Datasheet MAX812TEUS-T, MAX812SEUS-T, MAX812REUS-T, MAX812MEUS-T, MAX811LEUS-T Datasheet (Maxim)

________________General Description

The MAX811/MAX812 are low-power microprocessor
(µP) supervisory circuits used to monitor power sup­plies in µP and digital systems. They provide excellent
circuit reliability and low cost by eliminating external
components and adjustments when used with 5V­powered or 3V-powered circuits. The MAX811/MAX812
also provide a debounced manual reset input.

These devices perform a single function: They assert a
reset signal whenever the VCCsupply voltage falls
below a preset threshold, keeping it asserted for at
least 140ms after VCChas risen above the reset thresh­old. The only difference between the two devices is that
the MAX811 has an active-low RESET output (which is
guaranteed to be in the correct state for V

CC

down to
1V), while the MAX812 has an active-high RESET out­put. The reset comparator is designed to ignore fast
transients on VCC. Reset thresholds are available for
operation with a variety of supply voltages.

Low supply current makes the MAX811/MAX812 ideal
for use in portable equipment. The devices come in a
4-pin SOT143 package.

________________________Applications

Computers

Controllers

Intelligent Instruments

Critical µP and µC Power Monitoring

Portable/Battery-Powered Equipment

____________________________Features

♦ Precision Monitoring of 3V, 3.3V, and 5V

Power-Supply Voltages

♦ 6µA Supply Current

♦ 140ms Min Power-On Reset Pulse Width;

RREESSEETT

Output (MAX811), RESET Output (MAX812)

♦ Guaranteed Over Temperature

♦ Guaranteed

RREESSEETT

Valid to V

CC

= 1V (MAX811)

♦ Power-Supply Transient Immunity

♦ No External Components

♦ 4-Pin SOT143 Package

MAX811/MAX812

4-Pin µP Voltage Monitors

with Manual Reset Input

________________________________________________________________ Maxim Integrated Products 1

1

2

4

3

V

CC

MR(RESET) RESET

GND

MAX811
MAX812

SOT143

TOP VIEW

( ) ARE FOR MAX812

NOTE: SEE LAST PAGE FOR MARKING INFORMATION.

___________________Pin Configuration

MAX811
MAX812

V

CC

V

CC

RESET

(RESET)

RESET
INPUT

GND

V

CC

GND

µP

( ) ARE FOR MAX812

PUSHBUTTON

SWITCH

MR

___________Typical Operating Circuit

19-0411; Rev 3; 3/99

PART*

MAX811_EUS-T

MAX812_EUS-T -40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

4 SOT143

4 SOT143

_______________Ordering Information

* This part offers a choice of five different reset threshold

voltages. Select the letter corresponding to the desired
nominal reset threshold voltage, and insert it into the blank
to complete the part number.

RESET THRESHOLD

SUFFIX VOLTAGE (V)

L 4.63

M 4.38

T 3.08

S 2.93

R 2.63

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone].

MAX811/MAX812

4-Pin µP Voltage Monitors
with Manual Reset Input

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= 5V for L/M versions, VCC= 3.3V for T/S versions, VCC= 3V for R version, TA= -40°C to +85°C, unless otherwise noted.
Typical values are at T

A

= +25°C.) (Note 1)

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.

Terminal Voltage (with respect to GND)

V

CC

......................................................................-0.3V to 6.0V

All Other Inputs.......................................-0.3V to (V

CC

+ 0.3V)

Input Current, V

CC,

MR .......................................................20mA

Output Current, RESET or RESET .......................................20mA

Continuous Power Dissipation (T

A

= +70°C)

SOT143 (derate 4mW/°C above +70°C) 320mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +160°C

Lead Temperature (soldering, 10sec) .............................+300°C

I

SOURCE

= 150µA, 1.8V < VCC< V

TH(MIN)

MAX81_R/S/T, VCC= 3.6V, I

OUT

= 0

MAX81_L/M, VCC= 5.5V, I

OUT

= 0

TA= -40°C to +85°C

VOD= 125mV, MAX81_R/S/T

VOD= 125mV, MAX81_L/M

MAX81_S

MAX81_L

MAX81_M

VCC= V

TH(MAX)

CONDITIONS

0.8V

CC

2.3V

IH

µs0.5t

MD

MR to Reset Propagation Delay
(Note 2)

ns100

MR Glitch Immunity (Note 3)

µs10t

MR

MR Minimum Pulse Width

ms140 560t

RP

Reset Active Timeout Period

µA

2.7 10

I

CC

Supply Current

615

V

1.2

V

CC

Operating Voltage Range

µs

20

VCCto Reset Delay (Note 2)

40

2.88 2.93 2.98

3.03 3.08 3.14

Reset Threshold

4.54 4.63 4.72

4.50 4.75

4.30 4.38 4.46

4.25 4.50

UNITSMIN TYP MAXSYMBOLPARAMETER

MAX812L/M only, I

SINK

= 3.2mA,

VCC= V

TH(MAX)

MAX812R/S/T only, I

SINK

= 1.2mA,

VCC= V

TH(MAX)

V

0.4

V

OL

RESET Output Voltage
(MAX812)

0.3

V

OH

VCC> V

TH(MAX)

, MAX81_L/M

0.8V

IL

VCC> V

TH(MAX)

, MAX81_R/S/T

V

0.25 x V

CC

V

IL

MR Input Threshold

0.7 x V

CC

V

IH

kΩ10 20 30

MR Pull-Up Resistance

TA= 0°C to +70°C 1.0 5.5

3.00 3.15

2.85 3.00

ppm/°C30Reset Threshold Tempco

MAX81_R

2.58 2.63 2.68

2.55 2.70

TA = +25°C

TA = -40°C to +85°C

TA = +25°C

TA = -40°C to +85°C

MAX81_T

TA = +25°C

TA = -40°C to +85°C

TA = +25°C

TA = -40°C to +85°C

TA = +25°C

TA = -40°C to +85°C

V

TH

V

MAX811/MAX812

4-Pin µP Voltage Monitors

with Manual Reset Input

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 5V for L/M versions, VCC= 3.3V for T/S versions, VCC= 3V for R version, TA= -40°C to +85°C, unless otherwise noted.
Typical values are at T

A

= +25°C.) (Note 1)

Note 1: Production testing done at T

A

= +25°C, over temperature limits guaranteed by design using six sigma design limits.

Note 2: RESET output for MAX811, RESET output for MAX812.
Note 3: “Glitches” of 100ns or less typically will not generate a reset pulse.

MAX811R/S/T only, I

SINK

= 1.2mA,

VCC= V

TH(MIN)

MAX811L/M only, I

SOURCE

= 800µA,

VCC> V

TH(MAX)

MAX811L/M only, I

SINK

= 3.2mA,

VCC= V

TH(MIN)

I

SINK

= 50µA, VCC> 1.0V

MAX811R/S/T only, I

SOURCE

= 500µA,

V

CC

> V

TH(MAX)

CONDITIONS

0.3

V

VCC- 1.5

V

OH

RESET Output Voltage
(MAX811)

0.4

0.3

V

OL

0.8V

CC

UNITSMIN TYP MAXSYMBOLPARAMETER

MAX811/MAX812

4-Pin µP Voltage Monitors
with Manual Reset Input

4 _______________________________________________________________________________________

190

POWER-UP RESET TIMEOUT

vs. TEMPERATURE

230

MAX811/12-TOC5

TEMPERATURE (°C)

POWER-UP RESET TIMEOUT (ms)

210

200

220

-40

85

35-15 10 60

MAX81_R/S/T

MAX81_L/M

RESET THRESHOLD DEVIATION

vs. TEMPERATURE

0.9995

1.0000

1.0005

MAX811/12-TOC6

TEMPERATURE (°C)

NORMALIZED THRESHOLD (V)

0.9985

0.9980

0.9990

-40 8535-15 10 60

0

POWER-DOWN RESET DELAY vs. TEMPERATURE

(MAX81_L/M)

200

MAX811/12-TOC4

TEMPERATURE (°C)

POWER-DOWN RESET DELAY (µs)

100

50

150

-40 8510-15 6035

VOD = VTH - V

CC

VOD = 125mV

VOD = 200mV

VOD = 20mV

__________________________________________Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

0

-40

85

SUPPLY CURRENT vs. TEMPERATURE

(MAX81_R/S/T)

2.0

2.5

3.0

MAX811/12-TOC1

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

10

1.0

0.5

-15

60

1.5

35

VCC = 3.6V

VCC = 3.3V

V

CC

= 1V

0

SUPPLY CURRENT vs. TEMPERATURE

(MAX81_L/M)

8

MAX811/12-TOC2

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

4

2

6

-40

85

10-15 6035

VCC = 5.5V

VCC = 3V

V

CC

= 1V

0

POWER-DOWN RESET DELAY vs. TEMPERATURE

(MAX81_R/S/T)

80

100

MAX811/12-TOC3

TEMPERATURE (°C)

POWER-DOWN RESET DELAY (µs)

40

20

60

-40

85

10-15 6035

VOD = VTH - V

CC

VOD = 20mV

VOD = 200mV

VOD = 125mV

MAX811/MAX812

4-Pin µP Voltage Monitors

with Manual Reset Input

_______________________________________________________________________________________ 5

______________________________________________________________ Pin Description

_______________ Detailed Description

Reset Output

A microprocessor’s (µP’s) reset input starts the µP in a
known state. These µP supervisory circuits assert reset
to prevent code execution errors during power-up,
power-down, or brownout conditions.

RESET is guaranteed to be a logic low for VCC> 1V.
Once VCCexceeds the reset threshold, an internal
timer keeps RESET low for the reset timeout period;
after this interval, RESET goes high.

If a brownout condition occurs (VCCdips below the
reset threshold), RESET goes low. Any time VCCgoes
below the reset threshold, the internal timer resets to
zero, and RESET goes low. The internal timer starts
after VCCreturns above the reset threshold, and RESET
remains low for the reset timeout period.

The manual reset input (MR) can also initiate a reset.
See the Manual Reset Input section.

The MAX812 has an active-high RESET output that is
the inverse of the MAX811’s RESET output.

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 reset. Reset remains asserted while MR is low,
and for the Reset Active Timeout Period (tRP) after MR
returns high. This input has an internal 20kΩ pull-up
resistor, so it can be left open if it is not used. MR can
be driven with TTL or CMOS-logic levels, or with open­drain/collector outputs. Connect a normally open
momentary switch from MR to GND to create a manual­reset function; external debounce circuitry is not
required. If MR is driven from long cables or if the
device is used in a noisy environment, connecting a

0.1µF capacitor from MR to ground provides additional
noise immunity.

Reset Threshold Accuracy

The MAX811/MAX812 are ideal for systems using a 5V
±5% or 3V ±5% power supply with ICs specified for 5V
±10% or 3V ±10%, respectively. They are designed to
meet worst-case specifications over temperature. The
reset is guaranteed to assert after the power supply
falls out of regulation, but before power drops below
the minimum specified operating voltage range for the
system ICs. The thresholds are pre-trimmed and exhibit
tight distribution, reducing the range over which an
undesirable reset may occur.

Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is
low and for 180ms after MR returns high. This active-low input has an internal 20kΩ pull-up
resistor. It can be driven from a TTL or CMOS-logic line, or shorted to ground with a switch.
Leave open if unused.

33

+5V, +3.3V, or +3V Supply Voltage44

Active-High Reset Output. RESET remains high while VCCis below the reset threshold or while
MR is held low. RESET remains high for Reset Active Timeout Period (t

RP

) after the reset condi-

tions are terminated.

2—

Active-Low Reset Output. RESET remains low while VCCis below the reset threshold or while
MR is held low. RESET remains low for the Reset Active Timeout Period (t

RP

) after the reset

conditions are terminated.

—2

Ground

11

FUNCTION

PIN

MR

V

CC

RESET

RESET

GND

NAME

MAX811 MAX812

MAX811/MAX812

__________ Applications Information

Negative-Going VCCTransients

In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX811/
MAX812 are relatively immune to short duration nega­tive-going VCCtransients (glitches).

Figure 1 shows typical transient durations vs. reset
comparator overdrive, for which the MAX811/MAX812
do not generate a reset pulse. This graph was generat­ed using a negative-going pulse applied to V

CC

, start­ing above the actual reset threshold and ending below
it by the magnitude indicated (reset comparator over­drive). The graph indicates the typical maximum pulse
width a negative-going V

CC

transient may have without
causing a reset pulse to be issued. As the magnitude
of the transient increases (goes farther below the reset
threshold), the maximum allowable pulse width
decreases. Typically, a VCCtransient that goes 125mV
below the reset threshold and lasts 40µs or less
(MAX81_L/M) or 20µs or less (MAX81_T/S/R) will not
cause a reset pulse to be issued. A 0.1µF capacitor
mounted as close as possible to VCCprovides addi­tional transient immunity.

Ensuring a Valid RESET Output

Down to V

CC

= 0V

When VCCfalls below 1V, the MAX811 RESET output
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS-logic inputs con­nected to the RESET output can drift to undetermined
voltages. This presents no problem in most applica­tions, since most µP and other circuitry is inoperative
with VCCbelow 1V. However, in applications where the
RESET output must be valid down to 0V, adding a pull­down resistor to the RESET pin will cause any stray
leakage currents to flow to ground, holding RESET low
(Figure 2). R1’s value is not critical; 100kΩ is large
enough not to load RESET and small enough to pull
RESET to ground.

A 100kΩ pull-up resistor to VCCis also recommended
for the MAX812 if RESET is required to remain valid for
VCC< 1V.

4-Pin µP Voltage Monitors
with Manual Reset Input

6 _______________________________________________________________________________________

5

6

7

8

4

0

1 100 1000

2

1

3

RESET COMPARATOR OVERDRIVE , V

TH

- VCC (mV)

MAXIMUM TRANSIENT DURATION (ms)

10

TA = +25°C

MAX81 _L/M

MAX81 _R/S/T

R1

V

CC

GND

MAX811

RESET

Figure 1. Maximum Transient Duration without Causing a
Reset Pulse vs. Comparator Overdrive

Figure 2. RESET Valid to VCC= Ground Circuit

Interfacing to µPs with

Bidirectional Reset Pins

µPs with bidirectional reset pins (such as the Motorola
68HC11 series) can contend with the MAX811/MAX812
reset outputs. If, for example, the MAX811 RESET out-
put is asserted high and the µP wants to pull it low,
indeterminate logic levels may result. To correct such
cases, connect a 4.7kΩ resistor between the MAX811
RESET (or MAX812 RESET) output and the µP reset I/O
(Figure 3). Buffer the reset output to other system com­ponents.

MAX811/MAX812

4-Pin µP Voltage Monitors

with Manual Reset Input

_______________________________________________________________________________________ 7

4.7k

V

CC

GND

RESET

MAX811

RESET

V

CC

GND

µP

BUFFER

BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS

Figure 3. Interfacing to µPs with Bidirectional Reset I/O

TRANSISTOR COUNT: 341

___________________Chip Information

MAX811/MAX812

4-Pin µP Voltage Monitors
with Manual Reset Input

________________________________________________________Package Information

4.0 ±0.1

4.0 ±0.1

2.0 ±0.05

1.75 ±0.1

ø1.5 ±0.1

ø1.1 ±0.1

8.0 ±0.2

3.5 ±0.05

X X X X

LOT SPECIFIC
CODE

MARKING

INFORMATION

NOTE: DIMENSIONS ARE IN MM.

AND FOLLOW EIA481-1 STANDARD.

ICs MAY ALSO BE MARKED WITH FULL PART NAME: 811L, 811M_…

†

†

AMAA or KABB = MAX811L
ANAA or KABC = MAX811M
APAA or KABD = MAX811T
AQAA or KABE = MAX811S
ARAA or KABF = MAX811R
ASAA or KABG = MAX812L
ATAA or KABH = MAX812M
AVAA or KABI = MAX812T
AWAA or KABJ = MAX812S
AXAA or KABK = MAX812R

SOT1434.EPS

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implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

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