DS1308 Datasheet, PDF (7/16 Pages) Dallas Semiconductor – 64 X 8 Serial Real Time Clock

DS1308
Low-Current I²C RTC with 56-Byte NV RAM
Pin Configuration
TOP VIEW
X1 1 ⁺
X2 2
VBAT 3
DS1308
GND 4
µSOP
8 V_CC
7 SQW/CLKIN
6 SCL
5 SDA
Pin Description
PIN
NAME
FUNCTION
1
X1
32.768kHz Crystal Connections. The internal oscillator circuitry is designed for use with a crystal
having a specified load capacitance (C_L) of 6pF.
Note: For more information about crystal selection and crystal layout considerations, refer to
2
X2
Application Note 58: Crystal Considerations with Maxim Real-Time Clocks (RTCs).
Battery Supply Input for Lithium Cell or Other Energy Source. Battery voltage must be held between
3
V_BAT
the minimum and maximum limits for proper operation. Diodes placed in series between the backup
source and the V_BAT pin can prevent proper operation. If a backup supply is not required, V_BAT
must be grounded. UL recognized to ensure against reverse charging when used with a lithium cell.
4
GND
Ground
5
SDA
Serial Data Input/Output for the I²C serial interface. It is an open-drain output and requires an
external pullup resistor. The pullup voltage can be up to 5.5V, regardless of the voltage on V_CC.
6
SCL
Serial Clock Input for the I²C serial interface. Used to synchronize data movement on the serial
interface. The pullup voltage can be up to 5.5V, regardless of the voltage on V_CC.
Square-Wave Output/Clock Input. This I/O pin is used to output one of four square-wave
frequencies (1Hz, 4kHz, 8kHz, 32kHz) or accept an external clock input to drive the RTC counter.
7
SQW/CLKIN In the output mode (ECLK = 0), it is open drain and requires an external pullup resistor. The
square-wave operates on V_CC, or on V_BAT with BBCLK = 1. The pullup voltage can be up to 5.5V,
regardless of the voltage on V_CC. If not used, this pin may be left unconnected.
8
V_CC
Primary Power Supply. Decouple the power supply with a 0.1FF capacitor to ground.
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