Datasheet

RESET
A μP’s reset input puts the μP in a known state.
The MAX16033–MAX16040 μP supervisory circuits
assert a reset to prevent code-execution errors during
power-up, power-down, and brownout conditions. RESET
asserts when V
CC
is below the reset threshold volt-
age and for at least 140ms (t
RP
) after V
CC
rises above
the reset threshold. RESET also asserts when MR
is low (MAX16033/MAX16037) or when RESETIN is
below 1.235V (MAX16036/MAX16040). The MAX16034/
MAX16038 watchdog function causes RESET to assert
in pulses following a watchdog timeout (Figure 2). The
MAX160_ _L devices provide push-pull RESET outputs.
The MAX160_ _P devices provide open-drain RESET
outputs.
Applications Information
Operation Without a Backup Power Source
The MAX16033–MAX16040 provide a battery-backup
function. If a backup power source is not used, connect
BATT to GND and OUT to V
CC
.
Using a Super Cap as a
Backup Power Source
Super caps are capacitors with extremely high capaci-
tance, such as 0.47F. Figure 5 shows two methods to
use a super cap as a backup power source. Connect the
super cap through a diode to the 3V input (Figure 5a)
or connect the super cap through a diode to 5V (Figure
5b), if a 5V supply is available. The 5V supply charges
the super cap to a voltage close to 5V, allowing a longer
backup period. Since V
BATT
can be higher than V
CC
while V
CC
is above the reset threshold voltage, there
are no special precautions required when using these μP
supervisors with a super cap.
Figure 5. Using a Super Cap as a Backup Source
(a)
3V OR 3.3V
0.47F
1N4148
V
CC
BATT
MAX16033
MAX16040
(b)
3V OR 3.3V
5V
0.47F
1N4148
V
CC
BATT
MAX16033
MAX16040
MAX16033–MAX16040 Low-Power Battery-Backup
Circuits in Small μDFN Packages
www.maximintegrated.com
Maxim Integrated │ 12