Extremely Accurate SPI Bus RTC with

Integrated Crystal and SRAM

8

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Pin Description

PIN

NAME

FUNCTION

1

CS

Active-Low Chip Select Input. Used to select or deselect the device.

2, 7–14

N.C.

No Connection. Not connected internally. Must be connected to ground.

3

32kHz

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.

5

INT/SQW

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.

6

RST

pin is driven high impedance. The active-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 50kΩ nominal value pullup

bypassed and RST immediately goes high.

15

GND

Ground

16

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.

17

DIN

SPI Data Input. Used to shift address and data into the device.

18, 20

SCLK

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.

19

DOUT

SPI Data Output. Data is output on this pin when the device is in read mode; CMOS push-pull driver.