PRELIMINARY
DS1672
Low Voltage Serial Timekeeping Chip
FEATURES
32-bit counter
2-wire serial interface
Automatic power-fail detect and switch
circuitry
Power-fail reset output
Low-voltage oscillator operation (1.3V min.)
Trickle charge capability
PIN ASSIGNMENT
X1
X2
V
BACKUP
GND
1
2
3
4
8
7
6
5
V
CC
RST
SCL
SDA
PIN DESCRIPTION
ORDERING INFORMATION
DS1672X-X
2 2.0V operation
3 3.0V operation
33 3.3V operation
blank
S
U
V
CC,
V
BACKUP
GND
X1, X2
SCL
SDA
RST
- Power Supply Inputs
- Ground
- 32.768 kHz crystal pins
- Serial clock
- Serial data
- Reset output
8-pin DIP
8-pin SOIC
8-pin µSOP
DESCRIPTION
The DS1672 incorporates a 32-bit counter and power monitoring functions. The 32-bit counter is
designed to count seconds and can be used to derive time of day, week, month, month, and year by using
a software algorithm. A precision temperature-compensated reference and comparator circuit monitors
the status of V
CC
. When an out-of-tolerance condition occurs, an internal power-fail signal is generated
which forces the reset to the active state. When V
CC
returns to an in-tolerance condition, the reset signal
is kept in the active state for 250 ms to allow the power supply and processor to stabilize.
OPERATION
The block diagram in Figure 1 shows the main elements of the DS1672. As shown, communications to
and from the DS1672 occur serially over a 2-wire bi-directional bus. The DS1672 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 a register address. Subsequent registers can be accessed sequentially until
a STOP condition is executed.
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082800
DALLAS [ DALLAS SEMICONDUCTOR ]
