DS1672 Datasheet, PDF (1/13 Pages) Dallas Semiconductor – Low Voltage Serial Timekeeping Chip

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
ORDERING INFORMATION
DS1672X-X
2 2.0V operation
3 3.0V operation
33 3.3V operation
blank 8-pin DIP
S
8-pin SOIC
U
8-pin µSOP
PIN ASSIGNMENT
X1 1
X2 2
V_BACKUP
3
GND 4
8
V_CC
7 RST
6 SCL
5 SDA
PIN DESCRIPTION
V_CC, V_BACKUP
GND
- Power Supply Inputs
- Ground
X1, X2
- 32.768 kHz crystal pins
SCL
- Serial clock
SDA
- Serial data
RST
- Reset output
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.
1 of 13
082800