RTC/TCXO/Crystal

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9

Pin Description

PIN

NAME

FUNCTION

1

32kHz

32kHz Output. This open-drain pin requires an external pullup resistor. It may 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.

If not used, connect to ground.

3

INT/SQW

Active-Low Interrupt or Square-Wave Output. This open-drain pin requires an external pullup resistor. It may 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.

4

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 50k

Ω nominal value

5–12

N.C.

No Connection. Must be connected to ground.

13

GND

Ground

14

Backup Power-Supply Input. This pin should be decoupled using a 0.1µF to 1.0µF low-leakage capacitor.

used with a lithium battery. Go to www.maxim-ic.com/qa/info/ul.

15

SDA

requires an external pullup resistor.

16

SCL

movement on the serial interface.

Detailed Description

The DS3231 is a serial RTC driven by a temperature-

compensated 32kHz crystal oscillator. The TCXO pro-

vides a stable and accurate reference clock, and

maintains the RTC to within ±2 minutes per year accu-

racy from -40°C to +85°C. The TCXO frequency output

is available at the 32kHz pin. The RTC is a low-power

clock/calendar with two programmable time-of-day

alarms and a programmable square-wave output. The

INT/SQW provides either an interrupt signal due to

alarm conditions or a square-wave output. The clock/cal-

endar provides seconds, minutes, hours, day, date,

month, and year information. The date at the end of the

month is automatically adjusted for months with fewer

than 31 days, including corrections for leap year. The

clock operates in either the 24-hour or 12-hour format

with an AM/PM indicator. The internal registers are

A temperature-compensated voltage reference and

power failures and to automatically switch to the back-

up supply when necessary. The RST pin provides an

external pushbutton function and acts as an indicator

of a power-fail event.