MAX6726KAZWD3-T
更新时间:2024-09-18 03:08:38
品牌:MAXIM
描述:Dual/Triple Ultra-Low-Voltage SOT23 µ.P Supervisory Circuits
MAX6726KAZWD3-T 概述
Dual/Triple Ultra-Low-Voltage SOT23 µ.P Supervisory Circuits
双/三超低电压SOT23 &# 181.P监控电路\n
MAX6726KAZWD3-T 数据手册
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Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
General Description
Features
o V 1 (primary supply) Reset Threshold Voltages
The MAX6715–MAX6729 are ultra-low-voltage microproces-
sor (µP) supervisory circuits designed to monitor two or three
system power-supply voltages. These devices assert a sys-
tem reset if any monitored supply falls below its factory-
trimmed or adjustable threshold and maintain reset for a
minimum timeout period after all supplies rise above their
thresholds. The integrated dual/triple supervisory circuits sig-
nificantly improve system reliability and reduce size com-
pared to separate ICs or discrete components.
CC
from 1.58V to 4.63V
o V 2 (secondary supply) Reset Threshold
CC
Voltages from 0.79V to 3.08V
o Externally Adjustable RSTIN Threshold for
Auxiliary/Triple-Voltage Monitoring
(0.62V internal reference)
o Watchdog Timer Option
These devices monitor primary supply voltages (V 1) from
CC
35s (min) Long Startup Period
1.12s (min) Normal Timeout Period
1.8V to 5.0V and secondary supply voltages (V 2) from
CC
0.9V to 3.3V with factory-trimmed reset threshold voltage
options (see Reset Voltage Threshold Suffix Guide). An
externally adjustable RSTIN input option allows customers to
monitor a third supply voltage down to 0.62V. These devices
are guaranteed to be in the correct reset output logic state
o Manual Reset Input Option
o Power-Fail Input/Power-Fail Output Option
(Push-Pull and Open-Drain Active-Low)
when either V 1 or V 2 remains greater than 0.8V.
CC
CC
o Guaranteed Reset Valid Down to V 1 or
CC
A variety of push-pull or open-drain reset outputs along with
watchdog input, manual reset input, and power-fail input/out-
put features are available (see Selector Guide). Select reset
timeout periods from 1.1ms to 1120ms (min) (see Reset
Timeout Period Suffix Guide). The MAX6715–MAX6729 are
available in small 5, 6, and 8-pin SOT23 packages and oper-
ate over the -40°C to +85°C temperature range.
V
2 = 0.8V
CC
o Reset Output Logic Options
o Immune to Short V Transients
CC
o Low Supply Current 14µA (typ) at 3.6V
o Small 5, 6, and 8-Pin SOT23 Packages
Ordering Information
Applications
Multivoltage Systems
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
6 SOT23-6
6 SOT23-6
5 SOT23-5
5 SOT23-5
6 SOT23-6
6 SOT23-6
Telecom/Networking Equipment
Computers/Servers
MAX6715UT_ _D_ -T
MAX6716UT_ _D_ -T
MAX6717UK_ _D_ -T
MAX6718UK_ _D_ -T
MAX6719UT_ _D_ -T
MAX6720UT_ _D_ -T
Portable/Battery-Operated Equipment
Industrial Equipment
Printer/Fax
Set-Top Boxes
Note: The first “_ _” are placeholders for the threshold voltage
levels of the devices. Desired threshold levels are set by the part
number suffix found in the Reset Voltage Threshold Suffix Guide.
The “_” after the D is a placeholder for the reset timeout delay
time. Desired delay time is set using the timeout period suffix
found in the Reset Timeout Period Suffix Guide. For example the
Typical Operating Circuit
OUT2
DC/DC
UNREGULATED
IN
CONVERTER
DC
MAX6716UTLTD3-T is a dual-voltage supervisor V 1 = 4.625V,
OUT1
1.8V
I/O
0.9V
CORE
TH
V 2 = 3.075V, and 210ms (typ) timeout period.
TH
V
1
CC
V
2
CC
SUPPLY SUPPLY
R1
R2
RESET
RST
WDI
PFO
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
Selector Guide appears at end of data sheet.
µP
RSTIN/PFI
MR
I/O
NMI
MAX67_ _
PUSHBUTTON
SWITCH
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
Continuous Power Dissipation (T = +70°C)
A
V
1, V 2 ..........................................................-0.3V to +6V
5-Pin SOT23-5 (derate 7.1mW/°C above +70°C) ........571mW
6-Pin SOT23-6 (derate 8.7mW/°C above +70°C) ........696mW
8-Pin SOT23-8 (derate 8.9mW/°C above +70°C) ........714mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
CC
CC
Open-Drain RST, RST1, RST2, PFO, RST ................-0.3V to +6V
Push-Pull RST, RST1, PFO, RST...............-0.3V to (V 1 + 0.3V)
Push-Pull RST2.........................................-0.3V to (V 2 + 0.3V)
RSTIN, PFI, MR, WDI................................................-0.3V to +6V
Input Current/Output Current (all pins) ...............................20mA
CC
CC
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
(V 1 = V 2 = 0.8V to 5.5V, GND = 0, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
CC
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
5.5
UNITS
Supply Voltage
Supply Current
V
0.8
V
CC
V
V
V
V
1 < 5.5V, all I/O pins open
1 < 3.6V, all I/O pins open
2 < 3.6V, all I/O pins open
2 < 2.75V, all I/O pins open
15
39
CC
CC
CC
CC
I
CC1
10
28
µA
4
11
I
CC2
3
9
L (falling)
M (falling)
T (falling)
S (falling)
R (falling)
Z (falling)
Y (falling)
W (falling)
V (falling)
T (falling)
S (falling)
R (falling)
Z (falling)
Y (falling)
W (falling)
V (falling)
I (falling)
H (falling)
G (falling)
F (falling)
E (falling)
D (falling)
4.500
4.250
3.000
2.850
2.550
2.250
2.125
1.620
1.530
3.000
2.850
2.550
2.250
2.125
1.620
1.530
1.350
1.275
1.080
1.020
0.810
0.765
4.625
4.375
3.075
2.925
2.625
2.313
2.188
1.665
1.575
3.075
2.925
2.625
2.313
2.188
1.665
1.575
1.388
1.313
1.110
1.050
0.833
0.788
20
4.750
4.500
3.150
3.000
2.700
2.375
2.250
1.710
1.620
3.150
3.000
2.700
2.375
2.250
1.710
1.620
1.425
1.350
1.140
1.080
0.855
0.810
V
1 Reset Threshold
V
V
CC
TH1
V
2 Reset Threshold
CC
V
V
TH2
Reset Threshold Tempco
Reset Threshold Hysteresis
ppm/°C
V
Referenced to V typical
0.5
%
HYST
TH
2
_______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V 1 = V 2 = 0.8V to 5.5V, GND = 0, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
CC
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
1 = (V 1+ 100mV) to (V 1 - 100mV) or
MIN
TYP
MAX
UNITS
V
CC
V
CC
TH
TH
V
to Reset Output Delay
t
20
µs
CC
RD
2 = (V 2 + 75mV) to (V 2 - 75mV)
TH
TH
D1
D2
D3
D5
D6
D4
1.1
8.8
1.65
13.2
210
2.2
17.6
280
140
280
560
1120
Reset Timeout Period
t
ms
RP
420
560
840
1120
2240
1680
ADJUSTABLE RESET COMPARATOR INPUT (MAX6719/MAX6720/MAX6723–MAX6727)
RSTIN Input Threshold
RSTIN Input Current
V
611
-25
626.5
642
+25
mV
nA
RSTIN
RSTIN
I
RSTIN Hysteresis
3
mV
µs
RSTIN to Reset Output Delay
t
V
to (V - 30mV)
RSTIN
22
RSTIND
RSTIN
POWER-FAIL INPUT (MAX6728/MAX6729)
PFI Input Threshold
PFI Input Current
PFI Hysteresis
V
611
-25
626.5
642
+25
mV
nA
mV
µs
PFI
PFI
I
V
3
2
PFH
DPF
PFI to PFO Delay
t
(V + 30mV) to (V - 30mV)
PFI PFI
MANUAL RESET INPUT (MAX6715–MAX6722/MAX6725–MAX6729)
V
0.3 ✕ V
1
CC
IL
MR Input Voltage
V
V
0.7 ✕ V
1
CC
IH
MR Minimum Pulse Width
MR Glitch Rejection
MR to Reset Delay
1
µs
ns
ns
kΩ
100
200
50
t
MR
MR Pullup Resistance
25
35
80
WATCHDOG INPUT (MAX6721–MAX6729)
First watchdog period after reset timeout
period
54
72
Watchdog Timeout Period
t
s
WD
Normal mode
(Note 2)
1.12
50
1.68
2.24
WDI Pulse Width
WDI Input Voltage
WDI Input Current
t
ns
V
WDI
V
0.3 ✕ V
1
CC
IL
V
0.7 ✕ V
1
CC
IH
I
WDI = 0 or V
1
CC
-1
+1
µA
WDI
_______________________________________________________________________________________
3
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V 1 = V 2 = 0.8V to 5.5V, GND = 0, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
CC
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RESET/POWER-FAIL OUTPUTS
V
1 or V 2 ≥ 0.8V, I
= 1µA,
CC
CC
SINK
SINK
SINK
SINK
SINK
0.3
0.3
0.3
0.3
0.4
output asserted
V
1 or V 2 ≥ 1.0V, I
= 50µA,
CC
CC
output asserted
RST/RST1/RST2/PFO
Output LOW
V
1 or V 2 ≥ 1.2V, I
= 100µA,
= 1.2mA,
= 3.2mA,
CC
CC
V
V
OL
output asserted
(Push-Pull or Open-Drain)
V
1 or V 2 ≥ 2.7V, I
CC
CC
output asserted
V
1 or V 2 ≥ 4.5V, I
CC
CC
output asserted
V
1 ≥ 1.8V, I
= 200µA, output not
= 500µA, output not
= 800µA, output not
= 200µA, output not
= 500µA, output not
= 800µA, output not
CC
SOURCE
SOURCE
SOURCE
SOURCE
SOURCE
SOURCE
0.8 ✕ V
0.8 ✕ V
0.8 ✕ V
0.8 ✕ V
0.8 ✕ V
0.8 ✕ V
1
1
1
2
2
CC
CC
CC
CC
CC
asserted
RST/RST1/PFO
Output HIGH
(Push-Pull Only)
V
1 ≥ 2.7V, I
CC
V
V
V
OH
asserted
V
1 ≥ 4.5V, I
CC
asserted
V
2 ≥ 1.8V, I
CC
asserted
RST2
Output HIGH
(Push-Pull Only)
V
2 ≥ 2.7V, I
CC
V
OH
asserted
V
2 ≥ 4.5V, I
CC
2
1
1
CC
CC
CC
asserted
V
V
1 ≥ 1.0V, I
1 ≥ 1.8V, I
= 1µA, reset asserted 0.8 ✕ V
CC
SOURCE
= 150µA,
CC
SOURCE
0.8 ✕ V
reset asserted
RST
Output HIGH
(Push-Pull Only)
V
V
V
V
1 ≥ 2.7V, I
= 500µA,
OH
CC
SOURCE
SOURCE
0.8 ✕ V
1
CC
CC
reset asserted
V
1 ≥ 4.5V, I
CC
= 800µA,
0.8 ✕ V
1
reset asserted
V
1 or V 2 ≥ 1.8V, I
= 500µA,
= 1.2mA,
= 3.2mA,
CC
CC
SINK
SINK
SINK
0.3
0.3
0.4
0.5
0.5
reset not asserted
RST
Output LOW
(Push-Pull or Open Drain)
V
1 or V 2 ≥ 2.7V, I
CC
CC
V
OL
reset not asserted
V
1 or V 2 ≥ 4.5V, I
CC
CC
reset not asserted
RST/RST1/RST2/PFO Output
Open-Drain Leakage Current
Output not asserted
µA
µA
RST Output Open-Drain
Leakage Current
Output asserted
Note 1: Devices tested at +25°C. Overtemperature limits are guaranteed by design and not production tested.
Note 2: Parameter guaranteed by design.
4
_______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Typical Operating Characteristics
(V 1 = 5V, V 2 = 3.3V, T = +25°C, unless otherwise noted.)
CC
CC
A
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
V
1 = 5V, V 2 = 3.3V
V
1 = 3.3V, V 2 = 2.5V
V 1 = 2.5V, V 2 = 1.8V
CC CC
CC
CC
CC
CC
18
16
14
12
10
8
18
16
14
12
10
8
18
16
14
12
10
8
TOTAL
TOTAL
I
1
CC
TOTAL
I
1
CC
I
I
1
2
CC
6
6
6
4
I
2
4
4
CC
I
2
CC
CC
2
2
2
0
0
0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
SUPPLY CURRENT vs. TEMPERATURE
MAXIMUM V TRANSIENT DURATION
CC
vs. RESET THRESHOLD OVERDRIVE
NORMALIZED RESET/WATCHDOG
TIMEOUT PERIOD vs. TEMPERATURE
V
1 = 1.8V, V 2 = 1.2V
CC
CC
18
16
14
12
10
8
1.007
1.006
1.005
1.004
1.003
1.002
1.001
1.000
0.999
0.998
10,000
1000
RESET OCCURS ABOVE
THIS LINE
TOTAL
6
I
I
1
100
10
CC
CC
4
2
2
0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
1
10
100
1000
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV)
NORMALIZED V RESET THRESHOLD
CC
RESET INPUT AND POWER-FAIL INPUT
THRESHOLD vs. TEMPERATURE
V
TO RESET DELAY
CC
vs. TEMPERATURE
vs. TEMPERATURE
54
1.004
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
631
630
629
628
627
626
625
100mV OVERDRIVE
53
52
51
50
49
48
47
46
45
44
-40
-15
10
35
60
85
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Typical Operating Characteristics (continued)
(V 1 = 5V, V 2 = 3.3V, T = +25°C, unless otherwise noted.)
CC
CC
A
RESET INPUT TO RESET OUTPUT DELAY
vs. TEMPERATURE
POWER-FAIL INPUT TO POWER-FAIL
OUTPUT DELAY vs. TEMPERATURE
MR TO RESET OUTPUT DELAY
MAX6715-29 toc12
24.4
30mV OVERDRIVE
30mV OVERDRIVE
2.4
2.3
2.2
2.1
2.0
24.2
24.0
23.8
23.6
23.4
23.2
23.0
22.8
V
MR
2V/div
0
0
V
RST
2V/div
-40
-15
10
35
60
85
50ns/div
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
Pin Description
PIN
NAME
FUNCTION
MAX6715/ MAX6717/ MAX6719/ MAX6721/ MAX6723/ MAX6725/
MAX6716 MAX6718 MAX6720 MAX6722 MAX6724 MAX6726
MAX6728/
MAX6729
MAX6727
Active-Low Reset Output,
Open-Drain or Push-Pull.
RST/RST1 changes from
high to low when V 1 or
CC
V
2 drops below the
CC
selected reset thresholds,
RSTIN is below threshold,
MR is pulled low, or the
watchdog triggers a
reset. RST/RST1 remains
low for the reset timeout
RST/
RST1
1
1
1
1
1
1
1, 4
1
period after V 1/
CC
V
2/RSTIN exceed the
CC
device reset thresholds,
MR goes low to high, or
the watchdog triggers a
reset. Open-drain outputs
require an external pullup
resistor. Push-pull
outputs are referenced to
V
1.
CC
6
_______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Pin Description (continued)
PIN
NAME
FUNCTION
MAX6715/ MAX6717/ MAX6719/ MAX6721/ MAX6723/ MAX6725/
MAX6716 MAX6718 MAX6720 MAX6722 MAX6724 MAX6726
MAX6728/
MAX6729
MAX6727
Active-Low Reset Output,
Open-Drain or Push-Pull.
RST2 changes from high
to low when V 1 or
CC
V
2 drops below the
CC
selected reset thresholds
or MR is pulled low. RST2
remains low for the reset
5
—
—
—
—
—
—
—
RST2 timeout period after
1/V 2 exceed the
V
CC
CC
device reset thresholds
or MR goes low to high.
Open-drain outputs
require an external pullup
resistor. Push-pull
outputs are referenced to
V
2.
CC
2
3
2
3
2
3
2
3
2
2
5
2
5
2
5
GND Ground
Active-Low Manual Reset
Input. Internal 50kΩ
pullup to V 1. Pull low
CC
to force a reset. Reset
remains active as long as
MR is low and for the
—
MR
reset timeout period after
MR goes high. Leave
unconnected or connect
to V 1 if unused.
CC
Secondary Supply
Voltage Input. Powers the
device when it is above
4
6
4
5
4
6
4
6
4
6
6
8
6
8
6
8
V
2
CC
V
1 and input for
CC
secondary reset
threshold monitor.
Primary Supply Voltage
Input. Powers the device
V
1
CC
when it is above V
2
CC
and input for primary
reset threshold monitor.
_______________________________________________________________________________________
7
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Pin Description (continued)
PIN
NAME
FUNCTION
MAX6715/ MAX6717/ MAX6719/ MAX6721/ MAX6723/ MAX6725/
MAX6716 MAX6718 MAX6720 MAX6722 MAX6724 MAX6726
MAX6728/
MAX6729
MAX6727
Watchdog Input. If WDI
remains high or low for
longer than the watchdog
timeout period, the
internal watchdog timer
runs out and the reset
output asserts for the
reset timeout period. The
internal watchdog timer
clears whenever a reset
is asserted or WDI sees a
rising or falling edge. The
watchdog has a long
timeout period (35s min)
after each reset event
and a short timeout
—
—
—
5
3
3
3
3
WDI
period (1.12s min) after
the first valid WDI
transition. Leave WDI
floating to disable the
watchdog timer function.
Undervoltage Reset
Comparator Input. High-
impedance input for
adjustable reset monitor.
The reset output is
asserted when RSTIN falls
—
—
5
—
5
7
7
—
RSTIN below the 0.626V internal
reference voltage. Set the
monitored voltage reset
threshold with an external
resistor-divider network.
Connect RSTIN to V 1 or
CC
V
2 if not used.
CC
Power-Fail Voltage
Monitor Input. High-
impedance input for
internal power-fail monitor
comparator. Connect PFI
to an external resistor-
divider network to set the
power-fail threshold
voltage (0.626V typical
internal reference
—
—
—
—
—
—
—
7
PFI
voltage). Connect to
GND, V 1, or V 2 if
CC
CC
not used.
8
_______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Pin Description (continued)
PIN
NAME
FUNCTION
MAX6715/ MAX6717/ MAX6719/ MAX6721/ MAX6723/ MAX6725/
MAX6716 MAX6718 MAX6720 MAX6722 MAX6724 MAX6726
MAX6728/
MAX6729
MAX6727
Active-Low Power-Fail
Monitor Output, Open-
Drain or Push-Pull. PFO is
asserted low when PFI is
less than 0.626V. PFO
deasserts without a reset
timeout period. Open-
drain outputs require an
external pullup resistor.
Push-pull outputs are
—
—
—
—
—
—
—
4
PFO
referenced to V 1.
CC
Active-High Reset
Output, Open-Drain or
Push-Pull. RST changes
from low to high when
V
1 or V 2 drops
CC CC
below selected reset
thresholds, RSTIN is
below threshold, MR is
pulled low, or the
watchdog triggers a
reset. RST remains HIGH
for the reset timeout
—
—
—
—
—
4
—
—
RST
period after V 1/
CC
V
2/RSTIN exceed the
CC
device reset thresholds,
MR goes low to high, or
the watchdog triggers a
reset. Open-drain outputs
require an external pullup
resistor. Push-pull
outputs are referenced to
V
1.
CC
Suffix Guide (Table 1). Contact factory for availability of
Detailed Description
other voltage threshold combinations.
Supply Voltages
Reset Outputs
The MAX6715–MAX6729 provides an active-low reset
output (RST) and the MAX6725/MAX6726 provides
both an active-high (RST) and an active-low reset out-
put (RST). RST, RST, RST1, and RST2 are asserted
The MAX6715–MAX6729 microprocessor (µP) supervi-
sory circuits maintain system integrity by alerting the µP
to fault conditions. These ICs are optimized for systems
that monitor two or three supply voltages. The output-
reset state is guaranteed to remain valid while either
when the voltage at either V 1 or V 2 falls below the
CC
CC
V
1 or V 2 is above 0.8V.
CC
CC
voltage threshold level, RSTIN drops below threshold,
Threshold Levels
or MR is pulled low. Once reset is asserted it stays low
Input voltage threshold level combinations are indicat-
for the reset timeout period (see Table 2). If V 1,
CC
ed by a two-letter code in the Reset Voltage Threshold
V
2, or RSTIN goes below the reset threshold before
the reset timeout period is completed, the internal timer
CC
_______________________________________________________________________________________
9
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
restarts. The MAX6715/MAX6717/MAX6719/MAX6721/
MAX6723/MAX6725/MAX6727/MAX6728 contain open-
drain reset outputs, while the MAX6716/MAX6718/
MAX6720/MAX6722/MAX6724/MAX6726/MAX6729
contain push-pull reset outputs. The MAX6727 provides
two separate open-drain RST outputs driven by the
same internal logic.
MAX6719/
V
EXT_TH
MAX6720/
MAX6723–
MAX6727
R1
R2
RSTIN
Manual Reset Input
Many microprocessor-based products require manual
reset capability, allowing the operator, a test techni-
cian, or external logic circuitry to initiate a reset. A logic
low on MR asserts the reset output. Reset remains
asserted while MR is low and for the reset timeout peri-
GND
od (t ) after MR returns high. This input has an internal
RP
50kΩ pullup resistor to V 1 and can be left uncon-
CC
Figure 1. Monitoring a Third Voltage
nected if not used. MR can be driven with TTL or
CMOS logic levels, or with open-drain/collector outputs.
Connect a normally open momentary switch from MR to
GND to create a manual reset function; external
debounce circuitry is not required. If MR is driven from
long cables or if the device is used in a noisy environ-
ment, connect a 0.1µF capacitor from MR to GND to
provide additional noise immunity.
when processor activity fails. After each reset event
(V
power-up/brownout, manual reset, or watchdog
CC
reset), there is a long initial watchdog period of 35s
minimum. The long watchdog period mode provides an
extended time for the system to power-up and fully ini-
tialize all µP and system components before assuming
responsibility for routine watchdog updates.
Adjustable Input Voltage
The MAX6719/MAX6720 and MAX6723–MAX6727 provide
an additional input to monitor a third system voltage. The
threshold voltage at RSTIN is typically 626mV. Connect a
resistor-divider network to the circuit as shown in Figure 1
to establish an externally controlled threshold voltage,
The normal watchdog timeout period (1.12s min)
begins after the first transition on WDI before the con-
clusion of the long initial watchdog period (Figure 2).
During the normal operating mode, the supervisor will
issue a reset pulse for the reset timeout period if the µP
does not update the WDI with a valid transition (high-to-
low or low-to-high) within the standard timeout period
(1.12s min).
V
.
EXT_TH
V
= 626mV((R1 + R2)/R2)
EXT_TH
Power-Fail Comparator
PFI is the noninverting input to a comparator. If PFI is
less than V
(626.5mV), PFO goes low. Common uses
for the power-fail comparator include monitoring prereg-
ulated input of the power supply (such as a battery) or
PFI
Low leakage current at RSTIN allows the use of large-
valued resistors resulting in reduced power consump-
tion of the system.
Watchdog Input
The watchdog monitors µP activity through the watch-
dog input (WDI). To use the watchdog function, con-
nect WDI to a bus line or µP I/O line. When WDI
remains high or low for longer than the watchdog time-
out period, the reset output asserts. Leave WDI floating
to disable the watchdog function.
V
TH
V
CC
t
WDI-NORMAL
1.12s MAX
t
WDI-STARTUP
35s MAX
WDI
The MAX6721–MAX6729 include a dual-mode watch-
dog timer to monitor µP activity. The flexible timeout
architecture provides a long period initial watchdog
mode, allowing complicated systems to complete
lengthy boots, and a short period normal watchdog
mode, allowing the supervisor to provide quick alerts
1.12s MAX
t
RP
RESET
Figure 2. Normal Watchdog Startup Sequence
10 ______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
A
RESET TO OTHER SYSTEM COMPONENTS
V
1 V 2
CC
CC
V
IN
MAX6728/
MAX6729
R1
R1 + R2
R2
MAX6715–
MAX6729
V
= V
PFI
TRIP
(
)
PFI
PFO
µP
4.7kΩ
V
V
2
1
RESET
R2
RST
CC
CC
GND
GND
GND
B
V
CC
MAX6728/
MAX6729
Figure 4. Interfacing to µPs with Bidirectional Reset I/O
R1
R2
V
CC
R1
1
1
+
-
(V
= R2
)
PFI
V
TRIP
Applications Information
Interfacing to µPs with Bidirectional
Reset Pins
(R1 )
[
]
R2
PFI
PFO
V
PFI
= 626.5mV
Most microprocessors with bidirectional reset pins can
interface directly to open-drain RST output options.
Systems simultaneously requiring a push-pull RST out-
put and a bidirectional reset interface can be in logic
contention. To prevent contention, connect a 4.7kΩ
resistor between RST and the µP’s reset I/O port as
shown in Figure 4.
V
IN
GND
Figure 3. Using Power-Fail Input to Monitor an Additional
Power-Supply a) V is Positive b) V is Negative
IN
IN
providing an early power-fail warning so software can
conduct an orderly system shutdown. It can also be
Adding Hysteresis to the Power-Fail
Comparator
used to monitor supplies other than V 1 or V 2 by
CC
CC
The power-fail comparator has a typical input hysteresis
of 3mV. This is sufficient for most applications where a
power-supply line is being monitored through an external
voltage-divider (see the Power-Fail Comparator section).
If additional noise margin is desired, connect a resistor
between PFO and PFI as shown in Figure 5. Select the
setting the power-fail threshold with a resistor-divider, as
shown in Figure 3. PFI is the input to the power-fail com-
parator. The typical comparator delay is 2µs from PFI to
PFO. Connect PFI to ground of V 1 if unused.
CC
Ensuring a Valid Reset Output
values of R1, R2, and R3 so PFI sees V (626mV) when
PFI
Down to V
= 0
CC
The MAX6715–MAX6729 are guaranteed to operate
properly down to V = 0.8V. In applications that
V
falls to its power-fail trip point (V
) and when VIN
EXT
FAIL
rises to its power-good trip point (V
). The hysteresis
GOOD
CC
window extends between the specified V
and V
GOOD
FAIL
require valid reset levels down to V
= 0 use a pull-
CC
thresholds. R3 adds the additional hysteresis by sinking
current from the R1/R2 divider network when PFO is logic
low and sourcing current into the network when PFO is
logic high. R3 is typically an order of magnitude greater
than R1 or R2.
down resistor at RST to ground. The resistor value used
is not critical, but it must be large enough not to load
the reset output when V
is above the reset threshold.
CC
For most applications, 100kΩ is adequate. This config-
uration does not work for the open-drain outputs of the
MAX6715/MAX6717/MAX6719/MAX6721/MAX6723/
MAX6725/MAX6727/MAX6728. For push-pull, active-
high RST output connect the external resistor as a
The current through R2 should be at least 2.5µA to
ensure that the 25nA (max) PFI input current does not
significantly shift the trip points. Therefore, R2 <
V
PFI
/2.5µA < 248kΩ for most applications. R3 will provide
pullup from RST to V 1.
CC
additional hysteresis for PFO push-pull (V
= V 1) or
CC
OH
open-drain (V
= V
) applications.
OH
PULLUP
______________________________________________________________________________________ 11
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
R3
START
A
V
V
GOOD
FAIL
V
IN
PFO
V
MAX6728/
MAX6729
EXT
SET WDI
HIGH
R1
PROGRAM
CODE
PFI
PFO
V
V
V
= DESIRED V GOOD VOLTAGE THRESHOLD
EXT
GOOD
R2
= DESIRED V FAIL VOLTAGE THRESHOLD
FAIL
EXT
= V 1 (FOR PUSH-PULL PFO)
OH
CC
R2 = 200kΩ (FOR > 2.5µA R2 CURRENT)
R1 = R2 ((V
R3 = (R1 x V ) / (V
- V ) - (V )(V
- V ) / V ) / V
GOOD
OH
PFI
PFI GOOD FAIL OH PFI
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
GND
- V
)
GOOD
FAIL
HANG IN
SUBROUTINE
Figure 5. Adding Hysteresis to Power-Fail for Push-Pull PFO
SUBROUTINE
COMPLETED
Monitoring an Additional Power Supply
These µP supervisors can monitor either positive or
negative supplies using a resistor voltage-divider to
PFI. PFO can be used to generate an interrupt to the µP
or cause reset to assert (Figure 3).
RETURN
Figure 6. Watchdog Flow Diagram
Monitoring a Negative Voltage
The power-fail comparator can be used to monitor a
negative supply voltage using the circuit shown in
Figure 3. When the negative supply is valid, PFO is low.
When the negative supply voltage drops, PFO goes
high. The circuit’s accuracy is affected by the PFI
watchdog timer to closely monitor software execution.
This technique avoids a “stuck” loop where the watch-
dog timer continues to be reset within the loop, keeping
the watchdog from timing out. Figure 6 shows an exam-
ple flow diagram where the I/O driving the watchdog
input is set high at the beginning of the program, set low
at the beginning of every subroutine or loop, then set
high again when the program returns to the beginning. If
the program should “hang” in any subroutine, the I/O is
continually set low and the watchdog timer is allowed to
time out, causing a reset or interrupt to be issued.
threshold tolerance, V , R1, and R2.
CC
Negative-Going V
Transients
CC
The MAX6715–MAX6729 supervisors are relatively
immune to short-duration negative-going V
transients
CC
(glitches). It is usually undesirable to reset the µP when
experiences only small glitches. The Typical
V
CC
Operating Characteristics show Maximum Transient
Duration vs. Reset Threshold Overdrive, for which reset
pulses are not generated. The graph was produced
Chip Information
TRANSISTOR COUNT: 1072
using negative-going V
pulses, starting above V
TH
CC
PROCESS: BiCMOS
and ending below the reset threshold by the magnitude
indicated (reset threshold overdrive). The graph shows
the maximum pulse width that a negative-going V
CC
transient may typically have without causing a reset
pulse to be issued. As the amplitude of the transient
increases (i.e., goes farther below the reset threshold),
the maximum allowable pulse width decreases. A 0.1µF
bypass capacitor mounted close to the V
vides additional transient immunity.
pin pro-
CC
Watchdog Software Considerations
Setting and resetting the watchdog input at different
points in the program, rather than “pulsing” the watch-
dog input high-low-high or low-high-low, helps the
12 ______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Functional Diagram
V
1
CC
V
1
CC
MR
MR
PULLUP
V
1
CC
V
1
V 2
CC
CC
V
REF
RST
RST
RESET
TIMEOUT
PERIOD
RESET
OUTPUT
DRIVER
V
2
CC
RSTIN/PFI
PFO
V
1
CC
V
V 1
CC
REF
WATCHDOG
TIMER WITH
WDI
FLOAT DISABLE
V
REF/2
______________________________________________________________________________________ 13
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Selector Guide
POWER-
FAIL
INPUT/
OUTPUT
NUMBER OF
VOLTAGE
MONITORS
OPEN-
DRAIN
RESET
OPEN-
DRAIN
RESET
PUSH-
PULL
RESET
PUSH-
PULL
RESET
WATCH-
DOG
INPUT
PART
NUMBER
MANUAL
RESET
MAX6715
MAX6716
MAX6717
MAX6718
MAX6719
MAX6720
MAX6721
MAX6722
MAX6723
MAX6724
MAX6725
MAX6726
MAX6727
MAX6728
MAX6729
2
2
2
2
3
3
2
2
3
3
3
3
3
2
2
2
—
1
—
—
—
—
—
—
—
—
—
—
1
—
2
—
—
—
—
—
—
—
—
—
—
—
1
√
√
—
—
—
—
—
—
√
—
—
—
1
√
—
—
1
√
—
—
1
√
—
—
1
√
—
—
1
√
—
—
1
√
√
—
—
1
—
—
√
√
—
—
1
√
—
—
1
√
—
—
—
2
—
—
—
—
√
√
—
—
1
—
—
—
√
√
—
1
√
√
√ (open drain)
√ (push-pull)
—
√
√
Ordering Information (continued)
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
MAX6721UT_ _D_ -T
MAX6722UT_ _D_ -T
MAX6723UT_ _D_ -T
MAX6724UT_ _D_ -T
MAX6725KA_ _D_ -T
MAX6726KA_ _D_ -T
MAX6727KA_ _D_ -T
MAX6728KA_ _D_ -T
MAX6729KA_ _D_ -T
Note: The first “_ _” are placeholders for the threshold voltage
levels of the devices. Desired threshold levels are set by the part
number suffix found in the Reset Voltage Threshold Suffix Guide.
The “_” after the D is a placeholder for the reset timeout delay
time. Desired delay time is set using the timeout period suffix
found in the Reset Timeout Period Suffix Guide. For example the
MAX6716UTLTD3-T is a dual-voltage supervisor V 1 = 4.625V,
TH
V 2 = 3.075V, and 210ms (typ) timeout period.
TH
14 ______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Table 1. Reset Voltage Threshold Suffix
Guide**
Table 2. Reset Timeout Period Suffix
Guide
ACTIVE TIMEOUT PERIOD
TIMEOUT
PART NUMBER
SUFFIX
V
1 NOMINAL
VOLTAGE
V
2 NOMINAL
CC
VOLTAGE
CC
PERIOD SUFFIX
MIN [ms]
1.1
MAX [ms]
2.2
(_ _)
THRESHOLD (V)
4.625
4.375
4.375
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
2.313
2.188
2.313
2.188
2.313
2.188
2.313
2.188
1.665
1.575
1.665
1.575
1.665
1.575
THRESHOLD (V)
3.075
2.925
2.625
2.313
2.188
2.188
1.665
1.575
1.575
1.388
1.313
1.313
1.110
1.050
1.050
0.833
0.788
0.788
1.665
1.575
1.388
1.313
1.110
1.050
0.833
0.788
1.388
1.313
1.110
1.050
0.833
0.788
D1
D2
D3
D5
D6
D4
LT
MS
MR
TZ
8.8
17.6
140
280
280
560
560
1120
2240
SY
RY
TW
SV
RV
TI
1120
SH
RH
TG
SF
RF
TE
SD
RD
ZW
YV
ZI
YH
ZG
YF
ZE
YD
WI
VH
WG
VF
WE
VD
**Standard versions are shown in bold and are available in a D3
timeout option only. Standard versions require 2,500 piece order
increments and are typically held in sample stock. There is a
10,000 order increment on nonstandard versions. Other thresh-
old voltages may be available, contact factory for availability.
______________________________________________________________________________________ 15
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Pin Configurations
TOP VIEW
RST1
1
2
3
6
5
4
V
1
RST
GND
MR
1
2
3
5
4
V
V
V
1
2
1
RST
GND
MR
1
2
3
6
5
4
V 1
CC
CC
CC
CC
CC
MAX6715/
MAX6716
MAX6717/
MAX6718
MAX6719/
MAX6720
GND
MR
RST2
RSTIN
V
2
V 2
CC
CC
CC
SOT23-6
SOT23-5
SOT23-6
RST
1
2
3
4
8
7
6
5
V 1
CC
RST
GND
MR
1
2
3
6
5
4
V
1
RST
GND
WDI
1
2
3
6
5
4
GND
WDI
RST
RSTIN
MAX6721/
MAX6722
MAX6723/
MAX6724
MAX6725/
MAX6726
WDI
RSTIN
V
2
CC
MR
V
2
V 2
CC
CC
SOT23-8
SOT23-6
SOT23-6
RST
1
2
3
4
8
7
6
5
V
1
RST
GND
WDI
PFO
1
2
3
4
8
7
V
1
2
CC
CC
GND
WDI
RST
RSTIN
PFI
MAX6727
MAX6728/
MAX6729
V
2
6
5
V
CC
CC
MR
MR
SOT23-8
SOT23-8
16 ______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Package Information
______________________________________________________________________________________ 17
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Package Information (continued)
18 ______________________________________________________________________________________
Dual/Triple Ultra-Low-Voltage SOT23 µP
Supervisory Circuits
Package Information (continued)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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