DS1338U-33 ,I2C RTC with 56-Byte NV RAMELECTRICAL CHARACTERISTICS (V = V to V , T = -40°C to +85°C.) (Note 1) CC CC(MIN) CC(MAX) APARAMETE ..
DS1338U-33 ,I2C RTC with 56-Byte NV RAMFEATURES The DS1338 serial real-time clock (RTC) is a low- RTC Counts Seconds, Minutes, Hours, D ..
DS1338U-33+ ,I²C RTC with 56-Byte NV RAMFEATURES The DS1338 serial real-time clock (RTC) is a low-• Completely Manages All Timekeeping powe ..
DS1338U-33+ ,I²C RTC with 56-Byte NV RAMELECTRICAL CHARACTERISTICS (V = 0V, T = -40°C to +85°C, unless otherwise noted. Typical values are ..
DS1338U-33+T&R ,I²C RTC with 56-Byte NV RAMApplications Modem) • Underwriters Laboratories (UL®) Recognized UL is a registered trademark o ..
DS1338Z ,I²C RTC with 56-Byte NV RAMGENERAL DESCRIPTION BENEFITS AND
DTC124TM , 100mA / 50V Digital transistors (with built-in resistor)
DTC124XE ,Bias Resistor TransistorFeatures(OUTPUT)PIN 1R1• Simplifies Circuit DesignBASE(INPUT)• Reduces Board SpaceR2• Reduces Compo ..
DTC124XET1 ,Bias Resistor TransistorTHERMAL CHARACTERISTICSSee detailed ordering, marking, and shipping information inthe package dimen ..
DTC124XK , DTA/DTC SERIES
DTC124XM , 100mA / 50V Digital transistors (with built-in resistors)
DTC124XS , DTA/DTC SERIES
DS1338C+33-DS1338C-3-DS1338U-33-DS1338Z-33
I2C RTC with 56-Byte NV RAM
GENERAL DESCRIPTION The DS1338 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD)
clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I2C™
interface. The clock/calendar provides seconds, minutes, hours, day, date, month, and year
information. The end of the month date is automatically adjusted for months with fewer than 31
days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with
AM/PM indicator. The DS1338 has a built-in power-sense circuit that detects power failures and
automatically switches to the battery supply.
APPLICATIONS Handhelds (GPS, POS Terminal)
Consumer Electronics (Set-Top Box, Digital
Recording, Network Appliance)
Office Equipment (Fax/Printer, Copier)
Medical (Glucometer, Medicine Dispenser)
Telecommunications (Router, Switcher, Server)
Other (Utility Meter, Vending Machine, Thermostat, Modem)
TYPICAL OPERATING CIRCUIT
FEATURES RTC Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year
with Leap-Year Compensation Valid Up to 2100 Available in a Surface-Mount Package with an
Integrated Crystal (DS1338C) 56-Byte Battery-Backed NV RAM for Data
Storage I2C Serial Interface Programmable Square-Wave Output Signal Automatic Power-Fail Detect and Switch Circuitry Underwriters Laboratory (UL) Recognized
ORDERING INFORMATION rr = second line, revision level
Pin Configurations appear at end of data sheet.
DS13382C RTC with 56-Byte NV RAM2C is a trademark of Philips Corp. Purchase of I2C components from
Maxim Integrated Products, Inc., or one of its sublicensed Associated
Companies, conveys a license under the Philips I2C Patent Rights to
use these components in an I2C system, provided that the system
conforms to the I2C Standard Specification as defined by Philips.
DS1338 I2C RTC with 56-Byte NV RAM
ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground………………………………………………………..……..-0.3V to +6.0V
Operating Temperature Range…………………………………………………………………………..……-40°C to +85°C Storage Temperature Range………………………………………………………………………………...-55°C to +125°C
Soldering Temperature…………….....See precautions in the Handling, PC Board Layout, and Assembly Section
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 the absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS (VCC = VCC(MIN) to VCC(MAX), TA = -40°C to +85°C.) (Note 1)
DC ELECTRICAL CHARACTERISTICS (VCC = VCC(MIN) to VCC(MAX), TA = -40°C to +85°C.) (Note 1)
DS1338 I2C RTC with 56-Byte NV RAM
DC ELECTRICAL CHARACTERISTICS (VCC = 0V, TA = -40°C to +85°C.) (Note 1)
AC ELECTRICAL CHARACTERISTICS (TA = -40°C to +85°C) (Note 1)
DS1338 I2C RTC with 56-Byte NV RAM
POWER-UP/POWER-DOWN CHARACTERISTICS (TA = -40°C to +85°C) (Note 1, Figure 1)
Note 1: Limits at -40°C are guaranteed by design and not production tested.
Note 2: All voltages are referenced to ground.
Note 3: SCL only.
Note 4: SDA and SQW/OUT.
Note 5: ICCA—SCL clocking at max frequency = 400kHz.
Note 6: Specified with the I2C bus inactive.
Note 7: Measured with a 32.768kHz crystal attached to 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: CB—total capacitance of one bus line in pF.
Note 13: Guaranteed by design. Not production tested.
Note 14: The parameter tOSF is the time period the oscillator must be stopped for the OSF flag to be set over the voltage range of
0.0V ≤ VCC ≤ VCC MAX and 1.3V ≤ VBAT ≤ 3.7V.
Note 15: This delay applies only if the oscillator is enabled and running. If the oscillator is disabled or stopped, no power-up delay occurs.
Figure 1. Power-Up/Power-Down Timing
DS1338 I2C RTC with 56-Byte NV RAM
Figure 2. Timing Diagram
Figure 3. Block Diagram
DS1338 I2C RTC with 56-Byte NV RAMTYPICAL OPERATING CHARACTERISTICS
(VCC = 3.3V, TA =+25°C, unless otherwise noted.)
DS1338 I2C RTC with 56-Byte NV RAM
PIN DESCRIPTION DETAILED DESCRIPTION
The DS1338 serial RTC is a low-power, full BCD clock/calendar plus 56 bytes of NV SRAM. Address and data are
transferred serially through an I2C interface. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31
days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1338 has a built-in power-sense circuit that detects power failures and automatically switches to
the battery supply.
DS1338 I2C RTC with 56-Byte NV RAM
OPERATION
The DS1338 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 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. The block diagram (Figure 3) shows the main elements
of the DS1338.
An enable bit in the seconds register controls the oscillator. Oscillator startup times are highly dependent upon crystal characteristics, PC board leakage, and layout. High ESR and excessive capacitive loads are the major
contributors to long start-up times. A circuit using a crystal with the recommended characteristics and proper layout usually starts within 1 second.
OSCILLATOR CIRCUIT
The DS1338 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.
Table 1. Crystal Specifications*
*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.
Figure 4. Oscillator Circuit Showing Internal Bias Network
