LM3706XQBPX-308 NSC [National Semiconductor], LM3706XQBPX-308 Datasheet - Page 8

• Manufacturer Part Number: LM3706XQBPX-308
• Description: Microprocessor Supervisory Circuits with Low Line Output and Watchdog Timer
• Manufacturer: NSC [National Semiconductor]

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Typical Performance Characteristics
Circuit Information
Reset Output
The Reset input of a µP initializes the device into a known
state. The LM3706/LM3707 microprocessor supervisory cir-
cuits assert a forced reset output to prevent code execution
errors during power-up, power-down, and brownout condi-
tions.
RESET is guaranteed valid for V
ceeds the reset threshold, an internal timer maintains the
output for the reset timeout period. After this interval, reset
goes high. The LM3706 offers an active-low RESET; The
LM3707 offers an active-high RESET.
Any time V
during a brownout), the reset activates. When V
rises above the reset threshold, the internal timer starts.
Reset holds until V
than the reset timeout period. After this time, reset releases.
Reset Threshold
The LM3706/LM3707 family is available with a reset voltage
of 3.08V. Other reset thresholds in the 2.20V to 5.0V range,
in steps of 10 mV, are available; contact National Semicon-
ductor for details.
Low-Line Output (LLO)
The low-line output comparator is typically used to provide a
non-maskable interrupt to a µP when V
monitors V
(typically 1.02 • V
Watchdog Timer Input (WDI)
The watchdog timer input monitors one of the microproces-
sor’s output lines for activity. Each time a transition occurs on
this monitored line, the watchdog counter is reset. However,
Watchdog Timeout Period vs Temperature
CC
CC
and goes low when V
(t
drops below the reset threshold (such as
WD
RST
CC
programmed as 6.2ms)
) with hysteresis of 0.0032 • V
exceeds the reset threshold for longer
CC
>
CC
CC
1V. Once V
begins falling. LLO
falls below V
CC
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RST
CC
again
LLOT
.
ex-
8
(Continued)
Low-Line Comparator Propagation Delay vs Temperature
if no transition occurs and the timeout period is reached, the
LM3706/LM3707 assumes that the microprocessor has
locked up and the reset output is activated.
WDI is a high impedance input.
Special Precautions for the micro SMD Package
As with most integrated circuits, the LM3706 and LM3707
are sensitive to exposure from visible and infrared (IR) light
radiation. Unlike a plastic encapsulated IC, the micro SMD
package has very limited shielding from light, and some
sensitivity to light reflected from the surface of the PC board
or long wavelength IR entering the die from the side may be
experienced. This light could have an unpredictable affect on
the electrical performance of the IC. Care should be taken to
shield the device from direct exposure to bright visible or IR
light during operation.
Micro SMD Mounting
The micro SMD package requires specific mounting tech-
niques which are detailed in National Semiconductor Appli-
cation Note AN-1112. Referring to the section Surface
Mount Technology (SMT) Assembly Considerations, it
should be noted that the pad style which must be used with
the 9-pin package is the NSMD (non-solder mask defined)
type.
For best results during assembly, alignment ordinals on the
PC board may be used to facilitate placement of the micro
SMD device.
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