Datasheet

INPUT VOLTAGE, PIN 2
V
IN
V
DET+
V
DET-
V
IN
V
DET+
V
DET-
0V
RESET OUTPUT (ACTIVE LOW), PIN 1
INPUT VOLTAGE, PIN 2
V
DET+
+2
1V
0V
5V
0V
0.5V
2.5V
t
PLH
t
PHL
RESET OUTPUT (ACTIVE LOW), PIN 1
LM8364
www.ti.com SNVS232B –MARCH 2003–REVISED APRIL 2013
APPLICATION NOTES
The propagation delay time for the LM8364 is measured using a 470kΩ pull-up resistor connected to from the
RESET output pin to 5V in addition to a 10pF capacitive load connected from the same pin to GND. Figure 7
shows the timing diagram for the measurement for the propagation delay. V
DET+
is equal to the sum of the
detector threshold, V
DET−
, and the built in hysteresis, V
HYS
.
Figure 7. Propagation Delay Timing Diagrams
The LM8364 ultra-low current voltage detector was designed to monitor voltages and to provide an indication
when the monitored voltage, V
IN
, dropped below a precisely trimmed threshold voltage. This characteristic is
displayed in the typical operating timing diagram below. V
IN
is the voltage that is being monitored and a pull up
resistor is connected from the RESET output pin to V
IN
. V
IN
is at some value above V
DET+
and then begins to
decrease. Since this is an Active Low device the RESET output is pulled High through the pull-up resistor and
tracks V
IN
until V
IN
crosses the trimmed threshold V
DET−
. At this point the LM8364 recognizes that V
IN
is now in a
fault condition and the output immediately changes to the Logic Low State. The RESET output will remain in this
low state until V
IN
increases above the threshold V
DET−
+ V
HYS
. This point is also known as V
DET+
as indicated
earlier. This built-in hysteresis has been added to the design to help prevent erratic reset operation when the
input voltage crosses the threshold.
The LM8364 has a wide variety of applications that can take advantage of its precision and low current
consumption to monitor Input voltages even though it was designed as a reset controller in portable
microprocessor based systems. It is a very cost effective and space saving device that will protect your more
expensive investments of microprocessors and other devices that need a specified supply voltage for proper
operation.
Figure 8. Timing Waveforms
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