12032IVZ データシートの表示（PDF） - Renesas Electronics

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12032IVZ

Low Power RTC with Battery Backed SRAM and 50/60 Cycle AC Input and Crystal Back-up

Renesas Electronics 

ISL12032 Real Time Clock with 50/60 Hz clock and Crystal Backup

General Description

The ISL12032 device is a low power real time clock with 50/60

AC input for timing synchronization. It also has an oscillator

utilizing an external crystal for timing back-up, clock/calendar

registers, intelligent battery back-up switching, battery voltage

monitor, brownout indicator, integrated trickle charger for super

capacitor, single periodic or polled alarms, POR supervisory

function, and up to 4 Event Detect with time stamp. There are

128 bytes of battery-backed user SRAM.

The oscillator uses a 50/60 cycle sine wave input, backed by

an external, low-cost, 32.768kHz crystal. The real time clock

tracks time with separate registers for hours, minutes, and

seconds. The calendar registers contain the date, month, year,

and day of the week. The calendar is accurate through year

2100, with automatic leap year correction and auto daylight

savings correction.

The ISL12032’s alarm can be set to any clock/calendar value

for a match. Each alarm’s status is available by checking the

Status Register. The device also can be configured to provide

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

for the alarms 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 Super

Capacitor with automatic switchover from VDD to VBAT. The

ISL12032 devices are specified for 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). The VBAT

level is monitored and warnings are reported against

preselected levels. The first report is registered when the VBAT

level falls below 85% of nominal level, the second level is set

for 75% of nominal level. Battery levels are stored in the

PWRBAT registers.

The ISL12032 offers a “Brownout” alarm once the VDD falls

below a pre-selected trip level. In the ISL12032, this allows the

system microcontroller to save vital information to memory

before complete power loss. There are six VDD trip levels for

the brownout alarm.

The event detection function accepts a normally low logic

input, and when triggered will store the time/date information

for the event. The first event is stored in the memory until reset;

subsequent events are stored on-chip memory and the last 3

events are retained and accessible by performing an indexed

register read.

Pin Descriptions

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 device to supply a backup timebase for the real

time clock if there is no AC input. The device also can be

driven directly from a 32.768kHz source at pin X1, in which

case, pin X2 should be left unconnected. No external load

capacitors are needed for the X1 and X2 pins.

X1

X2

FIGURE 2. RECOMMENDED CRYSTAL CONNECTION

VBAT (Battery Input)

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 can be connected to a battery, a Super

Capacitor or tied to ground if not used.

AC (AC Input)

The AC input is the main clock input for the real time clock. It

can be either 50Hz or 60Hz, sine wave. The preferred

amplitude is 2.5VP-P, although amplitudes >0.25VDD are

acceptable. An AC coupled (series capacitor) sine wave clock

waveform is desired as the AC clock input provides DC

biasing.

LV (Low Voltage)

This pin indicates the VDD supply is below the programmed

level. This signal notifies a host processor that the main supply

is low and requests action. It is an open drain active LOW

output.

EVIN (Event Input)

The EVIN pin input detects an externally monitored event.

When a HIGH signal is present at the EVIN pin, an “event” is

detected.This input may be used for various monitoring

functions, such as the opening of a detection switch on a

chassis or door. The event detection circuit can be user

enabled or disabled (see EVIN bit) and provides the option to

be operational in battery backup modes (see EVATB bit).

When the event detection is disabled, the EVIN pin is gated

OFF. See “Functional Pin Descriptions” on page 3 for more

details.

EVDET (Event Detect Output)

The EVDET is an open drain output, which will go low when an

event is detected at the EVIN pin. If the event detection

function is enabled, the EVDET output will go LOW and stay

there until the EVT bit is cleared.

FN6618 Rev 3.00

May 5, 2011

Page 8 of 26

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