ADM6326/ADM6328/ADM6346/ADM6348

Rev. 0 | Page 7 of 12

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

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

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.

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

ADM6328/ADM6348

GND

RESET

MICROPROCESSOR

SYSTEM

GND

RESET

INPUT

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

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.

0V

0V

1V

RESET

Figure 9. RESET Timing