ADM6328 Просмотр технического описания (PDF) - Analog Devices
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ADM6328 Datasheet PDF : 12 Pages
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THEORY OF OPERATION
The ADM6326/ADM6328/ADM6346/ADM6348 are designed
to protect the integrity of a system’s operation by ensuring the
proper operation of the system during power-up, power-down,
and brownout conditions. Ultralow supply currents make these
devices particularly suitable for use in low power, portable
equipment.
RESET OUTPUT
The ADM6326 and ADM6346 have an active low, push-pull
reset output, whereas the ADM6328 and ADM6348 have an
active low, open-drain reset output, which requires an external
pull-up resistor. The RESET signal is guaranteed to be valid for
VCC down to 1 V.
When the ADM6326/ADM6328/ADM6346/ADM6348 are
powered up, the RESET output remains low for a period typically
equal to the RESET active timeout period of 185 ms. This feature
allows adequate time for the system to power up correctly and
for the power supply to stabilize before any devices are brought out
of reset and are allowed to begin executing instructions. Initializing
a system in this way provides a more reliable startup for micro-
processor systems.
When the monitored voltage falls below its associated threshold
(VTH), RESET is asserted within 20 μs (typical). Asserting RESET
this quickly means that the entire system can be reset at once
before any part of the system’s voltage falls below its recommended
operating voltage. This system reset can avoid dangerous and/or
erroneous operation of a microprocessor based system.
ADM6326/ADM6328/ADM6346/ADM6348
INTERFACING TO OTHER DEVICES
The active low, open-drain reset output of the ADM6328 and
ADM6348 makes these devices ideal for integration with devices
such as microprocessors with bidirectional reset pins. Simply
connect the RESET output of the ADM6328 or ADM6348 to
the RESET input of the microprocessor using a single pull-up
resistor to allow either device to initiate a system reset (see
Figure 8).
VCC
VCC
ADM6328/ADM6348
RESET
GND
RPULL-UP
VCC
MICROPROCESSOR
SYSTEM
RESET
INPUT
GND
Figure 8. Interfacing to a Microprocessor with a Bidirectional Reset Pin
TRANSIENT IMMUNITY
To avoid unnecessary resets caused by fast power supply transients,
the ADM6326/ADM6328/ADM6346/ADM6348 provide glitch
immunity from negative-going VCC transients.
Figure 5 shows the RESET comparator overdrive (that is, the
maximum magnitude of negative-going pulses with respect to
the typical threshold) vs. the pulse duration without a reset.
VCC
VCC
1V
0V
VCC
RESET
0V
VTH
tRP
Figure 9. RESET Timing
VTH
tRD
Rev. 0 | Page 7 of 12
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