Datasheet MAX6343ZUT-T, MAX6343LUT-T, MAX6343MUT-T, MAX6343RUT-T, MAX6343SUT-T Datasheet (Maxim)

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General Description

The MAX6342–MAX6345 family of microprocessor (µP)
supervisory circuits monitors power supplies in digital sys­tems. These devices significantly improve system reliabili­ty and accuracy compared to separate ICs or discrete
components.

The MAX6342–MAX6345 provide factory-trimmed V

CC

reset threshold voltages from 2.33V to 4.63V and operate
with supply voltages between +1V and +5.5V. A +1.25V
threshold detector allows for a power-fail warning, for low­battery detection, or for monitoring another power supply.
The MAX6342 contains an MR input and an active-low
push-pull reset. The MAX6343 and MAX6344 are identical
to the MAX6342 except they provide an active-low, open­drain reset and an active-high, push-pull reset, respective­ly. The MAX6345 provides a second reset output in place
of the MR input to give it an active-high push-pull reset
and an active-low push-pull reset.

All of the devices are packaged in a miniature 6-pin
SOT23.

Applications

Portable Computers
Telecom Equipment
Networking Equipment
Portable/Battery-Powered Equipment
Multivoltage Systems
Embedded Control Systems

Features

♦ Small 6-Pin SOT23 Package
♦ Precision Factory-Set V

CC

Reset Thresholds

Between 2.33V and 4.63V

♦ Guaranteed RESET Valid to V

CC

= +1V

♦ 100ms min Reset Pulse Width
♦ Debounced CMOS-Compatible Manual-Reset

Input

♦ Voltage Monitor for Power-Fail or Low-Battery

Warning

MAX6342–MAX6345

6-Pin µP Reset Circuit with

Power-Fail Comparator

________________________________________________________________

Maxim Integrated Products

1

GND

PFI

16

5

V

CC

( ) ARE FOR MAX6344 ONLY.

TOP VIEW

2

34

RESET (RESET)

PFO

MR

MAX6342
MAX6343
MAX6344

SOT23-6

Selector Guide 1

Selector Guide 2

19-1568; Rev 0; 10/99

PART
MAX6342_UT-T
MAX6343_UT-T
MAX6344_UT-T

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

6 SOT23-6
6 SOT23-6
6 SOT23-6

Note:

The MAX6342–MAX6345 are available with factory-set
reset thresholds from 2.33V to 4.63V (see Selector Guides 1, 2).
Insert the letter corresponding to the desired nominal reset
threshold into the blank following the part number. There is a
2500 piece order increment required for the SOT package. SOT
Top Marks table appears at end of data sheet. All versions of
these products may not be available at time of announcement.
Contact factory for availability.

Pin Configurations

Ordering Information

MAX6345_UT-T

-40°C to +85°C 6 SOT23-6

SUFFIX RESET THRESHOLD (V)

L

4.63

M 4.38

T 3.08
S 2.93
R 2.63
Z 2.33

PART

PUSH-PULL

RESET OUTPUT

OPEN-DRAIN

RESET OUTPUT

PUSH-PULL RESET

OUTPUT

MAX6342

✔

— —

MAX6343 —

✔

—

MAX6344 — —

✔

MAX6345

✔

—

✔

MANUAL-RESET

INPUT

✔
✔
✔

—

Typical Operating Circuit appears at end of data sheet.

Pin Configurations continued at end of data sheet.

V

MAX6342–MAX6345

6-Pin µP Reset Circuit with
Power-Fail Comparator

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +1.0V to +5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C and VCC= +3V.) (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.

VCCto GND..............................................................-0.3V to +6V

RESET, RESET

(MAX6342/MAX6344/MAX6345) ......... -0.3V to (V

CC

+ 0.3V)

RESET (MAX6343)................................................... -0.3V to +6V

MR, PFI, PFO ..............................................-0.3V to (V

CC

+ 0.3V)

Input Current, V

CC

..............................................................50mA

Output Current, RESET, RESET ..........................................50mA

Continuous Power Dissipation (T

A

= +70°C)

6-Pin SOT23 (derate 4mW/°C above +70°C).............320mW

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

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

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

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

VCC> 2.7V, I

SOURCE

= 500µA

(MAX6342/MAX6345 only)

VCC> 1.2V, I

SOURCE

= 50µA

VCC> 4.5V, I

SINK

= 3.2mA

VCC> 2.7V, I

SINK

= 1.2mA

TA= -40°C to +85°C

VCC> 1.2V, I

SINK

= 100µA

TA= 0°C to +70°C

VCC= VTHto (VTH- 100mV)

µA

MAX634_S

MAX634_Z

MAX634_T

No load

MAX634_L

MAX634_R

MAX634_M

CONDITIONS

0.8 · V

CC

0.8 · V

CC

0.4

0.3

V

0.4

V

OL

ms

100 180 280

t

RP

Reset Timeout Period

µs

20

VCCto Reset Delay

V

2.25 2.38

2.30 2.33 2.36

2.55 2.70

2.59 2.63 2.67

2.85 3.00

25 40

I

CC

Supply Current

1.2 5.5

V

1.0 5.5

V

CC

Supply Voltage Range

2.89 2.93 2.97

3.00 3.15

3.03 3.08 3.13

4.25 4.50

30 50

4.56 4.63 4.70

V

TH

Reset Threshold

4.50 4.75

4.31 4.38 4.45

UNITSMIN TYP MAXSYMBOLPARAMETER

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
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

VCC= 3V
VCC= 5.5V

VCC> 4.5V, I

SOURCE

= 800µA

(MAX6342/MAX6345 only)

0.8 · V

CC

V

OH

RESET and RESET Outputs
Drive Capability (Note 2)

MAX6342–MAX6345

6-Pin µP Reset Circuit with

Power-Fail Comparator

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +1.0V to +5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C and VCC= +3V.) (Note 1)

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

MAX6343 only, VCC> V

TH(MAX)

MR Pull-Up Resistance

V

0.7 · V

CC

V

IH

MR Input High

V

0.3 · V

CC

V

IL

MR Input Low

µA

1

I

LKG

Open-Drain RESET Output
Leakage Current

60

kΩ

MR Minimum Pulse Width

1

µs

MR Glitch Rejection

0.1

µs

MR to Reset Delay

0.2

µs

PFI Input Threshold

1.2 1.25 1.3

V

PFI Leakage Current

±0.01 ±25

nA

PFO Output Voltage

V

OL

VCC= 4.5V, I

SINK

= 3.2mA

0.4

V

PFO Output Voltage

V

OH

VCC= 4.5V, I

SOURCE

= 800µA

0.8 · V

CC

PFO Output Short-Circuit
Current

Output sink current

20

mA

Output source current

5

PFI to PFO Delay

V

OVERDRIVE

= 15mV

3

µs

Typical Operating Characteristics

(V

PFI

= VCC= +5V, TA= +25°C, unless otherwise noted.)

0

10

5

20

15

25

30

-40 10-15 35 60 85

SUPPLY CURRENT vs. SUPPLY VOLTAGE

AND TEMPERATURE

MAX6342-01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

VCC = 5V

VCC = 3.3V

VCC = 2.5V

VCC = 1V

0

0

1sec/div

MAX6342-02

MAX6344L/MAX6345L

RESET OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE

V

CC

RESET

1V/div

0

0

1sec/div

MAX6342-03

MAX6342M/MAX6345M

RESET OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE

V

CC

RESET

1V/div

V

Note 1: Overtemperature limits are guaranteed by design and not production tested.
Note 2: Apply to each part in accordance with threshold voltage, output configuration, and manual reset status selected.

MAX6342–MAX6345

6-Pin µP Reset Circuit with
Power-Fail Comparator

4 _______________________________________________________________________________________

0

2

1

4

3

5

6

0213456

MAX6342-04

SUPPLY VOLTAGE (V)

PFO OUTPUT VOLTAGE HIGH

vs. SUPPLY VOLTAGE

PFO (V)

R

L

= 10kΩ

0.20

0.30

0.35

0.25

0.45

0.40

0.50

0.55

0.60

0213456

MAX6342-05

SUPPLY VOLTAGE (V)

PFO OUTPUT VOLTAGE LOW

vs. SUPPLY VOLTAGE

PFO (V)

R

L

= 1kΩ

10µs/div

MAX6342-06

MAX6344/MAX6345

RESET RESPONSE TIME

V

CC

RESET

0

4V

5V

4V

2µs/div

MAX6342-07

MAX6342/MAX6345

RESET RESPONSE TIME

V

CC

0

4V

5V
4V

RESET

5V

Typical Operating Characteristics (continued)

(V

PFI

= VCC= +5V, TA= +25°C, unless otherwise noted.)

Pin Description

MAX6344

1 1 Supply Voltage

2 2 Ground

MAX6342

3 3

Power-Fail Voltage Monitor Input. When PFI is <1.25V, PFO
goes low. Connect PFI to GND or V

CC

when not used.

4 4 Power-Fail Voltage Monitor Output

FUNCTION

PIN

NAME

1

2

MAX6343

3

4

MAX6345

1

2

3

4

V

CC

GND

PFI

PFO

MAX6342–MAX6345

6-Pin µP Reset Circuit with

Power-Fail Comparator

_______________________________________________________________________________________ 5

MAX6344MAX6342

— 6

Active-High Push-Pull Reset Output. It remains high for 180ms
after V

CC

rises above the reset threshold or MR goes from low

to high.

6 —

Active-Low Reset Output. Push-pull for MAX6342/MAX6345.
Open-drain for MAX6343. It remains low for 180ms after V

CC

rises above the reset threshold or MR goes from low to high.

5 5

Manual-Reset Input. Pull low to force a reset. RESET or RESET
remains active as long as MR is low and for the reset timeout
period after MR goes high. Leave unconnected or connect to
V

CC

if unused.

Pin Description (continued)

MAX6343

—

6

5

MAX6345

6

5

—

RESET

RESET

MR

FUNCTION

PIN

NAME

_______________Detailed Description

Reset Output

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

RESET and RESET are guaranteed to be asserted at a
valid logic level for VCC> +1V (see

Electrical Char-

acteristics

). Once RESET asserts, it remains asserted
for at least 100ms (tRP) after VCCrises above its thresh­old value or after MR returns high (Figures 1 and 2).

Open-Drain

RESET

Output

The MAX6343 has an active-low, open-drain reset out­put. This output sinks current when RESET is asserted.

Connect a pull-up resistor from RESET to any positive
supply voltage up to +5.5V (Figure 3). Select a resistor
value large enough to register a logic low (see

Elec-

trical Characteristics

), and small enough to register a

logic high while supplying all input current and leakage
paths connected to the RESET line. A 10kΩ pull-up is
sufficient in most applications.

Manual Reset

The MAX6342–MAX6344’s manual-reset input (MR)
allows reset to be triggered by a pushbutton switch. The
switch is effectively debounced by the 1µs minimum
reset pulse width. MR is CMOS-logic compatible.

Power-Fail Comparator

The power-fail comparator is useful for various purpos­es because the power-fail output (PFO) is independent

RESET

GENERATOR

V

CC

6

(RESET)

5

RESET

4

PFO

1.25V

GND

100k

V

TH

( ) ARE FOR MAX6344 ONLY.

1

MR

2

V

CC

3

PFI

MAX6342
MAX6343
MAX6344

RESET

GENERATOR

6

RESET

5

RESET

4

PFO

1.25V

GND

V

TH

1

2

V

CC

3

PFI

MAX6345

Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram

Figure 2. MAX6345 Functional Diagram

MAX6342–MAX6345

of the reset output. The inverting input is internally con­nected to a +1.25V reference.

To build an early-warning circuit for power failure, con­nect the PFI pin to a voltage divider (see

Typical Oper-

ating Circuit

). Choose the voltage-divider ratio so that
the voltage at PFI falls below +1.25V just before the
+5V regulator drops out. Use PFO to interrupt the µP to
prepare for an orderly shutdown.

__________Applications Information

Negative-Going VCCTransients

The MAX6342–MAX6345 supervisors are immune to
short-duration, negative-going VCCtransients (glitches)
that usually do not require the entire system to shut down.

Figure 4 shows typical transient duration vs. reset com­parator overdrive, for which the MAX6342–MAX6345 do
not generate a reset pulse. The graph was generated
using a negative-going pulse applied to VCC, starting

0.5V above the actual reset threshold and ending below
it by the magnitude indicated (reset comparator over­drive). The graph indicates the maximum pulse width a

negative-going V

CC

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.

Typically, a VCCtransient that goes 100mV below the
reset threshold and lasts 12µs or less will not cause a
reset pulse. A 1µF bypass capacitor mounted as close
as possible to the VCCpin provides additional transient
immunity.

Ensuring a Valid Reset Output

Down to V

CC

= 0

The MAX6342–MAX6345 are guaranteed to operate
properly down to VCC= +1V. In applications that require
valid reset levels down to VCC= 0, a pull-down resistor
to active-low outputs (MAX6342/MAX6345) and a pull-up
resistor to active-high outputs (MAX6344/MAX6345)
ensure that the reset line is valid when the reset output is
no longer sinking or sourcing current (Figures 5 and 6).
Note that this method does not work with the open-drain
output of the MAX6343. The resistor value used is not
critical, but it must be large enough not to load the reset

6-Pin µP Reset Circuit with
Power-Fail Comparator

6 _______________________________________________________________________________________

MAX6343

V

CC

GND

RESET

RESET

µP

+5.0V

+3.3V

10k

V

CC

160

100

120

140

0

1 100 1000

60

40

20

80

RESET COMPARATOR OVERDRIVE , V

TH

- VCC (mV)

MAXIMUM TRANSIENT DURATION (µs)

10

MAX634_L/M

MAX634_T/S/R/Z

Figure 4. Maximum Transient Duration Magnitude Rejection

Figure 3. Open-Drain RESET Output Allows Use with Multiple
Supplies

V

CC

V

CC

GND

100k

RESET

MAX6342
MAX6345

V

CC

V

CC

GND

100k

RESET

MAX6344
MAX6345

Figure 5. Ensuring RESET Valid to VCC= 0 on Active-Low
Push-Pull Outputs

Figure 6. Ensuring RESET Valid to VCC= 0 on Active-High
Push-Pull Outputs

output when V

CC

is above the reset threshold. For most

applications, 100kΩ is adequate.

Monitoring Two Supplies

Monitor another voltage by connecting a resistor-divider
to PFI as shown in Figure 7. The threshold voltage will
then be given by:

V

TH(PFI)

= 1.25[(R1 + R2) / R2]

where V

TH(PFI)

is the threshold at which the monitored

voltage will trip PFO.
A good rule of thumb for selecting the resistors is to

choose R2 between 250kΩ and 500kΩ and solve for R1.
Connect PFO to MR in applications that require reset to
assert when the second voltage falls below its threshold.

Monitoring a Negative Voltage

Connect the circuit as shown in Figure 8 to use the
power-fail comparator to monitor a negative supply rail.
PFO stays low when V- is good. When V- rises to cause
PFI to be above +1.25V, PFO goes high. By adding the

resistors and transistor as shown, a high PFO triggers
reset. As long as PFO remains high, the MAX6342/
MAX6343/MAX6344 will keep reset asserted. Note that
the accuracy of this circuit depends on the PFI thresh­old tolerance, the V

CC

line voltage, and the resistors.
Also, ensure that the voltage at PFI remains above
GND.

Interfacing to µPs with

Bidirectional Reset Pins

Use the circuit shown in Figure 9 to interface the
MAX6342 or MAX6345 with a µP with bidirectional reset
pins. The 4.7kΩ resistor between the reset output and
the µP I/O line will ensure that the resets do not cause
an indeterminate logic level.

MAX6342–MAX6345

6-Pin µP Reset Circuit with

Power-Fail Comparator

_______________________________________________________________________________________ 7

V

CC

V

CC

R1

R2

V+

GND

( ) ARE FOR MAX6344 ONLY.

TO µP

PFI MR

PFO

RESET

(RESET)

MAX6342
MAX6343
MAX6344

Figure 7. Monitoring Two Supplies

V

CC

V

CC

R1

R1 R2

R2

V-

GND

( ) ARE FOR MAX6344 ONLY.

V

CC

- 1.25V = 1.25V - V

TRIP

100k

100k

PFI

MR

PFO

RESET

(RESET)

MAX6342
MAX6343
MAX6344

V

TRIP

< 0

Figure 8. Monitoring a Negative Voltage

V

CC

GND

BUFFERED RESET TO
OTHER SYSTEM
COMPONENTS

4.7k

RESET

MAX6342
MAX6345

V

CC

GND

µP

RESET

Figure 9. Interfacing to µPs with Bidirectional Reset I/O

SOT Top Marks

PART

SOT TOP

MARK

PART

SOT TOP

MARK

MAX6342LUT-T AACP MAX6344LUT-T AADQ
MAX6342MUT-T AACQ MAX6344MUT-T AADR
MAX6342TUT-T AACR MAX6344TUT-T AADS
MAX6342SUT-T AACS MAX6344SUT-T AADT
MAX6342RUT-T AACT MAX6344RUT-T AADU
MAX6342ZUT-T AACU MAX6344ZUT-T AADV
MAX6343LUT-T AACV MAX6345LUT-T AADW
MAX6343MUT-T AACW MAX6345MUT-T AADX
MAX6343TUT-T AACX MAX6345TUT-T AADY
MAX6343SUT-T AACY MAX6345SUT-T AADZ
MAX6343RUT-T AACZ MAX6345RUT-T AAEA
MAX6343ZUT-T AADA MAX6345ZUT-T AAEB

MAX6342–MAX6345

6-Pin µP Reset Circuit with
Power-Fail Comparator

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

© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

V

CC

PFI

MR

PFO

µP

RESET

UNREGULATED DC

PUSHBUTTON

SWITCH

INTERRUPT

MAX6342

LINEAR

REGULATOR

RESET

V

CC

GND

PFI

16

5

V

CC

TOP VIEW

2

34

RESET

RESET

PFO

MAX6345

SOT23-6

Typical Operating Circuit Pin Configurations (continued)

TRANSISTOR COUNT: 403

Chip Information

________________________________________________________Package Information

6LSOT.EPS