19-1137; Rev 3; 5/08
4-Pin Micropower Voltage Monitors
______________
General Description
The MAX836/MAX837 micropower voltage monitors
contain a 1.204V precision bandgap reference and a
comparator in a SOT143 package. The MAX836 has an
open-drain, n-channel output driver, while the MAX837
has a push-pull output driver. Two external resistors set
the trip threshold voltage.
____________________________Features
o
±1.25% Precision Voltage Threshold
o
SOT143 Package
o
Low Cost
o
< 5µA Typical Supply Current
o
Open-Drain Output (MAX836)
Push-Pull Output (MAX837)
MAX836/MAX837
________________________Applications
Precision Battery Monitor
Load Switching
Battery-Powered Systems
Threshold Detectors
_______________Ordering Information
PART*
MAX836EUS-T
MAX837EUS-T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
4 SOT143-4
4 SOT143-4
TOP
MARK
EQAA
ERAA
*All
devices available in tape-and-reel only. Contact factory for
availability.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
__________Typical Operating Circuit
V
CC
MAX836
ONLY
GND
1.204V
REF
OUT
___________________Pin Configuration
TOP VIEW
GND
1
4
OUT
MAX836
MAX837
V
CC
V
CC
MAX836
MAX837
IN
V
CC
2
3
IN
0.1μF
SOT143
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
4-Pin Micropower Voltage Monitors
MAX836/MAX837
ABSOLUTE MAXIMUM RATINGS
V
CC
, OUT to GND (MAX836) ....................................-0.3V to 12V
IN, OUT to GND (MAX837).........................-0.3V to (V
CC
+ 0.3V)
Input Current
V
CC
.................................................................................20mA
IN.....................................................................................10mA
Output Current, OUT...........................................................20mA
Rate of Rise, V
CC
............................................................100V/µs
Continuous Power Dissipation
4-Pin SOT143 (derate 4mW/°C above +70°C).............320mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°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
= +2.5V to +11.0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Operating Voltage Range
(Note 1)
SYMBOL
V
CC
V
IN
= 1.16V,
OUT = low
Supply Current (Note 2)
I
CC
V
IN
= 1.25V,
OUT = high
Trip Threshold Voltage
Trip Threshold Voltage
Hysteresis
IN Operating Voltage Range
(Note 1)
IN Leakage Current (Note 3)
Propagation Delay
Glitch Immunity
OUT Rise Time
OUT Fall Time
Output Leakage Current
(Note 4)
Output-Voltage High
Output-Voltage Low
Note 1:
Note 2:
Note 3:
Note 4:
t
RT
t
FT
I
LOUT
V
OH
V
OL
V
TH
V
HYST
V
IN
I
IN
t
PL
V
IN
= V
TH
V
CC
= 5.0V, 50mV overdrive
V
CC
= 5.0V, 100mV overdrive
V
CC
= 5.0V, no load (MAX837 only)
V
CC
= 5.0V, no load (MAX836 pull-up = 10kΩ)
V
IN
> V
THMAX
(MAX836 only)
V
IN
> V
THMAX
, I
SOURCE
= 500µA (MAX837 only)
V
IN
< V
THMIN,
I
SINK
= 500µA
V
CC
- 0.5
0.4
±3
80
35
260
680
±1
V
IN
falling
V
CC
= 3.6V
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
1.185
1.169
1.204
1.204
6
V
CC
- 1
±12
2.0
CONDITIONS
MIN
2.5
3.5
TYP
MAX
11.0
6.5
10
15
5.0
8.0
13
1.215
1.231
V
mV
V
nA
µs
µs
ns
ns
µA
V
V
μA
UNITS
V
V
CC
= full operating range
V
CC
= 3.6V
V
CC
= full operating range
T
A
= +25°C
T
A
= -40°C to +85°C
V
CC
= 5V, IN = low to high
The voltage-detector output remains in the direct state for V
CC
down to 1.2V when V
IN
≤
V
CC
/2.
Supply current has a monotonic dependence on V
CC
(see the
Typical Operating Characteristics).
IN leakage current has a monotonic dependence on V
CC
(see the
Typical Operating Characteristics).
The MAX836 open-drain output can be pulled up to a voltage greater than V
CC
, but may not exceed 11V.
2
______________________________________________________________________________________
4-Pin Micropower Voltage Monitors
__________________________________________Typical Operating Characteristics
(V
CC
= +5V, R
LOAD
= 1MΩ, R
PULLUP
= 10kΩ (MAX836 only), T
A
= +25°C, unless otherwise noted.)
TRIP THRESHOLD VOLTAGE
vs. TEMPERATURE
MAX836/7 01
MAX836/MAX837
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX836/7 02
SUPPLY CURRENT vs. IN VOLTAGE
MAX836/7 03
1.207
TRIP THRESHOLD VOLTAGE (V)
1.206
5.0
16
14
SUPPLY CURRENT (μA)
12
10
8
6
4
V
CC
= 3.6V
2
V
CC
= 11V
4.0
SUPPLY CURRENT (μA)
1.205
1.204
1.203
1.202
1.201
-60 -40
3.0
2.0
1.0
V
IN
= 1.22V
2
3
4
5
6
7
V
CC
(V)
8
9
10
11 12
0
-20
0
20
40
60
80
100
TEMPERATURE (°C)
0
0
1
2
3
4
5
6
7
8
9 10 11 12
V
IN
(V)
IN LEAKAGE CURRENT vs. IN VOLTAGE
70
IN LEAKAGE CURRENT (nA)
60
50
40
T
A
= +25°C
30
20
10
0
0
1
2
3
4
5
6
7
8
9 10 11
V
IN
(V)
T
A
= +85°C
V
CC
= 11V
T
A
= -40°C
MAX836/7 04
IN LEAKAGE CURRENT
vs. SUPPLY VOLTAGE
MAX836/7 05
MAX837 OUTPUT VOLTAGE
vs. OUTPUT SOURCE CURRENT
5.0
4.5
OUTPUT VOLTAGE (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.01
0.1
1
10
100
T
A
= +25°C
T
A
= +85°C
T
A
= -40°C
MAX836/7-06A
80
4.8
4.4
IN LEAKAGE CURRENT (nA)
4.0
3.6
3.2
2.8
2.4
2.0
2
V
IN
= 1.2V
3
4
5
6
7
V
CC
(V)
8
T
A
= +85°C
9
10
T
A
= +25°C
T
A
= -40°C
5.5
11 12
OUTPUT SOURCE CURRENT (mA)
OUTPUT VOLTAGE
vs. OUTPUT SINK CURRENT
MAX836/7-06B
OUTPUT LOW VOLTAGE
vs. SUPPLY VOLTAGE
MAX836/7 07
SHORT-CIRCUIT SINK CURRENT vs.
SUPPLY VOLTAGE
SHORT-CIRCUIT SINK CURRENT (mA)
T
A
= -40°C
MAX836/7 08
10,000
T
A
= +25°C
1,000
OUTPUT VOLTAGE (mV)
T
A
= +85°C
T
A
= -40°C
130
120
OUTPUT LOW VOLTAGE (mV)
110
100
90
80
70
60
50
40
30
20
I
SINK
= 500μA
70
60
50
T
A
= +25°C
40
30
20
10
0
T
A
= +85°C
100
10
1
0.1
0.01
0.1
1
10
100
OUTPUT SINK CURRENT (mA)
2
3
4
5
6
7
V
CC
(V)
8
9
10 11 12
2
3
4
5
6
7
V
CC
(V)
8
9
10
11 12
_______________________________________________________________________________________
3
4-Pin Micropower Voltage Monitors
MAX836/MAX837
_____________________________Typical Operating Characteristics (continued)
(V
CC
= +5V, R
LOAD
= 1MΩ, R
PULLUP
= 10kΩ (MAX836 only), T
A
= +25°C, unless otherwise noted.)
V
CC
FALLING PROPAGATION DELAY
vs. TEMPERATURE
1mV/μs
V
TRIP
= 4.63V
MAX836/7 09
OUT RISE/FALL-TIME
vs. SUPPLY VOLTAGE
1600
1400
1200
TIME (ns)
MAX836/7 10
160
140
PROPAGATION DELAY (μs)
120
100
80
60
40
-60
10mV/μs
V
TRIP
= 3.0V
1800
1000
800
RISE TIME
MAX837 ONLY
FALL TIME
V
TRIP
= 4.63V
600
400
V
TRIP
= 3.0V
200
0
100
2
3
4
5
6
7
V
CC
(V)
8
9
10
11 12
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
_____________________Pin Description
PIN
NAME
GND
V
CC
IN
FUNCTION
System Ground
System Supply Input
Noninverting Input to the Comparator.
The inverting input connects to the
internal 1.204V bandgap reference.
Open-Drain (MAX836) or
Push-Pull (MAX837) Output
Detailed Description
The MAX836/MAX837 micropower voltage monitors
contain a 1.204V precision bandgap reference and a
comparator (see the
Typical Operating Circuit).
The
only difference between the two parts is the structure of
the comparator output driver. The MAX836 has an
open-drain n-channel output driver that can be pulled
up to a voltage higher than V
CC
, but under 11V. The
MAX837’s output is push-pull, and can both source
and sink current.
1
2
3
4
OUT
Programming the Trip Voltage
Two external resistors set the trip voltage, V
TRIP
(Figure 1).
V
TRIP
is the point at which the applied voltage (typically
V
CC
) toggles OUT. The MAX836/MAX837’s high input
impedance allows large-value resistors without compro-
mising trip-voltage accuracy. To minimize current con-
sumption, select a value for R2 between 500kΩ and
1MΩ, then calculate R1 as follows:
⎛
V
⎞
R1 = R2
⎜
TRIP
- 1
⎟
⎝
V
TH
⎠
V
CC
R
PULLUP
GND
OUT
MAX836
V
CC
0.1μF
V
CC
IN
where V
TRIP
= desired trip voltage (in volts), V
TH
=
threshold trip voltage (1.204V).
Applications Information
V
TRIP
= (1.204) R1 + R2
R2
R1
R2
Adding Hysteresis
Hysteresis adds noise immunity to the MAX836/MAX837
and prevents repeated triggering when V
IN
is near the
threshold trip voltage. Figure 2 shows how to add hys-
teresis to the comparator. The technique is similar for
NOTE: UNITS ARE OHMS AND VOLTS
Figure 1. Programming the Trip Voltage, V
TRIP
4
_______________________________________________________________________________________
4-Pin Micropower Voltage Monitors
both parts. For the MAX836, select the ratio of resistors
R1 and R2 so that IN sees 1.204V when the monitor volt-
age falls to or rises above the desired trip point (V
TRIP
).
R3 adds hysteresis and is typically an order of magni-
tude larger than R1 or R2. The current through R1 and
R2 should be at least 500nA to ensure that the 12nA
maximum input current does not shift the trip point sig-
nificantly. Capacitor C1 adds additional noise rejection.
Determine the thermistor’s resistance (R2) at the
desired temperature. Then, using R2’s resistance and
half the resistance of R3, calculate R1’s value with the
following formula:
⎛
V
⎞
R1 = (R2 + R3)
⎜
CC
- 1
⎟
⎝
1.204
⎠
MAX836/MAX837
Monitoring Voltages Other than V
CC
The MAX836/MAX837 can monitor voltages other than
V
CC
(Figure 3). Calculate V
TRIP
as shown in the
Programming the Trip Voltage
section. The monitored
voltage (V
MON
) is independent of V
CC
. V
IN
must be 1V
less than V
CC
.
GND
OUT
V
MON
MAX837
R1
Heater Temperature Control
Figure 4 shows a basic heater temperature-control cir-
cuit. Upon power-up, OUT is high and the n-channel
MOSFET turns on. Current flows through the heating
element (R4), warming the surrounding area. R2 is a
negative-temperature-coefficient thermistor and as tem-
perature increases, its resistance decreases. As the
thermistor heats up and its resistance decreases, the
MAX837’s voltage at IN decreases until it reaches the
1.204V threshold voltage. At this point, OUT goes low,
turning off the heating element. The thermistor cools
and the voltage at IN rises until it overcomes the
MAX837’s hysteresis (6mV). OUT returns high when this
point is reached, turning on the heating element again.
This cycle repeats as long as power is applied.
V
CC
0.1μF
V
CC
IN
R2
Figure 3. Monitoring Voltages Other than V
CC
V
CC
GND
OUT
R3
V
CC
IN
THERMISTOR
WITH
NEGATIVE
COEFFICIENT
R3
R2
C1
GND
NOTE: C1 ADDS ADDITIONAL NOISE IMMUNITY
OUT
R1
= (
R2 + R3)
V
CC
(
1.204 - 1
)
Ω
R2
T
HEATING
ELEMENT
R4
OUT
0.1μF
R1
MAX837
V
CC
V
CC
IN
MAX837
R1
0.1μF
Figure 2. Adding Hysteresis to the Comparator
Figure 4. Heater Temperature Control
_______________________________________________________________________________________
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