MAX6887KETE+_技术文档

19-0291; Rev 2; 2/10

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

General Description

Features

The MAX6887/MAX6888 multivoltage supply supervi-

sors provide several voltage-detector inputs, one watch-

dog input, and three outputs. Each voltage-detector

input offers a factory-set undervoltage and overvoltage

threshold. Manual reset and margin disable inputs offer

additional flexibility.

o Hex/Quad Voltage Detectors

o Undervoltage and Overvoltage Thresholds

o 1% Threshold Accuracy

o Margining Disable and Manual Reset Input

o Watchdog Timer

o Open-Drain RESET, OV, and WDO Outputs

o 180ms (min) Reset Timeout Period

o Few External Components

The MAX6887 offers six voltage-detector inputs, while

the MAX6888 offers four inputs. Output RESET asserts

when any input voltage drops below its respective

undervoltage threshold or manual reset MR is asserted.

Output OV asserts when any input voltage exceeds its

respective overvoltage threshold. Monitor standard

supply voltages listed in the Selector Guide.

o Small 5mm x 5mm, 16-Pin Thin QFN Packages

The MAX6887/MAX6888 offer a watchdog timer with an

initial and normal timeout periods of 102.4s and 1.6s,

respectively. Watchdog output WDO asserts when the

watchdog timer expires. Connect WDO to manual reset

input MR to generate resets when the watchdog timer

expires. RESET, OV, and WDO are active-low, open-

drain outputs.

Ordering Information

PART

TEMP RANGE

-40°C to +85°C

PIN-PACKAGE

16 Thin QFN-EP*

MAX6887_ETE+

MAX6888_ETE+

The MAX6887/MAX6888 are available in a 5mm x 5mm

x 0.8mm, 16-pin thin QFN package and operate over

the extended -40°C to +85°C temperature range.

Note: Insert the desired letter from the Selector Guide into the

blank to complete the part number.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Applications

Multivoltage Systems

Telecom

Networking

Pin Configurations and Typical Operating Circuit appear at

end of data sheet.

Servers/Workstations/Storage Systems

Selector Guide

NOMINAL INPUT VOLTAGE (V)*

TOL

NOMINAL INPUT VOLTAGE (V)*

TOL

PART

MAX6887IETE 5.0

(%)

IN1 IN2

IN3

2.5

1.8

1.5

Adj

IN4

1.8

Adj

1.5

Adj

IN5

Adj

IN6

Adj

IN1 IN2

IN3

2.5

1.8

1.5

Adj

IN4

1.8

Adj

1.5

Adj

IN5

Adj

IN6

Adj

MAX6887AETE 5.0

3.3

2.5

1.8

5

3.3

2.5

1.8

10

MAX6887BETE 5.0

MAX6887CETE 5.0

MAX6887DETE 3.3

MAX6887EETE 3.3

MAX6887FETE 3.3

MAX6887GETE 3.3

MAX6887HETE 3.3

MAX6887JETE 5.0

MAX6887KETE 5.0

MAX6887LETE 3.3

MAX6887METE 3.3

MAX6887NETE 3.3

MAX6887OETE 3.3

MAX6887PETE 3.3

MAX6887QETE Adj Adj

MAX6887RETE Adj Adj

*See thresholds options tables (Tables 1 and 2) for actual undervoltage and overvoltage thresholds.

Selector Guides continued at end of data sheet.

________________________________________________________________ Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Hex/Quad, Power-Supply Supervisory Circuits

ABSOLUTE MAXIMUM RATINGS

(All voltages referenced to GND.)

Maximum Junction Temperature .....................................+150°C

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

Storage Temperature Range.............................-65°C to +150°C

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

IN1–IN6, V , RESET, OV, WDO .............................-0.3V to +6V

CC

WDI, MR, MARGIN ...................................................-0.3V to +6V

BP.............................................................................-0.3V to +3V

Input/Output Current (all pins).......................................... 20mA

Continuous Power Dissipation (T = +70°C)

A

16-Pin 5mm x 5mm Thin QFN

(derate 20.8mW/°C above +70°C)..............................1667mW

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

= 2.7V to 5.8V, WDI = GND, MARGIN = MR = BP, T = -40°C to +85°C, unless otherwise noted. Typical values are

CC A

(V –V

IN1 IN4

or V

at T = +25°C.) (Notes 1, 2)

A

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

V

7/MAX68

Operating Voltage Range

(Note 3)

Voltage on either one of IN1–IN4 or V

guarantee the part is fully operational

to

CC

2.7

5.8

Supply Current

I

V

= 5.8V, IN2–IN6 = GND, no load

IN1

0.9

1.2

+1

mA

CC

IN1–IN6, IN_ falling, T = +25°C to +85°C

-1

A

Threshold Accuracy

(See the Selector Guide)

V

% V

TH

IN1–IN6, IN_ falling, T = -40°C to +85°C

-1.5

+1.5

A

Threshold Hysteresis

Threshold Tempco

V

0.3

10

% V

TH-HYST

TH

∆V /°C

ppm/°C

TH

For V

< highest V

and

IN_

IN1–IN4

< V (not ADJ), thresholds are not set

CC

IN_ Input Impedance

R

V

130

200

300

kΩ

IN

IN_

as adjustable

IN5, IN6 (MAX6887 only)

IN_ Input Leakage Current

I

-150

+150

2.5

nA

IN

IN1–IN4 set as adjustable thresholds

Power-Up Delay

t

V

≥ 2.5V

CC

ms

µs

D-PO

IN_ to RESET or OV Delay

RESET Timeout Period

OV Timeout Period

t

IN_ falling/rising, 100mV overdrive

20

200

25

D-R

t

180

-1

220

ms

µs

RP

OP

t

RESET, OV, and WDO Output

Low

V

I

= 4mA, output asserted

0.4

+1

V

OL

SINK

RESET, OV, and WDO Output

Open-Drain Leakage Current

I

Output high impedance

µA

LKG

2

_______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

ELECTRICAL CHARACTERISTICS (continued)

= 2.7V to 5.8V, WDI = GND, MARGIN = MR = BP, T = -40°C to +85°C, unless otherwise noted. Typical values are

CC A

(V –V

IN1 IN4

or V

at T = +25°C.) (Notes 1, 2)

A

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

V

0.6

IL

IH

MR, MARGIN, WDI Input Voltage

V

1.4

1

MR Input Pulse Width

t

µs

ns

µA

MR

MR Glitch Rejection

100

200

10

MR to RESET or OV Delay

MR to Internal BP Pullup Current

t

D-MR

I

V

= 1.4V

5

15

MR

MARGIN to Internal BP Pullup

Current

I

= 1.4V

= 0.6V

WDI

10

µA

MARGIN

WDI Pulldown Current

WDI Input Pulse Width

I

t

5

µA

ns

WDI

50

Initial

92.16

1.44

102.4 112.64

1.6 1.76

WDI

Watchdog Timeout Period

s

t

Normal

WD

Note 1: 100% production tested at T = +25°C and T = +85°C. Specifications at T = -40°C are guaranteed by design.

A

Note 2: Device may be supplied from any one of IN1–IN4 or V

.

CC

Note 3: The internal supply voltage, measured at V , equals the maximum of IN1–IN4.

CC

Note 4: Versions Q and R require that power be applied through V

.

CC

Typical Operating Characteristics

(V –V

IN1 IN4

or V

= 5V, WDI = GND, MARGIN = MR = BP, T = +25°C, unless otherwise noted.)

CC A

IN1–IN4 SUPPLY CURRENT

vs. IN1–IN4 SUPPLY VOLTAGE

V

SUPPLY CURRENT

CC

RESET TIMEOUT PERIOD

vs. TEMPERATURE

CC

vs. V SUPPLY VOLTAGE

1.00

0.95

0.90

0.85

0.80

0.75

0.70

1.00

0.95

0.90

0.85

0.80

0.75

0.70

220

215

210

205

200

195

190

185

180

T

A

= +85°C

T

= +85°C

A

T

A

= +25°C

T

A

= +25°C

T

A

= -40°C

T

A

= -40°C

2.6

3.6

4.6

5.6

2.6

3.6

4.6

5.6

-40

-15

10

35

60

85

SUPPLY VOLTAGE (V)

TEMPERATURE (°C)

_______________________________________________________________________________________

3

Hex/Quad, Power-Supply Supervisory Circuits

Typical Operating Characteristics (continued)

(V –V

IN1 IN4

or V

= 5V, WDI = GND, MARGIN = MR = BP, T = +25°C, unless otherwise noted.)

A

CC

IN_ TO RESET OR OV

PROPAGATION DELAY vs. TEMPERATURE

WATCHDOG TIMEOUT PERIOD

vs. TEMPERATURE

NORMALIZED IN_ THRESHOLD

vs. TEMPERATURE

30

29

28

27

26

25

24

23

22

21

20

1.700

1.675

1.650

1.625

1.600

1.575

1.550

1.525

1.500

1.005

1.004

1.003

1.002

1.001

1.000

0.999

0.998

0.997

0.996

0.995

100mV OVERDRIVE

-40

-15

10

35

60

85

-40

-15

10

35

60

85

-40

-15

10

35

60

85

TEMPERATURE (°C)

7/MAX68

MAXIMUM IN_ TRANSIENT

vs. IN_THRESHOLD OVERDRIVE

MR TO RESET OUTPUT PROPAGATION

DELAY vs. TEMPERATURE

OUTPUT-VOLTAGE LOW vs. SINK CURRENT

200

175

150

125

100

75

400

350

300

250

200

150

100

50

3.00

2.75

2.50

2.25

2.00

1.75

1.50

1.25

1.00

PO_ ASSERTION OCCURS

ABOVE THIS LINE

50

25

0

1

10

100

1000

0

2

4

6

8

10

12

14

-40

-15

10

35

60

85

IN_ THRESHOLD OVERDRIVE (mV)

SINK CURRENT (mA)

TEMPERATURE (°C)

Pin Description

MAX6887 MAX6888

NAME

FUNCTION

Open-Drain, Active-Low Reset Output. RESET asserts when any input voltage falls below its

undervoltage threshold or when MR is pulled low. RESET remains low for 200ms after all

assertion-causing conditions are cleared. An external pullup resister is required.

1

2

1

2

RESET

Open-Drain, Active-Low Watchdog Timer Output. Logic output for the watchdog timer function.

WDO goes low when WDI is not strobed high-to-low or low-to-high within the watchdog timeout

period.

WDO

Open-Drain Active-Low Overvoltage Output. OV asserts when any input voltage exceeds its

3

4

3

4

OV

overvoltage threshold. OV remains low for 25µs after all overvoltage conditions are cleared.

An external pullup resistor is required.

GND

Ground

4

_______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

Pin Description (continued)

NAME

FUNCTION

MAX6887 MAX6888

Manual Reset Input. Pull MR low to assert RESET. Connect MR to WDO to generate resets

when the watchdog timer expires. Leave MR unconnected or connect to DBP if unused. MR is

internally pulled up to BP through a 10µA current source.

5

MR

Margin Input. When MARGIN is pulled low, RESET is held in its existing state independent of

subsequent changes in monitored input voltages or the watchdog timer expiration. MARGIN is

internally pulled up to BP through a 10µA current source. Leave MARGIN unconnected or

connect to BP if unused. MARGIN overrides MR if both are asserted at the same time.

6

MARGIN

Watchdog Timer Input. Logic input for the watchdog timer function. If WDI is not strobed with a

valid low-to-high or high-to-low transition within the selected watchdog timeout period, WDO

asserts. WDI is internally pulled down to GND through a 10µA current sink.

7

8

7

8

WDI

I.C.

Internal Connection. Leave unconnected.

Internal Power-Supply Voltage. Bypass V

to GND with a 1µF ceramic capacitor as close to

CC

the device as possible. V

from the highest of the monitored IN1–IN4 voltages. Do not use V

supplies power to the internal circuitry. V is internally powered

CC

9

V

CC

to supply power to external

CC

circuitry. To externally supply V , see the Powering the MAX6887/MAX6888 section.

CC

Bypass Voltage. The internally generated voltage at BP supplies power to internal logic and

output RESET. Connect a 1µF capacitor from BP to GND as close to the device as possible. Do

not use BP to supply power to external circuitry.

10

11

10

—

BP

Input Voltage Detector 6. IN6 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. IN6 cannot power the device. For

improved noise immunity, bypass IN6 to GND with a 0.1µF capacitor installed as close to the

device as possible.

IN6

IN5

IN4

IN3

IN2

IN1

Input Voltage Detector 5. IN5 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. IN5 cannot power the device. For

improved noise immunity, bypass IN5 to GND with a 0.1µF capacitor installed as close to the

device as possible.

12

13

14

15

16

—

13

14

15

16

Input Voltage Detector 4. IN4 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. Power the device through IN1–IN4

or V

(see the Powering the MAX6887/MAX6888 section). For improved noise immunity,

CC

bypass IN4 to GND with a 0.1µF capacitor installed as close to the device as possible.

Input Voltage Detector 3. IN3 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. Power the device through IN1–IN4

or V

(see the Powering the MAX6887/MAX6888 section). For improved noise immunity,

CC

bypass IN3 to GND with a 0.1µF capacitor installed as close to the device as possible.

Input Voltage Detector 2. IN2 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. Power the device through IN1–IN4

or V

(see the Powering the MAX6887/MAX6888 section). For improved noise immunity,

CC

bypass IN2 to GND with a 0.1µF capacitor installed as close to the device as possible.

Input Voltage Detector 1. IN1 monitors both undervoltage and overvoltage conditions. See the

thresholds options (Tables 1 and 2) for available thresholds. Power the device through IN1–IN4

or V

(see the Powering the MAX6887/MAX6888 section). For improved noise immunity,

CC

bypass IN1 to GND with a 0.1µF capacitor installed as close to the device as possible.

—

11, 12

—

N.C.

EP

No Connection. Not internally connected.

Exposed Paddle. Internally connected to GND. Connect EP to GND or leave unconnected.

_______________________________________________________________________________________

5

Hex/Quad, Power-Supply Supervisory Circuits

Functional Diagram

WDI

*IN_

DETECTOR

IN1

MARGIN

MR

RESET

RESET TIMING BLOCK

IN2

IN3

IN4

IN2 DETECTOR

IN3 DETECTOR

IN4 DETECTOR

IN5 DETECTOR

7/MAX68

OV

IN5

(N.C.)

OV TIMING BLOCK

IN6

(N.C.)

IN6 DETECTOR

WDO

WDO TIMING BLOCK

V

CC

REFERENCE

1µF

2.55V

LDO

MAX6887

MAX6888

BP

1µF

( ) MAX6888 ONLY

GND

*FOR ADJUSTABLE INPUTS REFER TO THE ADJUSTABLE THRESHOLD INPUTS SECTION.

6

_______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

The MAX6887/MAX6888 generate a supply voltage at

Detailed Description

BP for the internal logic circuitry. Bypass BP to GND with

The MAX6887/MAX6888 provide several supply-detector

a 1µF ceramic capacitor installed as close to the device

inputs, one watchdog input, and three outputs for power-

as possible. The nominal BP output voltage is +2.55V.

supply monitoring applications. The MAX6887 offers six

Do not use BP to provide power to external circuitry.

voltage-detector inputs, while the MAX6888 offers four.

Each voltage-detector input offers both an undervoltage

and overvoltage threshold.

Inputs

The MAX6887 offers six voltage-detector inputs, while

the MAX6888 offers four voltage-detector inputs. Each

voltage-detector input offers an undervoltage and over-

voltage threshold set at the factory to monitor standard

supply voltages (see the Selector Guide). The 5% and

10% tolerances are based on maximum and minimum

threshold values. Actual thresholds for the

MAX6887/MAX6888 are shown in Tables 1 and 2.

Inputs in the Selector Guide listing “Adj” allow an exter-

nal voltage-divider to be connected to set a user-

defined threshold.

The undervoltage and overvoltage thresholds are facto-

ry-set for monitoring standard supply voltages (see the

Selector Guide). Inputs in the Selector Guide that con-

tain “Adj” allow an external voltage-divider to be con-

nected to set a user-defined threshold.

RESET goes low when any input voltage drops below

its undervoltage threshold or when MR is brought low.

RESET stays low for 200ms after all assertion-causing

conditions have been cleared. OV goes low when an

input voltage rises above its overvoltage threshold. OV

typically stays low for 25µs (typ) after all inputs fall

back under their overvoltage thresholds.

Adjustable Threshold Inputs

Inputs listed in the Selector Guide containing “Adj” for

inputs allow external resistor voltage-dividers to be

connected at the voltage-detector inputs. These inputs

monitor any voltage supply higher than 0.6V (see

Figure 1). Use the following equation to set a voltage-

The MAX6887/MAX6888 offer a watchdog timer with

initial and normal timeout periods of 102.4s and 1.6s,

respectively. WDO goes low when the watchdog timer

expires and deasserts when WDI transitions from low-

to-high or high-to-low.

Powering the MAX6887/MAX6888

The MAX6887/MAX6888 derive power from the voltage-

detector inputs IN1–IN4 or through an externally sup-

V

IN

plied V . A virtual diode-ORing scheme selects the

CC

MAX6887

MAX6888

R1

R2

positive input that supplies power to the device (see

the Functional Diagram). The highest input voltage on

IN1–IN4 supplies power to the device. One of IN1–IN4

must be at least 2.7V to ensure proper operation.

IN_

Internal hysteresis ensures that the supply input that

initially powered the device continues to power the

device when multiple input voltages are within 50mV of

each other.

*V

REFUV

V

powers the analog circuitry and is the bypass con-

CC

nection for the MAX6887/MAX6888 internal supply.

Bypass V to GND with a 1µF ceramic capacitor

CC

installed as close to the device as possible. The inter-

nal supply voltage, measured at V , equals the maxi-

CC

*V

REFOV

mum of IN1–IN4. If V

is externally supplied, V

CC

must be at least 200mV higher than any voltage

applied to IN1–IN4 and V must be brought up first.

CC

V

CC

always powers the device when all IN_ are factory

set as “Adj.” Do not use the internally generated V

provide power to external circuitry.

to

CC

*V

REFOV

AND V

ARE REFERENCED

REFUV

TO 0.6V ACCORDING TO THE DEVICE'S TOLERANCE

Figure 1. Adjusting the Monitored Threshold

_______________________________________________________________________________________

7

Hex/Quad, Power-Supply Supervisory Circuits

detector input (IN1–IN6) to monitor a user-defined sup-

ply voltage:

V

and V

are the undervoltage and overvolt-

REFOV

REFUV

age thresholds listed in Tables 1 and 2 that allow

adjustable thresholds. Their values are based on toler-

ances of 7.5% and 12.5% from a 0.6V reference.

See the Selector Guide to find which thresholds in

Tables 1 and 2 are adjustable.

⎛

⎞

⎟

R2

0.6V = V

×

MON

⎜

R1+R2

⎝

⎠

where V

is the desired voltage to be monitored.

Manual Reset (MR)

Many µP-based products require manual reset capability

to allow an operator or external logic circuitry to initiate a

reset. The manual reset input (MR) can be connected

directly to a switch without an external pullup resistor or

debouncing network. MR is internally pulled up to BP.

Leave unconnected if not used. MR is internally pulled

up to BP through a 10µA current source. MR is designed

to reject fast, falling transients (typically 100ns pulses)

and MR must be held low for a minimum of 1µs to assert

RESET. Connect a 0.1µF capacitor from MR to ground to

provide additional noise immunity. After MR transitions

from low to high, RESET remains asserted for the dura-

tion of its time delay.

MON

Use the following procedure to design the proper volt-

age-divider and calculate thresholds:

1) Pick a value for R2. Use the equation above with

the desired supply voltage to be monitored and

solve for R1. Use high-value resistors R1 and R2 to

minimize current consumption due to low leakage

currents.

2) To find the actual undervoltage and overvoltage

thresholds, use the following equations:

7/MAX68

V

⎛

⎜

⎞

⎟

REFUV

V

= V

×

ACTUALUV

MON

⎝ 0.6V ⎠

V

⎛

⎞

Margin Output Disable (MARGIN)

MARGIN allows system-level testing while power sup-

plies exceed the normal operating ranges. Drive

MARGIN low to hold RESET, OV, and WDO in their

REFOV

0.6V

V

= V

MON

⎜

⎝

⎟

⎠

ACTUALOV

Table 1. MAX6887 Threshold Options

UV THRESHOLDS (V)

PART

OV THRESHOLDS (V)

IN1

IN2

IN3

IN4

IN5

IN6

IN1

IN2

IN3

IN4

IN5

IN6

MAX6887AETE

MAX6887BETE

MAX6887CETE

MAX6887DETE

MAX6887EETE

MAX6887FETE

MAX6887GETE

MAX6887HETE

MAX6887QETE

MAX6887IETE

MAX6887JETE

MAX6887KETE

MAX6887LETE

MAX6887METE

MAX6887NETE

MAX6887OETE

MAX6887PETE

MAX6887RETE

4.620

3.060

0.557

4.380

2.880

0.527

3.060

2.310

1.670

0.557

2.880

2.190

1.580

0.527

2.310

1.670

1.390

0.557

2.190

1.580

1.310

0.527

1.670

0.557

1.390

0.557

1.580

0.527

1.310

0.527

0.557

0.527

0.557

0.527

0.557

0.527

0.557

0.527

5.360

3.540

0.643

5.620

3.700

0.673

3.540

2.680

1.930

0.643

3.700

2.810

2.020

0.673

2.680

1.930

1.610

0.643

2.810

2.020

1.680

0.673

1.930

0.643

1.610

0.643

2.020

0.673

1.680

0.673

0.643

0.673

0.643

0.673

8

_______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

Table 2. MAX6888 Threshold Options

UV THRESHOLDS (V)

OV THRESHOLDS (V)

PART

IN1

IN2

IN3

IN4

IN1

IN2

IN3

IN4

MAX6888AETE

MAX6888BETE

MAX6888CETE

MAX6888DETE

MAX6888EETE

MAX6888FETE

MAX6888GETE

MAX6888HETE

MAX6888QETE

MAX6888IETE

MAX6888JETE

MAX6888KETE

MAX6888LETE

MAX6888METE

MAX6888NETE

MAX6888OETE

MAX6888PETE

MAX6888RETE

4.620

3.060

0.557

4.380

2.880

0.527

3.060

2.310

1.670

0.557

2.880

2.190

1.580

0.527

2.310

1.670

1.390

0.557

2.190

1.580

1.310

0.527

1.670

0.557

1.390

0.557

1.580

0.527

1.310

0.527

5.360

3.540

0.643

5.620

3.700

0.673

3.540

2.680

1.930

0.643

3.700

2.810

2.020

0.673

2.680

1.930

1.610

0.643

2.810

2.020

1.680

0.673

1.930

0.643

1.610

0.643

2.020

0.673

1.680

0.673

existing state while system-level testing occurs. Leave

MARGIN unconnected or connect to BP if unused. An

internal 10µA current source pulls MARGIN to BP.

MARGIN overrides MR if both are asserted at the

same time. The state of RESET, OV, and WDO does not

change while MARGIN = GND.

RESET asserts when any monitored input is below its

undervoltage threshold or MR is asserted. RESET

remains asserted for 200ms after all assertion-causing

conditions have been cleared. Configure RESET to

assert when the watchdog timer expires by connecting

WDO to MR. RESET requires a pullup resistor.

WDO asserts when the watchdog timer expires. See

the Configuring the Watchdog Timer section for a com-

plete description. WDO requires a pullup resistor.

RESET, OV, and WDO Outputs

The MAX6887/MAX6888 feature three active-low open-

drain outputs: RESET, OV, and WDO. After power-up or

overvoltage/undervoltage conditions, RESET and OV

remain in their active states until their timeout periods

expire and no undervoltage/overvoltage conditions are

present (see Figure 2).

Configuring the Watchdog Timer

A watchdog timer monitors microprocessor (µP) soft-

ware execution for a stalled condition and resets the µP

if it stalls. Connect the watchdog timer output WDO to

the reset input or a nonmaskable interrupt of the µP.

The watchdog timer features independent initial and

normal watchdog timeout periods of 102.4s and 1.6s,

respectively.

OV asserts when any monitored input is above its over-

voltage threshold and remains asserted until all inputs

are below their thresholds and its respective 25µs time-

out period expires. Connect OV to MR to bring RESET

low during an overvoltage condition. OV requires a

pullup resistor (unless connected to MR).

_______________________________________________________________________________________

9

Hex/Quad, Power-Supply Supervisory Circuits

OVERVOLTAGE

THRESHOLD

V

IN

PRIMARY

THRESHOLD

OV

t

OP

7/MAX68

RESET

t

RP

Figure 2. Output Timing Diagram

2.5V

.

2.5V

V

CC

OR IN1–IN4

V

CC

OR IN1–IN4

WDO

RESET

WDI

RESET

WDI

t

RP

*t

WDI

t

RP

*t

DWI

D-PO

WD

t

RP

*t

WDI

t

*t

WDI

D-PO

WD

WDO CONNECTED TO MR

WDO NOT CONNECTED TO MR

*t IS THE INITIAL WATCHDOG TIMER PERIOD

WDI

Figure 3. Watchdog, Reset, and Power-Up Timing Diagram

10 ______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

At power-up, WDO goes high after t

(see Figure 3).

) applies imme-

Selector Guide (continued)

D-PO

The initial watchdog timeout period (t

WDI

NOMINAL INPUT

diately after WDO is high. The initial watchdog timeout

TOLERANCE

VOLTAGE (V)*

PART

period allows the µP to perform its initialization process.

(%)

A normal watchdog timeout period (t ) applies when-

WD

IN1

5.0

3.3

Adj

5.0

3.3

Adj

IN2

3.3

2.5

1.8

Adj

3.3

2.5

1.8

Adj

IN3

2.5

1.8

1.5

Adj

2.5

1.8

1.5

Adj

IN4

1.8

Adj

1.5

Adj

1.8

Adj

1.5

Adj

ever WDI transitions from high to low after the initial

watchdog timeout period occurs. WDI monitors the tog-

gling output of the µP, indicating normal processor

behavior. If WDI does not toggle during the normal

MAX6888AETE

MAX6888BETE

MAX6888CETE

MAX6888DETE

MAX6888EETE

MAX6888FETE

MAX6888GETE

MAX6888HETE

MAX6888QETE

MAX6888IETE

MAX6888JETE

MAX6888KETE

MAX6888LETE

MAX6888METE

MAX6888NETE

MAX6888OETE

MAX6888PETE

MAX6888RETE

5

watchdog timeout period (t

), indicating that the

5

WD

processor has stopped operating or is stuck in an infinite

execution loop, WDO goes low. WDO stays low until the

next transition on WDI. An initial watchdog timeout peri-

5

od (t ) starts when WDO goes high.

WDI

5

If WDO is connected to MR, the WDO will assert for a

short duration (~5µs), long enough to assert the RESET

output. Asserting RESET clears the watchdog timer and

WDO goes high. The reset output will remain asserted

for its timeout period after a watchdog fault. The watch-

dog timer stays cleared as long as RESET is low.

5

10

Applications Information

Layout and Bypassing

For better noise immunity, bypass each of the voltage-

detector inputs to GND with 0.1µF capacitors installed

as close to the device as possible. Bypass V

and BP

CC

to GND with 1µF capacitors installed as close to the

device as possible. V (when not externally supplied)

CC

*See thresholds options tables (Tables 1 and 2) for actual under-

voltage and overvoltage thresholds.

and BP are internally generated voltages and should

not be used to supply power to external circuitry.

Package Information

Chip Information

For the latest package outline information and land patterns, go

to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in

the package code indicates RoHS status only. Package draw-

ings may show a different suffix character, but the drawing per-

tains to the package regardless of RoHS status.

PROCESS: BiCMOS

PACKAGE TYPE

PACKAGE CODE

DOCUMENT NO.

21-0140

16-TQFN-EP

T1655+2

______________________________________________________________________________________ 11

Hex/Quad, Power-Supply Supervisory Circuits

Pin Configurations

TOP VIEW

12

11

10

9

12

11

10

9

IN4

13

14

15

16

IN4

8

7

6

5

I.C.

8

7

6

5

I.C.

IN3 14

IN3

IN2

WDI

MAX6888

MAX6887

15

IN2

MARGIN

MR

MARGIN

MR

16

IN1

*EXPOSED PAD

IN1

1

2

3

4

1

2

3

4

7/MAX68

THIN QFN

*EXPOSED PAD CONNECTED TO GND.

Typical Operating Circuit

12V

5V

12V

DC-DC

1

DC-DC

2

3.3V

2.5V

DC-DC

3

DC-DC

1.8V

4

1.5V

1.2V

IN1

IN2

IN3

IN4

IN5*

IN6*

V

CC

LOGIC INPUT

OV

V

CC

WDO

LOGIC INPUT

µP

RESET

WDI

BP

RESET

MAX6887

MAX6888

LOGIC OUTPUT

GND

MARGIN

MR

GND

*MAX6887 ONLY

12 ______________________________________________________________________________________

Hex/Quad, Power-Supply Supervisory Circuits

7/MAX68

Revision History

REVISION

NUMBER

REVISION

DATE

PAGES

CHANGED

DESCRIPTION

0

1

2

5/05

3/07

1/10

Initial release

—

1, 5, 14

1, 9

Revised Pin Description.

Revised Ordering Information to add lead-free information and revised Table 2.

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 ____________________ 13

Maxim is a registered trademark of Maxim Integrated Products, Inc.


型号：	MAX6887KETE+
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Power Supply Management Circuit, Adjustable, 6 Channel, BICMOS, 5 X 5 MM, 0.80 MM HEIGHT, ROHS COMPLIANT, MO-220WHHB, TQFN-16 输入元件信息通信管理
文件：	总13页 (文件大小：127K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX6887KETE+ [MAXIM]

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