MAX6826RUT+T - Maxim Integrated

Standard Versions Table continued at end of data sheet.

Typical Operating Circuit, Threshold Suffix Guide, and

Selector Guide appear at end of data sheet.

●Portable/Battery-

Powered Equipment

●Embedded Controllers

●Intelligent Instruments

●Critical µP Monitoring

●Multivoltage Systems

General Description

The MAX6826–MAX6831 are ultra-low-voltage micropro-

cessor (µP) supervisory circuits designed to monitor two

power supplies and have manual reset and watchdog

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

discrete components. These devices monitor primary

voltages from +1.8V to +5.0V and secondary voltages

from +0.9V to +2.5V. These devices are guaranteed to be

in the correct state for VCC down to +1.0V.

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

auxiliary monitor that allows user adjustable input to

monitor voltages down to +0.6V. see Selector Guide for

functions available.

Applications

Features

●Monitor Primary VCC Supplies from +1.8V

to +5.0V and Secondary VCC2 Supplies

from +0.9V to +2.5V

●User Adjustable RESET IN Down to +0.63V

(MAX6826/MAX6827/MAX6828)

●140ms (min) Reset Timeout Delay

●1.6s Watchdog Timeout Period

●Manual Reset Input

●Three Reset Output Options

Push-Pull RESET

Open-Drain RESET

●Guaranteed Reset Valid Down to VCC = +1.0V

●Immune to Short Negative VCC Transients

●No External Components

●Small 6-pin SOT23 Packages

*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.

†Insert the desired suffix letter (from Standard versions table)

into the blanks to complete the part number.

Devices are available in both leaded and lead-free packaging.

Specify lead-free by replacing “-T” with “+T” when ordering.

MAX6826/MAX6827/MAX6828

PART†TEMP RANGE PIN-PACKAGE

MAX6826_UT-T -40°C to +125°C 6 SOT23

MAX6827_UT-T -40°C to +125°C 6 SOT23

MAX6828_UT-T -40°C to +125°C 6 SOT23

MAX6829_ _UT-T -40°C to +125°C 6 SOT23

MAX6830_ _UT-T -40°C to +125°C 6 SOT23

MAX6831_ _UT-T -40°C to +125°C 6 SOT23

GND

WDIMR

1 6 VCC

5 RESET IN/VCC2

RESET(RESET)

(RESET) MAX6827/MAX6830 ONLY

RESET IN FOR MAX6826/MAX6827/MAX6828 ONLY

VCC2 FOR MAX6829/MAX6830/MAX6831 ONLY

MAX6826–

MAX6831

SOT23-6

TOP VIEW

3 4

MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors

with Manual Reset and Watchdog Timer

19-1867; Rev 3; 7/14

Standard Versions Table*

Ordering Information

Pin Conguration

VCC, VCC2 to GND...............................................-0.3V to +6.0V

Open-Drain RESET .............................................. -0.3V to +6.0V

Push-Pull RESET, RESET ....................... -0.3V to (VCC + 0.3V)

MR, WDI, RESET IN ................................ -0.3V to (VCC + 0.3V)

Input Current (VCC) ............................................................20mA

Output Current (RESET, RESET) ......................................20mA

Continuous Power Dissipation (TA = +70°C)

6-Pin SOT23 (derate 8.7mW/°C above +70°C) ..........696mW

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

(VCC = +4.5V to +5.5V for MAX68_ _L/M, VCC = +2.7V to +3.6V for MAX68_ _T/S/R, VCC = +2.1V to +2.75V for MAX68_ _Z/Y,

VCC = +1.53V to +2.0V for MAX68_ _W/V; TA = -40°C to +125°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Voltage Range VCC

TA = 0°C to +85°C 1.0 5.5 V

TA = -40°C to +125°C 1.2 5.5

VCC Supply Current

MR and WDI Unconnected ICC

VCC = +5.5V,

no load

TA = -40°C to +85°C 10 20

µA

TA = -40°C to +125°C 30

VCC = +3.6V,

no load

TA = -40°C to +85°C 7 16

TA = -40°C to +125°C 25

VCC2 Supply Current VCC2 ≤ +2.5V 2 µA

VCC Reset Threshold

(VCC Falling) VTH

MAX68_ _L TA = -40°C to +85°C 4.50 4.63 4.75

TA = -40°C to +125°C 4.47 4.63 4.78

MAX68_ _M TA = -40°C to +85°C 4.25 4.38 4.50

TA = -40°C to +125°C 4.22 4.38 4.53

MAX68_ _T TA = -40°C to +85°C 3.00 3.08 3.15

TA = -40°C to +125°C 2.97 3.08 3.17

MAX68_ _S TA = -40°C to +85°C 2.85 2.93 3.00

TA = -40°C to +125°C 2.83 2.93 3.02

MAX68_ _R TA = -40°C to +85°C 2.55 2.63 2.70

TA = -40°C to +125°C 2.53 2.63 2.72

MAX68_ _Z TA = -40°C to +85°C 2.25 2.32 2.38

TA = -40°C to +125°C 2.24 2.32 2.40

MAX68_ _Y TA = -40°C to +85°C 2.12 2.19 2.25

TA = -40°C to +125°C 2.11 2.19 2.26

MAX68_ _W TA = -40°C to +85°C 1.62 1.67 1.71

TA = -40°C to +125°C 1.61 1.67 1.72

MAX68_ _V TA = -40°C to +85°C 1.52 1.58 1.62

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Electrical Characteristics

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.

Absolute Maximum Ratings

(VCC = +4.5V to +5.5V for MAX68_ _L/M, VCC = +2.7V to +3.6V for MAX68_ _T/S/R, VCC = +2.1V to +2.75V for MAX68_ _Z/Y,

VCC = +1.53V to +2.0V for MAX68_ _W/V; TA = -40°C to +125°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

VCC2 Reset Threshold VTH2

ZTA = -40°C to +85°C 2.244 2.313 2.381

TA = -40°C to +125°C 2.238 2.313 2.388

YTA = -40°C to +85°C 2.119 2.188 2.257

TA = -40°C to +125°C 2.113 2.188 2.263

WTA = -40°C to +85°C 1.615 1.665 1.715

TA = -40°C to +125°C 1.611 1.665 1.719

VTA = -40°C to +85°C 1.525 1.575 1.625

TA = -40°C to +125°C 1.521 1.575 1.629

ITA = -40°C to +85°C 1.346 1.388 1.429

TA = -40°C to +125°C 1.343 1.388 1.433

HTA = -40°C to +85°C 1.271 1.313 1.354

TA = -40°C to +125°C 1.268 1.313 1.358

GTA = -40°C to +85°C 1.077 1.110 1.143

TA = -40°C to +125°C 1.074 1.110 1.146

FTA = -40°C to +85°C 1.017 1.050 1.083

TA = -40°C to +125°C 1.014 1.050 1.086

ETA = -40°C to +85°C 0.808 0.833 0.858

TA = -40°C to +125°C 0.806 0.833 0.860

DTA = -40°C to +85°C 0.762 0.788 0.813

TA = -40°C to +125°C 0.761 0.788 0.815

Reset Threshold Temperature

Coefficient 60 ppm/°C

Reset Threshold Hysteresis 2 x VTH mV

RESET IN Threshold VRSTINTH VRSTINTH falling TA = 0°C to +85°C 0.615 0.630 0.645 V

TA = -40°C to +125°C 0.610 0.650

RESET IN Hysteresis 2.5 mV

RESET IN Input Current (Note 2) IRSTIN

TA = -40°C to +85°C -25 +25 nA

TA = -40°C to +125°C -100 +100

VCC to Reset Output Delay tRD VCC = VTH to (VTH - 100mV) 20 µs

RESET IN to Reset Output Delay VRSTIN = VRSTINTH to (VRSTINTH - 30mV) 15 µs

Reset Timeout Period tRP

TA = -40°C to +85°C 140 200 280 ms

TA = -40°C to +125°C 100 320

RESET Output LOW

(Push-Pull or Open-Drain) VOL

VCC ≥ 1.0V, ISINK = 50µA, reset asserted,

TA = 0°C to +85°C 0.3

VVCC ≥ 1.2V, ISINK = 100µA, reset asserted 0.3

VCC ≥ 2.55V, ISINK = 1.2mA, reset asserted 0.3

VCC ≥ 4.25V, ISINK = 3.2mA, reset asserted 0.4

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Electrical Characteristics (continued)

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.

(VCC = +4.5V to +5.5V for MAX68_ _L/M, VCC = +2.7V to +3.6V for MAX68_ _T/S/R, VCC = +2.1V to +2.75V for MAX68_ _Z/Y,

VCC = +1.53V to +2.0V for MAX68_ _W/V; TA = -40°C to +125°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RESET Output HIGH

(Push-Pull Only) VOH

VCC ≥ 1.8V, ISOURCE = 200µA, reset not asserted 0.8 × VCC

VVCC ≥ 3.15V, ISOURCE = 500µA, reset not asserted 0.8 × VCC

VCC ≥ 4.75V, ISOURCE = 800µA, reset not asserted 0.8 × VCC

Open-Drain RESET Output

Leakage Current (Note 1) ILKG RESET not asserted 1.0 µA

RESET Output HIGH

(Push-Pull Only) VOH

VCC ≥ 1.0V, ISOURCE = 1µA, reset asserted,

TA = 0°C to +85°C 0.8 × VCC

VCC ≥ 1.50V, ISOURCE = 100µA, reset asserted 0.8 × VCC

VCC ≥ 2.55V, ISOURCE = 500µA, reset asserted 0.8 × VCC

VCC ≥ 4.25V, ISOURCE = 800µA, reset asserted 0.8 × VCC

RESET Output LOW

(Push-Pull Only) VOH

VCC ≥ 1.8V, ISINK = 500µA, reset asserted 0.3

VVCC ≥ 3.15V, ISINK = 1.2mA, reset asserted 0.3

VCC ≥ 4.75V, ISINK = 3.2mA, reset asserted 0.3

MANUAL RESET INPUT

MR Input voltage VIL0.3 × VCC V

VIH 0.7 × VCC

MR Minimum Input Pulse 1 µs

MR Glitch Rejection 100 ns

MR to Reset Delay 200 ns

MR Pullup Resistance 25 50 75 kΩ

WATCHDOG INPUT

Watchdog Timeout Period tWD

TA = -40°C to +85°C 1.12 1.6 2.4 s

TA = -40°C to +125°C 0.80 2.60

WDI Pulse Width (Note 2) tWDI 50 ns

WDI Input Voltage VIL 0.3 × VCC V

VIH 0.7 × VCC

WDI Input Current IWDI

WDI = VCC, time average 120 160 µA

WDI = 0, time average -20 -15

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

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Electrical Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

100

0 806020 40 100 120 140 160 180 200

MAXIMUM VRSTIN TRANSIENT DURATION

vs. RESET THRESHOLD OVERDRIVE

MAX6826 toc08

RESET THRESHOLD OVERDRIVE (mV), VRSTINTH - VRSTIN

TRANSIENT DURATION (µs)

RESET OCCURS

ABOVE CURVE

-40 0 20-20 40 60 80 100 120

VRSTIN TO RESET OUTPUT DELAY

vs. TEMPERATURE

MAX6826 toc07

TEMPERATURE (C)

PROPAGATION DELAY (µs)

VRSTIN FALLING

VRSTIN = VRSTINTH - 30mV

100

120

0 806020 40 100 120 140 160 180 200

MAXIMUM VCC TRANSIENT DURATION

vs. RESET THRESHOLD OVERDRIVE

MAX6826 toc06

RESET THRESHOLD OVERDRIVE (mV), VTH - VCC

TRANSIENT DURATION (µs)

RESET OCCURS

ABOVE CURVE

0.94

0.96

1.00

0.98

1.04

1.02

1.06

-40 0 20-20 40 60 80 100 120

NORMALIZED RESET THRESHOLD

DELAY vs. TEMPERATURE

MAX6826 toc05

TEMPERATURE (°C)

RESET THRESHOLD (V)

1.0

1.2

1.1

1.4

1.3

1.6

1.5

1.7

1.9

1.8

2.0

-40 0 20 40-20 60 80 100 120

WATCHDOG TIMEOUT PERIOD

vs. TEMPERATURE

MAX6826 toc04

TEMPERATURE (°C)

WATCHDOG TIMEOUT PERIOD (s)

-40 0 20-20 40 60 80 100 120

VCC TO RESET OUTPUT DELAY

vs. TEMPERATURE

MAX6826 toc03

TEMPERATURE (C)

PROPAGATION DELAY (µs)

VCC FALLING, VCC = VTH - 100mV

150

170

160

190

180

210

200

220

240

230

250

-40 0 20 40-20 60 80 100 120

RESET TIMEOUT PERIOD

vs. TEMPERATURE

MAX6826 toc02

TEMPERATURE (°C)

RESET TIMEOUT PERIOD (ms)

-40 0 20 40-20 60 80 100 120

SUPPLY CURRENT

vs. TEMPERATURE

MAX6826 toc01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

VCC = +5V, L VERSION

VCC = +3.3V, S VERSION

VCC = +1.8V, V VERSION

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

NAME FUNCTION

MAX

6826

MAX

6827

MAX

6828

MAX

6829

MAX

6830

MAX

6831

1 1 1 1 RESET

Active-Low Open-Drain or Push-Pull Reset Output. RESET changes from high

to low when VCC1, VCC2, or RESET IN input drops below the selected 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.

1 1 RESET

Active-High Push-Pull Reset Output. RESET changes from low to high when

VCC1, VCC2, or RESET IN input drops below the selected reset threshold, MR

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 2 2 2 2 2 GND Ground

3 3 3 3 3 3 MR Manual-Reset Input, Active-Low, Internal 50kW pullup to VCC. Pull low to force a

reset. Reset remains active as long as MR is low and for the reset timeout period

after MR goes high. Leave unconnected or connect to VCC, if unused.

4 4 4 4 4 4 WDI

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.

2.74

2.78

2.76

2.82

2.80

2.84

2.86

2.90

2.88

2.92

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

VOLTAGE OUTPUT HIGH vs. ISOURCE

MAX6826 toc10

ISOURCE (mA)

VOUT (V)

VCC = +2.9V

0.010

0.005

0.200

0.150

0.300

0.250

0.350

0 2 31 4 5 6 7

VOLTAGE OUTPUT LOW vs. ISINK

MAX6826 toc09

ISINK (mA)

VOUT (V)

VCC = +2.9V

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Pin Description

Typical Operating Characteristics (continued)

Figure 1. Functional Diagram of RESET IN

NAME FUNCTION

MAX

6826

MAX

6827

MAX

6828

MAX

6829

MAX

6830

MAX

6831

5 5 5 RESET

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.

5 5 5 VCC2 Factory-Trimmed VCC2 Monitor. Connect this pin to a secondary power-

supply voltage.

6 6 6 6 6 6 VCC Supply Voltage. Input for primary reset threshold monitor.

MAX6826/MAX6827/MAX6828

VCC

WDI

RESET

RESET TIMEOUT

DELAY GENERATOR

1.26V

0.63V

WATCHDOG

TIMER

WATCHDOG

TRANSITION

DETECTOR

RESET IN

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Pin Description (continued)

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 conditions. 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

period (tRP); after this interval, reset output returns to its

original state (Figure 3).

Manual-Reset Input

Many µP-based products require manual-reset

capability, allowing the operator, a test technician, or

external logic circuitry to initiate a reset. A logic low on

MR 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

Figure 3. Reset Timing Diagram

Figure 2. Functional Diagram of VCC2

VCC

tRD

VTH VTH

tRD

RESET

GND

RESET

tRP

MAX6829/MAX6830/MAX6831

VCC

VCC2 VCC

WDI

RESET

RESET TIMEOUT

DELAY GENERATOR

1.26V

0.63V

WATCHDOG

TIMER

WATCHDOG

TRANSITION

DETECTOR

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

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.

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

period (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,

the maximum allowable leakage current is 10µA and the

maximum allowable load capacitance is 200pF.

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

threshold at VMONITOR is:

MONITOR_TRIP

R1 R2

V 0.63V R2







Note that RSTIN is powered by VCC, and its voltage must

therefore remain lower than VCC.

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 consumption),

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.

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

directly to the microcontroller’s RESET pin with a single

pullup resistor allows the device to assert a reset

(Figure 6).

Figure 6. Interfacing Open-Drain RESET to µPs with

Bidirectional Reset I/O

Figure 5. Monitoring a Voltage

Figure 4. Watchdog Timing Relationship

MAX6828

MAX6831

RESET

GENERATOR

GND GND

VCC VCC

RESET RESET

µP

VMONITOR

VCC ≥ VRSTIN

RSTIN

MAX6826

MAX6827

MAX6828

VCC

tWD tRP

tRP

tRST

WDI

RESET*

*RESET IS THE INVERSE OF RESET.

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MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Negative-Going VCC Transients

These supervisors are relatively immune to short-

duration, negative-going VCC transients (glitches),

which 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 Characteristics show a graph of the Maximum

VCC Transient Duration vs. Reset Threshold Overdrive,

for which reset pulses are not generated. The graph

was produced using negative-going VCC pulses, start-

ing at 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 VCC transient can

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 VCC transient that 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

VCC = 0

The MAX6826–MAX6831 are guaranteed to operate

properly down to VCC = 1V. In applications that require

valid reset levels down to VCC = 0, a pulldown resistor 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 critical, but it must be small

enough not to load the reset output when VCC is above

the reset threshold. For falling slew rates greater than

1V/s, a 100kW is adequate.

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.

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.

Figure 8. Watchdog Flow Diagram

Figure 7. RESET Valid to VCC = Ground Circuit

START

SET WDI

HIGH

PROGRAM

CODE

SUBROUTINE OR

PROGRAM LOOP

SET WDI LOW

RETURN

MAX6826

MAX6829

VCC

100kΩ

RESET

GND

www.maximintegrated.com Maxim Integrated

│

MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

*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 sam-

ples. Contact factory for availability.

MAX6829/MAX6830/MAX6831

VCC VCC2

3.3V 2.5V 1.8V —

TZ — — 2.5V

SV ZW — 1.8V

SH YH WI 1.5V

SF YG VF 1.2V

SD YD VD 0.9V

FUNCTION ACTIVE-LOW

RESET ACTIVE-HIGH

RESET

OPEN-DRAIN

RESET WATCHDOG

INPUT

MANUAL

RESET INPUT

FIXED VCC2

MONITOR

ADJUSTABLE

RESET

INPUT

MAX6826 ✔— — ✔ ✔ —✔

MAX6827 — ✔—✔ ✔ —✔

MAX6828 — — ✔✔✔—✔

MAX6829 ✔— — ✔ ✔ ✔ —

MAX6830 — ✔—✔ ✔ ✔ —

MAX6831 — — ✔ ✔ ✔ ✔ —

VCC THRESHOLD RESET THRESHOLD (V) VCC2 THRESHOLD RESET THRESHOLD (V)

L 4.63 Z 2.313

M 4.38 Y 2.188

T 3.08 W 1.665

S 2.93 V 1.575

R 2.63 I 1.388

Z 2.32 H 1.313

Y 2.19 G 1.110

W 1.67 F 1.050

V 1.58 E 0.833

D 0.788

www.maximintegrated.com Maxim Integrated

│

MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Standard Versions Table* (continued)

Selector Guide

Threshold Sufx Guide

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

6 SOT U6+1 21-0058 90-0175

www.maximintegrated.com Maxim Integrated

│

MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

MAX6829

MAX6830

MAX6831

µP

VCC

VCC2

GND

MANUAL

RESET

I/O

CORE

SUPPLY

I/O

SUPPLY

RESET

WDI

Typical Operating Circuit Chip Information

TRANSISTOR COUNT: 750

PROCESS TECHNOLOGY: BiCMOS

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.

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

3 7/14 No /V OPNs; removed Automotive reference from Applications section 1

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 specications 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.

│

MAX6826-MAX6831 Dual Ultra-Low-Voltage SOT23 µP Supervisors with

Manual Reset and Watchdog Timer

Revision History

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.

Mouser Electronics

Authorized Distributor

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MAX6826LUT+T MAX6826MUT+T MAX6826RUT+T MAX6826SUT+T MAX6826TUT+T MAX6826VUT+T

MAX6826WUT+T MAX6826YUT+T MAX6826ZUT+T MAX6827LUT+T MAX6827MUT+T MAX6827RUT+T

MAX6827SUT+T MAX6827TUT+T MAX6827VUT+T MAX6827WUT+T MAX6827YUT+T MAX6827ZUT+T

MAX6828LUT+T MAX6828MUT+T MAX6828RUT+T MAX6828SUT+T MAX6828TUT+T MAX6828VUT+T

MAX6828ZUT+T MAX6829SDUT+T MAX6829SFUT+T MAX6829SHUT+T MAX6829SVUT+T MAX6829TIUT+T

MAX6829TWUT+T MAX6829TZUT+T MAX6829VDUT+T MAX6829VFUT+T MAX6829WIUT+T MAX6829YDUT+T

MAX6829YGUT+T MAX6829YHUT+T MAX6829ZWUT+T MAX6830SDUT+T MAX6830SFUT+T MAX6830SHUT+T

MAX6830SVUT+T MAX6830TZUT+T MAX6830VDUT+T MAX6830VFUT+T MAX6830WIUT+T MAX6830YDUT+T

MAX6830YGUT+T MAX6830YHUT+T MAX6830ZGUT+T MAX6830ZWUT+T MAX6831SDUT+T MAX6831SFUT+T

MAX6831SHUT+T MAX6831SVUT+T MAX6831SZUT+T MAX6831TZUT+T MAX6831VDUT+T MAX6831VFUT+T

MAX6831WIUT+T MAX6831YDUT+T MAX6831YGUT+T MAX6831YHUT+T MAX6831ZGUT+T MAX6831ZWUT+T

MAX6828YUT+T MAX6829SYUT+T