PT7C433833 2 Real-time Clock Module (I C Bus) Product Features Product Description The PT7C4338 serial real-time clock is a low-power Using external 32.768kHz quartz crystal 2 clock/calendar with a programmable square-wave output Supports I C-Bus s high speed mode (400 kHz) and 56 bytes of nonvolatile RAM. Includes time (Hour/Minute/Second) and calendar (Year/Month/Date/Day) counter functions (BCD Address and data are transferred serially via a 2-wire, code) bidirectional bus. The clock/calendar provides seconds, Programmable square wave output signal minutes, hours, day, date, month, and year information. 56-byte, battery-backed, nonvolatile (NV) RAM for The date at the end of the month is automatically data storage adjusted for months with fewer than 31 days, including Automatic power-fail detect and switch circuitry of corrections for leap year. The clock operates in either the battery backup 24-hour or 12-hour format with AM/PM indicator. UL Recognized: E348121 The PT7C4338 series have a built-in power sense circuit that detects power failures and automatically switches to the battery supply. Table 1 shows the basic functions of PT7C4338. More details are shown in section: overview of functions. Table 1. Basic functions of PT7C4338 Item Function PT7C4338 Source: Crystal: 32.768kHz 1 Oscillator Oscillator enable/disable Oscillator fail detect 12-hour Time display 2 Time 24-hour Century bit - 3 Alarm interrupt - 4 Programmable square wave output (Hz) 1, 4.096k, 8.192k, 32.768k 5 RAM 56 8 6 Battery backup 12-07-0001 PT0321-6 07/04/12 1 PT7C433833 2 Real-time Clock Module (I C Bus) Pin Assignment PT7C4338 8 1 X1 VCC 2 X2 SQW/OUT 7 6 3 VBAT SCL 5 4 GND SDA SOIC-8 MSOP-8 Pin Description Pin no. Pin Type Description 32.768kHz Crystal Connections. The internal oscillator circuitry is designed for operation with 1 X1 I a crystal having a specified load capacitance (CL) of 12.5pF. Pin X1 is the input to the oscillator and can optionally be connected to an external 32.768kHz oscillator. The output of the internal oscillator, pin X2, is floated if an external oscillator is connected to pin X1. An external 2 X2 O 32.768kHz oscillator can also drive the PT7C4338. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is floated. 2 6 SCL I Serial Clock Input. SCL is used to synchronize data movement on the I C serial interface. Serial Data Input/Output. SDA is the input/output pin for the 2-wire serial interface. The SDA 5 SDA I/O pin is open-drain output and requires an external pull-up resistor. Square-Wave/Output Driver. When enabled and the SQWE bit set to 1, the SQW/OUT pin 7 SQW/OUT O outputs one of four square-wave frequencies (1Hz, 4kHz, 8kHz, 32kHz). It is open drain and requires an external pull up resistor. Operates with either VCC or VBAT applied. Supply Voltage. When voltage is applied within normal limits, the device is fully accessible and data can be written and read. When a backup supply is connected to the device and VCC is 8 VCC P below VPF, reads and writes are inhibited. However, the timekeeping function continues unaffected by the lower input voltage. +3V Battery Input. Backup supply input for any standard 3V lithium cell or other energy source. Battery voltage must be held between the minimum and maximum limits for proper 3 VBAT P operation. If a backup supply is not required, VBAT must be grounded. UL recognized to ensure against reverse charging when used with a lithium battery. Ground. DC power is provided to the device on these pins. VCC is the primary power input. When voltage is applied within normal limits, the device is fully accessible and data can be 4 GND P written and read. When a backup supply is connected to the device and VCC is below VPF, reads and writes are inhibited. However, the timekeeping function continues unaffected by the lower input voltage. 12-07-0001 PT0321-6 07/04/12 2