19-1568; Rev 0; 10/99
6-Pin µP Reset Circuit with
Power-Fail Comparator
General Description
The MAX6342–MAX6345 family of microprocessor (µP)
supervisory circuits monitors power supplies in digital sys-
tems. These devices significantly improve system reliabili-
ty 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 low-
battery 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, open-
drain reset and an active-high, push-pull reset, respective-
ly. 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.
o
Small 6-Pin SOT23 Package
o
Precision Factory-Set V
CC
Reset Thresholds
Between 2.33V and 4.63V
o
Guaranteed
RESET
Valid to V
CC
= +1V
o
100ms min Reset Pulse Width
o
Debounced CMOS-Compatible Manual-Reset
Input
o
Voltage Monitor for Power-Fail or Low-Battery
Warning
Features
MAX6342–MAX6345
Ordering Information
PART
MAX6342_UT-T
MAX6343_UT-T
MAX6344_UT-T
MAX6345_UT-T
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
6 SOT23-6
Applications
Portable Computers
Telecom Equipment
Networking Equipment
Portable/Battery-Powered Equipment
Multivoltage Systems
Embedded Control Systems
Typical Operating Circuit appears at end of data sheet.
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
TOP VIEW
V
CC
1
6
RESET (RESET)
Selector Guide 1
SUFFIX
RESET THRESHOLD (V)
4.63
4.38
3.08
2.93
2.63
2.33
L
M
T
S
R
Z
GND
2
MAX6342
MAX6343
MAX6344
5
MR
PFI
3
( ) ARE FOR MAX6344 ONLY.
4
PFO
SOT23-6
Pin Configurations continued at end of data sheet.
Selector Guide 2
PART
MAX6342
MAX6343
MAX6344
MAX6345
—
—
—
—
—
1
PUSH-PULL
RESET
OUTPUT
OPEN-DRAIN
RESET
OUTPUT
—
PUSH-PULL RESET
OUTPUT
—
—
MANUAL-RESET
INPUT
________________________________________________________________
Maxim Integrated Products
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.
6-Pin µP Reset Circuit with
Power-Fail Comparator
MAX6342–MAX6345
ABSOLUTE MAXIMUM RATINGS
V
CC
to 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
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
(V
CC
= +1.0V to +5.5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C and V
CC
= +3V.) (Note 1)
PARAMETER
Supply Voltage Range
SYMBOL
V
CC
I
CC
CONDITIONS
T
A
= 0°C to +70°C
T
A
= -40°C to +85°C
Supply Current
No load
MAX634_L
MAX634_M
MAX634_T
Reset Threshold
V
TH
MAX634_S
MAX634_R
MAX634_Z
V
CC
to Reset Delay
Reset Timeout Period
t
RP
V
CC
> 1.2V, I
SINK
= 100µA
V
OL
RESET
and RESET Outputs
Drive Capability (Note 2)
V
OH
V
CC
> 2.7V, I
SINK
= 1.2mA
V
CC
> 4.5V, I
SINK
= 3.2mA
V
CC
> 1.2V, I
SOURCE
= 50µA
V
CC
> 2.7V, I
SOURCE
= 500µA
(MAX6342/MAX6345 only)
V
CC
> 4.5V, I
SOURCE
= 800µA
(MAX6342/MAX6345 only)
0.8
·
V
CC
0.8
·
V
CC
0.8
·
V
CC
V
CC
= 3V
V
CC
= 5.5V
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
4.56
4.50
4.31
4.25
3.03
3.00
2.89
2.85
2.59
2.55
2.30
2.25
20
100
180
280
0.4
0.3
0.4
V
V
2.33
2.63
2.93
3.08
4.38
MIN
1.0
1.2
25
30
4.63
TYP
MAX
5.5
5.5
40
50
4.70
4.75
4.45
4.50
3.13
3.15
2.97
3.00
2.67
2.70
2.36
2.38
µs
ms
V
µA
UNITS
V
V
CC
= V
TH
to (V
TH
- 100mV)
2
_______________________________________________________________________________________
6-Pin µP Reset Circuit with
Power-Fail Comparator
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +1.0V to +5.5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C and V
CC
= +3V.) (Note 1)
PARAMETER
Open-Drain
RESET
Output
Leakage Current
MR
Input Low
MR
Input High
MR
Pull-Up Resistance
MR
Minimum Pulse Width
MR
Glitch Rejection
MR
to Reset Delay
PFI Input Threshold
PFI Leakage Current
PFO
Output Voltage
PFO
Output Voltage
PFO
Output Short-Circuit
Current
PFI to
PFO
Delay
V
OL
V
OH
V
CC
= 4.5V, I
SINK
= 3.2mA
V
CC
= 4.5V, I
SOURCE
= 800µA
Output sink current
Output source current
V
OVERDRIVE
= 15mV
0.8
·
V
CC
20
5
3
1.2
SYMBOL
I
LKG
V
IL
V
IH
0.7
·
V
CC
60
1
0.1
0.2
1.25
±0.01
1.3
±25
0.4
CONDITIONS
MAX6343 only, V
CC
> V
TH(MAX)
MIN
TYP
MAX
1
0.3
·
V
CC
UNITS
µA
V
V
kΩ
µs
µs
µs
V
nA
V
V
mA
µs
MAX6342–MAX6345
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.
Typical Operating Characteristics
(V
PFI
= V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
MAX6344L/MAX6345L
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX6342-02
SUPPLY CURRENT vs. SUPPLY VOLTAGE
AND TEMPERATURE
V
CC
= 5V
25
SUPPLY CURRENT (µA)
V
CC
= 3.3V
20
15
10
V
CC
= 1V
5
0
-40
-15
10
35
60
85
V
CC
= 2.5V
1V/div
MAX6342-01
MAX6342M/MAX6345M
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX6342-03
30
V
CC
V
CC
1V/div
RESET
0
0
RESET
0
0
1sec/div
1sec/div
TEMPERATURE (°C)
_______________________________________________________________________________________
3
6-Pin µP Reset Circuit with
Power-Fail Comparator
MAX6342–MAX6345
Typical Operating Characteristics (continued)
(V
PFI
= V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
PFO OUTPUT VOLTAGE HIGH
vs. SUPPLY VOLTAGE
MAX6342-04
PFO OUTPUT VOLTAGE LOW
vs. SUPPLY VOLTAGE
R
L
= 1kΩ
0.55
0.50
MAX6342-05
6
R
L
= 10kΩ
5
4
PFO (V)
3
2
1
0
0
1
2
3
4
5
6
SUPPLY VOLTAGE (V)
0.60
0.45
PFO (V)
0.40
0.35
0.30
0.25
0.20
0
1
2
3
4
5
6
SUPPLY VOLTAGE (V)
MAX6344/MAX6345
RESET RESPONSE TIME
5V
4V
4V
V
CC
MAX6342-06
MAX6342/MAX6345
RESET RESPONSE TIME
5V
4V
5V
4V
MAX6342-07
V
CC
RESET
RESET
0
0
10µs/div
2µs/div
Pin Description
PIN
NAME
MAX6342
1
2
3
4
4
MAX6343
1
2
3
4
MAX6344
1
2
3
4
MAX6345
1
2
3
4
V
CC
GND
PFI
PFO
Supply Voltage
Ground
Power-Fail Voltage Monitor Input. When PFI is <1.25V,
PFO
goes low. Connect PFI to GND or V
CC
when not used.
Power-Fail Voltage Monitor Output
FUNCTION
_______________________________________________________________________________________
6-Pin µP Reset Circuit with
Power-Fail Comparator
Pin Description (continued)
PIN
NAME
MAX6342
MAX6343
MAX6344
MAX6345
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.
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.
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.
FUNCTION
MAX6342–MAX6345
5
5
5
—
MR
6
6
—
5
RESET
—
—
6
6
RESET
1 V
CC
RESET
GENERATOR
6
RESET
V
CC
(RESET)
100k
1 V
CC
RESET
GENERATOR
RESET 6
V
TH
2
GND
3
PFI
V
TH
5
MR
3
PFI
PFO 4
2
GND
MAX6342
MAX6343
MAX6344
MAX6345
RESET 5
4
PFO
1.25V
1.25V
( ) ARE FOR MAX6344 ONLY.
Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram
Figure 2. MAX6345 Functional Diagram
_______________Detailed Description
Reset Output
A µP’s reset input starts the µP in a known state. These
µP supervisory circuits assert reset to prevent code-
execution errors during power-up, power-down, or
brownout conditions.
RESET
and RESET are guaranteed to be asserted at a
valid logic level for V
CC
> +1V (see
Electrical Char-
acteristics).
Once RESET asserts, it remains asserted
for at least 100ms (t
RP
) after V
CC
rises above its thresh-
old value or after
MR
returns high (Figures 1 and 2).
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.
Open-Drain
RESET
Output
The MAX6343 has an active-low, open-drain reset out-
put. This output sinks current when
RESET
is asserted.
Power-Fail Comparator
The power-fail comparator is useful for various purpos-
es because the power-fail output (PFO) is independent
5
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