MAX6830TIUT-T [MAXIM]
Power Supply Management Circuit, Fixed, 2 Channel, BICMOS, PDSO6, SOT-23, 6 PIN;
| 型号： | MAX6830TIUT-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Management Circuit, Fixed, 2 Channel, BICMOS, PDSO6, SOT-23, 6 PIN 信息通信管理 光电二极管 |
| 文件： | 总12页 (文件大小：590K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1867; Rev 2; 12/05
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
General Description
Features
The MAX6826–MAX6831 are ultra-low-voltage micro-
processor (µP) supervisory circuits designed to monitor
two power supplies and have manual reset and watch-
dog input functions. These devices assert a system reset
if any of the monitored supplies fall below the prepro-
grammed thresholds, and maintain reset for a minimum
timeout period after the supplies rise above the threshold.
Microprocessor supervisors significantly improve system
reliability and accuracy compared to separate ICs or dis-
crete components. These devices monitor primary volt-
ages from +1.8V to +5.0V and secondary voltages from
+0.9V to +2.5V. These devices are guaranteed to be in
♦ Monitor Primary V
Supplies from +1.8V
CC
to +5.0V and Secondary V
from +0.9V to +2.5V
♦ User Adjustable RESET IN Down to +0.63V
(MAX6826/MAX6827/MAX6828)
Supplies
CC2
♦ 140ms (min) Reset Timeout Delay
♦ 1.6s Watchdog Timeout Period
♦ Manual Reset Input
♦ Three Reset Output Options
Push-Pull RESET
Push-Pull RESET
Open-Drain RESET
the correct state for V down to +1.0V.
CC
A variety of preprogrammed reset threshold voltages
are available (see the Threshold Suffix Guide). The
devices include manual reset and watchdog inputs. The
MAX6829/MAX6830/MAX6831 provide a factory-
trimmed threshold to monitor a 2nd voltage down to
+0.9V. The MAX6826/MAX6829 have a push-pull
RESET, the MAX6827/MAX6830 have a push-pull
RESET and the MAX6828/MAX6831 have an open-drain
RESET. The MAX6826/MAX6827/MAX6828 have an aux-
iliary monitor that allows user adjustable input to monitor
voltages down to +0.6V. See Selector Guide for func-
tions available.
♦ Guaranteed Reset Valid Down to V
= +1.0V
CC
♦ Immune to Short Negative V
♦ No External Components
Transients
CC
♦ Small 6-pin SOT23 Packages
Ordering Information
†
PART
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
MAX6826_UT-T
MAX6827_UT-T
MAX6828_UT-T
MAX6829_ _UT-T
MAX6830_ _UT-T
MAX6831_ _UT-T
________________________Applications
Portable/Battery-
Powered Equipment
Automotive Systems
Critical µP Monitoring
Multivoltage Systems
Embedded Controllers
Intelligent Instruments
†
Insert the desired suffix letter (from Standard Versions table) into
the blanks to complete the part number.
Pin Configuration
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
TOP VIEW
Standard Versions Table*
RESET(RESET)
1
2
3
6
5
4
V
CC
MAX6826–
MAX6831
MAX6826/MAX6827/MAX6828
GND
MR
RESET IN/V
WDI
L
S
R
Z
V
CC2
SOT23-6
(RESET) MAX6827/MAX6830 ONLY
RESET IN FOR MAX6826/MAX6827/MAX6828 ONLY
*Samples are typically available for standard versions only.
The MAX6826/MAX6827/MAX6828 require a 2.5k minimum
order increment for all versions. Contact factory for availability.
V
FOR MAX6829/MAX6830/MAX6831 ONLY
CC2
Typical Operating Circuit, Threshold Suffix Guide, and
Selector Guide appear at end of data sheet.
Standard Versions Table continued at end of data sheet.
________________________________________________________________ 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 Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
ABSOLUTE MAXIMUM RATINGS
CC CC2
Open-Drain RESET................................................-0.3V to +6.0V
Push-Pull RESET, RESET............................-0.3V to (V
MR, WDI, RESET IN....................................-0.3V to (V
V
, V
to GND.................................................-0.3V to +6.0V
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
+ 0.3V)
+ 0.3V)
CC
CC
Input Current (V ).............................................................20mA
CC
Output Current (RESET, RESET).........................................20mA
Continuous Power Dissipation (T = +70°C)
A
6-Pin SOT23 (derate 8.7mW/°C above +70°C)..............696mW
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
= +4.5V to +5.5V for MAX68_ _L/M, V
= +2.7V to +3.6V for MAX68_ _T/S/R, V
= +2.1V to +2.75V for MAX68_ _Z/Y,
CC
CC
CC
V
CC
= +1.53V to +2.0V for MAX68_ _W/V; T = -40°C to +125°C, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
A
A
PARAMETER
Operating Voltage Range
SYMBOL
CONDITIONS
= 0°C to +85°C
MIN
1.0
TYP
MAX
5.5
UNITS
T
T
A
V
V
CC
= -40°C to +125°C
1.2
5.5
A
T
A
T
A
T
A
T
A
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
10
7
20
V
= +5.5V,
CC
no load
30
V
Supply Current
CC
I
µA
µA
CC
MR and WDI Unconnected
16
V
= +3.6V,
CC
no load
25
V
Supply Current
V
≤ +2.5V
2
CC2
CC2
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
4.50
4.47
4.25
4.22
3.00
2.97
2.85
2.83
2.55
2.53
2.25
2.24
2.12
2.11
1.62
1.61
1.52
4.63
4.63
4.38
4.38
3.08
3.08
2.93
2.93
2.63
2.63
2.32
2.32
2.19
2.19
1.67
1.67
1.58
4.75
4.78
4.50
4.53
3.15
3.17
3.00
3.02
2.70
2.72
2.38
2.40
2.25
2.26
1.71
1.72
1.62
MAX68_ _L
MAX68_ _M
MAX68_ _T
MAX68_ _S
MAX68_ _R
MAX68_ _Z
MAX68_ _Y
V
(V
Reset Threshold
Falling)
CC
V
V
TH
CC
MAX68_ _W
MAX68_ _V
2
_______________________________________________________________________________________
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
ELECTRICAL CHARACTERISTICS (continued)
(V
= +4.5V to +5.5V for MAX68_ _L/M, V
= +2.7V to +3.6V for MAX68_ _T/S/R, V
= +2.1V to +2.75V for MAX68_ _Z/Y,
CC
CC
CC
V
CC
= +1.53V to +2.0V for MAX68_ _W/V; T = -40°C to +125°C, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
2.381
2.388
2.257
2.263
1.715
1.719
1.625
1.629
1.429
1.433
1.354
1.358
1.143
1.146
1.083
1.086
0.858
0.860
0.813
0.815
UNITS
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
2.244
2.238
2.119
2.113
1.615
1.611
1.525
1.521
1.346
1.343
1.271
1.268
1.077
1.074
1.017
1.014
0.808
0.806
0.762
0.761
2.313
2.313
2.188
2.188
1.665
1.665
1.575
1.575
1.388
1.388
1.313
1.313
1.110
1.110
1.050
1.050
0.833
0.833
0.788
0.788
Z
Y
W
V
I
V
Reset Threshold
V
V
CC2
TH2
H
G
F
E
D
Reset Threshold Temperature
Coefficient
60
ppm/°C
mV
Reset Threshold Hysteresis
2 x V
TH
T
T
= 0°C to +85°C
0.615
0.610
0.630
0.645
0.650
A
RESET IN Threshold
V
V
falling
RSTINTH
V
RSTINTH
= -40°C to +125°C
A
RESET IN Hysteresis
2.5
mV
T
T
= -40°C to +85°C
= -40°C to +125°C
-25
+25
A
RESET IN Input Current (Note 2)
I
nA
RSTIN
-100
+100
A
V
to Reset Output Delay
t
V
V
= V to (V - 100mV)
20
15
µs
µs
CC
RD
CC
TH
TH
RESET IN to Reset Output Delay
= V
to (V
- 30mV)
RSTINTH
RSTIN
RSTINTH
T
A
T
A
= -40°C to +85°C
= -40°C to +125°C
140
100
200
280
320
Reset Timeout Period
t
ms
RP
V
≥ 1.0V, I
= 0°C to +85°C
= 50µA, reset asserted,
≥ 1.2V, I = 100µA, reset asserted
SINK
CC
SINK
0.3
T
A
RESET Output LOW
(Push-Pull or Open-Drain)
V
V
V
V
0.3
0.3
0.4
V
OL
CC
CC
CC
≥ 2.55V, I
= 1.2mA, reset asserted
= 3.2mA, reset asserted
SINK
SINK
≥ 4.25V, I
_______________________________________________________________________________________
3
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
ELECTRICAL CHARACTERISTICS (continued)
(V
= +4.5V to +5.5V for MAX68_ _L/M, V
= +2.7V to +3.6V for MAX68_ _T/S/R, V
= +2.1V to +2.75V for MAX68_ _Z/Y,
CC
CC
CC
V
CC
= +1.53V to +2.0V for MAX68_ _W/V; T = -40°C to +125°C, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
✕
V
CC
V
CC
V
CC
≥ 1.8V, I
= 200µA, reset not asserted 0.8
V
CC
V
CC
V
CC
SOURCE
RESET Output HIGH
(Push-Pull Only)
✕
✕
V
≥ 3.15V, I
= 500µA, reset not asserted 0.8
V
OH
SOURCE
SOURCE
≥ 4.75V, I
= 800µA, reset not asserted 0.8
Open-Drain RESET Output
Leakage Current (Note 1)
I
RESET not asserted
1.0
µA
V
LKG
V
≥ 1.0V, I
= 1µA, reset asserted,
0.8
CC
SOURCE
✕
V
CC
T
A
= 0°C to +85°C
RESET Output HIGH
(Push-Pull Only)
V
V
✕
✕
✕
V
V
V
V
V
V
≥ 1.50V, I
= 100µA, reset asserted
= 500µA, reset asserted
= 800µA, reset asserted
0.8
0.8
0.8
V
CC
V
CC
V
CC
OH
OH
CC
SOURCE
≥ 2.55V, I
≥ 4.25V, I
CC
CC
CC
CC
CC
SOURCE
SOURCE
≥ 1.8V, I
= 500µA, reset asserted
0.3
0.3
0.3
SINK
RESET Output LOW
(Push-Pull Only)
≥ 3.15V, I
≥ 4.75V, I
= 1.2mA, reset asserted
= 3.2mA, reset asserted
V
V
SINK
SINK
MANUAL RESET INPUT
✕
V
0.3
V
IL
CC
MR Input voltage
✕
V
0.7
V
CC
IH
MR Minimum Input Pulse
MR Glitch Rejection
MR to Reset Delay
1
µs
ns
ns
kΩ
100
200
50
MR Pullup Resistance
WATCHDOG INPUT
25
75
T
T
= -40°C to +85°C
= -40°C to +125°C
1.12
0.80
50
1.6
2.4
A
Watchdog Timeout Period
WDI Pulse Width (Note 2)
WDI Input Voltage
t
s
ns
V
WD
2.60
A
t
WDI
✕
V
0.3
V
IL
CC
✕
V
0.7
V
CC
IH
WDI = V , time average
CC
120
-15
160
WDI Input Current
I
µA
WDI
WDI = 0, time average
-20
Note 1: Over-temperature limits are guaranteed by design and not production tested. Devices tested at +25°C.
Note 2: Guaranteed by design and not production tested.
4
_______________________________________________________________________________________
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
RESET TIMEOUT PERIOD
vs. TEMPERATURE
SUPPLY CURRENT
vs. TEMPERATURE
V
TO RESET OUTPUT DELAY
vs. TEMPERATURE
CC
250
240
230
220
210
200
190
180
170
160
150
13
35
30
25
20
15
10
5
V
FALLING, V = V - 100mV
CC TH
CC
12
V
V
= +5V, L VERSION
11
10
9
CC
8
= +3.3V, S VERSION
= +1.8V, V VERSION
CC
7
6
V
CC
5
4
3
0
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
DELAY vs. TEMPERATURE
MAXIMUM V TRANSIENT DURATION
CC
vs. RESET THRESHOLD OVERDRIVE
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
1.06
1.04
120
100
80
60
40
20
0
1.02
1.00
RESET OCCURS
ABOVE CURVE
0.98
0.96
0.94
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
0
20 40 60 80 100 120 140 160 180 200
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV), V - V
TH
CC
V
RSTIN
TO RESET OUTPUT DELAY
vs. TEMPERATURE
MAXIMUM V
vs. RESET THRESHOLD OVERDRIVE
TRANSIENT DURATION
RSTIN
25
20
15
10
100
90
V
V
FALLING
RSTIN
RSTIN
= V
- 30mV
RSTINTH
80
70
60
50
40
30
20
10
RESET OCCURS
ABOVE CURVE
5
0
0
0
-40 -20
0
20 40 60 80 100 120
20 40 60 80 100 120 140 160 180 200
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV), V
- V
RSTIN
RSTINTH
_______________________________________________________________________________________
5
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
VOLTAGE OUTPUT HIGH vs. I
SOURCE
VOLTAGE OUTPUT LOW vs. I
SINK
2.92
2.90
2.88
2.86
2.84
2.82
2.80
2.78
2.76
2.74
0.350
0.300
0.250
0.200
0.150
0.010
0.005
0
V
= +2.9V
CC
V
CC
= +2.9V
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
(mA)
0
1
2
3
4
5
6
7
I
SOURCE
I
(mA)
SINK
Pin Description
PIN
NAME
FUNCTION
MAX MAX MAX MAX MAX MAX
6826 6827 6828 6829 6830 6831
Active-Low Open-Drain or Push-Pull Reset Output. RESET changes from high
to low when V , V , or RESET IN input drops below the selected reset
CC1 CC2
1
1
1
1
RESET threshold, MR is pulled low, or the watchdog triggers a reset. RESET remains
low for the reset timeout period after all voltages exceed the device reset
threshold, MR goes low to high, or the watchdog triggers a reset.
Active-High Push-Pull Reset Output. RESET changes from low to high when
V
, V , or RESET IN input drops below the selected reset threshold, MR
CC1 CC2
1
1
RESET is pulled low, or the watchdog triggers a reset. RESET remains HIGH for the
reset timeout period after all voltages exceed the device reset threshold, MR
goes low to high, or the watchdog triggers a reset.
2
3
2
3
2
3
2
3
2
3
2
3
GND
Ground
Manual Reset Input, Active-Low, Internal 50kΩ pullup to V . Pull low to force a
reset. Reset remains active as long as MR is low and for the reset timeout period
CC
MR
after MR goes high. Leave unconnected or connect to V , if unused.
CC
Watchdog Input. If WDI remains high or low for longer than the watchdog timeout
period, the internal watchdog timer runs out and a reset is triggered for the reset
timeout period. The internal watchdog timer clears whenever reset is asserted, the
manual reset is asserted, or WDI sees a rising or falling edge. If WDI is left
unconnected or is connected to a three-stated buffer output, the watchdog feature
is disabled.
4
4
4
4
4
4
WDI
6
_______________________________________________________________________________________
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Pin Description (continued)
PIN
NAME
FUNCTION
MAX MAX MAX MAX MAX MAX
6826 6827 6828 6829 6830 6831
Input for User Adjustable RESET IN Monitor. High-impedance input for
internal reset comparator. Connect this pin to an external resistor-divider
network to set the reset threshold voltage. 0.63V (typ) threshold.
RESET
IN
5
5
5
Factory-Trimmed V
supply voltage.
Monitor. Connect this pin to a secondary power-
CC2
5
6
5
6
5
6
V
CC2
6
6
6
V
Supply Voltage. Input for primary reset threshold monitor.
CC
V
CC
MAX6826/MAX6827/MAX6828
RESET
OR
RESET
RESET TIMEOUT
DELAY GENERATOR
1.26V
0.63V
V
CC
RESET IN
MR
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
Figure 1. Functional Diagram of RESET IN
_______________________________________________________________________________________
7
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
V
CC
MAX6829/MAX6830/MAX6831
RESET
OR
RESET
RESET TIMEOUT
DELAY GENERATOR
1.26V
0.63V
V
CC2
V
CC
MR
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
Figure 2. Functional Diagram of V
CC2
asserts a reset. Reset remains asserted while MR is
low, and for the timeout period (140ms min) after it
returns high. MR has an internal 50kΩ pullup resistor,
so it can be left open if not used. This input can be dri-
ven with CMOS logic levels or with open-drain/collector
Detailed Description
RESET/RESET Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX6826–MAX6831 µP supervisory
circuits assert a reset to prevent code-execution errors
during power-up, power-down, and brownout condi-
tions. Whenever a monitored voltage falls below the
reset threshold, the reset output asserts low for RESET
and high for RESET. Once all monitored voltages
exceed their reset thresholds, an internal timer keeps
the reset output asserted for the specified reset timeout
V
CC
V
V
TH
TH
1V
1V
t
t
RP
RP
t
RD
RESET
period (t ); after this interval, reset output returns to its
RP
original state (Figure 3).
t
RESET
RD
Manual Reset Input
Many µP-based products require manual-reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on MR
GND
Figure 3. Reset Timing Diagram
8
_______________________________________________________________________________________
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
V
CC
t
V
CC
V
CC
RST
MAX6828
MAX6831
RESET*
WDI
RESET
RESET
µP
t
RP
t
t
RP
WD
RESET
GENERATOR
GND
GND
*RESET IS THE INVERSE OF RESET.
Figure 6. Interfacing Open-Drain RESET to µPs with
Bidirectional Reset I/O
Figure 4. Watchdog Timing Relationship
the maximum allowable leakage current is 10µA and the
maximum allowable load capacitance is 200pF.
V
MONITOR
MAX6826
MAX6827
MAX6828
Adjustable Reset Thresholds
The MAX6826/MAX6827/MAX6828 provide a user
adjustable input to monitor a second voltage. The
threshold voltage at RSTIN is typically 0.63V. To moni-
tor a voltage higher than 0.63V, connect a resistor-
divider to the circuit as shown in Figure 5. The
R1
R2
RSTIN
threshold at V
is:
MONITOR
V
≥ V
RSTIN
CC
R1 + R2
V
= 0.63V
MONITOR_TRIP
R2
Figure 5. Monitoring a Voltage
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 dri-
ven from long cables or the device is used in a noisy
environment, connect a 0.1µF capacitor from MR to
GND to provide additional noise immunity.
Note that RSTIN is powered by V , and its voltage
CC
.
must therefore remain lower than V
CC
Applications Information
Watchdog Input Current
The WDI inputs are internally driven through a buffer
and series resistor from the watchdog timer (Figure 1).
When WDI is left unconnected, the watchdog timer is
serviced within the watchdog timeout period by a low-
high-low pulse from the counter chain. For minimum
watchdog input current (minimum overall power con-
sumption), leave WDI low for the majority of the watch-
dog timeout period, pulsing it low-high-low once within
the first 7/8 of the watchdog timeout period to reset the
watchdog timer. If WDI is externally driven high for the
majority of the timeout period, up to 160µA can flow into
WDI.
Watchdog Input
The watchdog circuit monitors the µP’s activity. If the
µP does not toggle (low to high or high to low) the
watchdog input (WDI) within the watchdog timeout peri-
od (1.6s nominal), reset asserts for the reset timeout
period. The internal 1.6s timer can be cleared by either
a reset pulse or by toggling WDI. The WDI can detect
pulses as short as 50ns. While reset is asserted, the
timer remains cleared and does not count. As soon as
reset is released, the timer starts counting (Figure 4).
Disable the watchdog function by leaving WDI uncon-
nected or by three-stating the driver connected to WDI.
The watchdog input is internally driven low during the
first 7/8 of the watchdog timeout period and high for the
last 1/8 of the watchdog timeout period. When WDI is left
unconnected, this internal driver clears the 1.6s timer
every 1.4s. When WDI is three-stated or unconnected,
Interfacing to µPs
with Bidirectional Reset Pins
Since the RESET output on the MAX6828/MAX6831
is open drain, these devices interface easily with µPs
that have bidirectional reset pins, such as the Motorola
68HC11. Connecting the µP supervisor’s RESET output
_______________________________________________________________________________________
9
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Watchdog Software Considerations
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
input at different points in the program, rather than
pulsing the watchdog input high-low-high or low-high-
low. This technique avoids a stuck loop, in which the
watchdog timer would continue to be reset inside the
loop, keeping the watchdog from timing out.
directly to the microcontroller’s RESET pin with a single
pullup resistor allows the device to assert a reset
(Figure 6).
Negative-Going V
Transients
CC
These supervisors are relatively immune to short-dura-
tion, negative-going V transients (glitches), which
CC
usually do not require the entire system to shut down.
Resets are issued to the µP during power-up, power-
down, and brownout conditions. The Typical Operating
Figure 8 shows an example of a flow diagram where the
I/O driving the watchdog input is set high at the begin-
ning of the program, set low at the beginning of every
subroutine or loop, then set high again when the pro-
gram returns to the beginning. If the program should
hang in any subroutine, the problem would quickly be
corrected, since the I/O is continually set low and the
watchdog timer is allowed to time out, causing a reset
or interrupt to be issued. As described in the Watchdog
Input Current section, this scheme results in higher time
average WDI input current than does leaving WDI low
for the majority of the timeout period and periodically
pulsing it low-high-low.
Characteristics show a graph of the Maximum V
CC
Transient Duration vs. Reset Threshold Overdrive, for
which reset pulses are not generated. The graph was
produced using negative-going V
pulses, starting at
CC
the standard monitored voltage 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
transient can
CC
typically have without triggering a reset pulse. As the
amplitude of the transient increases (i.e., goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Typically, a V
transient that
CC
goes 100mV below the reset threshold and lasts for
20µs or less will not trigger a reset pulse.
Ensuring a Valid RESET
Output Down to V
= 0
CC
The MAX6826–MAX6831 are guaranteed to operate
properly down to V = 1V. In applications that require
START
CC
valid reset levels down to V
= 0, a pulldown resistor
CC
SET WDI
HIGH
to active-low outputs (push/pull only, Figure 7) and a
pullup resistor to active-high outputs (push/pull only) will
ensure that the reset line is valid while the reset output
can no longer sink or source current. This scheme does
not work with the open-drain outputs of the
MAX6828/MAX6831. The resistor value used is not criti-
cal, but it must be small enough not to load the reset
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
output when V
is above the reset threshold. For falling
slew rates greater than 1V/s, a 100kΩ is adequate.
CC
SET WDI LOW
V
CC
RETURN
Figure 8. Watchdog Flow Diagram
MAX6826
MAX6829
RESET
R1
100kΩ
GND
Figure 7. RESET Valid to V = Ground Circuit
CC
10 ______________________________________________________________________________________
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Threshold Suffix Guide
V
CC
THRESHOLD
RESET THRESHOLD (V)
V
CC2
THRESHOLD
RESET THRESHOLD (V)
L
M
T
4.63
4.38
3.08
2.93
2.63
2.32
2.19
1.67
Z
Y
W
V
I
2.313
2.188
1.665
1.575
1.388
1.313
1.110
1.050
0.833
0.788
S
R
Z
H
G
F
Y
W
E
D
V
1.58
Selector Guide
ADJUSTABLE
ACTIVE-LOW ACTIVE-HIGH OPEN-DRAIN WATCHDOG
MANUAL
RESET INPUT
FIXED V
CC2
MONITOR
FUNCTION
RESET
INPUT
RESET
RESET
RESET
INPUT
MAX6826
MAX6827
MAX6828
MAX6829
MAX6830
MAX6831
✔
—
—
✔
—
✔
—
—
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
—
—
—
✔
✔
✔
✔
✔
—
—
✔
✔
—
—
✔
—
—
—
—
—
—
Standard Versions
Table* (continued)
Chip Information
TRANSISTOR COUNT: 750
PROCESS TECHNOLOGY: BiCMOS
MAX6829/MAX6830/MAX6831
V
V
CC2
CC
Typical Operating Circuit
3.3V
TZ
2.5V
—
1.8V
—
—
2.5V
1.8V
1.5V
1.2V
0.9V
V
CC
SV
ZW
YH
YG
YD
—
CORE
I/O
V
CC2
SH
SF
WI
VF
VD
SUPPLY SUPPLY
V
CC
V
CC2
RESET
RESET
SD
*Samples are typically available for standard versions only. For
the MAX6829/MAX6830/MAX6831, standard versions require a
2.5k minimum order increment, while nonstandard versions
require a 10k minimum order increment and are not typically
available in samples. Contact factory for availability.
MAX6829
MAX6830
MAX6831 WDI
µP
I/O
MR
GND
MANUAL
RESET
______________________________________________________________________________________ 11
Dual Ultra-Low-Voltage SOT23 µP Supervisors
with Manual Reset and Watchdog Timer
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, SOT 6L BODY
1
21-0058
G
1
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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