The recommended crystal oscillator frequency for the DS1337U+ is 32.768 kHz.
To ensure proper reset during power-up, connect the RST pin to VCC through a 1 kΩ resistor and a 0.1 μF capacitor to ground.
The VBAT pin is used to connect a battery backup source, which allows the DS1337U+ to maintain its clock and calendar information during power failures.
The clock frequency of the DS1337U+ is set by writing to the Clock Frequency Register (0x07). The clock frequency can be set to 1 Hz, 4 Hz, 8 Hz, or 32 Hz.
The maximum operating temperature range of the DS1337U+ is -40°C to +85°C.