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ISL1209IU10-TK View Datasheet(PDF) - Intersil

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ISL1209IU10-TK Datasheet PDF : 24 Pages
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ISL1209
Power Mode, is available to allow direct switching from VDD
to VBAT without requiring VDD to drop below VTRIP. Since
the additional monitoring of VDD vs. VTRIP is no longer
needed, that circuitry is shut down and less power is used
while operating from VDD. Power savings are typically
600nA at VDD = 5V. Low Power Mode is activated via the
LPMODE bit in the control and status registers.
Low Power Mode is useful in systems where VDD is normally
higher than VBAT at all times. The device will switch from
VDD to VBAT when VDD drops below VBAT, with about 50mV
of hysteresis to prevent any switchback of VDD after
switchover. In a system with a VDD = 5V and backup lithium
battery of VBAT = 3V, Low Power Mode can be used.
However, it is not recommended to use Low Power Mode in
a system with VDD = 3.3V ±10%, VBAT 3.0V, and when
there is a finite I-R voltage drop in the VDD line.
InterSeal™ Battery Saver
The ISL1209 has the InterSeal™ Battery Saver which
prevents initial battery current drain before it is first used. For
example, battery-backed RTCs are commonly packaged on
a board with a battery connected. In order to preserve
battery life, the ISL1209 will not draw any power from the
battery source until after the device is first powered up from
the VDD source. Thereafter, the device will switchover to
battery backup mode whenever VDD power is lost.
Event/Tamper Monitor and Detection
The ISL1209 provides an event detection and alarm function
to be used in a wide variety of applications ranging from
security, warranty monitoring, data collection and recording.
The tamper detect input pin, EVIN, can be used as a event
or tamper detection input of an external switch (mechanical
or electronic). When the EVIN pin is a valid HIGH, the
ISL1209 sets the EVT bit in the status register and, can
optionally: 1) Issue an Event output signal (EVDET pin), 2)
At the time event occurred, stop the RTC registers from
advancing.
To allow for flexibility of external switches used at the EVIN
pin, the internal pull-up (~1µA in full on mode) can be
disabled/enabled. This will allow more flexibility depending
on the capacitive and resistive loading at the EVIN pin.
A noise filter option is also provided for the event monitor
circuit. The EVIN pin has a time based filter where the EVIN
signal must be stable for a period of time to trigger a valid
detection. The time hysteresis filter can vary from 0, 3.9ms,
15.2ms or 31.25ms.
For low power applications the event monitor can be
sampled at a user selectable rate. The EVIN pin can be
always ON or periodically sampled with a frequency of 1/4, 1
or 2Hz.
Event Detect Timing Diagram With
Sampling Mode Enabled
Case 1, Switched Opened Before Ipu
ON
Ipu
OFF
15 clks (8x)
EXT.
OPEN
SWITCH
CLOSED
EVIN
HIGH
LOW
HIGH
EVDET
LOW
8 clks (8x)
Case 2, Switched Opened After Ipu
ON
Ipu
OFF
15 clks (8x)
EXT.
OPEN
SWITCH
CLOSED
EVIN
HIGH
LOW
HIGH
EVDET
LOW
8 clks (8x)
Case 3, Switched Bounced
ON
Ipu
OFF
15 clks (8x)
EXT.
OPEN
SWITCH
CLOSED
EVIN
HIGH
LOW
HIGH
EVDET
LOW
8 clks (8x)
The ISL1209 can operate independently or in conjunction
with a microcontroller for low power operation modes or in
battery backup modes.
The event detection circuits operate in either main VDD
power or battery backup mode.
9
FN6109.1
September 27, 2005
 

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