MAX6391 Datasheet, PDF (1/9 Pages) Maxim Integrated Products – Dual-Voltage uP Supervisory Circuits with Sequenced Reset Outputs

19-2210; Rev 1; 10/02
Dual-Voltage µP Supervisory Circuits
with Sequenced Reset Outputs
General Description
The MAX6391/MAX6392 microprocessor (µP) 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°C to
+85°C extended temperature range.
Applications
Computers
Controllers
Critical µP Power Monitoring
Set-Top Boxes
Printers
Servers/Workstations
Industrial Equipment
Multivoltage Monitoring
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 15µA Typical Supply Current
o Few External Components
o Small 8-Pin SOT23 Package
Ordering Information
PART*
MAX6391KA_ _-T
MAX6392KA_ _-T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
SOT23-8
SOT23-8
*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
GND 4
MAX6391
8 R1
7 RESET1
6 R2
5 RESET2
Typical Operating Circuit appears at end of data sheet.
SOT23-8
Pin Configurations continued at end of data sheet.
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