MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
General Description
The MAX6701–MAX6708 microprocessor (µP) supervisory
circuits reduce the complexity and components required
to monitor power-supply functions in µP systems. These
devices significantly improve system reliability and accuracy compared to separate ICs or discrete components.
The MAX6701−MAX6708 family provides four functions: a reset output during power-up, power-down, and
brownout conditions; an independent watchdog output
that goes low if the watchdog input has not been toggled
within 1.6s; a 0.62V threshold detector for power-fail
warning; and an active-low manual reset input.
The MAX6701–MAX6708 family offers several pinout
options to accommodate a variety of multivoltage microprocessor supervision applications.
The MAX6701(A)/MAX6702(A)/MAX6703(A) monitor
three supply voltages (one fixed threshold and two
adjustable) to drive a single reset output and include a
manual reset input and a watchdog timer with an independent output. The MAX6704 monitors a single-supply
voltage to drive complementary reset outputs and
includes an independent adjustable power-fail-in/powerfail-out comparator, a manual reset input, and a resetbased watchdog timer. The MAX6705(A)/MAX6706(A)/
MAX6707(A) monitor a single-supply voltage to drive
a single reset output and include an independent
adjustable power-fail-in/power-fail-out comparator, a
manual reset input, and a watchdog timer with an independent output. The MAX6708 is the same as the
MAX6704 but without the watchdog timer function.
See the Detailed Description for differences between
non-A and A versions.
Applications
●● Computers
●● Controllers
●● Intelligent Instruments
●● Critical µP Power
Monitoring
●● White Goods
●● Networking
●● Telecommunications
Typical Operating Circuit and Selector Guide appear at
end of data sheet.
Features
●● Small 8-Pin SOT23 Package
●● Precision Monitoring of +5.0V, +3.3V, +3.0V, +2.5V
Supply Voltages
●● 140ms Reset Timeout Delay
●● Power-Fail Input with Independent Output; Monitor
Inputs Down to 0.62V (MAX6704−MAX6708)
●● Dual Adjustable Reset Input for Triple-Voltage
Monitoring (MAX6701(A)/MAX6702(A)/MAX6703(A))
●● 1.6s Watchdog Timeout Period
(MAX6701(A)−MAX6707(A))
●● Independent Watchdog Output
(MAX6701(A)/MAX6702(A)/MAX6703(A)/
MAX6705(A)/MAX6706(A)/MAX6707(A))
●● Manual Reset Input
●● Four Reset Output Stage Options
Active Low Push-Pull (MAX6701(A), MAX6705(A))
Active Low Open Drain (MAX6703(A), MAX6707(A))
Active High Push-Pull (MAX6702(A), MAX6706(A))
Dual Active Low/High Push-Pull (MAX6704,
MAX6708)
●● Guaranteed Reset Valid to VCC = 1V
●● Immune to Short Falling VCC Transients
●● Low Cost, Few External Components
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6701_KA-T
-40°C to +125°C
8 SOT23
MAX6701A_KA-T
-40°C to +125°C
8 SOT23
Insert the desired suffix letter (from the Threshold Suffix Guide
table) into the blank to complete the part number. All devices
must be ordered in increments of 2500 pieces. Sample stock is
typically held on standard versions only. Contact factory for
availability.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Ordering Information continued at end of data sheet.
Pin Configurations
TOP VIEW
1
8
VCC 2
7
RESET (RESET)
6
WDI
5
RST_IN2
MR
GND
3
MAX6701(A)
MAX6702(A)
MAX6703(A)
RST_IN1 4
( ) ARE FOR MAX6702(A) ONLY.
WDO
SOT23
Pin Configurations continued at end of data sheet.
19-1952; Rev 4; 5/14
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Absolute Maximum Ratings
VCC........................................................................-0.3V to +6.0V
Open-Drain RESET, WDO, PFO .........................-0.3V to +6.0V
Push-Pull RESET, RESET, WDO, PFO.... -0.3V to (VCC + 0.3V)
MR, WDI, PFI, RST_IN1, RST_IN2.......... -0.3V to (VCC + 0.3V)
Input Current (VCC).............................................................20mA
Output Current (O, WDO)...................................................20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin SOT23 (derate 8.9mW/°C above +70°C)...........714mW
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
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 = +4.25V to +5.5V for L/M versions, VCC = +2.55V to +3.6V for the T/S/R versions, VCC = +2.1V to +2.75V for the Z/Y versions.
TA = -40°C to +125°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Operating Voltage Range
VCC
Supply Current
MR Unconnected
ICC
CONDITIONS
1.0
5.5
1.2
5.5
VCC < 5.5V, no load
12
25
VCC < 3.6V, no load
9
20
VCC < 3.6V, no load (MAX6708 only)
6
20
4.63
4.75
MAX670_T/MAX670_AT
MAX670_S/MAX670_AS
MAX670_R/MAX670_AR
MAX670_Z/MAX670_AZ
MAX670_Y/MAX670_AY
Reset Threshold
Temperature Coefficient
Reset Timeout Period
TA = -40°C to +85°C
4.50
TA = -40°C to +125°C
4.47
TA = -40°C to +85°C
4.25
TA = -40°C to +125°C
4.22
TA = -40°C to +85°C
3.00
TA = -40°C to +125°C
2.97
TA = -40°C to +85°C
2.85
TA = -40°C to +125°C
2.83
TA = -40°C to +85°C
2.55
TA = -40°C to +125°C
2.53
TA = -40°C to +85°C
2.25
TA = -40°C to +125°C
2.24
TA = -40°C to +85°C
2.12
TA = -40°C to +125°C
2.11
∆VTH
VCC to Reset Output Delay
VCC falling at 10mV/µs
tRP
TA = -40°C to +85°C
140
TA = -40°C to +125°C
120
VCC Falling to WDO Delay
MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/
MAX6706(A)/MAX6707(A)
PFI, RST_IN1, RST_IN2
Threshold
VCC = 1.8V to 5.5V
PFI Hysteresis
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MAX
TA = -40°C to +125°C
MAX670_M/MAX670_AM
VTH
TYP
TA = 0°C to +125°C
MAX670_L/MAX670_AL
VCC Reset Threshold
(VCC falling)
MIN
602
TA = -40°C to +125°C
593
V
µA
4.78
4.38
4.50
4.53
3.08
3.15
3.17
2.93
3.00
3.02
2.63
V
2.70
2.72
2.32
2.38
2.40
2.19
2.25
2.27
60
ppm/°C
12
µs
200
280
300
5
TA = -40°C to +85°C
UNITS
618
µs
634
642
6
ms
mV
mV
Maxim Integrated │ 2
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Electrical Characteristics (continued)
(VCC = +4.25V to +5.5V for L/M versions, VCC = +2.55V to +3.6V for the T/S/R versions, VCC = +2.1V to +2.75V for the Z/Y versions.
TA = -40°C to +125°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
PFI, RST_IN1, RST_IN2
Leakage Current
PFI to PFO Delay
MR Input Voltage
CONDITIONS
(Note 2)
MIN
TYP
TA = -40°C to +85°C
-50
+50
TA = -40°C to +125°C
-200
+200
tPF
1
VIL
VIH
0.7 x VCC
1
MR Glitch Rejection
tMD
MAX6701(A)/MAX6702(A)/MAX6703(A)/
MAX6705(A)/MAX6706(A)/MAX6707(A)
VCC Rising to WDO Delay
MR Pullup Resistance
Watchdog Timeout Period
tWD
WDI Pulse Width
tWDI
WDI Input Voltage
WDI Input Current
RESET, WDO Output Low
(Push-Pull or Open Drain)
PFO Output Low
(Push-Pull or Open Drain)
IWDI
VOL
VOL
RESET, WDO, PFO Output
High (Push-Pull Only)
VOH
RESET, WDO, PFO
Output Open-Drain
Leakage Current
ILKG
RESET Output High
(Push-Pull Only)
RESET Output Low
(Push-Pull Only)
VOH
VOL
ns
200
ns
100
ns
TA = -40°C to +85°C
1.12
1.6
TA = -40°C to +125°C
0.96
75
2.4
2.52
50
0.7 x VCC
VWDI = 0V or VCC
-1
+1
VCC ≥ 1.0V, ISINK = 50µA, output asserted
(TA = 0°C to +125°C)
0.3
VCC ≥ 1.2V, ISINK = 100µA, output asserted
0.3
VCC ≥ 4.25V, ISINK = 3.2mA, output asserted
0.4
VCC ≥ 2.55V, ISINK = 1.2mA, output asserted
0.3
VCC ≥ 2.55V, ISINK = 1.2mA, output asserted
0.3
VCC ≥ 1.80V, ISINK = 200µA, output asserted
0.3
VCC ≥ 4.25V, ISINK = 3.2mA, output asserted
VCC ≥ 2.7V, ISOURCE = 500µA, output not asserted
VCC ≥ 4.75V, ISOURCE = 800µA, output not asserted
1.0
0.8 x VCC
VCC ≥ 1.2V, ISOURCE = 50µA, reset asserted
0.8 x VCC
VCC ≥ 4.25V, ISOURCE = 800µA, reset asserted
0.8 x VCC
VCC ≥ 4.75V, ISINK = 3.2mA, reset not asserted
V
µA
V
V
V
0.8 x VCC
VCC ≥ 1.0V, ISOURCE = 1µA, reset asserted
(TA = 0°C to +125°C)
VCC ≥ 2.7V, ISINK = 1.2mA, reset not asserted
s
0.4
0.8 x VCC
VCC > VTH, output not asserted
VCC ≥ 2.55V, ISOURCE = 500µA, reset asserted
kΩ
ns
0.3 x VCC
VIH
V
µs
50
(Note 2)
nA
100
25
VIL
UNITS
µs
0.3 x VCC
MR Minimum Input Pulse
MR to Reset Delay
MAX
µA
V
0.8 x VCC
0.3
0.4
V
Note 1: Over-temperature limits are guaranteed by design and not production tested. Devices are tested at TA = +25°C.
Note 2: Guaranteed by design. Not production tested.
www.maximintegrated.com
Maxim Integrated │ 3
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6705(A)
VCC = 5V
8
-15
10
35
60
190
85
-15
10
35
60
-15
10
35
60
85
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAXIMUM VCC TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX6701 toc04
1.55
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
-15
10
35
60
85
0.95
-40
-15
10
35
OUTPUT-VOLTAGE LOW
vs. SINK CURRENT
40
RESET OCCURS
ABOVE LINE
30
20
10
0
0
VCC 4.25V
300
VCC - VOH (mV)
50
40
80
120
160
RESET THRESHOLD OVERDRIVE (mV)
VCC - VOH
vs. SOURCE CURRENT
350
MAX6701 toc07
VCC 4.25V
75
VOL (mV)
85
MAX670_Y
50
TEMPERATURE (°C)
TEMPERATURE (°C)
100
60
60
MAX6701 toc06
TEMPERATURE (°C)
1.60
-40
-40
TEMPERATURE (°C)
1.65
1.50
5
0
85
MAX6701 toc03
MAX6701 toc02
-40
10
TEMPERATURE (°C)
1.70
WATCHDOG TIMEOUT PERIOD (s)
195
15
MAX6701 toc08
-40
200
20
MAXIMUM TRANSIENT DURATION (µs)
0
MAX6708
VCC = 3.3V
4
205
MAX6701 toc05
12
RESET TIMEOUT PERIOD (ms)
MAX6701 toc01
16
210
NORMALIZED RESET THRESOLD
SUPPLY CURRENT (µA)
20
VCC TO RESET OUTPUT DELAY
vs. TEMPERATURE
VCC TO RESET OUTPUT DELAY (s)
SUPPLY CURRENT
vs. TEMPERATURE
250
200
150
100
25
50
0
0
400 800 1200 1600 2000 2400 2800 3200
SINK CURRENT (µA)
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0
0
400 800 1200 1600 2000 2400 2800 3200
SOURCE CURRENT (µA)
Maxim Integrated │ 4
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Pin Description
PIN
MAX6701(A)
MAX6702(A)
MAX6703(A)
MAX6704
MAX6705(A)
MAX6706(A)
MAX6707(A)
MAX6708
NAME
FUNCTION
1
1
1
1
MR
Active-Low, Manual Reset Input, Internal 50kΩ Pullup
to VCC. Pull low to force a reset. Reset remains active
as long as MR is low and the reset timeout period after
MR goes high. Leave unconnected or connect to VCC if
unused. WDO deasserts when MR is low (MAX6701(A)/
MAX6702(A)/MAX6703(A)/ MAX6705(A)/ MAX6706(A)/
MAX6707(A) only)
2
2
2
2
VCC
Supply Voltage for MAX6701–MAX6708 and Input for
Primary Reset Threshold Monitor. Push-pull outputs are
powered by VCC.
3
3
3
3
GND
Ground
—
4
4
4
PFI
Power-Fail Voltage Monitor Input. High-impedance
input for internal power-fail comparator. Connect this
pin to an external resistive-divider network to set the
reset threshold voltage; 0.62V (typ) threshold. Connect
to GND or VCC when not used.
—
5
5
5
PFO
Power-Fail Monitor Output. Open drain or push-pull
active low. PFO goes low when PFI is less than 0.62V.
6
6
6
—
WDI
Watchdog Input. If WDI remains high or low for longer
than the watchdog timeout period, the internal watchdog
timer runs out and WDO is asserted. WDO is asserted
low after each watchdog overflow and remains low until
the watchdog timer is cleared (the reset output is not
affected). The internal watchdog timer clears whenever
a VCC/RST_IN1/RST_IN2 reset is asserted, the manual
reset is asserted, or WDI sees a rising or falling edge.
The watchdog timer remains cleared until the reset output
is deasserted. On the MAX6704, RESET pulse asserts
for the reset timeout period after each watchdog timeout
overflow. The watchdog timer cannot be disabled.
—
—
—
6
N.C.
No Connection. Not internally connected.
7
7
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7
7
RESET
Active-Low Reset Output (Open Drain or Push-Pull).
RESET changes from high to low when the VCC input
drops below the selected reset threshold (or RST_IN1/
RST_IN2 for the MAX6701(A)/MAX6702(A)/MAX6703(A),
MR is pulled low, or the watchdog triggers a reset
(MAX6704 only). RESET remains low for the reset timeout
period after the reset conditions are terminated.
Maxim Integrated │ 5
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Pin Description (continued)
PIN
MAX6701(A)
MAX6702(A)
MAX6703(A)
8
7*
4
5
MAX6704
—
8
—
—
MAX6705(A)
MAX6706(A)
MAX6707(A)
8
7*
—
—
MAX6708
—
8
—
—
NAME
FUNCTION
WDO
Active-Low Watchdog Output (Open Drain or PushPull). WDO is asserted whenever the watchdog
times out and VCC or the reset inputs are below their
respective thresholds. WDO deasserts after a valid
WDI transition without a reset timeout period. In the A
versions, WDO deasserts without a timeout delay when
VCC, RST_IN1, and RST_IN2 rises above its threshold.
Pull MR low to assert WDO (MAX6701/MAX6702/
MAX6703/MAX6705/MAX6706/MAX6707 only). Pull
MR low to deassert WDO (MAX6701(A)/MAX6702(A) /
MAX6703(A)/ MAX6705(A)/MAX6706(A)MAX6707(A)
only)
RESET
Active-High Reset Output (Push-Pull). RESET changes
from low to high when the VCC input drops below the
selected reset threshold (or RST_IN1/RST_IN2 for
MAX6701(A)/MAX6702(A)/ MAX6703(A), MR is pulled
low, or the watchdog triggers a reset (MAX6704 only).
RESET remains high for the reset timeout period after
the reset conditions are terminated.
RST_IN1
Input for User-Adjustable V CC2 Monitor. Highimpedance input for second internal reset comparator.
Connect this pin to an external resistive-divider network
to set the reset threshold voltage; 0.62V (typ) threshold.
Connect to V CC when not used. Reset is asserted
when either V CC, RST_IN1, or RST_IN2 are below
threshold.
RST_IN2
Input for User-Adjustable V CC3 Monitor. Highimpedance input for third internal reset comparator.
Connect this pin to an external resistive-divider network
to set the reset threshold voltage; 0.62V (typ) threshold.
Connect to V CC when not used. Reset is asserted
when either V CC, RST_IN1, or RST_IN2 are below
threshold.
*RESET active-high for the MAX6702(A)/MAX6706(A).
Detailed Description
Figures 1, 2, and 3 are functional diagrams for the
MAX6705(A)/MAX6706(A)/MAX6707(A), MAX6704/
MAX6708, and MAX6701(A)/MAX6702(A)/MAX6703(A),
respectively.
Reset Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX6701–MAX6708 assert reset
during power-up and prevent code execution errors
during power-down or brownout conditions.
On power-up, once VCC reaches 1V, RESET is a
guaranteed logic-low of 0.4V or less. As VCC rises,
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RESET stays low. After VCC, RST_IN1, or RST_IN2 rise
above the reset threshold, an internal timer holds RESET
low for about 200ms. RESET pulses low whenever
VCC dips below the reset threshold, including brownout
conditions. If a brownout occurs in the middle of a
previously initiated reset pulse, the pulse continues for
at least another 140ms. On power-down, once VCC
falls below the reset threshold, RESET stays low and is
guaranteed to be 0.4V or less, until VCC drops below 1V.
The MAX6702(A)/MAX6704/MAX6706(A)/MAX6708
active-high RESET output is the complement of the
RESET output, and is guaranteed to be valid with VCC
down to 1V.
Maxim Integrated │ 6
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
VCC
6
WDI
8
WATCHDOG
TIMER
VCC
WDO
MR
50kΩ
VCC
MR 1
VCC 2
7
RESET
GENERATOR
4
RESET
GENERATOR
RESET
(RESET)
5
WDO
RST_IN1
RST_IN2
50kΩ
MR
VCC
GND
MAX6704
MAX6708
1
2
( ) ARE FOR MAX6702(A) ONLY.
Figure 3. MAX6701(A)/MAX6702(A)/MAX6703(A) Functional
Diagram
VCC
VTH
VTH
tRP
8
RESET
GENERATOR
7
WATCHDOG
TIMER
6
RESET
RESET
WDI
(MAX6704 ONLY)
tRP
VCC
RESET
0V
MR
VCC
0V
VREF
PFI
0.62V
0.62V
Figure 1. MAX6705(A)/MAX6706(A)/MAX6707(A) Functional
Diagram
VCC
WDI
PFO
0.62V
( ) ARE FOR MAX6706(A) ONLY. 3
RESET (RESET)
WATCHDOG
TIMER
VREF
MAX6705(A)
MAX6706(A)
MAX6707(A)
VREF
PFI
MAX6701(A)
MAX6702(A)
MAX6703(A)
50kΩ
tMD
VCC
WDO
4
5
0V
PFO
VCC
0.62V
MR EXTERNALLY DRIVEN LOW
WDI
0V
3
GND
Figure 2. MAX6704/MAX6708 Functional Diagram
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NOTE: THE MAX6706 RESET OUTPUT IS THE INVERSE OF THE RESET SHOWN.
Figure 4. MAX6705/MAX6706/MAX6707 RESET, MR, WDO,
and WDI Timing
Maxim Integrated │ 7
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Standard- vs. A-Version Comparison
threshold, WDO goes low whether or not the watchdog
timer has timed out. Normally this would trigger an NMI,
but RESET goes low simultaneously, and thus overrides
the NMI.
●● The watchdog timer times out (1.6s, typ).
The MAX6704 watchdog circuit does not have an independent watchdog output (WDO). If the µP does not
toggle the watchdog input within 1.6s, the MAX6704
asserts a reset output pulse for the reset timeout period.
The MAX6701/MAX6702/MAX6703/MAX6705/MAX6706/
MAX6707s’ WDO latches low when one of the following
events occurs:
●● VCC, RST_IN1, or RST_IN2 is below its reset
threshold.
●● MR is pulled low.
●● WDO only deasserts with a valid WDI transition.
The MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/
MAX6706(A)/ MAX6707(A)s’ WDO asserts when either
VCC, RST_IN1, or RST_IN2 is below its reset threshold. WDO deasserts without a timeout delay when the
undervoltage situation has expired. WDO is latched low
when the watchdog timer elapses without seeing a WDI
transition. WDO deasserts with a valid WDI transition
OR by pulling MR low.
See Figures 4 and 5 for standard-version timing. See
Figures 6 and 7 for A-version timing.
Watchdog Timer
The MAX6701–MAX6707 watchdog circuit monitors the
µP’s activity. If the µP does not toggle the WDI within 1.6s,
WDO goes low. When RESET is asserted, the watchdog
timer stays cleared and does not count. As soon as reset
is released, the timer starts counting. WDO deasserts
after a valid transition is detected at WDI. Pulses as short
as 50ns can be detected.
Typically, WDO is connected to the NMI input of a µP.
When VCC, RST_IN1, or RST_IN2 drop below the reset
tWDI
WDI
WDO
tWD
Manual Reset
The manual reset input (MR) allows reset to be
triggered by a pushbutton switch. The switch is
effectively debounced by the reset pulse width. MR is
CMOS logic compatible, so it can be driven by an external
logic line. MR can be used to force a watchdog timeout to
generate a reset pulse in the MAX6701(A)/MAX6702(A)/
MAX6703(A)/MAX6705(A)/MAX6706(A)/MAX6707(A) by
connecting WDO to MR.
Power-Fail Comparator
The uncommitted power-fail comparator can be used
for various purposes because its noninverting input and
output are externally available. The inverting input is
internally connected to a 0.62V reference. To build an
early warning circuit for power failure, connect the PFI
pin to a voltage-divider (see the Typical Operating
Circuit). Choose the voltage-divider ratio so that the
voltage at PFI falls below 0.62V just before the regulator
drops out. Use PFO to interrupt the µP so it can prepare
for an orderly power-down. The low-input current at this
pin allows for large resistor values in the divider.
tWD
VCC
+5V
VTH
VTH
tRP
0V
tRP
+5V
+5V
RESET
0V
0V
+5V
RESET
0V
+5V
(RESET)
0V
MR
RESET EXTERNALLY
TRIGGERED BY MR
t RP
MR
0V
+5V
+5V
0V
( ) ARE FOR MAX6702/MAX6706 ONLY.
Figure 5. MAX6701/MAX6702/MAX6703/MAX6705/MAX6706/
MAX6707 Watchdog
www.maximintegrated.com
+5V
tMD
tMR
WDO
0V
Figure 6. MAX6701(A)/MAX6702(A)/MAX6703(A)/
MAX6705(A)/ MAX6706(A)/MAX6707(A) RESET, MR, and
WDO Timing with WDI Three-Stated
Maxim Integrated │ 8
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
tWDI
WDI
WDO
tWD
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
tWD
+5V
tWD
0V
MAX6701(A)–
MAX6708
VEXTERNAL
+5V
R1
0V
+5V
RESET
0V
PFI, RST_IN1, OR RST_IN2
R2
0.62V
t RP
+5V
(RESET)
0V
MR
+5V
0V
(
)
VEXT-TH = 1 + R1 x 0.62V
R2
R1 = R2 x
- 1)
(VEXT-TH
0.62
WHERE VEXT-TH IS THE EXTERNAL VOLTAGE TRIP LEVEL.
( ) ARE FOR MAX6702(A)/MAX6706(A) ONLY.
Figure 7. MAX6701(A)/MAX6702(A)/MAX6703(A)/
MAX6705(A)/ MAX6706(A)/MAX6707(A) Watchdog Timing
Figure 8. Calculating Adjustable Voltage Thresholds
Reset Input
Monitoring Other System Voltages
The MAX6701(A)/MAX6702(A)/MAX6703(A) include two
adjustable reset inputs for monitoring up to a total of
three system voltages (including VCC). The thresholds
for the monitored RST_IN supplies are externally set
with resistor-divider networks (Figure 8). The reset
output is asserted if any of the monitored supplies (VCC,
RST_IN1, or RST_IN2) go below its specified threshold
and remains asserted for the reset timeout period after
all supplies are above their thresholds.
Applications Information
Ensuring a Valid RESET Output
Down to VCC = 0
When VCC falls below 1V, the MAX6701–MAX6708
RESET output no longer sinks current; it becomes an
open circuit. High-impedance CMOS logic inputs can
drift to undetermined voltages if left undriven. If a pulldown resistor is added to the RESET pin, as shown
in Figure 9, any stray charge or leakage currents are
drained to ground, holding RESET low. A resistor value
(R1) is not critical; 100kΩ is large enough not to load
RESET and small enough to pull RESET to ground.
This application works for push-pull output only (not for
open-drain resets).
www.maximintegrated.com
Other systems can be monitored by connecting a
voltage-divider to PFI and adjusting the ratio appropriately.
In noisy systems, a capacitor between PFI and GND
reduces the power-fail circuit’s sensitivity to highfrequency noise on the line being monitored. Reset can
be asserted on other voltages in addition to the VCC
supply line. Connect PFO to MR to initiate a reset output pulse when PFI drops below 0.62V. Figure 10
shows the MAX6704–MAX6708 configured to assert a
reset output when the secondary supply falls below the
reset threshold.
Generating a Reset from Watchdog Overflow
Connect WDO to MR to force a watchdog timeout to generate a reset pulse for only the reset timeout period on the
MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/
MAX6706(A)/MAX6707(A). When the MAX6704 watchdog times out, reset outputs are automatically asserted
(no external connections required). For the MAX6701/
MAX6702/MAX6703/MAX6705/MAX6706/MAX6707 non-A
versions, do not connect WDO to MR; this creates a
locked condition.
Maxim Integrated │ 9
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
0.9V
3.3V
MAX6701(A)
MAX6704
MAX6705(A)
MAX6708
VCC
RESET
I/O
SUPPLY
RESET
(RESET)
PFI
RESET
µP
MAX6704– MR
MAX6708 PFO
R1 (100kΩ)
CORE
SUPPLY
() ARE FOR MAX6704/MAX6706(A)/MAX6708 ONLY.
Figure 9. RESET Valid to Ground Circuit
Figure 10. Monitoring Other System Voltages
Selector Guide
RESET
PP LOW
RESET
PP HIGH
RESET
OD-LOW
WDI
WDO
PFI,
PFO
RST_IN1,
RST_IN2
MAX6701
✔
—
—
✔
✔ PP
—
✔
MAX6701A*
✔
—
—
✔
✔ PP
—
✔
MAX6702
—
✔
—
✔
✔ PP
—
✔
MAX6702A*
—
✔
—
✔
✔ PP
—
✔
MAX6703
—
—
✔
✔
✔ OD
—
✔
MAX6703A*
—
—
✔
✔
✔ OD
—
✔
MAX6704
✔
✔
—
✔
—
✔ PP
—
MAX6705
✔
—
—
✔
✔ PP
✔ PP
—
MAX6705A*
✔
—
—
✔
✔ PP
✔ PP
—
MAX6706
—
✔
—
✔
✔ PP
✔ PP
—
MAX6706A*
—
✔
—
✔
✔ PP
✔ PP
—
MAX6707
—
—
✔
✔
✔ OD
✔ OD
—
MAX6707A*
—
—
✔
✔
✔ OD
✔ OD
—
✔
—
—
—
✔ PP
—
PART
MAX6708
✔
PP = push-pull, OD = open drain.
*WDO deasserts when MR is pulled low. See the Standard- vs. A-Version Comparison section for the differences on WDO.
Threshold Suffix Guide
SUFFIX
RESET
THRESHOLD (V)
L
4.63
M
4.38
T
3.08
S
2.93
R
2.63
Z
2.32
Y
2.19
Bold indicates standard version.
www.maximintegrated.com
Maxim Integrated │ 10
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Pin Configurations (continued)
TOP VIEW
1
8
RESET
MR
7
RESET
VCC 2
3
6
WDI
GND
PFI 4
5
PFO
MR
VCC 2
GND
MAX6704
1
3
MAX6705(A)
MAX6706(A)
MAX6707(A)
PFI 4
SOT23
8
WDO
8
RESET
7
RESET (RESET) VCC 2
7
RESET
6
WDI
3
6
N.C.
5
PFO
PFI 4
5
PFO
MR
GND
1
MAX6708
SOT23
SOT23
( ) ARE FOR MAX6706(A) ONLY.
Typical Operating Circuit
UNREGULATED DC
Ordering Information (continued)
PART
TEMP RANGE
PIN-PACKAGE
DC-DC
MAX6702_ KA-T
-40°C to +125°C
8 SOT23
REGULATOR
MAX6702A_ KA-T
-40°C to +125°C
8 SOT23
MAX6703_ KA-T
-40°C to +125°C
8 SOT23
MAX6703A_ KA-T
-40°C to +125°C
8 SOT23
MAX6704_KA-T
-40°C to +125°C
8 SOT23
MAX6705_KA-T
-40°C to +125°C
8 SOT23
MAX6705A_KA-T
-40°C to +125°C
8 SOT23
MAX6706_KA-T
-40°C to +125°C
8 SOT23
MAX6706A_KA-T
-40°C to +125°C
8 SOT23
MAX6707_KA-T
-40°C to +125°C
8 SOT23
MAX6707A_KA-T
-40°C to +125°C
8 SOT23
MAX6708_KA-T
-40°C to +125°C
8 SOT23
µP
VCC
PUSHBUTTON
SWITCH
RESET
PFI MAX6705(A) WDI
MAX6706(A) WDO
MR MAX6707(A) PFO
VCC
RESET
I/O
NMI
INTERRUPT
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 SOT23
K8+2
21-0078
90-0176
Insert the desired suffix letter (from the Threshold Suffix Guide
table) into the blank to complete the part number. All devices
must be ordered in increments of 2500 pieces. Sample stock is
typically held on standard versions only. Contact factory for
availability.
Devices are available in both leaded and lead(Pb)-free
packaging. Specify lead-free by replacing “-T” with “+T” when
ordering.
T = Tape and reel.
Chip Information
TRANSISTOR COUNT: 716
PROCESS: BiCMOS
www.maximintegrated.com
Maxim Integrated │ 11
MAX6701-08/
MAX6701A-03A/
MAX6705A-07A
Low-Voltage, SOT23 µP Supervisors with Power-Fail
In/Out, Manual Reset, and Watchdog Timer
Revision History
REVISION
NUMBER
REVISION
DATE
4
5/14
PAGES
CHANGED
DESCRIPTION
No /V OPNs; removed Automotive reference from Applications section
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2014 Maxim Integrated Products, Inc. │ 12
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