19-1412; Rev 2; 12/05
4-Pin, Ultra-Low-Voltage, Low-Power
µP Reset Circuits with Manual Reset
General Description
The MAX6335/MAX6336/MAX6337 microprocessor (µP)
supervisory circuits monitor the power supplies in 1.8V
to 3.3V µP and digital systems. They increase circuit reli-
ability and reduce cost by eliminating external compo-
nents and adjustments. They also feature a debounced
manual-reset input.
These devices perform a single function: they assert a
reset signal whenever the V
CC
supply voltage declines
below a preset threshold or whenever manual reset is
asserted. Reset remains asserted for a preset timeout
period after V
CC
has risen above the reset threshold or
after manual reset is deasserted. The only difference
among the three devices is their output. The MAX6336
(push/pull) and MAX6337 (open-drain) have an active-
low
RESET
output, while the MAX6335 (push/pull) has
an active-high RESET output. The MAX6335/MAX6336
are guaranteed to be in the correct state for V
CC
down
to 0.7V. The MAX6337 is guaranteed to be in the cor-
rect state for V
CC
down to 1.0V.
The reset comparator in these ICs is designed to ignore
fast transients on V
CC
. Reset thresholds are factory-
trimmable between 1.6V and 2.5V, in approximately
100mV increments. There are 15 standard versions
available (2500 piece minimum-order quantity); contact
the factory for availability of nonstandard versions
(10,000 piece minimum-order quantity). For space-criti-
cal applications, the MAX6335/MAX6336/MAX6337
come packaged in a 4-pin SOT143.
♦
Low 3.3µA Supply Current
♦
Precision Monitoring of 1.8V and 2.5V Power-
Supply Voltages
♦
Reset Thresholds Available from 1.6V to 2.5V,
in Approximately 100mV Increments
♦
Debounced Manual Reset
♦
Fully Specified over Temperature
♦
Three Power-On Reset Pulse Widths Available
(1ms min, 20ms min, 100ms min)
♦
Low Cost
♦
Three Available Output Structures: Push/Pull
RESET,
Push/Pull RESET, Open-Drain
RESET
♦
Guaranteed RESET/RESET Valid to V
CC
= 0.7V
(MAX6335/MAX6336)
♦
Power-Supply Transient Immunity
♦
No External Components
♦
4-Pin SOT143 Package
♦
Pin Compatible with MAX811/MAX812 and
MAX6314/MAX6315
Features
♦
Ultra-Low 0.7V Operating Supply Voltage
MAX6335/MAX6336/MAX6337
Applications
Pentium II™ Computers
Computers
Controllers
Intelligent Instruments
Critical µP/µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
PART*
MAX6335US__D_-T
MAX6336US__D_-T
MAX6337US__D_-T
Ordering Information
TEMP. RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
4 SOT143
4 SOT143
4 SOT143
Typical Operating Circuit and Pin Configuration appear
at end of data sheet.
Selector Guide appears at end of data sheet.
Pentium II is a trademark of Intel Corp.
*
These devices are available in factory-set V
CC
reset thresh-
olds from 1.6V to 2.5V, in approximately 0.1V increments.
Choose the desired reset threshold suffix from Table 1 and
insert it in the blanks following “US” in the part number.
Factory-programmed reset timeout periods are also available.
Insert the number corresponding to the desired nominal reset
timeout period (1 = 1ms min, 2 = 20ms min, 3 = 100ms min) in
the blank following “D” in the part number. There are 15 stan-
dard versions with a required order increment of 2500 pieces.
Sample stock is generally held on the standard versions only
(see Selector Guide). Contact the factory for availability of non-
standard versions (required order increment is 10,000 pieces).
All devices 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.
________________________________________________________________
Maxim Integrated Products
1
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.
4-Pin, Ultra-Low-Voltage, Low-Power
µP Reset Circuits with Manual Reset
MAX6335/MAX6336/MAX6337
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
......................................................................-0.3V to +6V
Push/Pull RESET or
RESET, MR
............-0.3V to (V
CC
+ 0.3V)
Open-Drain
RESET
..............................................-0.3V to +6V
Input Current (V
CC
) .............................................................20mA
Output Current (RESET,
RESET).........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
SOT143 (derate 4mW/°C above +70°C) .....................320mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+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
= full range,
MR
=
V
CC
or unconnected, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C and
V
CC
= 3V, reset not asserted.)
PARAMETER
SYMBOL
CONDITIONS
T
A
= 0°C to +85°C
Supply Voltage Range
V
CC
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
Supply Current
I
CC
No load
MAX6335/MAX6336
MAX6337
MAX6335/MAX6336
MAX6337
MAX6335/MAX6336
MAX6337
MIN
0.7
1.0
0.78
1.2
1.2
3.0
3.3
V
TH -
1.8%
V
TH -
3%
1
20
100
V
TH
V
TH
24
1.5
30
150
2
40
200
0.4
0.3
0.8V
CC
0.8V
CC
0.8V
CC
0.8V
CC
0.3
0.3
1
V
CC
= 2.6V
V
CC
= 2.6V
V
MR
0.3V
CC
12
V
CC
> V
TH
,
RESET
deasserted
20
160
0.42
0.7V
CC
30
0.5
V
V
V
V
µs
ns
µs
V
kΩ
µA
ms
TYP
MAX
5.5
5.5
5.5
5.5
5.5
6.0
7.0
V
TH +
1.8%
V
TH +
3%
µA
V
UNITS
V
CC
= 1.8V
V
CC
= 2.5V
T
A
= +25°C
T
A
= -40°C to +125°C
Reset Threshold
V
TH
MAX633_US_ _D_-T,
Table 1
V
CC
falling at 10V/ms
MAX633_US_ _D1-T
V
V
CC
Falling Reset Delay
Reset Active Timeout Period
RESET
Output Low Voltage
(MAX6336/MAX6337)
RESET
Output High Voltage
(MAX6336)
µs
t
RP
MAX633_US_ _D2-T
MAX633_US_ _D3-T
Reset
asserted
Reset not
asserted
Reset
asserted
Reset not
asserted
I
SINK
= 50µA, V
CC
≥
1.0V
I
SINK
= 500µA, V
CC
≥
1.8V
I
SOURCE
= 200µA, V
CC
≥
1.8V
I
SOURCE
= 500µA, V
CC
≥
2.7V
I
SOURCE
= 1µA, V
CC
≥
1.0V
I
SOURCE
= 200µA, V
CC
≥
1.8V
I
SINK
= 500µA, V
CC
≥
1.8V
I
SINK
= 1.2mA, V
CC
≥
2.7V
V
OL
V
OH
V
OH
V
OL
RESET Output Voltage
(MAX6335)
MR
Minimum Pulse Width
MR
Glitch Immunity
MR
Reset Delay
MR
Threshold
MR
Pull-Up Resistance
RESET
Output Leakage
Current (MAX6337)
2
_______________________________________________________________________________________
4-Pin, Ultra-Low-Voltage, Low-Power
µP Reset Circuits with Manual Reset
__________________________________________Typical Operating Characteristics
(Reset not asserted, T
A
= +25°C, unless otherwise noted.)
MAX6335/MAX6336/MAX6337
SUPPLY CURRENT vs. TEMPERATURE
MAX6335/36/37 toc-1
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED RESET TIMEOUT PERIOD
1.040
1.030
1.020
1.010
1.000
0.990
0.980
0.970
0.960
0.950
V
TH
= 2.2V
MAX6335/36/37-2
OUTPUT VOLTAGE LOW
vs. SUPPLY VOLTAGE
70
OUTPUT VOLTAGE LOW (mV)
60
50
40
30
20
10
0
T
A
= -40°C
0.50
1.00
1.50
2.00
2.50
3.00
T
A
= +25°C
T
A
= +85°C
V
TH
= 2.5V
I
SINK
= 500µA
RESET ASSERTED
MAX6335/36/37 toc-3
4.0
3.8
3.6
3.4
I
CC
(µA)
3.2
3.0
2.8
2.6
2.4
2.2
2.0
-60
-40
-20
0
20
40
60
80
RESET NOT ASSERTED
V
CC
= 1.8V
V
CC
= 2.5V
1.050
80
100
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
V
CC
(V)
OUTPUT VOLTAGE HIGH
vs. SUPPLY VOLTAGE
OUTPUT VOLTAGE HIGH (V
CC
- V
OH
) (mV)
140
120
100
80
60
40
20
T
A
= +85°C
0
0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5
V
CC
(V)
0
T
A
= +25°C
T
A
= -40°C
MAXIMUM TRANSIENT DURATION (µs)
V
TH
= 2.2V
I
SOURCE
= 100µA
RESET ASSERTED
MAX6335/36/37 toc-4
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAX6335/36/37 toc-5
V
CC
FALLING PROPAGATION DELAY
vs. TEMPERATURE
MAX6332/33/34 toc-6
160
600
500
400
300
200
100
RESET DOES
NOT OCCUR
RESET OCCURS
80
70
PROPAGATION DELAY (µs)
60
50
40
30
20
10
V
CC
FALLING AT 10V/ms
V
CC
FALLING AT 1V/ms
0.1
100
1000
RESET COMPARATOR OVERDRIVE (mV)
1
10
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
3
4-Pin, Ultra-Low-Voltage, Low-Power
µP Reset Circuits with Manual Reset
MAX6335/MAX6336/MAX6337
Pin Description
PIN
MAX6335
1
MAX6336
MAX6337
1
NAME
GND
Ground
Active-Low Reset Output.
RESET
remains low while V
CC
is below the reset
threshold, or
MR
is asserted and for a reset timeout period (t
RP
) after V
CC
rises above the reset threshold, or
MR
is deasserted.
RESET
on the
MAX6337 is open-drain.
Active-High Reset Output. RESET remains high while V
CC
is below the
reset threshold, or
MR
is asserted and for a reset timeout period (t
RP
) after
V
CC
rises above the reset threshold, or
MR
is deasserted. RESET also
asserts when
MR
is low.
Manual-Reset Input. A logic low on
MR
asserts reset. Reset remains
asserted as long as
MR
is low, and for the reset timeout period (t
RP
) after
MR
goes high. Leave unconnected or connect to V
CC
if not used.
Supply Voltage (0.7V to 5.5V)
FUNCTION
—
2
RESET
2
—
RESET
3
4
3
4
MR
V
CC
Applications Information
Manual-Reset Inputs
Many µP-based products require manual-reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on
MR
asserts reset. Reset remains asserted while
MR
is low,
and for the reset active timeout period after
MR
returns
high.
MR
has an internal 20kΩ pull-up resistor, so it can
be left unconnected if not used. Connect a normally
open momentary switch from
MR
to GND to create a
manual-reset function; external debounce circuitry is
not required.
signal. As the amplitude of the transient increases, the
maximum allowable pulse width decreases.
Ensuring a Valid Reset Output
down to V
CC
= 0
When V
CC
falls below 1V and approaches the minimum
operating voltage of 0.7V, push/pull-structured reset
sinking (or sourcing) capabilities decrease drastically.
High-impedance CMOS-logic inputs connected to the
RESET
pin can drift to indeterminate voltages. This
does not present a problem in most cases, since most
µPs and circuitry do not operate at V
CC
below 1V. For
the MAX6336, where
RESET
must be valid down to 0,
adding a pull-down resistor between
RESET
and GND
removes stray leakage currents, holding
RESET
low
Interfacing to µPs with
Bidirectional Reset Pins
Since the
RESET
output on the MAX6337 is open-drain,
this device interfaces easily with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11.
Connecting the µP supervisor’s
RESET
output directly
to the microcontroller’s (µC’s)
RESET
pin with a single
pull-up resistor allows either device to assert reset
(Figure 1).
V
CC
V
CC
V
CC
µP
MOTOROLA
68HCXX
RESET
INPUT
MAX6337
Negative-Going V
CC
Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, these devices
are relatively immune to short-duration, negative-going
V
CC
transients (glitches). The
Typical Operating
Characteristics
show the Maximum Transient Duration
vs. Reset Comparator Overdrive graph. The graph
shows the maximum pulse width that a negative-going
V
CC
transient may typically have without issuing a reset
4
MR
RESET
GND
GND
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
_______________________________________________________________________________________
4-Pin, Ultra-Low-Voltage, Low-Power
µP Reset Circuits with Manual Reset
V
CC
Table 1. Factory-Trimmed Reset
Thresholds*
RESET
THRESHOLD
SUFFIX
MAX633_US25D_
MAX633_US24D_
100k
MAX633_US23D_
MAX633_US22D_
MAX633_US21D_
T
A
= +25°C
MIN TYP MAX
2.46 2.50
2.36 2.40
2.26 2.30
2.16 2.20
2.06 2.10
1.96 2.00
1.87 1.90
2.55
2.44
2.34
2.24
2.14
2.04
1.93
T
A
= -40°C to +125°C
MIN
2.43
2.33
2.23
2.13
2.04
1.94
1.84
1.75
1.65
1.55
MAX
2.58
2.47
2.37
2.27
2.16
2.06
1.96
1.85
1.75
1.65
MAX6335/MAX6336/MAX6337
MAX6336
MR
RESET
(a)
GND
V
CC
MAX633_US20D_
MAX633_US19D_
100k*
MAX633_US18D_
MAX633_US17D_
MAX633_US16D_
1.77 1.80 1.83
1.67 1.70 1.73
1.57 1.60
1.63
MAX6335
MR
RESET
(b)
GND
*
Factory-trimmed reset thresholds are available in approximately
100mV increments, with a ±1.8% room-temperature variance.
*ASSUMES HIGH-Z RESET INPUT TO THE
µP
Figure 2. Ensuring Reset Valid down to V
CC
= 0
(Figure 2a). The pull-down resistor value is not critical;
100kΩ is large enough not to load
RESET,
and small
enough to pull it low. For the MAX6335, where RESET
must be valid to V
CC
= 0, a 100kΩ pull-up resistor
between RESET and V
CC
will hold RESET high when
V
CC
falls below 0.7V (Figure 2b).
Since the MAX6337 has an open-drain, active-low out-
put, it typically uses a pull-up resistor. With this device,
RESET will most likely not maintain an active condition,
but will drift to a non-active level due to the pull-up
resistor and the reduced sinking capability of the open-
drain device. Therefore, this device is not recommend-
ed for applications where the
RESET
pin is required to
be valid down to V
CC
= 0.
_______________________________________________________________________________________
5
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