General Description
The MAX6841MAX6845 microprocessor (µP) supervi-
sory circuits monitor ultra-low-voltage power supplies in
µP and digital systems. They provide excellent circuit
reliability at low cost by eliminating external compo-
nents and adjustments when used with +0.9V to +1.5V
systems. Factory-trimmed reset thresholds are avail-
able for the MAX6841/MAX6842. The MAX6843/
MAX6844/MAX6845 provide a RESET IN input, allowing
the user to externally adjust the reset threshold. The
MAX6841MAX6845 family features a debounced man-
ual reset input (MR). The reset comparator is designed
to ignore fast transients on V
CC
.
The MAX6841MAX6845 assert a reset signal whenev-
er the V
CC
supply voltage declines below a preset or
adjustable threshold or whenever manual reset (MR) is
asserted. Reset remains asserted for a fixed timeout
delay after V
CC
has risen above the reset threshold and
when manual reset is deasserted. Five timeout periods
are available for each part: 150µs (voltage detector ver-
sion), 1.5ms, 30ms, 210ms, and 1.68s (typ).
The MAX6841/MAX6843 have an active-low push-pull
reset output. The MAX6841/MAX6842/MAX6844 have
an active-high push-pull reset output, and the
MAX6842/MAX6845 have an active-low open-drain
reset output. The active-low open-drain reset output
requires a pullup resistor that can be connected to a
voltage from 0 to V
CC
.
The low supply current (5.7µA) and small package
(SOT23-5) make the MAX6841MAX6845 ideal for use
in portable equipment.
Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Telecom/Networking Equipment
Basestations
Servers/Workstations
Features
o Factory-Set Reset Threshold Voltages for
Monitoring Supplies from 0.9V to 1.5V
(MAX6841/MAX6842)
o Adjustable Threshold RESET IN
(MAX6843/MAX6844/MAX6845)
o Low Power Consumption: 5.7µA (typ)
o ±2.5% Reset Threshold Accuracy
Over Temperature
o Five Timeout Periods: 150µs (Voltage Detector
Version), 1.5ms, 30ms, 210ms, and 1.68s
o Available in Three Output Configurations
Push-Pull RESET
Push-Pull RESET
Open-Drain RESET
o Guaranteed Reset Valid to V
CC
= 0.55V
(Active Low)
o Manual Reset Input
o Immune to Short V
CC
Transients
o Space-Saving 5-Pin SOT23 Package
MAX6841MAX6845
Ultra-Low-Voltage µP Reset Circuits and
Voltage Detectors
________________________________________________________________ Maxim Integrated Products
1
Ordering Information
19-2625; Rev 1; 2/03
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 and Typical Operating Circuit appear at end
of data sheet.
PART
TEMP RANGE
PIN-PACKAGE
MAX6841_UKD_-T
-40
°C to +85°C
5 SOT23-5
MAX6842_UKD_-T
-40
°C to +85°C
5 SOT23-5
MAX6843UKD_-T
-40
°C to +85°C
5 SOT23-5
MAX6844UKD_-T
-40
°C to +85°C
5 SOT23-5
MAX6845UKD_-T
-40
°C to +85°C
5 SOT23-5
GND
RESET
1
5 V
CC
MAX6841
MAX6842
SOT23-5
TOP VIEW
2
3
4
RESET
MR
( ) ARE FOR 6844
GND
RESET IN
1
5 V
CC
MAX6843
MAX6844
MAX6845
SOT23-5
2
3
4
RESET
(RESET)
MR
Pin Configurations
Note: Insert desired suffix letter (from the Threshold Suffix Guide
and the Active Timeout Period tables) into the blanks to com-
plete the part number. For example, the MAX6842GUKD1 has a
reset threshold of 1.11V and a typical reset timeout period of
1.5ms. Sample stock is generally available on standard versions
only (see the Standard Versions table). Standard versions
require a minimum order increment of 2.5k units. Nonstandard
versions must be ordered in 10k-unit increments. Contact factory
for availability. All parts are offered in tape-and-reel only.
MAX6841MAX6845
Ultra-Low-Voltage µP Reset Circuits and
Voltage Detectors
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= +0.55V to +1.8V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +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.
Terminal Voltage (with respect to GND)
V
CC
.......................................................................-0.3V to +6V
MR, RESET IN, RESET (open-drain).........................-0.3V to +6V
Push-Pull RESET and RESET .....................-0.3V to (V
CC
+ 0.3V)
Input Current (all pins) ........................................................20mA
Output Current (RESET, RESET).........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6843/MAX6845
0.55
1.80
Supply Voltage Range
V
CC
MAX6841/MAX6842/MAX6844 (Note 2)
0.75
1.80
V
V
CC
= 0.9V, no load, reset not asserted
5.7
20
V
CC
= 1.5V, no load, reset not asserted
7.3
20
Supply Current
I
CC
V
CC
= 1.8V, no load, reset not asserted
8.1
20
µA
I
1.350
1.388
1.425
H
1.275
1.313
1.350
G
1.080
1.110
1.140
F
1.020
1.050
1.080
E
0.810
0.833
0.855
Reset Threshold
(V
CC
Falling)
V
TH
D, T
A
= 0
°C to +85°C
0.765
0.788
0.810
V
RESET IN Threshold
V
RSTIN
MAX6843/MAX6844/MAX6845 (Note 3)
181.2
187.4
191.5
mV
RESET IN Leakage Current
I
RSTIN
-25
+25
nA
Reset Threshold Hysteresis
V
HYS
0.75
%V
TH
V
CC
or RESET IN to Reset Delay
V
CC
falling, step signal from (V
TH
+ 10%)
to (V
TH
- 10%) within 1µs
150
µs
D0 (voltage detector)
0.15
D1
1
1.5
2
D2
20
30
40
D3
140
210
280
Reset Active Timeout Period
t
RP
D4
1120
1680
2240
ms
V
IL
0.3
× V
CC
MR Input Voltage (Note 3)
V
IH
0.7
× V
CC
V
MR Minimum Input Pulse Width
MR driven from V
CC
to 0 (Note 3)
1
µs
MR Glitch Rejection
MR driven from V
CC
to 0 (Note 3)
150
ns
MR to Reset Delay
MR driven from V
CC
to 0 (Note 3)
500
ns
MR Pullup Resistance to V
CC
10
20
26
k
MAX6841MAX6845
Ultra-Low-Voltage µP Reset Circuits and
Voltage Detectors
_______________________________________________________________________________________
3
Note 1: 100% production tested at +25°C. Overtemperature limits are guaranteed by design.
Note 2: The active-low output RESET has V
CC(MIN)
= 0.55V (MAX6841/MAX6842).
Note 3: For V
CC
> 0.788V, T
A
= 0°C to +85°C, and for V
CC
> 0.833V, T
A
= -40°C to +85°C.
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +0.55V to +1.8V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
0.55V, I
SINK
= 10µA, reset asserted
0.2
× V
CC
Open-Drain RESET Output
Voltage
V
OL
V
CC
0.83V, I
SINK
= 80µA, reset asserted
0.2
× V
CC
V
Open-Drain RESET Output
Leakage Current
I
LKG
V
CC
> V
TH
, reset not asserted
1
µA
V
CC
0.55V, I
SINK
= 10µA, reset asserted
0.2
× V
CC
V
OL
V
CC
0.83V, I
SINK
= 80µA, reset asserted
0.2
× V
CC
Push-Pull RESET Output Voltage
V
OH
V
CC
0.83V, I
SOURCE
= 40µA, reset not
asserted
0.8
× V
CC
V
V
CC
0.75V, I
SOURCE
= 10µA, reset
asserted
0.8
× V
CC
V
OH
V
CC
0.83V, I
SOURCE
= 40µA, reset
asserted
0.8
× V
CC
Push-Pull RESET Output Voltage
V
OL
V
CC
0.83V, I
SINK
= 80µA, reset not
asserted
0.2
× V
CC
V
Typical Operating Characteristics
(V
CC
= 1.5V, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX6841-45 toc01
TEMPERATURE (
°C)
SUPPLY CURRENT (
µ
A)
60
40
20
0
-20
1
2
3
4
5
6
7
8
9
0
-40
80
V
CC
= 1.8V
V
CC
= 1.5V
V
CC
= 0.9V
POWER-DOWN RESET DELAY
vs. TEMPERATURE
MAX6841-45 toc02
TEMPERATURE (
°C)
POWER-DOWN RESET DELAY (
µ
s)
60
40
20
0
-20
50
100
150
200
250
300
350
0
-40
80
V
OD
= 10mV
V
OD
= 20mV
V
OD
= 100mV
V
OD
= OVERDRIVE (mV)
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6841-45 toc03
TEMPERATURE (
°C)
NORMALIZED RESET TIMEOUT PERIOD
60
40
20
0
-20
0.96
0.98
1.00
1.02
1.04
1.06
0.94
-40
80
D2 OPTION
D3 OPTION
D4 OPTION
MAX6841MAX6845
Ultra-Low-Voltage µP Reset Circuits and
Voltage Detectors
4
_______________________________________________________________________________________
Pin Description
Typical Operating Characteristics (continued)
(V
CC
= 1.5V, T
A
= +25°C, unless otherwise noted.)
NORMALIZED V
CC
RESET THRESHOLD
vs. TEMPERATURE
MAX6841-45 toc04
TEMPERATURE (
°C)
NORMALIZED V
CC
RESET THRESHOLD
60
40
20
0
-20
0.990
0.995
1.000
1.005
1.010
1.015
0.985
-40
80
V
TH
= 0.833V
NORMALIZED RESET IN THRESHOLD
vs. TEMPERATURE
MAX6841-45 toc05
TEMPERATURE (
°C)
NORMALIZED RESET IN THRESHOLD
60
40
20
0
-20
0.990
0.995
1.000
1.005
1.010
1.015
0.985
-40
80
POWER-UP/POWER-DOWN
CHARACTERISTICS (MAX6843AUKD3)
MAX6841-45 toc06
200ms/div
V
CC
1V/div
RESET
1V/div
PIN
MAX6841
MAX6842
MAX6843
MAX6845
MAX6844
NAME
FUNCTION
1
--
--
Push-Pull (MAX6841) or Open-Drain (MAX6842) Active-Low Reset Output. RESET
changes from high to low when V
CC
drops below the selected reset threshold or
MR is pulled low. RESET remains low for the reset timeout period after V
CC
exceeds the device reset threshold and MR is released high.
--
1
--
RESET
Push-Pull (MAX6843) or Open-Drain (MAX6845) Active-Low Reset Output. RESET
changes from high to low when RESET IN drops below the 187.4mV reset
threshold (referenced to V
CC
) or MR is pulled low. RESET remains low for the
reset timeout period after RESET IN exceeds the reset threshold and MR is
released high.
2
2
2
GND
Ground
3
--
--
Push-Pull Active-High Reset Output. RESET changes from low to high when V
CC
input drops below the selected reset threshold or MR is pulled low. RESET
remains high for the reset timeout period after V
CC
exceeds the device reset
threshold and MR is released high.
--
--
1
RESET
Push-Pull Active-High Reset Output. RESET changes from low to high when the
RESET IN input drops below the 187.4mV reset threshold (referenced to V
CC
).
RESET remains high for the reset timeout period after RESET IN exceeds the reset
threshold.
--
3
3
RESET IN
Adjustable Reset Input. High-impedance input for reset comparator. Connect this
pin to an external resistive-divider network to set the reset threshold voltage; the
typical threshold is 187.4mV (referenced to V
CC
). The MAX6843/MAX6844/
MAX6845 assert a reset signal when the V
CC
to RESET IN differential falls below
its threshold voltage.
4
4
4
MR
Active-Low Manual Reset Input. Internal 20k
pullup to V
CC
. Pull low to force a
reset. 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.
5
5
5
V
CC
Supply Voltage. Monitored supply for the MAX6841/MAX6842.
Detailed Description
Reset Output
A microprocessor's (µP's) reset input starts the µP in a
known state. The MAX6841MAX6845 assert a reset dur-
ing power-up, power-down, and brownout conditions.
When the V
CC
supply voltage falls below a preset thresh-
old (MAX6841/MAX6842) or RESET IN falls below the
adjustable threshold (MAX6843/MAX6844/MAX6845),
reset asserts and stays asserted for a fixed timeout delay
(Table 2) after V
CC
or RESET IN has risen above the
reset threshold. The MAX6841MAX6845 are available
with five typical timeout options for each part: 150µs
(voltage detector), 1.5ms, 30ms, 210ms, and 1.68s.
The MAX6841/MAX6842 have two reset outputs
(RESET and RESET); one is the inverse of the other.
The MAX6841 has one active-high push-pull output and
one active-low push-pull output. The MAX6842 has one
active-high push-pull output and one active-low open-
drain output. The MAX6843 features an active-low
push-pull output. The MAX6844 features an active-
high push-pull output, and the MAX6845 has an active-
low open-drain output stage. Connect a pullup resistor
from the open-drain RESET output to any voltage
between 0 and 6V.
Manual Reset Input
Many µP-based systems require a manual reset capa-
bility, allowing the operator, a test technician, or exter-
nal logic circuitry to initiate a reset. Reset remains
asserted while MR is low, and for a fixed timeout delay
after MR returns high. This input has an internal 20k
pullup resistor, so it can be left open if it is not used.
MR can be driven with CMOS logic level or with open-
drain/collector outputs. To create a manual reset func-
tion, connect a normally open momentary switch from
MR to ground; external debounce circuitry is not
required. If MR is driven from long cables or the device
is used in a noisy environment, connect a 0.1µF capac-
itor from MR to ground to provide additional noise
immunity.
RESET IN
The MAX6843/MAX6844/MAX6845 feature a RESET IN
input, which allows users to adjust the reset threshold
voltage. The internal reference voltage is 187.4mV with
respect to V
CC
. An external resistive-divider network
can be used to set voltage monitoring thresholds, as
shown in Figure 1. The resistive-divider network must
be referenced to V
CC
. As V
CC
falls, the voltage at
MAX6841MAX6845
Ultra-Low-Voltage µP Reset Circuits and
Voltage Detectors
_______________________________________________________________________________________
5
V
CC
RESET
OUTPUT
RESET
RESET
TIMEOUT
PERIOD
V
REF
MANUAL
RESET
DETECT
GND
MR
MR
PULLUP
RESET
MAX6841
MAX6842
Functional Diagrams
V
CC
RESET
OUTPUT
RESET
TIMEOUT
PERIOD
V
REF
= 187.4mV
MANUAL
RESET
DETECT
GND
MR
MR
PULLUP
RESET
RESET
RESET IN
MAX6843
MAX6844
MAX6845
MAX6843
MAX6844
MAX6845
V
CC
GND
RESET IN
MR
RESET
(RESET)
( ) ARE FOR
MAX6844
R1 =
R2
R2
R1
V
CC-TH
V
REF
- 1
WHERE V
REF
= 187.4mV (WITH RESPECT TO V
CC
) AND
V
CC-TH
IS THE V
CC
THRESHOLD.
V
CC
Figure 1. Setting the Adjustable Threshold Externally
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