General Description

The MAX6806/MAX6807/MAX6808 precision voltage
detectors are ideal for accurate monitoring of power
supplies in digital systems. They provide circuit reliabili-
ty and reduce total cost by eliminating external compo-
nents and adjustments.

The MAX6806/MAX6807/MAX6808 assert a reset signal
whenever the supply voltage (V

) falls below the factory-

preset, ±2% accurate threshold. Internal hysteresis
ensures stable switching. The MAX6806/MAX6807/
MAX6808 are available in 4.6V and 2.6V thresholds (2.3V
is also available for the MAX6806 only). The MAX6806 fea-
tures an active-low, push-pull RESET output; the MAX6807
features an active-high, push-pull RESET output; and the
MAX6808 features an active-low, open-drain RESET out-
put. RESET is valid for V

down to 1V (MAX6806/

MAX6808), and RESET (MAX6807) is guaranteed for V

down to 1.2V.

The MAX6806/MAX6807/MAX6808 are available in
3-pin SC70, 3-pin SOT23, and 4-pin SOT143 packages.
The SOT143 package includes a manual-reset input.

Applications

Computers

Controllers

Intelligent Instruments

Critical µP and µC Power Monitoring

Portable/Battery-Powered Equipment

Automotive

Bar-Code Scanners

Features

Preset Reset Thresholds: 4.6V and 2.6V
(2.3V also available for MAX6806 only)

±2% Accurate Reset Thresholds

Reset Output Available in Active-Low (MAX6806),
Active-High (MAX6807), and Open-Drain
(MAX6808) Versions

Immune to Power-Supply Transients

RESET

Valid to V

= 1.0V (MAX6806/MAX6808)

35µA Supply Current

No External Components

Manual Reset Available with 4-Pin SOT143
Package

Miniature 3-Pin SC70, 3-Pin SOT23, and 4-Pin
SOT143 Packages

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.

MAX6806/MAX6807/MAX6808

Voltage Detectors

________________________________________________________________

Maxim Integrated Products

19-1421; Rev 1; 4/99

PART

RESET OUTPUT

Selector Guide

Ordering Information

TOP MARK

NOMINAL

TH-

(V)

MAX6806

UR46-T

MAX6806UR26-T

Active-Low, Push-Pull

FZDP

FZDQ

4.6

2.6

MAX6806UR23-T

MAX6806US46-T

FZDR

KABT

2.3

4.6

MAX6806US26-T

MAX6806US23-T

KABU

KABV

2.6

2.3

Other reset thresholds may be available. Contact factory for availability.

TEMP. RANGE

MAX6806

XR_ _-T

-40°C to +85°C

PART

Typical Operating Circuit and Pin Configurations appear at
end of data sheet.

PIN-PACKAGE

3 SC70

MAX6806US_ _-T

-40°C to +85°C

4 SOT143

MAX6807US_ _-T

-40°C to +85°C

4 SOT143

MAX6807

XR_ _-T

-40°C to +85°C

3 SC70

MAX6808US_ _-T

-40°C to +85°C

4 SOT143

MAX6808

XR_ _-T

-40°C to +85°C

3 SC70

All devices available in tape-and-reel only, 2500 piece mini-

mum order quantity.

Note:

Insert the desired number from the Selector Guide into the

blank to complete the part number. Also see Selector Guide for
top mark.

Selector Guide continued at end of data sheet.

MAX6806UR_ _-T

-40°C to +85°C

3 SOT23

MAX6807UR_ _-T

-40°C to +85°C

3 SOT23

MAX6808UR_ _-T

-40°C to +85°C

3 SOT23

MAX6806/MAX6807/MAX6808

Voltage Detectors

_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

= +5V, T

= -40°C to +85°C, unless otherwise noted. Typical values are at T

= +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.

Note1:

All devices are 100% production tested at T

= +25°C, and are guaranteed by design for T

= T

MIN

to T

MAX

, as specified.

Note 2:

RESET output for MAX6806/MAX6808, RESET output for MAX6807.

to GND ..........................................................-0.3V to +6.0V

RESET, RESET to GND
(MAX6806/MAX6807) ................................-0.3V to (V

+ 0.3V)

RESET to GND (MAX6808)...................................-0.3V to + 6.0V
MR to GND (SOT143 package only) ....................-0.3V to + 6.0V
Input Current, V

...........................................................±20mA

Output Current, RESET, RESET .......................................±20mA

Rate of Rise, V

...........................................................100V/µs

Continuous Power Dissipation (T

= +70°C)

SOT23, SOT143 (derate 4mW/°C above +70°C) .........320mW
SC70 (derate 2.17mW/°C above +70°C) .....................174mW

Operating Temperature Range ..........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C

= +3.6V, no load

> V

TH+

= -40°C to +85°C

= 0°C to +70°C

falling at 1mV/µs

SINK

= 1.0mA, V

= 2.0V

SINK

= 3.2mA, V

= 5.0V

SOURCE

= 400µA, V

= 2.0V

SINK

= 20µA, V

= 1.0V

= +25°C, Figure 2

= +5.5V, no load

SOURCE

= 20µA, V

= 1.2V

= +25°C,

falling

CONDITIONS

0.7V

MR Input Threshold

0.6

120

MR Pull-Down Resistance

ppm/°C

Reset Threshold Tempco

µs

to Reset Delay (Note 2)

0.4

RESET Output Voltage
(MAX6807)

0.8V

1.2

5.5

1.0

5.5

Supply Voltage Range

0.4

0.3

0.02

0.03

TH-

HYST

Reset Threshold Hysteresis

µA

Supply Current

4.508

4.60

4.692

2.548

2.60

2.652

2.254

2.30

2.346

TH-

Reset Threshold

UNITS

MIN

TYP

MAX

SYMBOL

PARAMETER

MAX680_ _ _46

MAX680_ _ _26

MAX680_ _ _23

SOURCE

= 2.0mA, V

= 5.0V

(MAX6806 only)

RESET Output Voltage
(MAX6806/MAX6808)

0.8V

= 5.5V, RESET deasserted

(MAX6808 only)

µA

RESET Output Leakage Current

MAX6806/MAX6807/MAX6808

Voltage Detectors

_______________________________________________________________________________________

Typical Operating Characteristics

= +25°C, unless otherwise noted.)

-60

-30

120

SUPPLY CURRENT vs. TEMPERATURE

MAX6806/7/8-01

TEMPERATURE (°C)

SUPPLY CURRENT (

= 5.0V

= 3.3V

= 1.8V

= 1.0V

-60

-30-15 0

-45

15 30 45

90 105 120135

POWER-DOWN RESET DELAY

vs. TEMPERATURE

MAX6806/7/8toc02

TEMPERATURE (°C)

RESET DELAY (

= V

TH-

- V

= 100mV

FALLING AT 1mV/

-60

-30

120

POWER-UP RESET DELAY vs. TEMPERATURE

MAX6806/7/8-03

TEMPERATURE (°C)

DELAY TIME (

= V

- V

= 50mV

= 200mV

= 100mV

0.9900

0.9940

0.9920

0.9980

0.9960

1.0020

1.0000

1.0040

1.0080

1.0060

1.0100

-40

-15

-30

NORMALIZED RESET THRESHOLD

vs. TEMPERATURE

MAX6806/7/8-04

TEMPERATURE (°C)

NORMALIZED RESET THRESHOLD

RISING (V

TH+

)

FALLING (V

TH-

)

Active-Low Reset Output (MAX6806/MAX6808). RESET remains low
while V

is below the reset-threshold voltage or while MR is held high.

Active-High Reset Output (MAX6807). RESET remains high while V

below the reset-threshold voltage or while MR is held high.

Ground

Supply Voltage Input

Active-High Manual Reset Input. Internal 80k

resistor to GND.

SOT23/SC70

FUNCTION

Pin Description

RESET

GND

NAME

SOT143

PIN

MAX6806/MAX6807/MAX6808

Voltage Detectors

_______________________________________________________________________________________

_______________Detailed Description

Reset Output

The MAX6806 voltage detector features an active-low,
push-pull RESET output, while the MAX6807 features
an active-high, push-pull RESET output. Unlike micro-
processor (µP) supervisory circuits that offer a reset
timeout period, the MAX6806 and MAX6807 RESET
goes high and RESET goes low virtually immediately
once V

exceeds the reset threshold. If a brownout

occurs (V

falls below the reset threshold), RESET

goes low and RESET goes high. RESET is guaranteed
to be a logic low for V

1V and RESET is guaran-

teed to be a logic high for V

1.2V.

The MAX6808 features an active-low, open-drain RESET
output. The output sinks current when V

falls below

the reset threshold. Connect a pull-up resistor from
RESET to any supply voltage up to 6V (Figure 1). Select
a resistor value large enough to provide a logic low and
small enough to provide a logic high while supplying all
input and leakage currents connected to the RESET
line. A 100k

resistor is sufficient in applications driving

high-impedance loads.

The manual reset input (MR, 4-pin SOT143 package)
can also initiate a reset (see

Manual Reset Input sec-

tion).

Manual Reset Input

Many applications require manual-reset capabilities,
allowing an operator, a test technician, or external logic
circuitry to initiate a reset. A logic high on MR asserts a
reset and remains asserted while MR is high. This input
has an 80k

pull-down resistor, so the input may be left

unconnected if not used. Connect a normally open
momentary switch from MR to V

to create a manual-

reset function. 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 noise
immunity.

Hysteresis

The MAX6806/MAX6807/MAX6808 feature internal hys-
teresis that creates two trip points: one for the rising
supply voltage and one for the falling supply voltage
(Figure 2). The hysteresis prevents the output from oscil-
lating (chattering) when V

is near the reset threshold.

Reset Threshold Accuracy

The MAX6806/MAX6807/MAX6808 are ideal for sys-
tems using a 5V ±5%, 3V ±5%, or 2.5V ±5% power
supply with ICs specified for 5V ±10%, 3V ±10%, or
2.5V ±10%, respectively. The reset is guaranteed to
assert after the power supply falls out of regulation, but
before power drops below the minimum specified oper-
ating voltage range for the system ICs.

MAX6808

GND

+3.3V

GND

+5.0V

100k

5V SYSTEM

RESET

Figure 1. The MAX6808 open-drain RESET output allows use
with multiple supplies.

TH+

HYST

RESET

(MAX6806/MAX6808)

RESET

(MAX6807)

HYST

= V

TH+

- V

TH-

Figure 2. Input and Output Waveforms with V

Varied

Applications Information

Negative-Going V

Transients

In addition to asserting a reset signal during power-up,
power-down, and brown-out conditions, the MAX6806/
MAX6807/MAX6808 are immune to short-duration, neg-
ative-going V

transients.

Figure 3 displays typical transient durations vs. reset-
comparator overdrive for which the MAX6806/MAX6807/
MAX6808 do

not

generate a reset pulse. The graph was

generated using a negative-going pulse applied to V

starting 0.5V above the actual reset threshold and end-
ing below it by the magnitude indicated (reset-compara-
tor overdrive). The graph indicates the maximum pulse
width a negative-going V

transient can have without

causing a reset pulse. As the magnitude of the transient
increases (goes further below the reset threshold), the
maximum allowable pulse width decreases. A 0.1µF
capacitor mounted as close as possible to V

pro-

vides additional transient immunity.

Ensuring a Valid Reset Output Down to

= Ground

When V

falls below 1V, the MAX6806/MAX6808

RESET output no longer sinks current--it becomes an
open circuit. Therefore, high-impedance CMOS logic
inputs connected to RESET can drift to undetermined
voltages. This presents no problem in most applica-
tions, since most circuitry is inoperative when V

below 1V. In applications where RESET must be valid
down to ground, add a pull-down resistor to RESET so
any stray leakage currents flow to ground, holding
RESET low (Figure 4). Select R1 to be large enough not
to load RESET and small enough to pull RESET to
ground. For most applications, 100k

will not load

RESET and will pull RESET to ground. Similarly, if
RESET (MAX6807) must be valid below 1.2V, add a
pull-up resistor to RESET.

MAX6806/MAX6807/MAX6808

Voltage Detectors

_______________________________________________________________________________________

100

1000

RESET COMPARATOR OVERDRIVE, V

TH-

- V

(mV)

MAXIMUM TRANSIENT DURATION (

= +25°C

MAX680 46

Figure 3. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive

MAX6806

MAX6807

GND

RESET

R1
100k

Figure 4. RESET / RESET Valid to V

= Ground Circuit

Part Number MAX6808