW 0 BIT 2 INTCN 0 BIT 1 A1IE 0 BIT 0 A0IE 0
DS1343/DS1344
BIT 7 BIT 6 BIT 5
EOSC: Enable oscillator. During battery backup, when EOSC is set to 0, the oscillator is enabled during backup operation. When set to 1, the oscillator is stopped when the device is powered by the backup supply. This bit is set to logic 1 on the initial application of power. Not used. DOSF: Disable oscillator stop flag. When the DOSF bit is set to 1, sensing of the oscillator conditions that would set the OSF bit are disabled. OSF remains at 0 regardless of what happens to the oscillator. This bit is cleared (0) on the initial application of power. EGFIL: Enable glitch filter. When the EGFIL bit is 1, the 5Fs glitch filter at the output of crystal oscillator is enabled. The glitch filter is disabled when this bit is 0. This bit is cleared (0) on the initial application of power. SQW: Enable square wave. When the SQW bit is set to 1, a 32kHz square wave is output on the INT1 output. This bit is cleared (0) on the initial application of power. INTCN: Interrupt control. This bit controls the relationship between the two time-of-day alarms and the two interrupt output pins. When the INTCN bit is 1, a match between the timekeeping registers and the Alarm 0 registers activates the INT0 output (provided A0IE = 1), and a match between the timekeeping registers and the Alarm 1 registers activates the INT1 output (provided A1IE = 1). When the INTCN bit is 0, a match between the timekeeping registers and either the Alarm 0 registers or Alarm 1 registers activates the INT0 output (provided A0IE = A1IE = 1). The INT1 output has no function when INTCN = 0. The INTCN bit is cleared (0) on the initial application of power. A1IE: Alarm 1 interrupt enable. When A1IE is set to 0, the Alarm 1 interrupt function is disabled. When A1IE is 1, the Alarm 1 interrupt function is enabled and is routed to either INT0 (if INTCN = 0) or INT1 (if INTCN = 1). Regardless of the state of A1IE, a match between the timekeeping registers and the Alarm 1 registers (0Bh-0Eh) sets the interrupt request 1 flag bit (IRQF1). The A1IE bit is cleared (0) when power is first applied. A0IE: Alarm 0 interrupt enable. When A0IE is set to 0, the Alarm 0 interrupt function is disabled. When A0IE is 1, the Alarm 0 interrupt function is enabled and is routed to INT0. Regardless of the state of A0IE, a match between the timekeeping registers and the Alarm 0 registers (07h-0Ah) sets the interrupt register 0 flag bit (IRQF0). The A0IE bit is cleared (0) when power is first applied.
BIT 4 BIT 3
BIT 2
BIT 1
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BIT 0
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
Status Register (10h)
BIT 7 OSF 1 BIT 6 0 0 BIT 5 0 0 BIT 4 0 0 BIT 3 0 0 BIT 2 0 0 BIT 1 IRQF1 0 BIT 0 IRQF0 0
OSF: Oscillator stop flag. If the OSF bit is 1, the oscillator either has stopped or was stopped for some period and could be used to judge the validity of the clock and calendar data. This bit is edge triggered and is set to 1 when the internal circuitry senses the oscillator has transitioned from a normal run state to a stop condition. This bit remains at logic 1 until written to logic 0. Attempting to write OSF to 1 leaves the value unchanged. BIT 7 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 present on VCC is insufficient to support oscillation. 3) The EOSC bit is a logic one during battery backup. 4) External influences on the crystal (i.e., noise, leakage, etc.). IRQF1: Interrupt request 1 flag. A logic 1 in the IRQF1 bit indicates that the time 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 0 and IRQF1 is 1 (and the A1IE bit is also 1), INT0 goes low. If the INTCN bit is 1 and IRQF1 is 1 (and the A1IE bit is also 1), INT1 goes low. IRQF1 is cleared when the address pointer is set to any of the Alarm 1 registers during an I/O transaction. The IRQF1 bit can also be cleared by writing it to 0. This bit can only be written to 0. Attempting to write the IRQF1 bit to 1 leaves the value unchanged. IRQF0: Interrupt request 0 flag. A logic 1 in the IRQF0 bit indicates that the time matched the Alarm 0 registers. If the A0IE bit is also 1, INT0 goes low. IRQF0 is cleared when the address pointer is set to any of the Alarm 0 registers during an I/O transaction. The IRQF0 bit can also be cleared by writing it to 0. This bit can only be written to 0. Attempting to write the IRQF0 bit to 1 leaves the value unchanged.
BIT 1
BIT 0
Trickle Charger Register (11h)
BIT 7 TCS3
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BIT 6 TCS2 0
BIT 5 TCS1 0
BIT 4 TCS0 0
BIT 3 DS1 0
BIT 2 DS0 0
BIT 1 RS1 0
BIT 0 RS0 0
0
Register 11h controls the devices' trickle-charge characteristics. The simplified schematic of Figure 2 shows the basic components of the trickle charger. The tricklecharge select (TCS[3:0]) bits (bits 7:4) 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 devices power up with the trickle charger disabled. The diode-select
(DS[1:0]) bits (bits 3:2) select whether or not a diode is connected between VCC and VBAT. The resistor-select (RS[1:0]) bits (bits 1:0) select the resistor that is connected between VCC and VBAT. The RS and DS bits select the resistor and diodes, as shown in Table 3. The user determines diode and resistor selection according to the maximum current desired for secondary battery or super cap charging. The maximum charging current can be calculated using the equation that follows.
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
R1 1k VCC R2 2k R3 4k VBAT
1 0F 18 SELECT NOTE: ONLY 1010 CODE ENABLES CHARGER
1 OF 2 SELECT
1 OF 3 SELECT
TRICKLE CHARGER REGISTER
TCS = TRICKLE-CHARGER SELECT DS = DIODE SELECT RS = RESISTOR SELECT RS BIT 0
TCS BIT 7
TCS BIT 6
TCS BIT 5
TCS BIT 4
DS BIT 3
DS BIT 2
RS BIT 1
Figure 2. Trickle Charger Block Diagram
Table 3. Trickle-Charger Resistor and Diode Select
TCS3 X X X 1 1 1 1
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TCS2 X X X 0 0 0 0 0 0 0
TCS1 X X X 1 1 1 1 1 1 0
TCS0 X X X 0 0 0 0 0 0 0
DS1 X 0 1 0 0 0 1 1 1 0
DS0 X 0 1 1 1 1 0 0 0 0
RS1 0 X X 0 1 1 0 1 1 0
RS0 0 X X 1 0 1 1 0 1 0
FUNCTION Disabled Disabled Disabled No diode, 1kI No diode, 2kI No diode, 4kI One diode, 1kI One diode, 2kI One diode, 4kI Initial power-on state--disabled
1 1 0
X = Don't care.
Assume, for the purposes of the example, that a system power supply of 5V is applied to VCC and a super cap is connected to VBAT. Also assume that the trickle charger has been enabled with one diode and resistor R1. The maximum current IMAX would be calculated as follows: IMAX = (5.0V - diode drop)/R1 (5.0V - 0.6V)/2k 2.2mA As the super cap charges, the voltage drop between VCC and VBAT decreases, and therefore, the charge current decreases.
Serial Port Operation
The devices offer the flexibility to choose between two serial-interface modes. The component can communicate with the SPI interface or with a standard 3-wire interface. The interface method used is determined by SERMODE. When SERMODE is connected to VCC, SPI communication is selected. When SERMODE is connected to ground, standard 3-wire communication is selected.
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
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 connecting SERMODE to VCC. Four pins are used for the SPI. The four pins are SDO (serial-data out), SDI (serialdata in), CE (chip enable), and SCLK (serial clock). The IC is the slave device in an SPI application, with the microcontroller being the master. SDI and SDO are the serial-data input and output pins, respectively, for the device. The CE input is used to initiate and terminate a data transfer. SCLK is used to synchronize data movement between the master (microcontroller) and the slave (IC) devices. The input 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 device 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 3). There is one clock for each bit transferred. Address and data bits are transferred in groups of eight, MSB first. 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 (Figure 4 and Figure 5). The address byte is always the first byte entered after CE is driven high. The most significant bit (R/W) of this byte determines if a read or write takes place. If R/W is 0, one or more read cycles occur. If R/W is 1, one or more write cycles occur. Data transfers can occur 1 byte at a time or in multiplebyte burst mode. After CE is driven high an address is written to the device. After the address, one or more data bytes can be written or read. For a single-byte transfer, 1 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 device 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 address space is selected, the address wraps to 00h after incrementing from 1Fh. When the RAM address space is selected, the address wraps to 20h after incrementing from 7Fh.
Address and Data Bytes
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CE
CPOL = 1 SCLK SHIFT DATA OUT (READ) DATA LATCH (WRITE)
CPOL = 0
SCLK
SHIFT DATA OUT (READ)
DATA LATCH (WRITE)
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.
Figure 3. Serial Clock as a Function of Microcontroller Clock Polarity (CPOL)
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
CE
SCLK*
SDI
1 R/W
A6
A5
A4 HIGH-Z
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
SDO *SCLK CAN BE EITHER POLARITY. SERMODE = VCC.
Figure 4. SPI Single-Byte Write
CE
SCLK*
SDI
0 R/W
A6
A5
A4 HIGH-Z
A3
A2
A1
A0
SDO *SCLK CAN BE EITHER POLARITY. SERMODE = VCC.
D7
D6
D5
D4
D3
D2
D1
D0
Figure 5. SPI Single-Byte Read
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CE
SCLK
WRITE
SDI
ADDRESS BYTE
DATA BYTE 0
DATA BYTE 1
DATA BYTE N
SDI READ SDO
ADDRESS BYTE DATA BYTE 0 DATA BYTE 1 DATA BYTE N
Figure 6. SPI Multibyte Burst Transfer 17
Low-Current SPI/3-Wire RTCs DS1343/DS1344
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. The address pointer wraps around to 00h after reaching 1Fh (RTC), and the address pointer wraps around to 20h after reaching 7Fh (RAM). See Figure 6.
Reading and Writing in Burst Mode
input on the rising edge of SCLK and output on the falling edge of SCLK.
Applications Information
To achieve the best results when using the devices, decouple the VCC power supply with a 0.01F and/or 0.1F capacitor. Use a high-quality, ceramic, surfacemount capacitor if possible. Surface-mount components minimize lead inductance, which improves performance, and ceramic capacitors tend to have adequate highfrequency response for decoupling applications. The INT0 and INT1 outputs are open drain and therefore require external pullup resistors to realize a logic-high output level. The devices contain Maxim's redundant battery-charge protection circuit to prevent any charging of an external battery.
Power-Supply Decoupling
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 connected 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 7 illustrates a write cycle, and Figure 8 illustrates a read cycle. In 3-wire mode, data is
Using Open-Drain Outputs
Battery Charge Protection
CE
SCLK HIGH-Z
I/O*
A0
A1
A2
A3
A4
A5
A6
1 R/W
D0
D1
D2
D3
D4
D5
D6
D7
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*I/O IS SDI AND SDO CONNECTED TOGETHER. SERMODE = GND.
Figure 7. 3-Wire Single-Byte Write
CE
SCLK HIGH-Z
I/O*
A0
A1
A2
A3
A4
A5
A6
0 R/W
D0
D1
D2
D3
D4
D5
D6
D7
*I/O IS SDI AND SDO CONNECTED TOGETHER. SERMODE = GND
Figure 8. 3-Wire Single-Byte Read
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Low-Current SPI/3-Wire RTCs
Ordering Information
PART DS1343E-18+* DS1343E-3+* DS1343E-33+ DS1343D-18+* DS1343D-3+* DS1343D-33+* DS1344E-18+* DS1344E-3+* DS1344E-33+* DS1344D-18+* DS1344D-3+* DS1344D-33+* TEMP RANGE -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC -40NC to +85NC TYP OPERATING VOLTAGE (V) 1.8 3.0 3.3 1.8 3.0 3.3 1.8 3.0 3.3 1.8 3.0 3.3 OSC CL (pF) 6 6 6 6 6 6 12.5 12.5 12.5 12.5 12.5 12.5 PIN-PACKAGE 20 TSSOP 20 TSSOP 20 TSSOP 14 TDFN-EP** 14 TDFN-EP** 14 TDFN-EP** 20 TSSOP 20 TSSOP 20 TSSOP 14 TDFN-EP** 14 TDFN-EP** 14 TDFN-EP**
DS1343/DS1344
+Denotes a lead(Pb)-free/RoHS-compliant package. *Future product--Contact factory for availability. **EP = Exposed pad.
Chip Information
SUBSTRATE CONNECTED TO GROUND
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE 20 TSSOP PACKAGE CODE U20+1 T1433+2 OUTLINE NO. 21-0066 21-0137 LAND PATTERN NO. 90-0116 90-0063
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14 TDFN-EP
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Low-Current SPI/3-Wire RTCs DS1343/DS1344
Revision History
REVISION NUMBER 0 REVISION DATE 3/11 Initial release DESCRIPTION PAGES CHANGED --
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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.
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(c)
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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