DS32C35 Maxim Integrated Products, Inc., DS32C35 Datasheet - Page 9

• Manufacturer Part Number: DS32C35
• Description: Accurate I2c Rtc With Integrated Tcxo/crystal/fram
• Manufacturer: Maxim Integrated Products, Inc.

The DS32B35/DS32C35 accurate RTCs are clock/cal-
endars that include an integrated TCXO, crystal, and a
bank of nonvolatile memory (FRAM) in a single pack-
age. The nonvolatile memory is available in two sizes:
2048 x 8 or 8192 x 8 bits. The integration of the crystal
resonator enhances the long-term accuracy of the
device as well as reduces the piece part count in a
manufacturing line. The devices are available in both
commercial and industrial temperature ranges and is
offered in a 300-mil, 20-pin SO package.
The DS32B35/DS32C35 include a bank of nonvolatile
memory that do not require a backup energy source to
maintain the memory contents. In addition, there are no
15, 19
18, 20
7–14
PIN
16
17
2,
1
3
4
5
6
INT/SQW
NAME
32kHz
GND
V
N.C.
SDA
V
RST
SCL
WP
BAT
CC
Write Protect. When WP is high, the entire FRAM memory array is write protected. When WP is low, all
addresses can be written. This pin is internally pulled down.
No Connection. Must be connected to ground.
32kHz Output. This open-drain pin requires an external pullup resistor. When enabled, the output operates
on either power supply. It can be left open if not used.
DC Power Pin for Primary Power Supply. This pin should be decoupled using a 0.1µF to 1.0µF capacitor.
Active-Low Interrupt or Square-Wave Output. This open-drain pin requires an external pullup resistor
connected to V
determined by the state of the INTCN bit in the Control register (0Eh). When INTCN is set to logic 0, this pin
outputs a square wave and its frequency is determined by the RS2 and RS1 bits. When INTCN is set to logic
1, a match between the timekeeping registers and either of the alarm registers activates the INT/SQW pin (if
the alarm is enabled). Because the INTCN bit is set to logic 1 when power is first applied, the pin defaults to
an interrupt output with alarms disabled.
Active-Low Reset. This pin is an open-drain input/output. It indicates the status of V
V
open-drain pulldown transistor is shut off, and the internal pullup resistor pulls the RST pin to V
low, open-drain output is combined with a debounced pushbutton input function. This pin can be activated by
a pushbutton reset request. It has an internal 50k
resistors should be connected. If the EOSC bit is 1, t
Ground. Must be connected together to ground.
Backup Power-Supply Input. This pin should be decoupled using a 0.1µF to 1.0µF low-leakage capacitor.
If the I
is not required. If V
when used with a lithium battery. Go to www.maxim-ic.com/qa/info/ul.
Serial Data Input/Output. This pin is the data input/output for the I
requires an external pullup resistor.
Serial Clock Input. These pins are the clock input for the I
data movement on the serial interface.
PF
specification. As V
Detailed Description
2
C interface is inactive whenever the device is powered by the V
CC
Accurate I
or another supply of 5.5V or less. It can be left open if not used. This multifunction pin is
BAT
_____________________________________________________________________
CC
is not used, connect to ground. UL recognized to ensure against reverse charging
falls below V
PF
, the RST pin is driven low. When V
2
read or write cycle limitations. The memory array can
be accessed at maximum cycle rates for the life of the
product with no wear-out mechanisms.
A precision temperature-compensated reference and
comparator circuit monitors the status of V
matically switches to the backup supply when neces-
sary. Other device features include two time-of-day
alarms, a selectable output that provides either an
interrupt or programmable square wave, and a calibrat-
ed 32.768kHz square-wave output. A reset input/output
pin provides a power-on reset. Additionally, the reset
pin is monitored as a pushbutton input for generating a
reset externally. The devices are accessed through an
I
2
C RTC with Integrated
FUNCTION
C serial interface.
nominal value pullup resistor to V
REC
TCXO/Crystal/FRAM
is bypassed and RST immediately goes high.
2
C serial interface and are used to synchronize
2
C serial interface. This open-drain pin
BAT
CC
input, the decoupling capacitor
exceeds V
Pin Description
CC
CC
relative to the
. No external pullup
PF
, for t
CC
CC
RST
. The active-
and auto-
, the
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