Rainbow Electronics DS1678 User Manual
Page 4
DS1678
4 of 26
DS1678 BLOCK DIAGRAM Figure 1
SIGNAL DESCRIPTIONS
The following paragraphs describe the function of each pin.
V
CC
– V
CC
is a +5V input supply. Communication with the DS1678 can take place only when V
CC
is
connected to a +5V supply.
V
BAT
– Battery input for standard lithium cell or other energy source. All functions of the DS1678 with
the exception of the serial interface circuitry are powered by V
BAT
when V
CC
< V
BAT
. All functions are
powered by V
CC
when V
CC
> V
BAT
. If a battery or other energy source is not used, V
BAT
should be
connected directly to ground. UL recognized to ensure against reverse charging current when used in
conjunction with a lithium battery.
See “Conditions of Acceptability”
GND – Ground.
SCL (2-Wire Serial Clock Input) – The SCL pin is the serial clock input for the 2-wire synchronous
communications channel. The SCL pin is an open drain input, which requires an external pull-up resistor.
SDA (2-Wire Input/Output) – The SDA pin is the data input/output (I/O) signal for the 2-wire
synchronous communications channel. The SDA pin is an open drain I/O, which requires an external
pull-up resistor.
32.768 kHz
OSCILLATOR
AND DIVIDER
X1
X2
POWER
CONTROL
V
CC
V
BAT
2-WIRE SERIAL
INTERFACE
SCL
SDA
GND
RTC
DATA LOG
NV SRAM
CONTROL
LOGIC
INT
ADDRESS
REGISTER
USER
RAM
DATA LOG
RAM PORT