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ISL1221IUZ

Low Power RTC with Battery Backed SRAM and Event Detection

Renesas Electronics 

ISL1221

Typical Performance Curves Temperature is +25°C unless otherwise specified (Continued)

8.00E-06

5.0E-07

7.00E-06

6.00E-06

-40°C

4.0E-07

5.00E-06

4.00E-06

3.00E-06

2.00E-06

+25°C

+85°C

3.0E-07

2.0E-07

1.00E-06

0.00E-00

2.5

3.0 3.5

4.0 4.5

VDD

5.0 5.5 6.0

1.0E-07

-40 -25 -10

5 20 35 50 65 80

TEMPERATURE

FIGURE 7. EVIN IPULLUP vs VDD

FIGURE 8. IPULLUP vs TEMPERATURE AT VBAT = 1.8V

EQUIVALENT AC OUTPUT LOAD CIRCUIT FOR VDD = 5V

5.0V

SDA

AND

IRQ/EVDET

1533

FOR VOL= 0.4V

AND IOL = 3mA

100pF

FIGURE 9. STANDARD OUTPUT LOAD FOR TESTING THE

DEVICE WITH VDD = 5.0V

General Description

The ISL1221 device is a low power Real Time Clock with

Security and Event function, Time Stamp in both normal and

battery modes, timing and crystal compensation,

clock/calendar, power fail indicator, periodic or polled alarm,

intelligent battery backup switching, and battery-backed user

SRAM.

The Event Detection function can be used for tamper

detection, security or other chassis or generic system

monitoring. Upon a valid event detection, the ISL1221 sets the

Event Detection bit (EVT bit) in the status register, stores time

stamp information on board memory, and, can optionally: 1)

Issue an Event Output signal (EVDET pin), 2) At the time the

event occurred, stop the RTC registers from advancing. The

event monitor and time stamp functions in both main VDD and

battery back up modes. The event monitor can also be

configured for various input detection rates to optimize power

consumption for the application. In addition, the Event Monitor

pin (EVIN) has a selectable glitch filter to avoid switch de-

bouncing.

The oscillator uses an external, low-cost 32.768kHz crystal.

The real time clock tracks time with separate registers for

hours, minutes, and seconds. The device has calendar

registers for date, month, year and day of the week. The

calendar is accurate through 2099, with automatic leap year

correction.

The ISL1221's alarm can be set to any clock/calendar value for

a match. For example, every minute, every Tuesday or at 5:23

AM on March 21. The alarm status is available by checking the

Status Register, or the device can be configured to provide a

hardware interrupt via the IRQ pin. There is a repeat mode for

the alarm allowing a periodic interrupt every minute, every

hour, every day, etc.

The device also offers a backup power input pin. This VBAT pin

allows the device to be backed up by battery or SuperCap with

automatic switchover from VDD to VBAT. The entire ISL1221

device is fully operational from VDD = 2.7V to 5.5V and the

clock/calendar portion of the device remains fully operational in

battery backup mode down to 1.8V (Standby Mode).

Pin Description

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 ISL1221 to supply a timebase for the real time

clock. Internal compensation circuitry provides high accuracy

over the operating temperature range from -40°C to +85°C.

This oscillator compensation network can be used to calibrate

the crystal timing accuracy over temperature either during

manufacturing or with an external temperature sensor and

microcontroller for active compensation. The device can also

be driven directly from a 32.768kHz source at pin X1.

FN6316 Rev 1.00

July 15, 2010

Page 7 of 24

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