19-2210; Rev 1; 10/02
Dual-Voltage 碌P Supervisory Circuits
with Sequenced Reset Outputs
General Description
The MAX6391/MAX6392 microprocessor (碌P) supervisory
circuits provide sequenced logic reset outputs for multi-
component or dual-voltage systems. Each device can
monitor two supply voltages and time-sequence two reset
outputs to control the order in which system components
are turned on and off. The MAX6391/MAX6392 increase
system reliability and reduce circuit complexity and cost
compared to separate ICs or discrete components.
The MAX6391/MAX6392 monitor V
CC
as the master
reset supply. Both
RESET1
and
RESET2
are asserted
whenever V
CC
drops below the selected factory-fixed
reset threshold voltage.
RESET1
remains asserted as
long as V
CC
is below the threshold and deasserts
140ms (min) after V
CC
exceeds the thresholds.
RESET IN2 is monitored as the secondary reset supply
and is adjustable with an external resistive-divider net-
work.
RESET2
is asserted whenever either V
CC
or
RESET IN2 is below the selected thresholds.
RESET2
remains asserted 140ms (min) or a capacitor-
adjustable time period after V
CC
and RESET IN2
exceed their thresholds.
RESET2
is always deasserted
after
RESET1
during system power-up and is always
asserted before
RESET1
during power-down.
The MAX6391 includes two internal pullup resistors for
RESET1
and
RESET2
(the open-drain outputs can be
externally connected to the desired pullup voltages).
The MAX6392 includes an active-low manual reset
input (MR) that asserts both
RESET1
(push-pull) and
RESET2
(open drain).
The MAX6391/MAX6392 are available in small 8-pin
SOT23 packages and are specified over the -40擄C to
+85擄C extended temperature range.
Features
o
Preset VCC Reset Threshold Voltages from 1.58V
to 4.63V (master supply)
o
Customer-Adjustable RESET IN2 to Monitor
Voltages Down to 625mV (secondary supply)
o
Fixed (140ms min)
RESET1
Timeout
o
Fixed (140ms min) or Customer-Adjustable
RESET2
Timeout Period
o
Guaranteed Reset Valid to V
CC
= 1V
o
Active-Low Open-Drain Outputs or Push-
Pull/Open-Drain Combination
o
Internal Open-Drain Pullup Resistors (for external
V
OH
voltage connections)
o
Manual Reset Input (MAX6392 only)
o
Immune to Short Negative V
CC
Transients
o
15碌A(chǔ) Typical Supply Current
o
Few External Components
o
Small 8-Pin SOT23 Package
MAX6391/MAX6392
Ordering Information
PART*
MAX6391KA_
_-T
MAX6392KA_
_-T
TEMP RANGE
-40擄C to +85擄C
-40擄C to +85擄C
PIN-PACKAGE
SOT23-8
SOT23-8
Applications
Computers
Controllers
Critical 碌P Power Monitoring
Set-Top Boxes
Printers
Servers/Workstations
Industrial Equipment
Multivoltage Monitoring
*Insert
the desired suffix (see Selector Guide) into the blanks to
complete the part number. The MAX6391/MAX6392 require a
2.5k minimum order increment and are available in tape-and-
reel only. Samples are typically available for standard versions
(see Selector Guide for standard versions). Contact factory for
availability.
Pin Configurations
TOP VIEW
RESET IN2
1
V
CC
2
CSRT
3
8
7
R1
RESET1
R2
RESET2
MAX6391
6
5
GND
4
SOT23-8
Typical Operating Circuit appears at end of data sheet.
Pin Configurations continued at end of data sheet.
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________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim鈥檚 website at www.maxim-ic.com.
Maxim
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