Document
Preliminary Information
New Features Repetitive Alarms & Temperature Compensation
X1205
Real Time Clock/Calendar
FEATURES • Real Time Clock/Calendar —Tracks time in Hours, Minutes, and Seconds —Day of the Week, Day, Month, and Year • 2 Polled Alarms (Non-volatile) —Settable on the Second, Minute, Hour, Day of the Week, Day, or Month —Repeat Mode (periodic interrupts) • Oscillator Compensation on chip —Internal feedback resistor and compensation capacitors —64 position Digitally Controlled Trim Capacitor —6 digital frequency adjustment settings to ±30ppm • Battery Switch or Super Cap Input • 2-Wire™ Interface interoperable with I2C* —400kHz data transfer rate • Low Power CMOS —1.25µA Operating Current (Typical) • Small Package Options —8-Lead SOIC and 8-Lead TSSOP APPLICATIONS • • • • Utility Meters HVAC Equipment Audio / Video Components Set Top Box / Television • • • • • • • • • • •
2-Wire™ RTC
DESCRIPTION
IM
Oscillator
BLOCK DIAGRAM
PR
EL
OSC Compensation Frequency Divider 1Hz Timer Calendar Logic
32.768kHz
X1 X2
IN
Status Registers (SRAM) Alarm
The X1205 device is a Real Time Clock with clock/ calendar, two polled alarms, oscillator compensation, and battery backup switch. The oscillator uses an external, low-cost 32.768kHz crystal. All compensation and trim components are integrated on the chip. This eliminates several external discrete components and a trim capacitor, saving board area and component cost. The Real-Time Clock keeps track of time with separate registers for Hours, Minutes, and Seconds. The Calendar has separate registers for Date, Month, Year and Day-of-week. The calendar is correct through 2099, with automatic leap year correction.
A
R
Modems Network Routers, Hubs, Switches, Bridges Cellular Infrastructure Equipment Fixed Broadband Wireless Equipment Pagers / PDA POS Equipment Test Meters / Fixtures Office Automation (Copiers, Fax) Home Appliances Computer Products Other Industrial / Medical / Automotive
Y
Alarm
Time Keeping Registers (SRAM)
Mask 8 Interrupt Enable
SCL SDA
Serial Interface Decoder
Control Decode Logic
Control Registers (EEPROM)
Compare Alarm Regs (EEPROM)
IRQ
*I2C is a Trademark of Philips. REV 1.0.9 8/29/02
www.xicor.com
Characteristics subject to change without notice.
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X1205 – Preliminary Information
DESCRIPTION (continued) The powerful Dual Alarms can be set to any Clock/ Calendar value for a match. For instance, every minute, every Tuesday, or 5:23 AM on March 21. The alarms can be polled in the Status Register or provide a hardware interrupt (IRQ Pin). There is a repeat mode for the alarms allowing a periodic interrupt. The device offers a backup power input pin. This VBACK pin allows the device to be backed up by battery or SuperCap. The entire X1205 device is fully operational from 2.7 to 5.5 volts and the clock/calendar portion of the X1205 device remains fully operational down to 1.8 volts (Standby Mode). PIN DESCRIPTIONS
X1205 8-Pin SOIC X1 X2 IRQ VSS 1 2 3 4 8 7 6 5 VCC VBACK SCL SDA
R
Off
Figure 1. Recommended Crystal connection
X1 X2
8-Pin TSSOP VBACK VCC X1 X2 1 2 3 4 8 7 6 5 SCL SDA VSS IRQ
NC = No internal connection
IM
EL
Serial Clock (SCL) The SCL input is used to clock all data into and out of the device. The input buffer on this pin is always active (not gated).
IN
POWER CONTROL OPERATION The power control circuit accepts a VCC and a VBACK input. The power control circuit powers the clock from VBACK when VCC < VBACK - 0.2V. It will switch back to power the device from VCC when VCC exceeds VBACK.
Figure 2. Power Control
VCC
Voltage
A
VBACK
Y
X1, X2 The X1 and X2 pins are the input and output, respectively, of an inverting amplifier. An external 32.768kHz quartz crystal is used with the X1205 to supply a timebase for the real time clock. The recommended crystal is a Citizen CFS206-32.768KDZF. Internal compensation circuitry is included to form a complete oscillator circuit. Care should be taken in the placement of the crystal and the layout of the circuit. Plenty of ground plane around the device and short traces to X1 and X2 are highly recommended. See Application section for more recommendations.
On In
PR
Serial Data (SDA) SDA is a bidirectional pin used to transfer data into and out of the device. It has an open drain output and may be wire ORed with other open drain or open collector outputs. The input buffer is always active (not gated). An open drain output requires the use of a pull-up resistor. The output circuitry controls the fall time of the output signal with the use of a slope controlled pulldown. The circuit is designed for 400kHz 2-wire interface speeds. VBACK This input provides a backup supply voltage to the device. VBACK supplies power to the device in the event the VCC supply fails. This pin can be connected to a battery, a Supercap or tied to ground if not used. Interrupt Output – IRQ This is an interrupt signal output. This signal notifies a host processor that an alarm has occurre.