Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsIntegrated Circuits (ICs)Timer IC t- real time clock Clock/calendar SOIC 16 W

1 of 16

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 I

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 backup supply,

maintaining time and date operation

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 General-Purpose

RAM with Unlimited Writes

 I

C Serial Interface

 Programmable Square-Wave Output Signal

 Automatic Power-Fail Detect and Switch

Circuitry

 -40°C to +85°C Operating Temperature Range

 Underwriters Laboratories (UL) Recognized

ORDERING INFORMATION

PART TEMP RANGE PIN-PACKAGE TOP MARK†

DS1338Z-18+

-40°C to +85°C

8 SO (0.150″)

DS1338-18

DS1338Z-3+

-40°C to +85°C

8 SO (0.150

″

)

DS1338-3

DS1338Z-33+

-40°C to +85°C

8 SO (0.150″)

DS133833

DS1338U-18+ -40°C to +85°C

8 µSOP

1338

rr-18

DS1338U-3+ -40°C to +85°C

8 µSOP

1338

rr-3

DS1338U-33+ -40°C to +85°C

8 µSOP

1338

rr-33

DS1338C-18# -40°C to +85°C

16 SO (0.300″)

DS1338C-18

DS1338C-3#

-40°C to +85°C

16 SO (0.300″)

DS1338C-3

DS1338C-33#

-40°C to +85°C

16 SO (0.300″)

DS1338C-33

rr = second line, revision level

+ Denotes a lead(Pb)-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 denotes a lead-free device. A “#”

denotes a RoHS-compliant device.

Pin Configurations appear at end of data sheet.

DS1338

CPU

SDA

SCL

GND

CRYSTAL

SQW /OUT

BAT

= t

DS1338

C RTC with 56-

Byte NV RAM

19-6019; Rev 3/12

Summary of content (16 pages)

PAGE 1
9-6019; Rev 3/12 DS1338 I C RTC with 56-Byte NV RAM 2 GENERAL DESCRIPTION FEATURES The DS1338 serial real-time clock (RTC) is a lowpower, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address 2 and data are transferred serially through an I C 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.
PAGE 2
DS1338 I C 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 Lead Temperature (soldering, 10s) ……….………………………………………………………………………. +260°C Soldering Temperature (reflow) …………………………………………………………………………………….
PAGE 3
2 DS1338 I C RTC with 56-Byte NV RAM DC ELECTRICAL CHARACTERISTICS (VCC = 0V, T A = -40°C to +85°C, unless otherwise noted. Typical values are at VBAT = 3.0V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL VBAT Current (OSC ON); VBAT = 3.7V, SQW/OUT OFF (Note 7) MIN TYP MAX UNITS IBATOSC1 800 1200 nA VBAT Current (OSC ON); VBAT = 3.7V, SQW/OUT ON (32kHz) (Note 7) IBATOSC2 1025 1400 nA VBAT Data-Retention Current (Osc Off); VBAT = 3.
PAGE 4
2 DS1338 I C RTC with 56-Byte NV RAM POWER-UP/POWER-DOWN CHARACTERISTICS (TA = -40°C to +85°C) (Note 1, Figure 1) PARAMETER SYMBOL MIN TYP MAX UNITS 2 ms Recovery at Power-Up (Note 15) tREC VCC Fall Time; VPF(MAX) to VPF(MIN) tVCCF 300 µs VCC Rise Time; VPF(MIN) to VPF(MAX) tVCCR 0 µs Warning: Negative undershoots below -0.3V while the part is in battery-backed mode may cause loss of data.
PAGE 5
2 DS1338 I C RTC with 56-Byte NV RAM Figure 2. Timing Diagram Figure 3. Block Diagram SQW/OUT X1 CL 1Hz/4.096kHz/8.192kHz/32.
PAGE 6
2 DS1338 I C RTC with 56-Byte NV RAM TYPICAL OPERATING CHARACTERISTICS IBAT vs. VBAT ICC vs. VCC V CC=0V RS1=RS0=1 250 1250 1200 SCL=400kHz 225 1150 200 IBAT OSC2 1) (SQWE = 1050 1000 SUPPLY CURRENT (uA SUPPLY CURRENT (nA 1100 IBAT OSC1 (SQWE = 0) 950 900 850 800 750 175 SCL=SDA=0Hz 150 125 100 700 650 75 600 550 50 1.3 1.8 2.3 2.8 3.3 3.8 VBAT (V) 4.3 4.8 IBAT vs. Temperature 5.3 1.8 2.3 2.8 3.3 3.8 VCC (V) 4.3 4.8 5.3 Oscillator Frequency vs.
PAGE 7
2 DS1338 I C RTC with 56-Byte NV RAM PIN DESCRIPTION 8 PIN 16 NAME 1 — X1 2 — X2 3 14 VBAT 4 15 GND 5 16 SDA 6 1 SCL 7 2 SQW/OUT FUNCTION 32.768kHz Crystal Connections. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 12.5pF. An external 32.768kHz oscillator can also drive the DS1338. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is left unconnected.
PAGE 8
2 DS1338 I C 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.
PAGE 9
2 DS1338 I C RTC with 56-Byte NV RAM 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. Crystal frequency drift caused by temperature shifts creates additional error. External circuit noise coupled into the oscillator circuit can result in the clock running fast.
PAGE 10
2 DS1338 I C RTC with 56-Byte NV RAM whenever the seconds register is written. Write transfers occur on the acknowledge from the DS1338. Once the countdown chain is reset, to avoid rollover issues the remaining time and date registers must be written within 1 second. The 1Hz square-wave output, if enabled, transitions high 500ms after the seconds data transfer, provided the oscillator is already running. The DS1338 runs in either 12-hour or 24-hour mode.
PAGE 11
2 DS1338 I C RTC with 56-Byte NV RAM CONTROL REGISTER (07H) The control register controls the operation of the SQW/OUT pin and provides oscillator status. BIT 7 OUT 1 Bit # Name POR 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).
PAGE 12
2 DS1338 I C RTC with 56-Byte NV RAM I2C SERIAL DATA BUS The DS1338 supports the I2C protocol. A device that sends data onto the bus is defined as a transmitter and a device receiving data is 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, which generates the serial clock (SCL), controls the bus access, and generates the START and STOP conditions.
PAGE 13
2 DS1338 I C RTC with 56-Byte NV RAM 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 master transmits the first byte (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.
PAGE 14
2 DS1338 I C RTC with 56-Byte NV RAM S Figure 6. Data Write—Slave Receiver Mode 1101000 0 A XXXXXXXX A S - START A - ACKNOWLEDGE (ACK) P - STOP XXXXXXXX A MASTER TO SLAVE XXXXXXXX A ... XXXXXXXX A P DATA TRANSFERRED (X+1 BYTES + ACKNOWLEDGE) SLAVE TO MASTER Figure 7.
PAGE 15
2 DS1338 I C RTC with 56-Byte NV RAM HANDLING, PCB LAYOUT, AND ASSEMBLY The DS1338C 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. Exposure to reflow is limited to 2 times maximum. Avoid running signal traces under the package, unless a ground plane is placed between the package and the signal line. All N.C.
PAGE 16
2 DS1338 I C RTC with 56-Byte NV RAM REVISION HISTORY REVISION DATE 100108 9/11 3/12 DESCRIPTION Modified the Features bullet to indicate that battery-backed RAM has unlimited writes. Removed leaded part numbers from the Ordering Information table. Removed the pullup resistor voltage spec from the Recommended DC Operating Conditions table and added it to the pin descriptions. Updated the block diagram (Figure 3) to show that SQW is open drain.