MAX709SCUA+T - Maxim Integrated Products, Inc.

MAX709

Power-Supply Monitor with Reset

________________________________________________________________ Maxim Integrated Products 1

N.C.

RESET

VCC

N.C.

GND

N.C.

DIP/SO/µMAX

MAX709

__________________Pin Configuration

TOP VIEW

RESET

GND GND

VCC

µP

MAX709

RESET

__________Typical Operating Circuit

Call toll free 1-800-998-8800 for free samples or literature.

19-0136; Rev. 2; 12/05

_______________General Description

The MAX709 provides a system reset during power-up,

power-down, and brownout conditions. When VCC falls

below the reset threshold, RESET goes low and holds

the µP in reset for 140ms min after VCC rises above the

threshold.

The RESET output is guaranteed to be in the correct

state with VCC down to 1V. The MAX709 provides

excellent circuit reliability and low cost by eliminating

external components and adjustments when used with

+5V, +3.3V, or +3V powered systems. The MAX709 is

available 8-pin DIP, µMAX, and SO packages.

_______________________Applications

Minimum Component Count,

Low-Cost Processor Systems

___________________________Features

♦+5V, +3.3V, and +3V Versions

♦No External Components

♦Low Cost

♦Precise Power-Down Reset Threshold

♦140ms Min Power-On Reset Delay

♦Immune to Short Negative VCC Transients

♦8-Pin DIP, µMAX, and SO Packages

♦Low Supply Current: 35µA - MAX709R/S/T

65µA - MAX709L/M

______________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX709_CPA 0°C to +70°C

MAX709_CSA 0°C to +70°C 8 SO

MAX709_C/D 0°C to +70°C Dice

MAX709_EPA -40°C to +85°C 8 Plastic DIP

MAX709_ESA -40°C to +85°C 8 SO

8 Plastic DIP

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

Specify lead free by adding the + symbol at the end of the part

number when ordering.

*Dice are specified at TA= +25

°C

,DCparameters only.

Note: 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)

L4.65

M4.40

T3.08

S2.93

R2.63

MAX709_CUA 0°C to +70°C 8 µMAX

MAX709_EUA -40°C to +85°C 8 µMAX

MAX709

Power-Supply Monitor with Reset

2_______________________________________________________________________________________

Terminal Voltage (with respect to GND)

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

RESET....................................-0.3V to (VCC + 0.3V)

Input Current, VCC ..........................................20mA

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

Rate-of-Rise, VCC .........................................100V/µs

Continuous Power Dissipation (TA= +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C) ........727mW

µMAX (derate 4.10mW/°C above +70°C) .............330mW

SO (derate 5.88mW/°C above +70°C).................471mW

Operating Temperature Ranges

MAX709_C___ ...................................0°C to +70°C

MAX709_E___ . ................................-40°C to +85°C

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

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

ELECTRICAL CHARACTERISTICS

(VCC = full range, TA= TMIN to TMAX, unless otherwise noted.)

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.

Note 1: Supply current is measured with VCC = 3.6V for MAX709R/S/T, and VCC = 5.5V for all versions.

PARAMETER CONDITIONS MIN TYP MAX UNITS

VCC Range 1.0 5.5 V

1.2 5.5

Supply Current (Note 1)

35 85

µA

35 110

All versions 65 150

65 200

RESET Threshold, VTH

MAX709L 4.50 4.65 4.75

MAX709M 4.25 4.40 4.50

MAX709T 3.00 3.08 3.15

MAX709S 2.85 2.93 3.00

MAX709R 2.55 2.63 2.70

VCC to RESET Delay VCC = reset threshold max to reset threshold min 20 µs

Reset Active Timeout Period VCC = reset threshold max, VCC rising 140 280 560 ms

RESET Output Voltage

0.3

0.4

ISINK = 50µA, VCC ≥1.0V, MAX709_C 0.3

ISINK = 100µA, VCC ≥1.2V, MAX709_E 0.4

ISOURCE = 800µA, VCC ≥reset threshold max,

MAX709L/M only

MAX709_C

MAX709_E

MAX709_C, VCC < 3.6V

MAX709_E, VCC < 3.6V

MAX709_C, VCC < 5.5V

MAX709_E, VCC < 5.5V

MAX709R/S/T only

ISINK = 1.2mA, VCC = reset threshold min,

MAX709R/S/T only

ISINK = 3.2mA, VCC = reset threshold min,

MAX709L/M only

ISOURCE = 500µA, VCC ≥reset threshold max,

MAX709R/S/T only 0.8 x VCC

VCC - 1.5

ABSOLUTE MAXIMUM RATINGS

MAX709

Power-Supply Monitor with Reset

_________________________________________________________________________________________________ 3

300

-60 100

POWER-UP RESET DELAY

vs. TEMPERATURE

250

TEMPERATURE (°C)

POWER-UP RESET DELAY (ms)

150

100

-20 20

200

VCC = RESET THRESHOLD MAX,

VCC RISING

100

-60 -20 60 100

SUPPLY CURRENT

vs. TEMPERATURE

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

NOTE: STEADY-STATE SUPPLY

CURRENT IS INDEPENDENT

OF RESET OUTPUT STATUS

NO LOAD

VCC = +5V

VCC = +4V

VCC = +3V

VCC = +2V

VCC = +1V

-60 100

POWER-DOWN RESET DELAY

vs. TEMPERATURE

TEMPERATURE (°C)

POWER-DOWN RESET DELAY (µs)

-20 20

VCC STEPPED FROM RESET THRESHOLD

MAX TO RESET THRESHOLD MIN

__________________________________________Typical Operating Characteristics

1.005

0.997

-60 -20 60 100

NORMALIZED RESET THRESHOLD

vs. TEMPERATURE

0.999

1.003

TEMPERATURE (°C)

NORMALIZED RESET THRESHOLD

1.001

0.995

THE RESET THRESHOLD IS SHOWN

NORMALIZED TO 1, REPRESENTING

ALL AVAILABLE MAX709 RESET

THRESHOLDS

MAX709

Power-Supply Monitor with Reset

4_______________________________________________________________________________________

__________Applications Information

Negative-Going VCC Transients

In addition to issuing a reset to the microprocessor

(µP) during power-up, power-down, and brownout con-

ditions, the MAX709 is relatively immune to short dura-

tion negative-going VCC transients (glitches).

Figure 1 shows typical transient duration vs. reset com-

parator overdrive, for which the MAX709 does not gen-

erate a reset pulse. The graph was generated using a

negative-going pulse applied to VCC, starting 1.5V

above the actual reset threshold and ending below it

by the magnitude indicated (reset comparator over-

drive). The graph indicates the typical maximum pulse

width that a negative-going VCC 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, for the

MAX709L/MAX709M, a VCC transient that goes 100mV

below the reset threshold and lasts 40µs or less will not

cause a reset pulse to be issued.

A 0.1µF bypass capacitor mounted as close as possible

to pin 2 (VCC) provides additional transient immunity.

Ensuring a Valid RESET Output

Down to VCC = 0V

When VCC falls below 1V, the MAX709 RESET output

no longer sinks current—it becomes an open circuit.

Therefore, high-impedance CMOS logic inputs con-

nected to the RESET output can drift to undermined

voltages. This presents no problem in most applica-

tions, since most µP and other circuitry is inoperative

with VCC below 1V. However, in applications where the

RESET output must be valid down to 0V, adding a pull-

down resistor to the RESET pin will cause any stray

leakage currents to flow to ground, holding RESET low

(see Figure 2). The resistance value of R1 is not criti-

cal. It should be about 100kΩ, which is large enough

not to load RESET and small enough to pull RESET to

ground.

____________________Pin Description

PIN NAME FUNCTION

N.C. No Connect. There is no internal

connection to this pin.

2VCC +5V, +3.3V, or +3V Supply Voltage

3GND Ground

7RESET

1, 4, 5,

6, 8

Reset Output remains low while VCC is

below the reset threshold, and for

280ms after VCC rises above the reset

threshold.

150

10 100 10k

100

RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)

MAXIMUM TRANSIENT DURATION (µs)

MAX709L/M

MAX709R/S/T

TA = +25°C

10ns

Figure 1. Maximum Transient Duration without Causing a

Reset Pulse vs. Reset Comparator Overdrive

MAX709

Power-Supply Monitor with Reset

_______________________________________________________________________________________ 5

Interfacing to µPs with

Bidirectional Reset Pins

Microprocessors with bidirectional reset pins (such as

the Motorola 68HC11 series) can contend with the

MAX709 reset output. If, for example the MAX709

RESET output is asserted high and the µP wants to pull

it low, indeterminate logic levels may result. To correct

this, connect a 4.7kΩresistor between the MAX709

RESET output and the µP reset I/O (see Figure 3).

Buffer the MAX709 RESET output to other system com-

ponents.

VCC

GND

MAX709

RESET

Figure 2. RESET Valid to VCC = Ground Circuit

4.7k

VCC

GND

RESET

MAX709

VCC

GND

µP

BUFFER

BUFFERED RESET

TO OTHER SYSTEM

COMPONENTS

RESET

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

MAX709

Power-Supply Monitor with Reset

6_______________________________________________________________________________________

Minimum Nominal

Nominal Reset Watchdog Power-

Reset Pulse Timeout Backup- CCEE-Fail Manual- Watch- Low- Active- Battery-

Part Threshold Width Period Battery Write Com- Reset dog Line High On

Number (V) (ms) (sec) Switch Protect parator Input Output Output Reset Output

MAX690A/692A 4.65/4.40 140 1.6 ✔✔

MAX691A/693A 4.65/4.40 140/adj. 1.6/adj. ✔✔/10ns ✔✔✔✔✔

MAX696 Adj. 35/adj. 1.6/adj. ✔✔✔✔✔✔

MAX697 Adj. 35/adj. 1.6/adj. ✔✔ ✔✔ ✔

MAX700 4.65/adj. 200 - ✔✔

MAX703/704 4.65/4.40 140 - ✔✔✔

MAX705/706 4.65/4.40 140 1.6 ✔✔✔

MAX706P 2.63 140 1.6 ✔✔✔ ✔

MAX706R/S/T 2.63/2.93/ 140 1.6 ✔✔✔

3.08

MAX707/708 4.65/4.40 140 - ✔✔ ✔

MAX708R/S/T 2.63/2.93/ 140 - ✔✔ ✔

3.08

MAX709L/M/ 4.65/4.40/ 140 -

R/S/T 2.63/2.93/3.08

MAX791 4.65 140 1 ✔✔/10ns ✔✔✔✔ ✔✔

MAX792L/M/ 4.65/4.40/ 140 1 ✔/10ns ✔✔✔✔ ✔

R/S/T 2.63/2.93/3.08

MAX800L/M 4.60/4.40 140 1.6/adj. ✔✔/10ns ✔/±2% ✔✔ ✔✔

MAX802L/M 4.60/4.40 140 1.6 ✔✔/±2%

MAX805L 4.65 140 1.6 ✔✔ ✔

MAX813L 4.65 140 1.6 ✔✔✔ ✔

MAX820L/M/ 4.65/4.40/ 140 1 ✔/10ns ✔/±2% ✔✔✔ ✔

R/S/T 2.63/2.93/3.08

MAX1232 4.37/4.62 250 0.15/0.60/1.2 ✔

MAX1259 - - - ✔✔

_____________________________________________________µP Supervisory Circuits

MAX709

Power-Supply Monitor with Reset

_______________________________________________________________________________________ 7

RESET

VCC

GND

0.045"

(1.143mm)

0.056"

(1.422mm)

___________________Chip Topography

TRANSISTOR COUNT: 380

SUBSTRATE CONNECTED TO VCC

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.

8___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

MAX709

Power-Supply Monitor with Reset

8LUMAXD.EPS

PACKAGE OUTLINE, 8L uMAX/uSOP

21-0036 J

REV.DOCUMENT CONTROL NO.APPROVAL

PROPRIETARY INFORMATION

TITLE:

MAX

0.043

0.006

0.014

0.120

0.198

0.026

0.007

0.037

0.0207 BSC

0.0256 BSC

A2 A1

FRONT VIEW SIDE VIEW

E H

0.6±0.1

Ø0.50±0.1

TOP VIEW

A2 0.030

BOTTOM VIEW

16°

0°

0.010

0.116

0.188

0.016

0.005

4X S

INCHES

MIN

0.002

0.950.75

0.5250 BSC

0.25 0.36

2.95 3.05

4.78

0.41

0.65 BSC

5.03

0.66

6°0°

0.13 0.18

MAX

MIN

MILLIMETERS

-1.10

0.05 0.15

DIM

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.)