DS1672U-33/T&R Maxim Integrated Products, DS1672U-33/T&R Datasheet - Page 8

• Manufacturer Part Number: DS1672U-33/T&R
• Description: Real Time Clock Low Voltage I2C-Comp atibleTime Keeping C
• Manufacturer: Maxim Integrated Products

DETAILED DESCRIPTION
The DS1672 provides a 32-bit counter that increments once-per-second. The counter data is accessible
via an I
circuit monitors V
prevent data corruption. The device switches to the backup supply input, which maintains oscillator and
counter operation while V
(t
The block diagram in Figure 4 shows the main elements of the DS1672. As shown, communications to
and from the DS1672 occur serially over a I
on the I
identification code followed by a register address. Subsequent registers can be accessed sequentially until
a STOP condition is executed.
Figure 4. Block Diagram
Oscillator Circuit
The DS1672 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to
operate. Table 1 specifies several crystal parameters for the external crystal. Figure 4 shows a functional schematic of the
oscillator circuit. If using a crystal with the specified characteristics, the startup time is usually less than one second.
Table 1. Crystal Specifications*
*The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to Application Note 58:
Crystal Considerations with Dallas Real-Time Clocks.
Nominal Frequency
Series Resistance
Load Capacitance
RPU
PARAMETER
) to allow V
V
BACKUP
GND
SDA
RST
SCL
V
2
2
C serial interface. A precision, temperature-compensated, voltage reference and comparator
CC
C bus. Access is obtained by implementing a START condition and providing a device
OSCILLATOR
DIVIDER
CC
AND
N
CC
to stabilize.
. When V
SYMBOL
POWER CONTROL
X1
I
CC
ESR
2
C
C INTERFACE
C
f
L
O
L
is absent. When V
CC
C
drops below V
X2
L
MIN
2
C, bidirectional bus. The DS1672 operates as a slave device
32.768
TYP
CC
PF
6
ADDRESS REGISTER
8 of 15
rises above V
, RST becomes active and the interface is disabled to
CONTROL LOGIC
1Hz
MAX
45
PF
, RST remains low for a period of time
Semiconductor
UNITS
kHz
k
pF
TRICKLE CHARGER
DS1672
32-BIT COUNTER
Dallas
CONTROL
(4 BYTES)