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 active-low,
push-pull reset output. The MAX6413/MAX6416/
MAX6419 have an active-high, push-pull reset output
and the MAX6414/MAX6417/MAX6420 have an activelow, 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.
Features
o Monitor System Voltages from 1.6V to 5V
o Capacitor-Adjustable Reset Timeout Period
o Manual Reset Input
(MAX6412/MAX6413/MAX6414)
o Adjustable Reset Input Option (MAX6415–MAX6420)
o Dual-Voltage Monitoring
(MAX6418/MAX6419/MAX6420)
o Low Quiescent Current (1.7µA, typ)
o 3 RESET Output Options
Push-Pull RESET
Push-Pull RESET
Open-Drain RESET
o Guaranteed Reset Valid to VCC = 1V
o Power-Supply Transient Immunity
o Small SOT23-5 Packages
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6412UK_ _-T
-40°C to +125°C
5 SOT23
MAX6413UK_ _-T
-40°C to +125°C
5 SOT23
MAX6414UK_ _-T
-40°C to +125°C
5 SOT23
Automotive
MAX6414UK_ _/V+T*
-40°C to +125°C
5 SOT23
Medical Equipment
MAX6415UK-T
-40°C to +125°C
5 SOT23
Intelligent Instruments
MAX6416UK-T
-40°C to +125°C
5 SOT23
MAX6417UK-T
-40°C to +125°C
5 SOT23
MAX6418UK_ _-T
-40°C to +125°C
5 SOT23
MAX6419UK_ _-T
-40°C to +125°C
5 SOT23
MAX6420UK_ _-T
-40°C to +125°C
5 SOT23
Applications
Portable Equipment
Battery-Powered Computers/Controllers
Embedded Controllers
Critical µP Monitoring
Set-Top Boxes
Computers
Pin Configuration
TOP VIEW
RESET/RESET
1
GND 2
5
VCC
4
SRT
MAX6412–
MAX6420
RESET IN (MR) 3
SOT23-5
( ) FOR THE MAX6412/MAX6413/MAX6414.
MAX6420UK_ _/V-T
-40°C to +125°C
5 SOT23
Note: The MAX6412/MAX6413/MAX6414 and MAX6418/
MAX6419/MAX6420 are available with factory-set VCC reset
thresholds from 1.575V to 5.0V in approximately 0.1V increments. Insert the desired nominal reset threshold suffix (from
Table 1) into the blanks following the letters UK. There are 33
standard versions with a required order increment of 2500
pieces. Sample stock is generally held on standard versions
only (see Standard Versions Table). Required order increment is
10,000 pieces for nonstandard versions. Contact factory for
availability. All devices are available in tape-and-reel only.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
/V denotes an automotive qualified part.
*Future product—contact factory for availability.
Selector Guide and Typical Operating Circuit appear at end
of data sheet.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-2336; Rev 6; 3/14
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
Supply Voltage Range
Supply Current
VCC Reset Threshold Accuracy
Hysteresis
VCC to Reset Delay
Reset Timeout Period
VSRT Ramp Current
VSRT Ramp Threshold
SYMBOL
VCC
ICC
MIN
1.0
tRP
IRAMP
VTH-RAMP
RESET Output Leakage Current,
(Open-Drain)
RESET Output Voltage HIGH
2
VOH
ILKG
VOH
5.5
V
VCC ≤ 3.3V
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%
µA
V
4 x VTH
VCC falling at 1mV/µs
CSRT = 1500pF
mV
100
3.00
CSRT = 0F
4.375
µs
5.75
0.275
ms
VSRT = 0 to 0.65V; VCC = 1.6V to 5V
240
nA
VCC = 1.6V to 5V (VRAMP rising)
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
4.5
VRAMP falling threshold
VOL
MAX
2.6
VHYST
tRD
TYP
VCC ≤ 5.0V
VTH
RAMP Threshold Hysteresis
RESET Output Voltage LOW
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
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
CONDITIONS
MIN
TYP
MAX
VCC ≥ 1.8V, ISINK = 500µA
0.3
VCC ≥ 2.7V, ISINK = 1.2mA
0.3
VCC ≥ 4.5V, ISINK = 3.2mA
0.4
RESET IN Leakage Current
UNITS
V
10
RESET IN Threshold
VRST
VRST falling, VCC = 1.6V to 5.0V
VIL
VIL
V
2.4
V
0.3 x VCC
VCC < 4.0V
VIH
nA
1.255
0.8
VCC > 4.0V
VIH
MR Input
1.205
0.7 x VCC
MR Minimum Pulse Width
1
µs
MR Glitch Rejection
75
MR to RESET Delay
ns
20
MR Pullup Resistance
Pull up to VCC
12
ns
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.)
SUPPLY CURRENT vs.
TEMPERATURE
TA = +25°C
2
TA = -40°C
1
VCC = 5V
2.5
VCC = 3.3V
2.0
VCC = 1.8V
1.5
1.0
VCC = 1V
10,000
RESET TIMEOUT PERIOD (ms)
3
3.0
MAX6412-20 toc02
SUPPLY CURRENT (μA)
TA = +125°C
RESET TIMEOUT PERIOD vs. CSRT
3.5
SUPPLY CURRENT (μA)
MAX6412-20 toc01
4
MAX6412-20 toc03
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
1000
100
10
1
0.5
0
0
0
1
2
3
4
SUPPLY VOLTAGE (V)
Maxim Integrated
5
6
-50
-25
0
25
50
75
TEMPERATURE (°C)
100
125
0.1
0.001
0.01
0.1
1
10
100
1000
CSRT (nF)
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.)
RESET TIMEOUT PERIOD
vs. TEMPERATURE
4.20
4.15
4.10
CSRT = 0
550
500
MAX6412-20 toc05
4.25
600
RESET TIMEOUT PERIOD (μs)
CSRT = 1500pF
MAX6412-20 toc04
RESET TIMEOUT PERIOD (ms)
4.30
RESET TIMEOUT PERIOD
vs. TEMPERATURE
450
400
350
300
250
200
4.05
-50
-25
0
25
50
75
100
-50
125
-25
TEMPERATURE (°C)
RESET IN THRESHOLD VOLTAGE
vs. TEMPERATURE
100
1.270
1.265
1.260
125
MAX6412-20 toc07
175
150
TRANSIENT DURATION (μs)
1.275
25
75
50
TEMPERATURE (°C)
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX6412-20 toc06
RESET IN THRESHOLD VOLTAGE (V)
1.280
0
125
100
RESET OCCURS
ABOVE THE CURVE
75
50
1.255
25
1.250
0
VTH = 3.0V
-50
-25
0
25
50
75
TEMPERATURE (°C)
4
100
125
0
200
400
600
800
1000
RESET THRESHOLD OVERDRIVE (mV)
Maxim Integrated
MAX6412–MAX6420
Low-Power, Single/Dual-Voltage µP Reset Circuits
with Capacitor-Adjustable Reset Timeout Delay
Pin Description
PIN
MAX6412/
MAX6413/
MAX6414
1
2
MAX6415/
MAX6416/
MAX6417
1
2
MAX6418/
MAX6419/
MAX6420
NAME
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
FUNCTION
GND
Ground
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.
—
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) ✕ CSRT + 275µs with tRP in seconds and CSRT in Farads.
5
5
5
VCC
Supply Voltage and Input for Fixed-Threshold VCC Monitor
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 factorytrimmed 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.
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.
Reset Output
in a known state. The MAX6412–MAX6420 µP supervisory circuits provide the reset logic to prevent codeexecution 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.
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 Threshold
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
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 (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 = R2 x (VMON_TH/VRST - 1) (Ω)
R1
RESET IN
R2
VCC
MAX6415–
MAX6420
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
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
GND
RESET IN
VCC
R2
MAX6415
MAX6416
MAX6417
GND
VCC
MAX6415
MAX6416
MAX6417
SRT
SRT
VMON_TH = 1.26 x (R1 + R2)/R2
Figure 1. Calculating the Monitored Threshold Voltage (VMON_TH)
6
Figure 3. Monitoring External Voltages
Maxim Integrated
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
RL
RESET
CIRCUITRY
1.26V
(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 factory-trimmed 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:
CSRT = (tRP - 275µs) / (2.71 106)
where tRP is in seconds and CSRT is in Farads
Maxim Integrated
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 (
工商网监
湘ICP备2023018690号
