ADM8611/ADM8612/ADM8613/ADM8614/ADM8615

Data Sheet

Rev. G | Page 12 of 17

THEORY OF OPERATION

The ADM8611/ADM8612/ADM8613/ADM8614/ADM8615 low

power voltage supervisors protect the integrity of system

operation by ensuring the proper operation during power-up,

power-down, and brownout conditions. These devices monitor

the input voltage level and compare it against an internal reference.

The RESET output asserts whenever the monitored voltage level

is below the reference threshold, keeping the processor in a reset

state. The RESET output deasserts if the monitored voltage rises

above the threshold reference for a minimum period, the active

reset timeout period. This ensures that the supply voltage for

the processor is raised to an adequate level and stable before

exiting reset.

The ultralow supply current makes the ADM8611/ADM8612/

ADM8613/ADM8614/ADM8615 devices particularly suitable

for use in low power, portable equipment.

Figure 24. ADM8611 Functional Block Diagram

Figure 25. ADM8613 Functional Block Diagram

Figure 26. ADM8615 Functional Block Diagram

VOLTAGE MONITORING INPUT

The VCC pin of the ADM8611/ADM8613/ADM8614 acts as

both a device power input node and a voltage monitoring input

node. The ADM8612 uses separate pins for supply and voltage

monitoring to achieve a low voltage monitoring threshold to 0.5 V.

It is recommended to place a 0.1 μF decoupling capacitor as close

as possible to the device between the VCC pin and the GND pin.

VCC Slew Rate Consideration

A fast VCC ramp (μs range) on power-up can cause the device

to behave in an irregular manner. In applications where a high

slew rate on VCC is possible, for example, powering up using a

battery pack, it is recommended that an RC filter is used to reduce

the slew rate. RC combinations of 3.3 kΩ + 2.2 μF and 1 kΩ + 10 μF

have been tested and identified as safe options.

VIN AS AN ADJUSTABLE INPUT

Due to the low leakage nature of the VIN pin, the ADM8612 or

ADM8615 can be used as devices with an adjustable threshold. Use

an external resistor divider circuit to program the desired voltage

monitoring threshold based on the VIN threshold, as shown in

Figure 27.

Figure 27. ADM8615 Typical Application Circuit

TRANSIENT IMMUNITY

To avoid unnecessary resets caused by fast power supply transients,

an input glitch filter is added to the VCC pin of the ADM8611/

ADM8613/ADM8614 and the VIN pin of the ADM8612 and

ADM8615 to filter out the transient glitches on these pins.

Figure 16 shows the comparator overdrive (that is, the maximum

magnitude of negative going pulses with respect to the typical

threshold) vs. the pulse duration without a reset.

RESET OUTPUT

The ADM8611/ADM8612/ADM8613/ADM8614/ADM8615

devices all have an active low, open-drain reset output. For the

ADM8611/ADM8613/ADM8614, the state of the output is

the ADM8612 and ADM8615, the output is guaranteed to be

When the monitored voltage falls below its associated threshold,

RESET is asserted within 23 μs to 26 μs (typical). Asserting RESET

this quickly ensures that the entire system can be reset at once

before any part of the system voltage falls below its recommended

operating voltage. This system reset can avoid dangerous and/or

erroneous operation of a microprocessor-based system.

MR

GND

ADM8611

RESET

GENERATOR

DEBOUNCE

RESET

VCC

GND

WD_DIS

WDI

VCC

ADM8613

RESET

GENERATOR

RESET

WATCHDOG

DETECTOR

MR

DEBOUNCE

GND

WDI

VCC

VIN

ADM8615

RESET

GENERATOR

RESET

WATCHDOG

DETECTOR

MR

DEBOUNCE

ADM8615

MICROPROCESSOR

VCC

VIN

GND

RESET

RESET

MR

WDI

OUTPUT

3.3V

12V