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DATASHEET
REAL-TIME CLOCK WITH BATTERY BACKED NON-VOLATILE RAM General Description
The IDT1338 is a serial real-time clock (RTC) device that consumes ultra-low power and provides a full binary-coded decimal (BCD) clock/calendar with 56 bytes of battery backed Non-Volatile Static RAM. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. Access to the clock/calendar registers is provided by an I2C interface capable of operating in fast I2C mode. Built-in Power-sense circuitry detects power failures and automatically switches to the backup supply, maintaining time and date operation.
IDT1338
Features
* Real-Time Clock (RTC) counts seconds, minutes, hours,
day, date, month, and year with leap-year compensation valid up to 2100
* 56-Byte battery-backed Non Volatile RAM for data
storage
* * * *
Fast mode I2C Serial interface Automatic power-fail detect and switch circuitry Programmable square-wave output Packaged in 8-pin MSOP, 8-pin SOIC, or 16-pin SOIC (surface-mount package with an integrated crystal)
* Industrial temperature range (-40C to +85C)
Applications
* Telecom (Routers, Switches, Servers) * Handheld (GPS, Point of Sale POS terminals) * Consumer Electronics (Set-Top Box, Digital Recording,
Network Applications, Digital photo frames)
* Office (Fax/Printers, Copiers) * Medical (Glucometer, Medicine Dispensers) * Others (Thermostats, Vending Machines, Modems, Utility
Meters)
Block Diagram
Crystal inside package for 16-pin SOIC ONLY 1 Hz/4.096 kHz/ 8.192 kHz/32.768 kHz
X1
32.768 kHz Oscillator and Divider
MUX/ Buffer
SQW/OUT
X2 VCC GND VBAT Power Control Control Logic Clock, Calendar Counter
SCL SDA I2C Interface 56 Byte RAM 1 Byte Control 7 Bytes Buffer
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Pin Assignment (8-pin MSOP/8-pin SOIC)
X1 X2 VBAT GND 1 2 3 4 8 VCC SQW/OUT SCL SDA
Pin Assignment (16-pin SOIC)
SCL SQW/OUT VCC NC NC NC NC NC 1 2 3 4 5 6 7 8 16 15 14 SDA GND VBAT NC NC NC NC NC
IDT 1338
7 6 5
IDT 1338C
13 12 11 10 9
Pin Descriptions
Pin Number 8MSOP, 8SOIC
1 2
16SOIC
-- --
Pin Name
X1 X2
Pin Description/Function
Connections for standard 32.768 kHz quartz crystal. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 12.5 pF. An external 32.768 kHz oscillator can also drive the IDT1338. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is left floating. Backup Supply Input for Lithium Coin Cell or Other Energy Source. Battery voltage must be held between the minimum and maximum limits for proper operation. Diodes placed in series between the backup source and the VBAT pin may prevent proper operation. If a backup supply is not required, VBAT must be connected to ground. Connect to ground. Serial data input/output. SDA is the input/output pin for the I2C serial interface. It is an open-drain output and requires an external pull-up resistor (2 Kohm typical). Serial clock input. SCL is used to synchronize data movement on the serial interface. It is an open-drain output and requires an external pull-up resistor (2 Kohm typical)
3
14
VBAT
4 5 6 7
15 16 1 2
GND SDA SCL
SQW/OUT Square-Wave/Output driver. When enabled and the SQWE bit set to 1, the SQW/OUT pin outputs one of four square-wave frequencies (1 Hz, 4 kHz, 8 kHz, 32 kHz). It is an open drain output and requires an external pull-up resistor (10K ohm typical). Operates when the device is powered with VCC or VBAT. VCC NC Device power supply. When voltage is applied within specified limits, the device is fully accessible by I2C and data can be written and read. No connect. These pins are unused and must be connected to ground for proper operation.
8 --
3 4 - 13
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Typical Operating Circuit
VCC VCC CRYSTAL VCC
2k CPU
2k
X1 SCL SDA
X2
VCC SQW/OUT
10k
IDT1338
GND
VBAT + -
Detailed Description
The following sections discuss in detail the Oscillator block, Power Control block, Clock/Calendar Register Block and Serial I2C block.
Oscillator Block
Selection of the right crystal, correct load capacitance and careful PCB layout are important for a stable crystal oscillator. Due to the optimization for the lowest possible current in the design for these oscillators, losses caused by parasitic currents can have a significant impact on the overall oscillator performance. Extra care needs to be taken to maintain a certain quality and cleanliness of the PCB.
Crystal Selection
The key parameters when selecting a 32 kHz crystal to work with IDT1338 RTC are: In the above figure, X1 and X2 are the crystal pins of our device. Cin1 and Cin2 are the internal capacitors which include the X1 and X2 pin capacitance. Cex1 and Cex2 are the external capacitors that are needed to tune the crystal frequency. Ct1 and Ct2 are the PCB trace capacitances between the crystal and the device pins. CS is the shunt capacitance of the crystal (as specified in the crystal manufacturer's datasheet or measured using a network analyzer). Note: IDT1338CSRI integrates a standard 32.768 kHz crystal in the package and contributes an additional frequency error of 10ppm at nominal VCC (+3.3 V) and TA=+25 C.
* Recommended Load Capacitance * Crystal Effective Series Resistance (ESR) * Frequency Tolerance
Effective Load Capacitance
Please see diagram below for effective load capacitance calculation. The effective load capacitance (CL) should match the recommended load capacitance of the crystal in order for the crystal to oscillate at its specified parallel resonant frequency with 0ppm frequency error.
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ESR (Effective Series Resistance)
Choose the crystal with lower ESR. A low ESR helps the crystal to start up and stabilize to the correct output frequency faster compared to high ESR crystals.
the oscillator circuit locally on this separated island. The ground connections for the load capacitors and the oscillator should be connected to this island.
PCB Layout
Frequency Tolerance
The frequency tolerance for 32 KHz crystals should be specified at nominal temperature (+25C) on the crystal manufacturer datasheet. The crystals used with IDT1338 typically have a frequency tolerance of +/-20ppm at +25 C. Specifications for a typical 32kHz crystal used with our device are shown in the table below.
Parameter
Nominal Freq. Series Resistance Load Capacitance
Symbol
fO ESR CL
Min
Typ
32.768
Max Units
kHz 50 k pF
PCB Assembly, Soldering and Cleaning
Board-assembly production process and assembly quality can affect the performance of the 32 KHz oscillator. Depending on the flux material used, the soldering process can leave critical residues on the PCB surface. High humidity and fast temperature cycles that cause humidity condensation on the printed circuit board can create process residuals. These process residuals cause the insulation of the sensitive oscillator signal lines towards each other and neighboring signals on the PCB to decrease. High humidity can lead to moisture condensation on the surface of the PCB and, together with process residuals, reduce the surface resistivity of the board. Flux residuals on the board can cause leakage current paths, especially in humid environments. Thorough PCB cleaning is therefore highly recommended in order to achieve maximum performance by removing flux residuals from the board after assembly. In general, reduction of losses in the oscillator circuit leads to better safety margin and reliability.
12.5
PCB Design Consideration
* Signal traces between IDT device pins and the crystal
must be kept as short as possible. This minimizes parasitic capacitance and sensitivity to crosstalk and EMI. Note that the trace capacitances play a role in the effective crystal load capacitance calculation.
* Data lines and frequently switching signal lines should be
routed as far away from the crystal connections as possible. Crosstalk from these signals may disturb the oscillator signal.
* Reduce the parasitic capacitance between X1 and X2
signals by routing them as far apart as possible.
* The oscillation loop current flows between the crystal and
the load capacitors. This signal path (crystal to CL1 to CL2 to crystal) should be kept as short as possible and ideally be symmetric. The ground connections for both capacitors should be as close together as possible. Never route the ground connection between the capacitors all around the crystal, because this long ground trace is sensitive to crosstalk and EMI.
* To reduce the radiation / coupling from oscillator circuit,
an isolated ground island on the GND layer could be made. This ground island can be connected at one point to the GND layer. This helps to keep noise generated by
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Power Control
A precise, temperature-compensated voltage reference and a comparator circuit provides power-control function 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 VBAT, the device power is switched from VCC to VBAT when VCC drops below VPF. If VPF is greater than VBAT, the device power is switched from VCC to VBAT when VCC drops below VBAT. The registers are maintained from the VBAT source until VCC is returned to nominal levels (Table 1). After VCC returns above VPF, read and write access is allowed after tREC (see the "Power-Up/Down Timing" diagram).
Table 1. Power Control
Supply Condition
VCC < VPF, VCC < VBAT VCC < VPF, VCC > VBAT VCC > VPF, VCC < VBAT VCC > VPF, VCC > VBAT
Read/Write Access
No No Yes Yes
Powered By VBAT
VCC VCC VCC
Power-up/down Timing
Table 2. Power-up/down Characteristics
Ambient Temperature -40 to +85 C
Parameter
Recovery at Power-up VCC Fall Time; VPF(MAX) to VPF(MIN) VCC Rise Time; VPF(MIN) to VPF(MAX)
Symbol
tREC tVCCF tVCCR
Conditions
(see note below)
Min.
300 0
Typ.
Max.
2
Units
ms s s
Note: This delay applies only if the oscillator is running. If the oscillator is disabled or stopped, no power-up delay occurs.
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RTC and RAM Address Map
The address map for the RTC and RAM registers shown in Table 3. The RTC registers and control register are located in address locations 00H to 07H The RAM registers are located in address locations 08H to 3FH. During a multibyte access, when the register pointer reaches 3FH (the end of RAM space) it wraps around to location 00H (the beginning of the clock space). On an I2C START, STOP, or register pointer incrementing to location 00H, the current time and date is transferred to a second set of registers. The time and date in the secondary registers are read in a multibyte data transfer, while the clock continues 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. RTC and RAM Address Map
Address 00H 01H 02H 03H 04H 05H 06H 07H 08H 3FH Note: Bits listed as "0" should always be written and read as 0. OUT 0 Bit 7 CH 0 0 0 0 0 12/24 0 0 0 10 year OSF SQWE 0 0 0 Bit 6 Bit 5 10 seconds 10 minutes AM/PM 10 hour 0 10 date 10 month 10 hour 0 0 Date Month Year RS1 RS0 Hour Day Hours Day Date Month Year Control RAM 56 x 8 00H - FFH Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Function Seconds Minutes Range 00 - 59 00 - 59 1 - 12 + AM/PM 00 - 23 1-7 01 - 31 01 - 12 00 - 99 Seconds Minutes
Clock and Calendar
Table 3 shows the address map of the RTC registers. The time and date information is obtained by reading the appropriate register bytes. 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. Bit 7 of Register 0 is the clock halt (CH) bit. When this bit is set to 1, the oscillator is disabled. When cleared to 0, the oscillator is enabled. The clock can be halted whenever the timekeeping functions are not required, which decreases VBAT current. 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 1 Hz square-wave output transitions high 500 ms after the seconds data transfer, provided the oscillator is already running. Note that the initial power-on state of all registers, unless otherwise specified, is not defined. Therefore, it is important to enable the oscillator (CH = 0) during initial configuration. The IDT1338 runs in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12-hour 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
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being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20-23 hours). If the 12/24-hour mode select is changed, the hours register must be re-initialized to the new format. On an I2C START, the current time is transferred to a second set of registers. The time information is read from these secondary registers, while the clock continues to run. This eliminates the need to re-read the registers in case of an update of the main registers during a read.
Table 4. Control Register (07H)
The control register controls the operation of the SQW/OUT pin and provides oscillator status. Bit #
Name POR
Bit 7
OUT 1
Bit 6
0 0
Bit 5
OSF 1
Bit 4
SQWE 1
Bit 3
0 0
Bit 2
0 0
Bit 1
RS1 1
Bit 0
RS0 1
Bit 7: Output Control (OUT). Controls the output level of the SQW/OUT pin when the square-wave output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1; it is 0 if OUT = 0. Bit 5: Oscillator Stop Flag (OSF). A logic 1 in this bit indicates that the oscillator has stopped or was stopped for some time period and can be used to judge the validity of the clock and calendar data. This bit is edge triggered, and is set to logic 1 when the internal circuitry senses the oscillator has transitioned from a normal run state to a STOP condition. The following are examples of conditions that may cause the OSF bit to be set: 1) The first time power is applied. 2) The voltage present on VCC and VBAT are insufficient to support oscillation. 3) The CH bit is set to 1, disabling the oscillator. 4) External influences on the crystal (i.e., noise, leakage, etc.). This bit remains at logic 1 until written to logic 0. This bit can only be written to logic 0. Attempting to write OSF to logic 1 leaves the value unchanged. Bit 4: Square-Wave Enable (SQWE). When set to logic 1, this bit enables the oscillator output to operate with either VCC or VBAT applied. The frequency of the square-wave output depends upon the value of the RS0 and RS1 bits. Bits 1 and 0: Rate Select (RS1 and RS0). These bits control the frequency of the square-wave output when the square-wave output has been enabled. The table below lists the square-wave frequencies that can be selected with the RS bits.
Table 5. Square Wave Output
OUT
X X X X 0 1
RS1
0 0 1 1 X X
RS0
0 1 0 1 X X
SQW Output
1 Hz 4.096 kHz 8.192 kHz 32.768 kHz 0 1
SQWE
1 1 1 1 0 0
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I2C Serial Data Bus
The IDT1338 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 IDT1338 operates as a slave on the I2C bus. Within the bus specifications, a standard mode (100 kHz maximum clock rate) and a fast mode (400 kHz maximum clock rate) are defined. The IDT1338 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 (see the "Data Transfer on I2C Serial Bus" figure):
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. Timeout: Timeout is where a slave device resets its interface whenever Clock goes low for longer than the timeout, which is typically 35mSec. This added logic deals with slave errors and recovering from those errors. When timeout occurs, the slave interface should re-initialize itself and be ready to receive a communication from the master, but it will expect a Start prior to any new communication.
* 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. 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.
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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 IDT1338 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 (see the "Data Write-Slave Receiver Mode" figure). 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 IDT1338 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 IDT1338 acknowledges the slave address + write bit, the master transmits a register address to the IDT1338. This sets the register pointer on the IDT1338, with the IDT1338 acknowledging the transfer. The master may then transmit zero or more bytes of data, with the IDT1338 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 IDT1338 while the serial clock is input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer (see the "Data Read-Slave Transmitter Mode" figure). 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 IDT1338 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 IDT1338 then begins to transmit data starting with the register address pointed to by
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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 IDT1338 must receive a "not acknowledge" to end a read.
Data Write - Slave Receiver Mode
Data Read (from current Pointer location) - Slave Transmitter Mode
Data Read (Write Pointer, then Read) - Slave Receive and Transmit
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Handling, PCB Layout, and Assembly
The IDT1338 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 avioded. Ultarsonic cleaning equipment should be avioded 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 NC (no connect) pins must be connected to ground. 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-020 standard for moisture-sensitive device (MSD) classifications.
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the IDT1338. These ratings, which are standard values for IDT commercially rated parts, are stress ratings only. Functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods can affect product reliability. Electrical parameters are guaranteed only over the recommended operating temperature range.
Item
Voltage Range on Any Pin Relative to Ground Storage Temperature Soldering Temperature -0.3 V to +6.0 V -55 to +125 C 260 C
Rating
Recommended DC Operating Conditions
(VCC = VCC(MIN) to VCC(MAX), TA = -40 to +85C, unless otherwise noted. Typical values are at VCC = 3.3 V, C TA = +25C, unless otherwise noted.) (Note 1)
Parameter
Ambient Operating Temperature VBAT Input Voltage, Note 2 Pull-up Resistor Voltage (SQW/OUT), Note 2 Logic 1, Note 2 Logic 0, Note 2 Supply Voltage IDT1338-18 IDT1338-31 Power Fail Voltage IDT1338-18 IDT1338-31
Symbol
TA VBAT VPU VIH VIL
Min.
-40 1.3 0.7VCC -0.3 VPF VPF 1.40 2.45
Typ.
3.0
Max.
+85 3.7 5.5
VCC + 0.3
Units
C V V V
+0.3VCC 1.8 3.3 1.62 2.7 5.5 5.5 1.71 2.97
VCC
V
VPF
V
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DC Electrical Characteristics
(VCC = VCC(MIN) to VCC(MAX), TA = -40 to +85C, unless otherwise noted. Typical values are at VCC = 3.3 V, C TA = +25C, unless otherwise noted.) (Note 1)
Parameter
Input Leakage I/O Leakage SDA Logic 0 Output
Symbol
ILI ILO IOLSDA Note 3 Note 4
Conditions
Min.
Typ.
Max.
1 1 3.0 3.0 3.0 3.0 250
Units
A A mA mA mA A
VCC > 2 V; VOL = 0.4 V VCC < 2 V; VOL = 0.2VCC VCC > 2 V; VOL = 0.4 V
SQW/OUT Logic 0 Output
IOLSQW
1.71 V < VCC < 2 V; VOL = 0.2VCC 1.3 V < VCC < 1.71 V; VOL = 0.2VCC IDT1338-18 75 120 IDT1338-31; VCC < 3.63 V IDT1338-31; 3.63 V < VCC < 5.5 V IDT1338-18 60 85 IDT1338-31; VCC < 3.63 V IDT1338-31; 3.63 V < VCC < 5.5 V 25
150 200 325 100 125 200 100 nA A A
Active Supply Current (Note 5)
ICCA
Standby Current (Note 6)
ICCS
VBAT Leakage Current (VCC Active)
IBATLKG
DC Electrical Characteristics
(VCC = 0V, TA = -40 to +85 unless otherwise noted. Typical values are at VBAT = 3.0 V, TA = +25 unless C C, C, otherwise noted.) (Note 1)
Parameter
VBAT Current (OSC ON); VBAT =3.7 V, SQW/OUT OFF VBAT Current (OSC ON); VBAT =3.7 V, SQW/OUT ON VBAT Data-Retention Current (OSC OFF); VBAT =3.7 V
Symbol
Conditions
Min.
Typ.
800 1025 10
Max.
1200 1400 100
Units
nA nA nA
IBATOSC1 Note 7 IBATOSC2 Note 7 IBATDAT Note 7
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AC Electrical Characteristics
(VCC = VCC(MIN) to VCC(MAX), TA = -40 to +85C) (Note 1) C
Parameter
SCL Clock Frequency Bus Free Time Between a STOP and START Condition Hold Time (Repeated) START Condition, Note 8 Low Period of SCL Clock High Period of SCL Clock Setup Time for a Repeated START Condition Data Hold Time (Notes 9, 10) Data Setup Time (Note 11) Rise Time of Both SDA and SCL Signals (Note 12) Fall Time of Both SDA and SCL Signals (Note 12) Setup Time for STOP Condition Capacitive Load for Each Bus Line (Note 12) I/O Capacitance (SDA, SCL) Oscillator Stop Flag (OSF) Delay
Symbol
fSCL tBUF tHD:STA tLOW tHIGH tSU:STA tHD:DAT tSU:DAT tR tF tSU:STO CB CI/O tOSF
Conditions
Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode
Min.
100 0 1.3 4.7 0.6 4.0 1.3 4.7 0.6 4.0 0.6 4.7 0 0 100 250 20 + 0.1CB 20 + 0.1CB 20 + 0.1CB 20 + 0.1CB 0.6 4.0
Typ.
Max. Units
400 100 s s s s s 0.9 s ns 300 1000 300 300 s 400 pF pF ms ns ns kHz
Note 13 Note 14 100
10
WARNING: Negative undershoots below 0.3 V while the device is in battery-backed mode may cause loss of data. Note 1: Limits at -40C are guaranteed by design and are not production tested. Note 2: All voltages referenced to ground. Note 3: SCL only. Note 4: SDA and SQW/OUT. Note 5: ICCA--SCL clocking at max frequency = 400 kHz. Note 6: Specified with the I2C bus inactive.
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Note 7: Measured with a 32.768 kHz 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 300 ns 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 250 ns 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 = 1250 ns before the SCL line is released. Note 12: CB--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 1.3 V < VBACKUP < 3.7 V.
Timing Diagram
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Typical Operating Characteristics
IBAT vs VBAT (IDT1338-31)
734 694 654 614 574 534 494 1.3 1.8 2.3 VBat (V) 2.8 3.3 SQWE=1 SQWE=0 Supply Current (uA) Supply current (nA) 25 20 15 10 5 0 2.7 3.2 3.7 4.2 Vcc (V) 4.7 5.2
Icc vs Vcc (IDT1338-31)
SCL=400kHz SCL=0Hz
IBAT vs Temperature
800 IBAT (nA)
Frequency (Hz)
Oscillator Frequency vs Supply Voltage
32767.950000
700 600 500 400 -40 -20 0 20 40 60 80 SQWE=1 SQWE=0
32767.900000
32767.850000
Freq
32767.800000
32767.750000
Temperature (C)
2.7
3.2
3.7
4.2
4.7
5.2
Oscillator Supply Voltage (V)
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Thermal Characteristics for 8MSOP
Parameter
Thermal Resistance Junction to Ambient Thermal Resistance Junction to Case
Symbol
JA JC
Conditions
Still air
Min.
Typ.
95 48
Max. Units
C/W C/W
Thermal Characteristics for 8SOIC
Parameter
Thermal Resistance Junction to Ambient
Symbol
JA JA JA JC
Conditions
Still air 1 m/s air flow 3 m/s air flow
Min.
Typ.
150 140 120 40
Max. Units
C/W C/W C/W C/W
Thermal Resistance Junction to Case
Thermal Characteristics for 16SOIC
Parameter
Thermal Resistance Junction to Ambient
Symbol
JA JA JA JC
Conditions
Still air 1 m/s air flow 3 m/s air flow
Min.
Typ.
120 115 105 58
Max. Units
C/W C/W C/W C/W
Thermal Resistance Junction to Case
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Marking Diagram (8 MSOP)
Marking Diagram (16 SOIC)
16 9
38GI YWW$
IDT1338-31DVGI
18GI YWW$
IDT1338-18DVGI
IDT 1338C-31 SRI #YYWW**$
1 8
IDT1338C-31SRI
Marking Diagram (8 SOIC)
8 5
8
5
16
9
IDT1338 -31DCGI #YYWW$
1 4
IDT1339 -18DCGI #YYWW$
1 4
IDT 1338C-18 SRI #YYWW**$
1
IDT1338C-18SRI
IDT1338-31DCGI
Notes: 1. `#' is the lot number. 2. `$' is the assembly mark code.
IDT1338-18DCGI
8
3. YYWW is the last two digits of the year and week that the part was assembled. 4. "G" denotes RoHS compliant package. 5. "I" denotes industrial grade. 6. Bottom marking: country of origin if not USA.
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Package Outline and Package Dimensions (8-pin SOIC, 150 Mil. Body)
Package dimensions are kept current with JEDEC Publication No. 95
Millimeters Symbol Min Max Inches Min Max
8
E INDEX AREA
H
12 D
A A1 B C D E e H h L
1.35 1.75 0.10 0.25 0.33 0.51 0.19 0.25 4.80 5.00 3.80 4.00 1.27 BASIC 5.80 6.20 0.25 0.50 0.40 1.27 0 8
.0532 .0688 .0040 .0098 .013 .020 .0075 .0098 .1890 .1968 .1497 .1574 0.050 BASIC .2284 .2440 .010 .020 .016 .050 0 8
A A1
h x 45 C
-Ce
B SEATING PLANE
.10 (.004)
L
C
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Package Outline and Package Dimensions (8-pin MSOP, 3.00 mm Body)
Package dimensions are kept current with JEDEC Publication No. 95
Millimeters Symbol Min Max Inches* Min Max
8
E1 IN D E X AREA
E
1
2
D
A A1 A2 b C D E E1 e L aaa
-1.10 0 0.15 0.79 0.97 0.22 0.38 0.08 0.23 3.00 BASIC 4.90 BASIC 3.00 BASIC 0.65 Basic 0.40 0.80 0 8 0.10
-0.043 0 0.006 0.031 0.038 0.008 0.015 0.003 0.009 0.118 BASIC 0.193 BASIC 0.118 BASIC 0.0256 Basic 0.016 0.032 0 8 0.004
*For reference only. Controlling dimensions in mm.
A 2 A 1 A
c
-Ce
b S E A T IN G P LA N E
aaa
L
C
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Package Outline and Package Dimensions (16-pin SOIC, 300 mil Body)
Package dimensions are kept current with JEDEC Publication No. 95
16
Millimeters Symbol Min Max
Inches* Min Max
E1 INDEX AREA
E
12 D
A A1 A2 b c D E E1 e L aaa
-2.65 0.10 -2.05 2.55 0.33 0.51 0.18 0.32 10.10 10.50 10.00 10.65 7.40 7.60 1.27 Basic 0.40 1.27 0 8 0.10
-0.104 0.0040 -0.081 0.100 0.013 0.020 0.007 0.013 0.397 0.413 0.394 0.419 0.291 0.299 0.050 Basic 0.016 0.050 0 8 0.004
A 2 A 1
A
*For reference only. Controlling dimensions in mm.
c
- Ce
b SEATING PLANE aaa
L
C
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Ordering Information
Part / Order Number
1338-18DVGI 1338-18DVGI8 1338-18DCGI 1338-18DCGI8 1338C-18SRI 1338C-18SRI8 1338-31DVGI 1338-31DVGI8 1338-31DCGI 1338-31DCGI8 1338C-31SRI 1338C-31SRI8
Marking
Shipping Packaging
Tubes Tape and Reel Tubes Tape and Reel Tubes Tape and Reel Tubes Tape and Reel Tubes Tape and Reel Tubes Tape and Reel
Package
8-pin MSOP 8-pin MSOP 8-pin SOIC 8-pin SOIC 16-pin SOIC 16-pin SOIC 8-pin MSOP 8-pin MSOP 8-pin SOIC 8-pin SOIC 16-pin SOIC 16-pin SOIC
Temperature
-40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 -40 to +85 C C C C C C C C C C C C
see page 17
The IDT1338 packages are RoHS compliant. Packages without the integrated crystal are Pb-free; packages that include the integrated crystal (as designated with a "C" before the dash number) may include lead that is exempt under RoHS requirements. The lead finish is JESD91 category e3. While the information presented herein has been checked for both accuracy and reliability, Integrated Device Technology (IDT) assumes no responsibility for either its use or for the infringement of any patents or other rights of third parties, which would result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary environmental requirements are not recommended without additional processing by IDT. IDT reserves the right to change any circuitry or specifications without notice. IDT does not authorize or warrant any IDT product for use in life support devices or critical medical instruments.
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Revision History
Rev.
A B C D E F G H I J K S.S.
Originator
J. Sarma J.Sarma J.Sarma J.Sarma J.Sarma J.Sarma J.Sarma J.Sarma J.Sarma
Date
01/29/08 03/28/08 04/03/04 05/19/08 10/29/08 11/10/08 11/13/08 11/18/08 12/02/08 11/10/09 03/29/10
Description of Change
New device. Preliminary release. Added new note to Part Ordering information pertaining to RoHS compliance and Pb-free devices. combined -3 and -33 parts to -31 The part number for 16pin RoHS complaint part has now changed from IDT1338C-31SOGI to IDT1338C-31SRI and the IDT1338C-18SOGI changed to IDT1338C-18SRI
Updated Block Diagram; Typical Operating Characteristics charts. Updated graphs in "Typical Operating Characteristics; added "Typical Operating Circuit" diagram Updated graphs in "Typical Operating Characteristics; updated Block Diagram; added "Battery Backed" to device title. Updated Typical Operating Characteristics graphs; added marking diagrams. Added "Handling, PCB Layout, and Assembly" section. Added "Timeout" paragraph on page 8.
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IDT1338 REAL-TIME CLOCK WITH BATTERY BACKED NON-VOLATILE RAM
RTC
Innovate with IDT and accelerate your future networks. Contact:
www.IDT.com
For Sales
800-345-7015 408-284-8200 Fax: 408-284-2775
For Tech Support
www.idt.com/go/clockhelp
Corporate Headquarters
Integrated Device Technology, Inc. www.idt.com
(c) 2010 Integrated Device Technology, Inc. All rights reserved. Product specifications subject to change without notice. IDT, ICS, and the IDT logo are trademarks of Integrated Device Technology, Inc. Accelerated Thinking is a service mark of Integrated Device Technology, Inc. All other brands, product names and marks are or may be trademarks or registered trademarks used to identify products or services of their respective owners. Printed in USA

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