ISL12008 I2C Real Time Clock with Battery Backup

FN6690 Rev 1.00

Page 2 of 19

Sep 26, 2008

Block Diagram

I2C

INTERFACE

RTC

CONTROL

LOGIC

FREQUENCY

OUT

RTC

DIVIDER

SDA

BUFFER

CRYSTAL

OSCILLATOR

POR

SWITCH

SCL

BUFFER

SDA

SCL

X1

X2

VDD

VBAT

FT/OUT

INTERNAL

SUPPLY

VTRIP

SECONDS

MINUTES

HOURS

DAY OF WEEK

DATE

MONTH

YEAR

CONTROL

REGISTERS

Pin Descriptions

PIN

NUMBER SYMBOL

DESCRIPTION

1

X1

The X1 pin is the input of an inverting amplifier and is intended to be connected to one pin of an external 32.768kHz quartz

crystal. X1 can also be driven directly from a 32.768kHz source.

2

X2

The X2 pin is the output of an inverting amplifier and is intended to be connected to one pin of an external 32.768kHz quartz

crystal.

3VBAT

This input provides a backup supply voltage to the device. VBAT supplies power to the device in the event that the VDD supply

fails. This pin should be tied to ground if not used.

4

GND

Ground

5

SDA

Serial Data (SDA) is a bidirectional pin used to transfer serial data into and out of the device. It has an open drain output and

may be wire OR’ed with other open drain or open collector outputs.

6

SCL

The Serial Clock (SCL) input is used to clock all serial data into and out of the device.

7

FT/OUT

512Hz Frequency Output or digital output pin. The function is set via the configuration register. This pin is open drain and

requires an external pull-up resistor.

8VDD

Power supply