MAX6422XS20+ - Maxim Integrated Products, Inc.

General Description

The MAX6340/MAX6421–MAX6426 low-power micro-

processor supervisor circuits monitor system voltages

from 1.6V to 5V. These devices perform a single function:

they assert a reset signal whenever the VCC supply volt-

age falls below its reset threshold. The reset output

remains asserted for the reset timeout period after VCC

rises above the reset threshold. The reset timeout is exter-

nally set by a capacitor to provide more flexibility.

The MAX6421/MAX6424 have an active-low, push-

pull reset output. The MAX6422 has an active-high,

push-pull reset output and the MAX6340/MAX6423/

MAX6425/MAX6426 have an active-low, open-drain

reset output. The MAX6421/MAX6422/MAX6423 are

offered in 4-pin SC70 or SOT143 packages. The

MAX6340/MAX6424/MAX6425/MAX6426 are available

in 5-pin SOT23-5 packages.

Applications

Portable Equipment

Battery-Powered Computers/Controllers

Automotive

Medical Equipment

Intelligent Instruments

Embedded Controllers

Critical µP Monitoring

Set-Top Boxes

Computers

Features

♦Monitor System Voltages from 1.6V to 5V

♦Capacitor-Adjustable Reset Timeout Period

♦Low Quiescent Current (1.6µA typ)

♦Three RESET Output Options

Push-Pull RESET

Open-Drain RESET

♦Guaranteed Reset Valid to VCC = 1V

♦Immune to Short VCC Transients

♦Small 4-Pin SC70, 4-Pin SOT143, and 5-Pin SOT23

Packages

♦MAX6340 Pin Compatible with LP3470

♦MAX6424/MAX6425 Pin Compatible with

NCP300–NCP303, MC33464/MC33465,

S807/S808/S809, and RN5VD

♦MAX6426 Pin Compatible with PST92XX

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

GND

( ) ARE FOR THE MAX6422

VCC 14

SRT

MAX6421X

MAX6422X

MAX6423X

SC70

TOP VIEW

RESET

(RESET)

Pin Configurations

19-2440; Rev 4; 12/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Selector Guide appears at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX6340UK_ _-T -40°C to +125°C 5 SOT23-5

MAX6421XS_ _-T -40°C to +125°C 4 SC70-4

MAX6421US_ _-T -40°C to +125°C 4 SOT143-4

MAX6422XS_ _-T -40°C to +125°C 4 SC70-4

MAX6422US_ _-T -40°C to +125°C 4 SOT143-4

MAX6423XS_ _-T -40°C to +125°C 4 SC70-4

MAX6423US_ _-T -40°C to +125°C 4 SOT143-4

MAX6424UK_ _-T -40°C to +125°C 5 SOT23-5

MAX6425UK_ _-T -40°C to +125°C 5 SOT23-5

MAX6426UK_ _-T -40°C to +125°C 5 SOT23-5

Note: The MAX6340/MAX6421–MAX6426 are available with fac-

tory-trimmed reset thresholds from 1.575V to 5.0V in approxi-

mately 0.1V increments. Insert the desired nominal reset

threshold suffix (from Table 1) into the blanks. There are 50 stan-

dard versions with a required order increment of 2500 pieces.

Sample stock is generally held on standard versions only (see

Standard Versions Table). Required order increment is 10,000

pieces for nonstandard versions. Contact factory for availability.

All devices are available in tape-and-reel only.

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

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

Pin Configurations continued at end of data sheet.

Typical Operating Circuit appears at end of data sheet.

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC = 1V to 5.5V, TA= TMIN to TMAX, unless otherwise specified. Typical values are at VCC = 5V and TA= +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.

All Voltages Referenced to GND

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

SRT, RESET, RESET (push-pull).................-0.3V to (VCC + 0.3V)

RESET (open drain)...............................................-0.3V to +6.0V

Input Current (all pins)......................................................±20mA

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

Continuous Power Dissipation (TA= +70°C)

4-Pin SC70 (derate 3.1mW/°C above +70°C)..............245mW

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

5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW

Operating Temperature Range .........................-40°C to +125°C

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

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

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage Range VCC 1.0 5.5 V

VCC ≤ 5.0V 2.5 4.2

VCC ≤ 3.3V 1.9 3.4Supply Current ICC

VCC ≤ 2.0V 1.6 2.5

µA

TA = +25°C VTH - 1.5% VTH + 1.5%

VCC Reset Threshold Accuracy VTH TA = -40°C to +125°C VTH - 2.5% VTH + 2.5% V

Hysteresis VHYST 4 x VTH mV

VCC to Reset Delay tRD VCC falling at 1mV/µs 80 µs

CSRT = 1500pF 3.00 4.375 5.75

Reset Timeout Period tRP CSRT = 0 0.275 ms

VSRT Ramp Current IRAMP VSRT = 0 to 0.65V; VCC = 1.6V to 5V 240 nA

VSRT Ramp Threshold VTH-RAMP VCC = 1.6V to 5V (VRAMP rising) 0.65 V

RAMP Threshold Hysteresis VRAMP falling threshold 33 mV

VCC ≥ 1.0V, ISINK = 50µA 0.3

VCC ≥ 2.7V, ISINK = 1.2mA 0.3RESET Output Voltage Low VOL

VCC ≥ 4.5V, ISINK = 3.2mA 0.4

VCC ≥ 1.8V, ISOURCE = 200µA 0.8 x VCC

VCC ≥ 2.25V, ISOURCE = 500µA 0.8 x VCC

RESET Output Voltage High,

Push-Pull VOH

VCC ≥ 4.5V, ISOURCE = 800µA 0.8 x VCC

RESET Output Leakage Current,

Open-Drain ILKG VCC > VTH, reset not asserted 1.0 µA

VCC ≥ 1.0V, ISOURCE = 1µA 0.8 x VCC

VCC ≥ 1.8V, ISOURCE = 150µA 0.8 x VCC

VCC ≥ 2.7V, ISOURCE = 500µA 0.8 x VCC

RESET Output Voltage High VOH

VCC ≥ 4.5V, ISOURCE = 800µA 0.8 x VCC

VCC ≥ 1.8V, ISINK = 500µA 0.3

VCC ≥ 2.7V, ISINK = 1.2mA 0.3

RESET Output Voltage Low VOL

VCC ≥ 4.5V, ISINK = 3.2mA 0.4

Note 1: Devices production tested at +25°C. Overtemperature limits are guaranteed by design.

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________ 3

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

021 3456

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6421/26 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

TA = +25°C

TA = +125°C

TA = -40°C

0.1

100

1000

10,000

0.001 0.10.01 1 10 100 1000

RESET TIMEOUT PERIOD vs. CSRT

MAX6421/26 toc02

CSRT (nF)

RESET TIMEOUT PERIOD (ms)

4.10

4.20

4.15

4.25

4.30

-50 0-25 25 50 75 100 125

RESET TIMEOUT PERIOD

vs. TEMPERATURE

MAX6421/26 toc03

TEMPERATURE (°C)

RESET TIMEOUT PERIOD (ms)

CSRT = 1500pF

RESET TIMEOUT PERIOD

vs. TEMPERATURE

MAX6421/26 toc04

200

250

350

300

500

550

450

400

600

RESET TIMEOUT PERIOD (µs)

-50 0 25-25 50 75 100 125

TEMPERATURE (°C)

CSRT = 0

100

150

125

175

0 400200 600 800 1000

MAXIMUM TRANSIENT DURATION

vs. RESET THRESHOLD OVERDRIVE

MAX6421/26 toc05

RESET THRESHOLD OVERDRIVE (mV)

TRANSIENT DURATION (µs)

RESET OCCURS

ABOVE THE CURVE

VTH = 2.95V

VCC TO RESET DELAY

vs. TEMPERATURE (VCC FALLING)

MAX6421/26 toc06

110

100

140

150

130

120

160

VCC TO RESET DELAY (µs)

-50 0 25-25 50 75 100 125

TEMPERATURE (°C)

VCC FALLING AT 1mVµs

POWER-UP/POWER-DOWN

CHARACTERISTIC

MAX6421/26 toc07

1V/div

VCC

RESET

VTH = 1.6V

400µs/div

0.994

0.998

0.996

1.002

1.000

1.004

1.006

-50 25 50-25 0 75 100 125

NORMALIZED RESET THRESHOLD

vs. TEMPERATURE

MAX6421/26 toc08

TEMPERATURE (°C)

NORMALIZED RESET THRESHOLD

Typical Operating Characteristics

(VCC = 5V, CSRT = 1500pF, TA = +25°C, unless otherwise noted.)

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

4 _______________________________________________________________________________________

Detailed Description

Reset Output

The reset output is typically connected to the reset input

of a µP. A µP’s reset input starts or restarts the µP in a

known state. The MAX6340/MAX6421–MAX6426 µP

supervisory circuits provide the reset logic to prevent

code-execution errors during power-up, power-down,

and brownout conditions (see Typical Operating

Characteristics).

RESET changes from high to low whenever VCC drops

below the threshold voltage. Once VCC exceeds the

threshold voltage, RESET remains low for the capacitor-

adjustable reset timeout period.

The MAX6422 active-high RESET output is the inverse

logic of the active-low RESET output. All device outputs

are guaranteed valid for VCC > 1V.

The MAX6340/MAX6423/MAX6425/MAX6426 are open-

drain RESET outputs. Connect an external pullup resis-

tor to any supply from 0 to 5.5V. Select a resistor value

large enough to register a logic low when RESET is

asserted and small enough to register a logic high

while supplying all input current and leakage paths

connected to the RESET line. A 10kΩto 100kΩpullup

is sufficient in most applications.

Selecting a Reset Capacitor

The reset timeout period is adjustable to accommodate

a variety of µP applications. Adjust the reset timeout

period (tRP) by connecting a capacitor (CSRT) between

SRT and ground. Calculate the reset timeout capacitor

as follows:

Pin Description

MAX6340

MAX6421

MAX6422

MAX6423

MAX6424

MAX6425 MAX6426

SOT23 SOT143 SC70 SOT23 SOT23

NAME FUNCTION

1 3 3 5 1 SRT

Set Reset Timeout Input. Connect a capacitor between SRT

and ground to set the timeout period. Determine the period as

follows: tRP = 2.73 ✕ 106 ✕ CSRT + 275µs with tRP in seconds

and CSRT in farads.

2 1 2 3 2, 3 GND Ground

3 — — 4 — N.C. Not Internally Connected. Can be connected to GND.

42125V

CC Supply Voltage and Reset Threshold Monitor Input

514RESET

RESET changes from high to low whenever VCC drops below

the selected reset threshold voltage. RESET remains low for

the reset timeout period after VCC exceeds the reset

threshold.

—

— — RESET

RESET changes from low to high whenever VCC drops below

the selected reset threshold voltage. RESET remains high for

the reset timeout period after VCC exceeds the reset

threshold.

MAX6340

MAX6423

MAX6425

MAX6426

VREF

CSRT

SRT RESET

TIMEOUT

GND

RESET

LASER-TRIMMED

RESISTORS

VCC

3.3V

10kΩ

5.0V

SYSTEM

Figure 1. MAX6340/MAX6423/MAX6425/MAX6426 Open-Drain

RESET

Output Allows Use with Multiple Supplies

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________ 5

CSRT = (tRP - 275µs) / (2.73 ✕106)

where tRP is in seconds and CSRT is in farads.

The reset delay time is set by a current/capacitor-con-

trolled ramp compared to an internal 0.65V reference.

An internal 240nA ramp current source charges the

external capacitor. The charge to the capacitor is

cleared when a reset condition is detected. Once the

reset condition is removed, the voltage on the capacitor

ramps according to the formula: dV/dt = I/C. The CSRT

capacitor must ramp to 0.65V to deassert the reset.

CSRT must be a low-leakage (<10nA) type capacitor;

ceramic is recommended.

Operating as a Voltage Detector

The MAX6340/MAX6421–MAX6426 can be operated in a

voltage detector mode by floating the SRT pin. The reset

delay times for VCC rising above or falling below the

threshold are not significantly different. The reset output is

deasserted smoothly without false pulses.

Applications Information

Interfacing to Other Voltages for Logic

Compatibility

The open-drain outputs of the MAX6340/MAX6423/

MAX6425/MAX6426 can be used to interface to µPs with

other logic levels. As shown in Figure 1, the open-drain

output can be connected to voltages from 0 to 5.5V. This

allows for easy logic compatibility to various µPs.

Wired-OR Reset

To allow auxiliary circuitry to hold the system in reset,

an external open-drain logic signal can be connected

to the open-drain RESET of the MAX6340/MAX6423/

MAX6425/MAX6426, as shown in Figure 2. This config-

uration can reset the µP, but does not provide the reset

timeout when the external logic signal is released.

Negative-Going VCC Transients

In addition to issuing a reset to the µP during power-up,

power-down, and brownout conditions, these supervisors

are relatively immune to short-duration negative-going

transients (glitches). The graph Maximum Transient

Duration vs. Reset Threshold Overdrive in the Typical

Operating Characteristics shows this relationship.

The area below the curve of the graph is the region in

which these devices typically do not generate a reset

pulse. This graph was generated using a negative-

going pulse applied to VCC, starting above the actual

reset threshold (VTH) and ending below it by the magni-

tude indicated (reset-threshold overdrive). As the mag-

nitude of the transient decreases (farther below the

reset threshold), the maximum allowable pulse width

decreases. Typically, a VCC transient that goes 100mV

below the reset threshold and lasts 50µs or less does

not cause a reset pulse to be issued.

Ensuring a Valid RESET or

RESET

Down to VCC = 0

When VCC falls below 1V, RESET/RESET current-sink-

ing (sourcing) capabilities decline drastically. In the

case of the MAX6421/MAX6424, high-impedance

CMOS-logic inputs connected to RESET can drift to

undetermined voltages. This presents no problems in

most applications, since most µPs and other circuitry

do not operate with VCC below 1V.

In those applications where RESET must be valid down

to zero, adding a pulldown resistor between RESET

and ground sinks any stray leakage currents, holding

RESET low (Figure 3). The value of the pulldown resis-

tor is not critical; 100kΩis large enough not to load

RESET and small enough to pull RESET to ground. For

applications using the MAX6422, a 100kΩpullup resis-

VDD

VCC

MAX6340

MAX6423

MAX6425

MAX6426

RESET

GND

OPEN-DRAIN

LOGIC

µP

RESET

10kΩ

Figure 2. Wired-OR Reset Circuit

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

6 _______________________________________________________________________________________

tor between RESET and VCC holds RESET high when

VCC falls below 1V (Figure 4). Open-drain RESET ver-

sions are not recommended for applications requiring

valid logic for VCC down to zero.

Layout Consideration

SRT is a precise current source. When developing the

layout for the application, be careful to minimize board

capacitance and leakage currents around this pin.

Traces connected to SRT should be kept as short as

possible. Traces carrying high-speed digital signals

and traces with large voltage potentials should be rout-

ed as far from SRT as possible. Leakage current and

stray capacitance (e.g., a scope probe) at this pin

could cause errors in the reset timeout period. When

evaluating these parts, use clean prototype boards to

ensure accurate reset periods.

MAX6421

MAX6424

GND

VCC

RESET

100kΩ

Figure 3. Ensuring

RESET

Valid to VCC = 0

MAX6422

GND

VCC

RESET

100kΩ

Figure 4. Ensuring RESET Valid to VCC = 0

SUFFIX MIN TYP MAX

16 1.536 1.575 1.614

17 1.623 1.665 1.707

18 1.755 1.800 1.845

19 1.853 1.900 1.948

20 1.950 2.000 2.050

21 2.048 2.100 2.153

22 2.133 2.188 2.243

23 2.313 2.313 2.371

24 2.340 2.400 2.460

25 2.438 2.500 2.563

26 2.559 2.625 2.691

27 2.633 2.700 2.768

28 2.730 2.800 2.870

29 2.852 2.925 2.998

30 2.925 3.000 3.075

31 2.998 3.075 3.152

32 3.120 3.200 3.280

33 3.218 3.300 3.383

34 3.315 3.400 3.485

35 3.413 3.500 3.558

36 3.510 3.600 3.690

37 3.608 3.700 3.793

38 3.705 3.800 3.895

39 3.803 3.900 3.998

40 3.900 4.000 4.100

41 3.998 4.100 4.203

42 4.095 4.200 4.305

43 4.193 4.300 4.408

44 4.266 4.375 4.484

45 4.388 4.500 4.613

46 4.509 4.625 4.741

47 4.583 4.700 4.818

48 4.680 4.800 4.920

49 4.778 4.900 5.023

50 4.875 5.000 5.125

Table 1. Reset Threshold Voltage Suffix

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________ 7

PART* OUTPUT STAGE TOP MARK

MAX6340UK16-T Open-Drain RESET AEBE

MAX6340UK22-T Open-Drain RESET AEBG

MAX6340UK26-T Open-Drain RESET AEBI

MAX6340UK29-T Open-Drain RESET AEBJ

MAX6340UK46-T Open-Drain RESET AEBM

MAX6421US16-T Push-Pull RESET KADA

MAX6421XS16-T Push-Pull RESET ACU

MAX6421US22-T Push-Pull RESET KADE

MAX6421XS22-T Push-Pull RESET ACY

MAX6421US26-T Push-Pull RESET KADG

MAX6421XS26-T Push-Pull RESET ADA

MAX6421US29-T Push-Pull RESET KADH

MAX6421XS29-T Push-Pull RESET ADB

MAX6421US46-T Push-Pull RESET KADK

MAX6421XS46-T Push-Pull RESET ADE

MAX6422US16-T Push-Pull RESET KADB

MAX6422XS16-T Push-Pull RESET ACV

MAX6422US22-T Push-Pull RESET KADM

MAX6422XS22-T Push-Pull RESET ADG

MAX6422US26-T Push-Pull RESET KADO

MAX6422XS26-T Push-Pull RESET ADI

MAX6422US29-T Push-Pull RESET KADP

MAX6422XS29-T Push-Pull RESET ADJ

MAX6422US46-T Push-Pull RESET KADS

MAX6422XS46-T Push-Pull RESET ADM

Standard Versions Table

*Sample stock is generally held on all standard versions. Contact

factory for availability of nonstandard versions.

PART* OUTPUT STAGE TOP MARK

MAX6423US16-T Open-Drain RESET KADC

MAX6423XS16-T Open-Drain RESET ACW

MAX6423US22-T Open-Drain RESET KADU

MAX6423XS22-T Open-Drain RESET ADO

MAX6423US26-T Open-Drain RESET KADW

MAX6423XS26-T Open-Drain RESET ADQ

MAX6423US29-T Open-Drain RESET KADX

MAX6423XS29-T Open-Drain RESET ADR

MAX6423US46-T Open-Drain RESET KAEA

MAX6423XS46-T Open-Drain RESET ADU

MAX6424UK16-T Push-Pull RESET ADUF

MAX6424UK22-T Push-Pull RESET ADUK

MAX6424UK26-T Push-Pull RESET ADUM

MAX6424UK29-T Push-Pull RESET ADUN

MAX6424UK46-T Push-Pull RESET ADUQ

MAX6425UK16-T Open-Drain RESET ADUG

MAX6425UK22-T Open-Drain RESET ADUS

MAX6425UK26-T Open-Drain RESET ADUU

MAX6425UK29-T Open-Drain RESET ADUV

MAX6425UK46-T Open-Drain RESET ADUY

MAX6426UK16-T Open-Drain RESET ADUH

MAX6426UK22-T Open-Drain RESET ADVA

MAX6426UK26-T Open-Drain RESET ADVC

MAX6426UK29-T Open-Drain RESET ADVD

MAX6426UK46-T Open-Drain RESET ADVG

MAX6421

MAX6424

VREF

CSRT

SRT RESET

TIMEOUT

GND

RESET

LASER-TRIMMED

RESISTORS

VCC

µP

RESET

Typical Operating Circuit

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

8 _______________________________________________________________________________________

PART PUSH-PULL RESET PUSH-PULL RESET OPEN-DRAIN RESET PIN-PACKAGE

MAX6340 — — ✔5 SOT23

MAX6421 ✔— — 4 SOT143/SC70

MAX6422 — ✔— 4 SOT143/SC70

MAX6423 — — ✔4 SOT143/SC70

MAX6424 ✔— — 5 SOT23

MAX6425 — — ✔5 SOT23

Selector Guide

VCC

N.C.

1 5 SRT

MAX6424

MAX6425

SOT23

TOP VIEW

RESET

GND

15V

MAX6426

SOT23

SRT

GND RESET

VCC

N.C.

15SRT

MAX6340

SOT23

RESET

GND

VCC

SRT

MAX6421U

MAX6422U

MAX6423U

SOT143

RESET

(RESET)

Pin Configurations (continued)

Chip Information

TRANSISTOR COUNT: 295

PROCESS: BiCMOS

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________ 9

SC70, 4L.EPS

PACKAGE OUTLINE, 4L SC70

21-0098

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.)

MAX6340/MAX6421–MAX6426

Low-Power, SC70/SOT µP Reset Circuits with

Capacitor-Adjustable Reset Timeout Delay

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.

10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

SOT-143 4L.EPS

21-0052

PACKAGE OUTLINE, SOT-143, 4L

SOT-23 5L .EPS

21-0057

PACKAGE OUTLINE, SOT-23, 5L

Package Information (continued)

(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.)