Datasheet

DS1374
I
2
C, 32-Bit Binary Counter Watchdog RTC with
Trickle Charger and Reset Input/Output
8 _____________________________________________________________________
Pin Description
PIN
μSOP SO
NAME FUNCTION
1, 2 — X1, X2
Connections for a Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is designed
for operation with a crystal having a specified load capacitance (C
L
) of 6pF. Pin X1 is the input to the
oscillator and can optionally be connected to an external 32.768kHz oscillator. The output of the
internal oscillator, pin X2, is left unconnected if an external oscillator is connected to pin X1.
3 13 V
BACKUP
Connection for a Secondary Power Supply. This supply is used to operate the oscillator and
counters when V
CC
is absent. Supply voltage must be held between 1.3V and 3.7V (-18 and -3) or
1.3V and 5.5V (-33) for proper operation. This pin can be connected to a primary cell such as a
lithium cell. Additionally, this pin can be connected to a rechargeable cell or a super cap when
used with the trickle-charge feature. UL recognized to ensure against reverse charging when used
with a lithium battery. This pin must be grounded if not used.
4 14 RST
Active-Low, Open-Drain Output with a Debounced Pushbutton Input. This pin can be activated by a
pushbutton reset request, a watchdog alarm condition, or a power-fail event. It has an internal 50k
pullup resistor. No external resistors should be connected. If the crystal oscillator is disabled, the
startup time of the oscillator is added to the t
RST
delay.
5 15 GND Ground
6 16 SDA
Serial Data Input/Output. SDA is the input/output for the 2-wire serial interface. The SDA pin is open
drain and requires an external pullup resistor.
7 1 SCL
Serial Clock Input. SCL is the clock input for the 2-wire serial interface and is used to synchronize
data movement on the serial interface.
8 2 INT
Interupt. This pin is used to output the alarm interrupt or the watchdog reset signal. It is active-low
open drain and requires an external pullup resistor.
9 3 SQW
Square-Wave Output. This pin is used to output the programmable square-wave signal. It is open
drain and requires an external pullup resistor.
10 4 V
CC
DC Power for Primary Power Supply
— 5–12 N.C. No Connection. Must be connected to ground.
CLOCK
DIVIDER
32-BIT
COUNTER
MUX
4.096kHz
1Hz
X1
X2
8.192kHz
32.768kHz
1Hz/4.096kHz
ALARM/
WATCHDOG
STAT/CTRL/
TRICKLE
24-BIT
COUNTER
INT
CONTROL
RST
CONTROL
2-WIRE
INTERFACE
POWER
CONTROL
AND
TRICKLE
CHARGE
V
CC
V
BACKUP
GND
SDA
SCL
RST
SQW
INT
DS1374
Figure 4. Functional Diagram