MAX6866UK30D5L+T Maxim Integrated, MAX6866UK30D5L+T Datasheet - Page 12

• Manufacturer Part Number: MAX6866UK30D5L+T
• Description: Supervisory Circuits Nanopower ?P Supervisory Circuits with Optional Manual Reset Watchdog Timer
• Manufacturer: Maxim Integrated
• Series: MAX6854, MAX6855, MAX6856, MAX6858, MAX6860, MAX6861, MAX6862, MAX6863, MAX6864, MAX6865, MAX6866, MAX6867, MAX6868, MAX6869r

Specifications of MAX6866UK30D5L+T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 1.2 V to 5.5 V
• Output Type: Active Low, Open Drain
• Manual Reset: Resettable
• Watchdog: Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 15 ms
• Supply Voltage - Max: 5.5 V
• Chip Enable Signals: No
• Maximum Power Dissipation: 571 mW
• Power Fail Detection: No
• Supply Current (typ): 7 uA
• Supply Voltage - Min: 1.1 V

In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX6854/
MAX6855/MAX6856/MAX6858/MAX6860–MAX6869 are
relatively immune to short-duration supply transients, or
glitches. The Maximum V
Threshold Overdrive graph in the Typical Operating
Characteristics shows this relationship.
The area below the curve of the graph is the region in
which these devices typically do not generate a reset
pulse. This graph was generated using a falling pulse
applied to V
threshold, V
threshold overdrive). As the magnitude of the transient
increases, the maximum allowable pulse width
decreases. Typically, a 100mV V
of 40µs or less does not cause a reset.
The open-drain RESET output can be used to interface
to a µP with other logic levels. As shown in Figure 4, the
open-drain output can be connected to voltages from 0
to 5.5V.
Generally, the pullup resistor connected to RESET con-
nects to the supply voltage that is being monitored at
the IC’s V
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Figure 4. Interfacing with Other Voltage Levels
12
______________________________________________________________________________________
Interfacing to Other Voltages for Logic
CC
MAX6856
MAX6860
MAX6863
MAX6866
MAX6869
TH
CC
GND
1.8V
V
CC
input. However, some systems use the
, and ending below this threshold (reset-
, starting 100mV above the actual reset
N
RESET
CC
Transient Duration vs. Reset
Transient Immunity
100kΩ
CC
RESET
transient duration
Compatibility
3.3V
GND
V
µP
CC
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by another supply voltage.
Keep in mind that as the supervisor’s V
so does the IC’s ability to sink current at RESET.
When V
capability declines drastically. The high-impedance
CMOS logic inputs connected to RESET can drift to
undetermined voltages. This presents no problems in
most applications, since most µPs and other circuitry
do not operate with V
In those applications where RESET must be valid down
to 0, add a pulldown resistor between RESET and GND
for the MAX6854/MAX6858/MAX6861/MAX6864/
MAX6867 push-pull outputs. The resistor sinks any stray
leakage currents, holding RESET low (Figure 5). Choose
a pulldown resistor that accommodates leakages, such
that RESET is not significantly loaded and is capable of
pulling to GND. The external pulldown cannot be used
with the open-drain reset outputs.
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
Figure 5. Ensuring
Ensuring a Valid RESET Down to V
CC
Watchdog Software Considerations
falls below 1.1V, RESET’s current-sinking
RESET Valid to V CC = Ground
MAX6854
MAX6858
MAX6861
MAX6864
MAX6867
GND
CC
below 1.1V.
RESET
V
CC
(Push-Pull RESET )
V
CC
2MΩ
CC
decreases,
CC
= 0V