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MAX6443US29L+T-MAX6444US16K/V+T
µP Reset Circuits with Long Manual Reset Setup Period
General DescriptionThe MAX6443–MAX6452 low-current microprocessor
reset circuits feature single or dual manual reset inputs
with an extended setup period. Because of the extended
setup period, short switch closures (nuisance resets) are
ignored.
On all devices, the reset output asserts when any of
the monitored supply voltages drops below its specified
threshold. The reset output remains asserted for the reset
timeout period (210ms typ) after all monitored supplies
exceed their reset thresholds. The reset output is one-
shot pulse asserted for the reset timeout period (140ms
min) when selected manual reset input(s) are held low for
an extended setup timeout period. These devices ignore
manual reset transitions of less than the extended setup
timeout period.
The MAX6443–MAX6448 are single fixed-voltage µP
supervisors. The MAX6443/MAX6444 have a single
extended manual reset input. The MAX6445/MAX6446
have two extended manual reset inputs. The MAX6447/
MAX6448 have one extended and one immediate manual
reset input.
The MAX6449–MAX6452 have one fixed-threshold µP
supervisor and one adjustable-threshold µP supervisor.
The MAX6449/MAX6450 have two delayed manual reset
inputs. The MAX6451/MAX6452 have one delayed and
one immediate manual reset input.
The MAX6443–MAX6452 have an active-low RESET with
push-pull or open-drain output logic options. These devic-
es, offered in small SOT packages, are fully guaranteed
over the extended temperature range (-40°C to +85°C).
Applications●Set-Top Boxes●Consumer Electronics●DVD Players●Cable/DSL Modems●MP3 Players●Industrial Equipment●Automotive●Medical Devices
Features●Single or Dual-Supply Voltage Monitors●Precision Factory-Set Reset Thresholds from
1.6V to 4.6V●Adjustable Threshold to Monitor Voltages Down to
0.63V (MAX6449–MAX6452)●Single or Dual Manual Reset Inputs with Extended
Setup Period●Optional Short Setup Time Manual Reset Input
(MAX6447/MAX6448 and MAX6451/MAX6452)●Immune to Short Voltage Transients●Low 6µA Supply Current●Guaranteed Valid Reset Down to VCC = 1.0V●Active-Low RESET (Push-Pull or Open-Drain)
Outputs●140ms (min) Reset Timeout Period●Small SOT143 and SOT23 Packages
Note: The first “_ _” is a placeholder for the threshold voltage level of the devices. A desired threshold level is set by the two-number
suffix found in Table 1. The third “_” is a placeholder for the manual
reset setup period of the devices. A desired setup period is set by
the letter suffix found in Table 2. All devices are available in tape-
and-reel only. There is a 2500-piece minimum order increment for
standard versions (Table 2). Sample stock is typically held on stan-
dard versions only. Nonstandard versions require a minimum order
increment of 10,000 pieces. Contact factory for availability.
Most devices are available in lead(Pb)-free packaging only. See
Ordering Information for devices available in both leaded and
lead(Pb)-free packaging.
/V denotes an automotive qualified part.
*Future product—contact factory for availability.
+Denotes Lead(Pb)-free packages and - denotes leaded packages.
For top mark information, please go to https://www.maximinte-
grated.com/en/design/packaging/topmark/.
PARTTEMP RANGEPIN-PACKAGE
MAX6443US_ _ _+T-40°C to +85°C4 SOT143
MAX6444US_ _ _+T-40°C to +85°C4 SOT143
MAX6444US_ _ _/V+T*-40°C to +85°C4 SOT143
VCC
MR1RESET
GND
MAX6443
MAX6444
SOT143TOP VIEW
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period Pin Configurations continued at end of data sheet.
Ordering Information continued at end of data sheet.
Pin Conigurations
Ordering Information
(All voltages referenced to GND.)
VCC ........................................................................-0.3V to +6V
Open-Drain RESET ................................................-0.3V to +6V
Push-Pull RESET ....................................-0.3V to (VCC + 0.3V)
MR1, MR2, MR2, RSTIN ........................................-0.3V to +6V
Input Current, All Pins ......................................................±20mA
Continuous Power Dissipation (TA = +70°C)4-Pin SOT143 (derate 4.0mW/°C above +70°C) ........320mW5-Pin SOT23 (derate 7.1mW/°C above +70°C) ..........571mW6-Pin SOT23 (derate 8.7mW/°C above +70°C) ..........696mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free...............................................................+260°C Containing lead ............................................................+240°C
(VCC = 1.0V to 5.5V, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOperating Voltage RangeVCC1.05.5V
VCC Supply CurrentICCVCC = 5.5V, no load720µAVCC = 3.6V, no load616
VCC Reset ThresholdVTH4.504.634.754.254.384.503.003.083.152.852.933.002.552.632.702.252.322.382.122.192.251.621.671.711.521.581.62
Reset Threshold Tempco60ppm/°C
Reset Threshold Hysteresis2 × VTHmV
RSTIN ThresholdVTH-RSTINMAX6449–MAX6452TA = 0°C to +85°C0.6150.6300.645VTA = -40°C to +85°C0.6100.650
RSTIN Threshold HysteresisVHYSTMAX6449–MAX64522.5mV
RSTIN Input CurrentIRSTINMAX6449–MAX6452-25+25nA
RSTIN to Reset Output DelayMAX6449–MAX6452, VRSTIN falling at
1mV/µs15µs
Reset Timeout PeriodtRP140210280ms
VCC to RESET Output DelaytRDVCC falling at 1mV/µs20µs
Manual Reset Minimum Setup
Period Pulse WidthtMR6.7210.0813.44L4.486.728.962.243.364.48
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
Electrical CharacteristicsStresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Absolute Maximum Ratings
(VCC = 1.0V to 5.5V, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
Electrical Characteristics (continued)
Note 1: Devices production tested at TA = +25°C. Overtemperature limits are guaranteed by design.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMR2 Minimum Setup Period
Pulse WidthMAX6447/MAX6448/MAX6451/MAX64521µs
MR2 Glitch RejectionMAX6447/MAX6448/MAX6451/MAX6452100ns
MR2 to RESET DelayMAX6447/MAX6448/MAX6451/MAX6452200ns
Manual Reset Timeout PeriodtMRP140210280ms
MR1 to VCC Pullup Impedance255075kW
MR2 to VCC Pullup ImpedanceMAX6445/MAX6446/MAX6449/MAX6450255075kW
RESET Output Low
(Open Drain or Push-Pull)VOL
VCC ≥ 1.00V, ISINK = 50µA, RESET
asserted0.3
VCC ≥ 1.20V, ISINK = 100µA, RESET
asserted0.3
VCC ≥ 2.55V, ISINK = 1.2mA, RESET
asserted0.3
VCC ≥ 4.25V, ISINK = 3.2mA, RESET
asserted0.4
RESET Output High
(Push-Pull)VOH
VCC ≥ 1.80V, ISOURCE = 200µA, RESET
deasserted0.8 × VCCVCC ≥ 3.15V, ISOURCE = 500µA, RESET
deasserted0.8 × VCC
VCC ≥ 4.75V, ISOURCE = 800µA, RESET
deasserted0.8 × VCC
RESET Open-Drain Leakage
CurrentILKGRESET deasserted1µA
MR1, MR2, MR2
Input Low VoltageVIL0.3 × VCCV
MR1, MR2, MR2
Input High VoltageVIH0.7 × VCCV
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
VCC TO RESET DELAYMAX6443/52 toc08
TIME (100µs/div)
VCC (100mV/div)
RESET
(2V/div)
VCC = 4.5V
VCC = 4.3V
VTH = 4.392V
MANUAL RESET TO RESET DELAY
(MAX6445L/MAX6446L/MAX6449L/MAX6450L)MAX6443/52 toc07
TIME (1s/div)
MR1
(5V/div)
MR2
(5V/div)
RESET
(5V/div)
VCC = 5V
RSTIN TO RESET DELAY
vs. TEMPERATURE (RSTIN FALLING)MAX6443/52 toc06
TEMPERATURE (°C)
RSTIN TO RESET DELAY (3510-15
RSTIN FALLING AT 1mV/µs
VCC TO RESET DELAY
vs. TEMPERATUREMAX6443/52 toc05
TEMPERATURE (°C)
TO RESET DELAY (3510-15
VCC = FALLING AT 1mV/µs
NORMALIZED VCC RESET THRESHOLD
vs. TEMPERATUREMAX6443/52 toc04
TEMPERATURE (°C)
NORMALIZED V
RESET THRESHOLD3510-15
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX6443/52 toc03
RESET THRESHOLD OVERDRIVE (mV)
TRANSIENT DURATION (
VTH = 4.4V
RESET OCCURS
ABOVE THE CURVE
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATUREMAX6443/52 toc02
TEMPERATURE (°C)
NORMALIZED TIMEOUT PERIOD3510-15
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6443/52 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
TA = +25°C
TA = -40°C
TA = +85°C
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
Typical Operating Characteristics
Detailed Description
Reset OutputThe reset output is typically connected to the reset
input of a microprocessor (µP). A µP’s reset input starts
or restarts the µP in a known state. The MAX6443–
MAX6452 µP supervisory circuits provide the reset
logic to prevent code-execution errors during power-
up, power-down and brownout conditions (see the
Typical Operating Circuit).
RESET changes from high to low whenever the moni-
tored voltages (RSTIN or VCC) drop below the reset
threshold voltages. Once VRSTIN and VCC exceed their
respective reset threshold voltages, RESET remains low
for the reset timeout period and then goes high. RESET
is one-shot pulsed whenever selected manual reset
inputs are asserted. RESET stays asserted for the nor-
mal reset timeout period (140ms min).
RESET is guaranteed to be in the proper output logic
state for VCC inputs ≥ 1V. For applications requiring valid
reset logic when VCC is less than 1V, see the Ensuring a
Valid RESET Output Down to VCC = 0V section.
PIN
NAMEFUNCTIONMAX6443
MAX6444
MAX6445
MAX6446
MAX6447
MAX6448
MAX6449
MAX6450
MAX6451
MAX64522222GNDGround1111RESET
Active-Low Push-Pull or Open-Drain Output. RESET
changes from high to low when VCC or RSTIN drops below
its selected reset threshold and remains low for the 210ms
reset timeout period after all monitored power-supply inputs
exceed their selected reset thresholds. RESET is one-shot
pulsed low for the reset timeout period (140ms min) after
selected manual reset inputs are asserted longer than the
specified setup period. For the open-drain output, use a
minimum 20kW pullup resistor to VCC.—3—3
MR1
Manual Reset Input, Active Low. Internal 50kW pullup to
VCC. Pull MR1 low for the typical input pulse width (tMR)
to one-shot pulse RESET for the reset timeout period.3—3—
Manual Reset Input, Active Low. Pull both MR1 and
MR2 low for the typical input pulse width (tMR) to one-
shot pulse RESET for the reset timeout period.4444VCCVCC Voltage Input. Power supply and input for the
primary microprocessor voltage reset monitor.5—6—MR2
Manual Reset Input, Active Low. Internal 50kW pullup to
VCC. Pull both MR1 and MR2 low for the typical input
pulse width (tMR) to one-shot pulse RESET for the reset
timeout period.—5—6MR2Manual Reset Input. Pull the MR2 high to immediately
one-shot pulse RESET for the reset timeout period.——55RSTIN
Reset Input. High-impedance input to the adjustable
reset comparator. Connect RSTIN to the center point
of an external resistor-divider to set the threshold of the
externally monitored voltage.
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
Pin Description
Manual Reset Input OptionsUnlike typical manual reset functions associated with
supervisors, each device in the MAX6443–MAX6452 fam-
ily includes at least one manual reset input, which must be
held logic-low for an extended setup period (tMR) before
the RESET output asserts. When valid manual reset input
conditions/setup periods are met, the RESET output is
one-shot pulse asserted low for a fixed reset timeout peri-
od (140ms min). Existing front-panel pushbutton switches
(i.e., power on/off, channel up/down, or mode select) can
be used to drive the manual reset inputs. The extended
manual reset setup period prevents nuisance system
resets during normal front-panel usage or resulting from
inadvertent short-term pushbutton closure.
The MAX6443/MAX6444, MAX6447/MAX6448, and
MAX6451/MAX6452 include a single manual reset
input with extended setup period (MR1). The MAX6445/
MAX6446 and MAX6449/MAX6450 include two manual
reset inputs (MR1 and MR2) with extended setup peri-
ods. For dual MR1, MR2 devices, both inputs must be
held low simultaneously for the extended setup period
(tMR) before the reset output is pulse asserted. The
dual extended setup provides greater protection from
nuisance resets. (For example, the user or service
technician is informed to simultaneously push both the
on/off button and the channel-select button for 6.72s
(L suffix) to reset the system.)
The MAX6443/MAX6452 RESET output is pulse asserted
once for the reset timeout period after each valid manual
reset input condition. At least one manual reset input
must be released (go high) and then be driven low for
the extended setup period before RESET asserts again.
Internal timing circuitry debounces low-to-high manual
reset logic transitions, so no external circuitry is required.
Figure 1 illustrates the single manual reset function of
the MAX6443/MAX6444 single-voltage monitors, and
Figure 2 represents the dual manual reset function of the
MAX6445/MAX6446 and MAX6449/MAX6450.
The MAX6447/MAX6448 and MAX6451/MAX6452
include both an extended setup period and immediate
setup period manual reset inputs. A low-to-high MR2
rising edge transition immediately pulse asserts the
RESET output for the reset timeout period (140ms min).
If the MAX6447/MAX6448 and MAX6451/MAX6452
MR2 input senses another rising edge before the end
of the 140ms timeout period (Figure 3), the internal
timer clears and begins counting again. If no rising
edges are detected within the 210ms timeout period,
RESET deasserts. The high-to-low transition on MR2
there are no false RESET assertions when MR2 is driven
from high to low (Figure 4). The MR2 input can be used
for system test purposes or smart-card-detect applica-
tions (see the Applications Information section).
Adjustable Input Voltage (RSTIN)The MAX6449–MAX6452 monitor the voltage on RSTIN
using an adjustable reset threshold set with an external
resistor voltage-divider (Figure 5). Use the following
formula to calculate the externally monitored voltage
(VMON-TH):
VMON-TH = VTH-RSTIN × (R1 + R2)/R2
where VMON-TH is the desired reset threshold voltage and
VTH-RSTIN is the reset input threshold (0.63V). Resistors
R1 and R2 can have very high values to minimize current
consumption because of low leakage currents. Set R2 to
some conveniently high value (250kW, for example), and
calculate R1 based on the desired reset threshold volt-
age, using the following formula:
R1 = R2 × (VMON-TH/VTH-RSTIN - 1) W
Figure 2. MAX6445/MAX6446/MAX6449/MAX6450 Manual
Reset Timing Diagram
Figure 1. MAX6443/MAX6444 Manual Reset Timing Diagram
MR2
RESET
MR1
210ms
tMR
RESET TIMEOUT PERIOD
210ms
MR1 SETUP PERIOD
tMR
MR1
RESET
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
Applications Information
Interrupt Before ResetTo minimize data loss and speed system recovery,
many applications interrupt the processor or reset only
portions of the system before a processor hard reset is
asserted. The extended setup time of the MAX6443–
MAX6452 manual reset inputs allows the same push-
button (connected to both the processor interrupt and
the extended MR1 input, as shown in Figure 6) to
control both the interrupt and hard reset functions. If the
pushbutton is closed for less than tMR, the processor
is only interrupted. If the system still does not respond
properly, the pushbutton (or two buttons for the dual
manual reset) can be closed for the full extended setup
period to hard reset the processor. If desired, connect
an LED to the RESET output to blink off (or on) for the
reset timeout period to signify when the pushbutton is
closed long enough for a hard reset (the same LED might
be used as the front-panel power-on display).
Smart Card Insertion/RemovalThe MAX6447/MAX6448/MAX6451/MAX6452 dual man-
ual resets are useful in applications in which both an
extended and immediate setup periods are needed.
Figure 7 illustrates the insertion and removal of a smart
card. MR1 monitors a front-panel pushbutton. When
closed for tMR, RESET one-shot pulses low for 140ms
min. Because MR1 is internally pulled to VCC through a
50kW resistor, the front-panel switch can be connected
to a microprocessor for general-purpose I/O control.
MR2 monitors a switch to detect when a smart card is
inserted. When the switch is closed high (card inserted),
Figure 6. Interrupt Before Reset Application Circuit
Figure 5. Calculating the Monitored Threshold Voltages
Figure 4. MAX6447/MAX6448/MAX6451/MAX6452 MR2
Deassertion Debouncing Timing Diagram
Figure 3. MAX6447/MAX6448/MAX6451/MAX6452 MR2
Assertion DebouncingTiming Diagram
MAX6443LµP
VCCRESET
VCC
+3.3V
NMI
LED
RESET
MR1GND
PUSHBUTTON SWITCH:
CLOSE FOR < 4.48s
FOR SYSTEM INTERRUPT;
CLOSE FOR > 6.72s FOR
SYSTEM RESET
MAX6449
MAX6451
RSTINVCC
RESETGND
VMON_TH = 0.63 x (R1 + R2) / R2
VMON_TH VCC
MR2
RESET
210ms
DEBOUNCING PERIOD
210ms
TIMEOUT PERIOD
POSITIVE EDGE
NO RESET
OUTPUT
ASSERTED
MR2
RESET
t = 210ms
t < 210ms
COUNTER RESET
MAX6443–MAX6452µP Reset Circuits with Long Manual Reset
Setup Period
