MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
General Description
The MAX6412–MAX6420 low-power microprocessor
supervisor circuits monitor system voltages from 1.6V to
5V. These devices are designed to assert a reset signal
whenever the VCC supply voltage or RESET IN falls
below its reset threshold or the manual reset input is
asserted. The reset output remains asserted for the reset
timeout period after VCC and RESET IN rise above the
reset threshold and the manual reset input is deasserted.
The reset timeout is externally set by a capacitor to provide
more flexibility.
The MAX6412/MAX6413/MAX6414 feature fixed thresholds
from 1.575V to 5V in approximately 100mV increments
and a manual reset input. The MAX6415/MAX6416/
MAX6417 are offered with an adjustable reset input that
can monitor voltages down to 1.26V and the MAX6418/
MAX6419/MAX6420 are offered with one fixed input and
one adjustable input to monitor dual-voltage systems.
The MAX6412/MAX6415/MAX6418 have an activelow, push-pull reset output. The MAX6413/MAX6416/
MAX6419 have an active-high, push-pull reset output and
the MAX6414/MAX6417/MAX6420 have an active-low,
open-drain reset output. All of these devices are offered
in a SOT23-5 package and are fully specified from -40°C
to +125°C.
Pin Configuration
TOP VIEW
RESET/RESET 1
GND 2
VCC
4
SRT
MAX6412
MAX6420
RESET IN (MR) 3
SOT23-5
( ) FOR THE MAX6412/MAX6413/MAX6414.
19-2336; Rev 8; 3/18
5
Benefits and Features
●● Monitor System Voltages from 1.6V to 5V
●● Capacitor-Adjustable Reset Timeout Period
●● Manual Reset Input
(MAX6412/MAX6413/MAX6414)
●● Adjustable Reset Input Option (MAX6415–MAX6420)
●● Dual-Voltage Monitoring
(MAX6418/MAX6419/MAX6420)
●● Low Quiescent Current (1.7μA, typ)
●● 3 RESET Output Options
• Push-Pull RESET
• Push-Pull RESET
• Open-Drain RESET
●● Guaranteed Reset Valid to VCC = 1V
●● Power-Supply Transient Immunity
●● Small SOT23-5 Packages
●● AEC-Q100 Qualified, Refer to Ordering Information
for Specific /V Parts
Applications
●●
●●
●●
●●
●●
●●
●●
●●
●●
Automotive
Medical Equipment
Intelligent Instruments
Portable Equipment
Battery-Powered Computers/Controllers
Embedded Controllers
Critical μP Monitoring
Set-Top Boxes
Computers
Selector Guide, Ordering Information, and Typical
Operating Circuit appear at end of data sheet.
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Absolute Maximum Ratings
All Voltages Referenced to GND
VCC........................................................................-0.3V to +6.0V
SRT, MR, RESET IN................................. -0.3V to (VCC + 0.3V)
RESET, RESET (Push-Pull)...................... -0.3V to (VCC + 0.3V)
RESET (Open-Drain)............................................-0.3V to +6.0V
Input Current (All Pins)......................................................±20mA
Output Current (RESET, RESET).....................................±20mA
Continuous Power Dissipation (TA = +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)...........571mW
Operating Temperature Range.......................... -40°C to +125°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 packages...............................................+260°C
Packages containing lead (Pb).....................................+240°C
Stresses 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.
Electrical Characteristics
(VCC = 1V to 5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = 5V and TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Supply Voltage Range
VCC
Supply Current
ICC
VCC Reset Threshold
Accuracy
Hysteresis
VTH
tRD
Reset Timeout Period
tRP
VSRT Ramp Threshold
RAMP Threshold Hysteresis
RESET Output Voltage LOW
MIN
IRAMP
TYP
1.0
VOH
RESET Output Leakage
Current, (Open-Drain)
ILKG
RESET Output Voltage HIGH
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VOH
5.5
V
2.6
4.5
2
3.5
VCC ≤ 2.0V
1.7
2.5
TA = +25°C
VTH 1.25%
VTH +
1.25%
TA = -40°C to +125°C
VTH 2.5%
VTH +
2.5%
V
mV
100
µs
VCC falling at 1mV/µs
CSRT = 1500pF
µA
4 x VTH
3.00
CSRT = 0F
4.375
5.75
0.275
VSRT = 0 to 0.65V; VCC = 1.6V to 5V
ms
240
nA
0.65
V
33
mV
VCC ≥ 1.0V, ISINK = 50µA
0.3
VCC ≥ 2.7V, ISINK = 1.2mA
0.3
VCC ≥ 4.5V, ISINK = 3.2mA
RESET Output Voltage HIGH,
(Push-Pull)
UNITS
VCC ≤ 3.3V
VTH-RAMP VCC = 1.6V to 5V (VRAMP rising)
VRAMP falling threshold
VOL
MAX
VCC ≤ 5.0V
VHYST
VCC to Reset Delay
VSRT Ramp Current
CONDITIONS
V
0.4
VCC ≥ 1.8V, ISOURCE = 200µA
0.8 x VCC
VCC ≥ 2.25V, ISOURCE = 500µA
0.8 x VCC
VCC ≥ 4.5V, ISOURCE = 800µA
0.8 x VCC
VCC > VTH, reset not asserted
V
1.0
VCC ≥ 1.0V, ISOURCE = 1µA
0.8 x VCC
VCC ≥ 1.8V, ISOURCE = 150µA
0.8 x VCC
VCC ≥ 2.7V, ISOURCE = 500µA
0.8 x VCC
VCC ≥ 4.5V, ISOURCE = 800µA
0.8 x VCC
µA
V
Maxim Integrated │ 2
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Electrical Characteristics (continued)
(VCC = 1V to 5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = 5V and TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
RESET Output Voltage LOW
VOL
VRST
VIL
TYP
MAX
0.3
VCC ≥ 4.5V, ISINK = 3.2mA
0.4
VIL
V
10
VRST falling, VCC = 1.6V to 5.0V
1.205
nA
1.255
V
0.8
2.4
V
0.3 x VCC
VCC < 4.0V
VIH
UNITS
0.3
VCC > 4.0V
VIH
MR Input
MIN
VCC ≥ 2.7V, ISINK = 1.2mA
RESET IN Leakage Current
RESET IN Threshold
CONDITIONS
VCC ≥ 1.8V, ISINK = 500µA
0.7 x VCC
MR Minimum Pulse Width
1
µs
MR Glitch Rejection
75
ns
MR to RESET Delay
20
ns
MR Pullup Resistance
Pull up to VCC
12
20
28
kΩ
Note 1: Devices production tested at TA = +25°C. Over temperature limits are guaranteed by design.
Typical Operating Characteristics
(VCC = 5V, CSRT = 1500pF, TA = +25°C, unless otherwise noted.)
TA = +25°C
2
TA = -40°C
1
3.0
MAX6412-20 toc02
TA = +125°C
3
3.5
SUPPLY CURRENT (µA)
MAX6412-20 toc01
SUPPLY CURRENT (µA)
4
VCC = 5V
2.5
VCC = 3.3V
2.0
VCC = 1.8V
1.5
1.0
VCC = 1V
0.5
0
0
1
2
3
4
SUPPLY VOLTAGE (V)
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5
6
0
-50
-25
0
25
50
75
TEMPERATURE (°C)
100
125
10,000
RESET TIMEOUT PERIOD vs. CSRT
MAX6412-20 toc03
SUPPLY CURRENT vs.
TEMPERATURE
RESET TIMEOUT PERIOD (ms)
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
1000
100
10
1
0.1
0.001
0.01
0.1
1
10
100
1000
CSRT (nF)
Maxim Integrated │ 3
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Typical Operating Characteristics (continued)
(VCC = 5V, CSRT = 1500pF, TA = +25°C, unless otherwise noted.)
4.20
4.15
4.10
500
450
400
350
300
250
-50
200
TEMPERATURE (C)
25
75
50
TEMPERATURE (°C)
RESET IN THRESHOLD VOLTAGE
vs. TEMPERATURE
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
-25
0
25
50
75
100
125
MAX6412-20 toc06
1.280
RESET IN THRESHOLD VOLTAGE (V)
CSRT = 0
550
1.275
1.270
1.265
1.260
175
25
50
75
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100
125
125
RESET OCCURS
ABOVE THE CURVE
75
50
0
TEMPERATURE (°C)
100
100
1.250
0
0
125
25
-25
-25
150
1.255
-50
-50
MAX6412-20 toc07
4.05
MAX6412-20 toc05
4.25
RESET TIMEOUT PERIOD
vs. TEMPERATURE
600
RESET TIMEOUT PERIOD (µs)
CSRT = 1500pF
TRANSIENT DURATION (µs)
RESET TIMEOUT PERIOD (ms)
4.30
MAX6412-20 toc04
RESET TIMEOUT PERIOD
vs. TEMPERATURE
VTH = 3.0V
0
200
400
600
800
1000
RESET THRESHOLD OVERDRIVE (mV)
Maxim Integrated │ 4
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Pin Description
PIN
MAX6412/
MAX6413/
MAX6414
MAX6415/
MAX6416/
MAX6417
1
MAX6418/
MAX6419/
MAX6420
1
NAME
FUNCTION
RESET
RESET changes from high to low whenever VCC or RESET IN drops below the
selected reset threshold voltage (VTH or VRESET IN, respectively) or manual
reset is pulled low. RESET remains low for the reset timeout period after all
reset conditions are deasserted and then goes high.
RESET
RESET changes from low to high whenever the VCC or RESET IN drops below
the selected reset threshold voltage (VTH or VRESET IN) or manual reset is
pulled low. RESET remains high for the reset timeout period after all reset
conditions are deasserted and then goes low.
1
2
2
2
GND
Ground
—
3
3
RESET
IN
3
—
—
MR
Manual Reset Input. Pull this pin low to manually reset the device. Reset
remains asserted for the reset timeout period after MR is released.
4
4
4
SRT
Set Reset Timeout Input. Connect a capacitor between SRT and ground to
set the timeout period. Determine the period as follows:
tRP = (2.71 x 106) x CSRT + 275µs with tRP in seconds and CSRT in Farads.
5
5
5
VCC
Supply Voltage and Input for Fixed-Threshold VCC Monitor
Reset Input. High-impedance input to the adjustable reset comparator. Connect
RESET IN to the center point of an external resistor-divider network to set the
threshold of the externally monitored voltage. See Reset Threshold section.
Detailed Description
The MAX6412–MAX6420 low-power microprocessor (μP)
supervisory circuits provide maximum adjustability for
supply-voltage monitoring and reset functionality. In addition, the MAX6412–MAX6420 reset timeout period is
adjustable using an external capacitor.
The MAX6412/MAX6413/MAX6414 have factory-trimmed
reset threshold voltages in approximately 100mV increments from 1.575V to 5.0V with a manual reset input. The
MAX6415/MAX6416/MAX6417 contain a reset threshold
that can be adjusted to any voltage above 1.26V using
external resistors. The MAX6418/MAX6419/MAX6420
offer both a factory-trimmed reset threshold and an adjustable reset threshold input for dual-voltage monitoring.
known state. The MAX6412–MAX6420 μP supervisory
circuits provide the reset logic to prevent code-execution
errors during power-up, power-down, and brownout conditions (see Typical Operating Circuit).
For the MAX6413, MAX6416, and MAX6419, RESET
changes from low to high whenever VCC or RESET IN
drops below the reset threshold voltages. Once RESET
IN and VCC exceed their respective reset threshold
voltage(s), RESET remains high for the reset timeout
period, then goes low.
On power-up, once VCC reaches 1V, RESET is guaranteed to be a logic high. For applications requiring valid
reset logic when VCC is less than 1V, see the section
Ensuring a Valid RESET/RESET Output Down to VCC = 0V.
A reset signal is asserted when VCC and/or RESET IN
falls below the preset values or when MR is asserted.
The reset remains asserted for an externally programmed
interval after VCC and/or RESET IN has risen above the
reset threshold or MR is deasserted.
The active-low RESET output of the remaining supervisors is the inverse of the MAX6413, MAX6416, and
MAX6419 active-high RESET output and is guaranteed
valid for VCC ≥ 1V.
Reset Output
The MAX6415–MAX6420 monitor the voltage on RESET
IN with an external resistor voltage-divider (Figure 1).
The reset output is typically connected to the reset input
of a μP. A μP’s reset input starts or restarts the μP in a
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Reset Threshold
Maxim Integrated │ 5
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Use the following formula to calculate the externally monitored voltage (VMON_TH):
VCC
VMON_TH = VRST x (R1 + R2)/R2
where VMON_TH is the desired reset threshold voltage
and VRST is the reset input threshold (1.26V). Resistors
R1 and R2 can have very high values to minimize current
consumption due to low leakage currents. Set R2 to some
conveniently high value (1MΩ, for example) and calculate
R1 based on the desired monitored voltage, using the
following formula:
R1
RESET IN
R2
R1 = R2 x (VMON_TH/VRST - 1) (Ω)
GND
Manual Reset Input
(MAX6412/MAX6413/MAX6414)
Many μP-based products require manual reset capability, allowing the operator, a technician, or external logic
circuitry to initiate a reset. A logic low on MR asserts reset.
Reset remains asserted while MR is low and for the reset
timeout period after MR returns high.
The MR has an internal 20kΩ pullup resistor so it can be
left open if not used. Connect a normally open momentary
switch from MR to ground to create a manual reset function (external debounce circuitry is not required for long
reset timeout periods).
A manual reset option can easily be implemented with
the MAX6415–MAX6420 by connecting a normally open
momentary switch in parallel with R2 (Figure 2). When
the switch is closed, the voltage on RESET IN goes to
zero, initiating a reset. Similar to the MAX6412/MAX6413/
MAX6414 manual reset, reset remains asserted while the
switch is closed and for the reset timeout period after the
switch is opened.
VMON_TH
MAX6415
MAX6420
SRT
Figure 2. Adding an External Manual Reset Function to the
MAX6415–MAX6420
Monitoring Voltages Other than VCC
(MAX6415/MAX6416/MAX6417)
The MAX6415/MAX6416/MAX6417 contain an adjustable reset threshold input. These devices can be used
to monitor voltages other than VCC. Calculate VMON_TH
as shown in the Reset Threshold section. (See Figure 3.)
VMON_TH
VCC
R1
R1
RESET IN
R2
VCC
RESET IN
VCC
R2
MAX6415
MAX6416
GND MAX6417
SRT
VMON_TH = 1.26 x (R1 + R2)/R2
Figure 1. Calculating the Monitored Threshold Voltage (VMON_TH)
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VCC
MAX6415
MAX6416
GND MAX6417
SRT
Figure 3. Monitoring External Voltages
Maxim Integrated │ 6
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage μP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
VMON_TH
VCC
MAX6420
ONLY
VCC
LASER-TRIMMED
RESISTORS
1.26V
RL
RESET
CIRCUITRY
(RESET)
RESET
µP
R1
R2
RESET IN
GND
SRT
MAX6418
MAX6419
MAX6420
CSRT
Figure 4. MAX6418/MAX6419/MAX6420 Monitoring Two Voltages
Dual-Voltage Monitoring
(MAX6418/MAX6419/MAX6420)
The MAX6418/MAX6419/MAX6420 contain both factorytrimmed threshold voltages and an adjustable reset
threshold input, allowing the monitoring of two voltages,
VCC and VMON_TH (see Figure 4). Reset is asserted
when either of the voltages falls below its respective
threshold voltage.
Application Information
Selecting a Reset Capacitor
The reset timeout period is adjustable to accommodate a
variety of μP applications. Adjust the reset timeout period
(tRP) by connecting a capacitor (CSRT) between SRT and
ground. Calculate the reset timeout capacitor as follows:
The reset delay time is set by a current/capacitor-controlled ramp compared to an internal 0.65V reference. An
internal 240nA ramp current source charges the external
capacitor. The charge to the capacitor is cleared when a
reset condition is detected. Once the reset condition is
removed, the voltage on the capacitor ramps according to
the formula: dV/dt = I/C. The CSRT capacitor must ramp to
0.65V to deassert the reset. CSRT must be a low-leakage
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