MAX6362 MAXIM [Maxim Integrated Products], MAX6362 Datasheet - Page 6

• Manufacturer Part Number: MAX6362
• Description: SOT23, Low-Power ?P Supervisory Circuits with Battery Backup
• Manufacturer: MAXIM [Maxim Integrated Products]

In a brownout or power failure, it may be necessary to
preserve the contents of the RAM. With a backup bat-
tery installed at BATT, the MAX6361/MAX6363/
MAX6364 automatically switch the RAM to backup
power when V
output that goes high when in battery-backup mode.
These devices require two conditions before switching
to battery-backup mode:
1) V
2) V
Many µP-based products require manual reset capabili-
ty, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. For the MAX6361, a logic
low on MR asserts reset. Reset remains asserted while
MR is low, and for a minimum of 150ms (t
returns high. MR has an internal 20kΩ pull-up resistor.
This input can be driven with TTL/CMOS logic levels or
with open-drain/collector outputs. Connect a normally
open momentary switch from MR to GND to create a
manual reset function; external debounce circuitry is not
required. If MR is driven from long cables or the device
is used in a noisy environment, connect a 0.1µF capaci-
tor from MR to GND to provide additional noise immunity.
RESET IN is compared to an internal 1.235V reference.
If the voltage at RESET IN is less than 1.235V, reset is
asserted. The RESET IN comparator may be used as
an undervoltage detector to signal a failing power sup-
ply. It can also be used as a secondary power-supply
reset monitor.
A µP’s reset input starts the µP in a known state. The
MAX6361/MAX6363/MAX6364 µP supervisory circuits
assert a reset to prevent code-execution errors during
power-up, power-down, and brownout conditions.
RESET is guaranteed to be a logic low or high depend-
ing on the device chosen (see Ordering Information).
RESET or RESET asserts when V
threshold and for at least 150ms (t
above the reset threshold. RESET or RESET also
asserts when MR is low (MAX6361) and when RESET
IN is less than 1.235V (MAX6364).
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup
6
of the inputs and outputs in battery-backup mode.
The device will not power up if the only voltage
source is on BATT. OUT will only power up from
V
_______________________________________________________________________________________
CC
CC
CC
must be below the reset threshold.
at startup.
must be below V
Manual Reset Input (MAX6361 only)
CC
falls. The MAX6363 has a BATT ON
Backup-Battery Switchover
Reset In (MAX6364 only)
BATT
. Table 2 lists the status
CC
RP
is below the reset
Reset Output
) after V
RP
CC
) after it
rises
The MAX6361/MAX6363/MAX6364 were designed for
battery-backed applications. If a backup battery is not
used, connect V
If BATT is decoupled with a 0.1µF capacitor to ground,
the backup power source can be removed while V
remains valid without danger of triggering a reset pulse.
The device does not enter battery-backup mode when
V
These supervisors are relatively immune to short-dura-
tion, negative-going V
when V
desirable.
The Typical Operating Characteristics section shows a
graph of Maximum Transient Duration vs. Reset
Threshold Overdrive for which reset is not asserted.
The graph was produced using negative-going V
pulses, starting at V
threshold by the magnitude indicated (reset threshold
overdrive). The graph shows the maximum pulse width
Table 1. Reset Threshold Ranges
Table 2. Input and Output Status in
Battery-Backup Mode
CC
RESET/RESET
MR, RESET IN
SUFFIX
stays above the reset threshold voltage.
BATT ON
46
44
31
29
26
23
BATT
OUT
V
CC
PIN
CC
experiences only small glitches is usually not
Negative-Going V
Applications Information
CC
Replacing the Backup Battery
Disconnected from OUT
Connected to BATT
Connected to OUT. Current drawn from
the battery is less than 1µA (at V
2.8V, excluding I
Asserted
High state
Inputs ignored
Operation Without a Backup
4.50
4.25
3.00
2.85
2.55
2.25
RESET THRESHOLD RANGES (V)
MIN
to OUT and connect BATT to GND.
CC
CC
and ending below the reset
transients. Resetting the µP
STATUS
TYP
4.63
4.38
3.08
2.93
2.63
2.32
OUT
) when V
CC
Power Source
Transients
CC
MAX
4.75
4.50
3.15
3.00
2.70
2.38
BATT
= 0.
=
CC
CC