
D
Extremely Accurate SPI Bus RTC with
Integrated Crystal and SRAM
8
_____________________________________________________________________
Pin Description
PIN
1
2, 7–14
NAME
CS
N.C.
FUNCTION
Active-Low Chip Select Input. Used to select or deselect the device.
No Connection. Not connected internally. Must be connected to ground.
32kHz Push-Pull Output. If disabled with either EN32kHz = 0 or BB32kHz = 0, the state of the 32kHz pin will be
low.
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. It can be
left open if not used. This multifunction pin is 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 RS2
and RS1 bits. When INTCN is set to logic 1, then 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.
3
32kHz
4
V
CC
5
INT
/SQW
6
RST
Acti ve- Low Reset. Thi s p n i s an op en- d ai n i np ut/outp ut. It i nd cates the status of V
C C
r el ati ve to the
V
P F
sp eci i cati on. As V
C C
fal s b el ow V
P F
, the
RS T
p n i s d ven l ow W hen V
C C
exceed s V
P F
, for t
R S T
, the
RS T
p n i s d ven hi g h i m p ed ance. The acti ve- ow op en- d ai n outp ut i s com b ned w h a d eb ounced p ushb utton i np ut
functi on. Thi s p n can b e acti vated b y a p ushb utton r eset r eq uest. It has an i nter nal 50k
nom nal val ue p ul up
r esi stor to V
C C
. N o exter nal p ul up r esi stor s shoul d b e connected If the cr ystal osci ator i s d sab ed t
R S T
i s
b yp assed and
RST
i m m ed atel y g oes hi g h.
Ground
Backup Power-Supply Input. If V
B A T
is not used, connect to ground. Diodes placed in series between the V
B A T
pin and the battery can cause improper operation. UL recognized to ensure against reverse charging when
used with a lithium battery. Go to www.maxim-ic.com/qa/info/ul.
SPI Data Input. Used to shift address and data into the device.
SPI Clock Input. Used to control timing of data into and out of the device. Either clock polarity can be used. The
clock polarity is determined by the device based on the state of SCLK when
CS
goes low. Pins 18 and 20 are
electrically connected together internally.
SPI Data Output. Data is output on this pin when the device is in read mode; CMOS push-pull driver.
15
GND
16
V
BAT
17
DIN
18, 20
SCLK
19
DOUT