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DS3231 Series Datasheet

DS3231

Real-Time Clock

The DS3231M is a low-cost, extremely accurate, I2C real-time clock (RTC). The device incorporates a battery input and maintains accurate timekeeping when main power to the device is interrupted. The integration of the microelec-tromechanical systems (MEMS) resonator enhances the long-term accuracy of the device and reduces the piece-part count in a manufacturing line. The DS3231M is avail-able in the same footprint as the popular DS3231 RTC.

DS3231 Data sheet.pdf

DS3231 Pin Configuration and Function

Pin No	Pin Name	Description
1	32KHZ	32.768kHz Output (50% Duty Cycle). This open-drain pin requires an external pullup resistor. When enabled with the EN32KHZ bit in the Status register (0Fh), this output operates on either power supply. This pin can be left open circuit if not used.
2	Vcc	DC Power Pin for Primary Power Supply. This pin should be decoupled using a 0.1FF to 1.0FF capacitor. Connect to ground if not used.
3	SQW	Active-Low Interrupt or 1Hz Square-Wave Output. This open-drain pin requires an external pullup resistor connected to a supply at 5.5V or less. 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 1Hz square wave. 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.
4	RST	Active-Low Reset. This pin is an open-drain input/output. It indicates the status of VCC relative to the VPF specification. As VCC falls below VPF, the RST pin is driven low. When VCC exceeds VPF, for tRST, the RST pin is pulled high by the internal pullup resistor. 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 50kI (RPU) nominal value pullup resistor to VCC. No external pullup resistors should be connected. If the oscillator is disabled, tREC is bypassed and RST immediately goes high.
5-12	N.C.	No Connection. These pins must be connected to ground.
13	GND	Ground
14	VBAT	Backup Power-Supply Input. When using the device with the VBAT input as the primary power source, this pin should be decoupled using a 0.1FF to 1.0FF low-leakage capacitor. When using the device with the VBAT input as the backup power source, the capacitor is not required. If VBAT is not used, connect to ground. The device is UL recognized to ensure against reverse charging when used with a primary lithium battery.