_______________General Description
The MAX931-MAX934 single, dual, and quad micropower,
low-voltage comparators plus an on-board 2% accurate
reference feature the lowest power consumption available.
These comparators draw less than 4µA supply current
over temperature (MAX931), and include an internal
1.182V ±2% voltage reference, programmable hysteresis,
and TTL/CMOS outputs that sink and source current.
Ideal for 3V or 5V single-supply applications, the
MAX931-MAX934 operate from a single +2.5V to +11V
supply (or a ±1.25V to ±5V dual supply), and each
comparator’s input voltage range extends from the
negative supply rail to within 1.3V of the positive supply.
The MAX931-MAX934’s unique output stage continuously
sources as much as 40mA. And by eliminating power-
supply glitches that commonly occur when comparators
change logic states, the MAX931-MAX934 minimize
parasitic feedback, which makes them easier to use.
The single MAX931 and dual MAX932/MAX933 provide a
unique and simple method for adding hysteresis without
feedback and complicated equations, using the HYST pin
and two resistors.
For applications that require increased precision with
similar power requirements, see the MAX921-MAX924 data
sheet. These devices include a 1% precision reference.
________________________Applications
Battery-Powered Systems
Threshold Detectors
Window Comparators
Oscillator Circuits
Alarm Circuits
____________________________Features
♦Ultra-Low 4µA Max Quiescent Current
Over Extended Temp. Range (MAX931)
♦Power Supplies:
Single +2.5V to +11V
Dual ±1.25V to ±5.5V
♦Input Voltage Range Includes Negative Supply
♦Internal 1.182V ±2% Bandgap Reference
♦Adjustable Hysteresis
♦TTL-/CMOS-Compatible Outputs
♦12µs Propagation Delay (10mV Overdrive)
♦No Switching Crowbar Current
♦40mA Continuous Source Current
♦Available in Space-Saving µMAX Package
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
________________________________________________________________
Maxim Integrated Products
1
MAX931
OUT
V- GND
V+
21
8
3
4
5
6
7
THRESHOLD DETECTOR
VIN
IN+
IN-
HYST
REF
__________Typical Operating Circuit
19-0194; Rev 1; 2/97
8 SO-40°C to +85°CMAX931ESA
8 µMAX0°C to +70°CMAX931CUA 8 SO0°C to +70°CMAX931CSA 8 Plastic DIP0°C to +70°C
MAX931CPA PIN-PACKAGETEMP. RANGEPART
16-Pin
DIP/SO
No4YesMAX934
8-Pin
DIP/SO/
µMAX
Yes2YesMAX933
8-Pin
DIP/SO/
µMAX
Yes2YesMAX932
8-Pin
DIP/SO/
µMAX
Yes1YesMAX931
PACK-
AGE
INTERNAL
HYSTERESIS
COMPARATORS
PER
PACKAGE
INTERNAL
2%
REFERENCE
PART
Ordering Information continued on last page.
For similar devices guaranteed over the military temp. range, see
the MAX921-MAX924 data sheet. The MAX931, MAX933, and
MAX934 are pin-compatible with the 1% accurate MAX921,
MAX923, and MAX924, respectively. The MAX932 and
MAX922 are not pin-compatible.
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
8 Plastic DIP-40°C to +85°CMAX931EPA
______________Ordering Information
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
V+ to V-, V+ to GND, GND to V-................................-0.3V, +12V
Inputs
Current, IN_+, IN_-, HYST...............................................20mA
Voltage, IN_+, IN_-, HYST................(V+ + 0.3V) to (V- – 0.3V)
Outputs
Current, REF....................................................................20mA
Current, OUT_.................................................................50mA
Voltage, REF ....................................(V+ + 0.3V) to (V- – 0.3V)
Voltage, OUT_ (MAX931/934).....(V+ + 0.3V) to (GND – 0.3V)
Voltage, OUT_ (MAX932/933)..........(V+ + 0.3V) to (V- – 0.3V)
OUT_ Short-Circuit Duration (V+ ≤5.5V) ...............Continuous
Continuous Power Dissipation (TA= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ...727mW
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin µMAX (derate 4.1mW/°C above +70°C).............330mW
16-Pin Plastic DIP (derate 10.53mW/°C above +70°C)..842mW
16-Pin SO (derate 8.70mW/°C above +70°C)................696mW
Operating Temperature Ranges:
MAX93_C_ _ .......................................................0°C to +70°C
MAX93_E_ _.....................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec).............................+300°C
ELECTRICAL CHARACTERISTICS—5V Operation
(V+ = 5V, V- = GND = 0V, TA= TMIN to TMAX, unless otherwise noted.)
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.
PARAMETER
MAX933,
HYST = REF
MIN TYP MAX UNITS
MAX934
VV- V+ – 1.3
MAX931,
HYST = REF
5.5 6.5
Supply Current IN+ = IN- + 100mV µA
Supply Voltage Range
TA= +25°C, 100pF load
2.5 11 V
MAX932,
HYST = REF
2.5 3.2
Input Offset Voltage
CONDITIONS
±10 mV
TA= +25°C
nAInput Leakage Current (IN-, IN+)
(Note 1)
±0.01 ±5
Input Leakage Current (HYST)
TA= +25°C
±0.02 nA
Input Common-Mode Voltage Range
VCM = 2.5V
Common-Mode Rejection Ratio
IN+ = IN- = 2.5V, C/E temp. ranges
MAX931, MAX932, MAX933
0.1 1.0 mV/V
Power-Supply Rejection Ratio V- to (V+ – 1.3V)
V+ = 2.5V to 11V
100Hz to 100kHz 0.1 1.0 mV/V
Voltage Noise MAX931, MAX932, MAX933 Overdrive = 10mV
Overdrive = 100mV
20 µVRMS
Hysteresis Input Voltage Range REF – 0.05 REF V
TA= +25°C
12 µsResponse Time
TA= +25°C
4
3.1 4.5
3.1 4.5
C/E temp. ranges 4
C/E temp. ranges 6
C/E temp. ranges 6
C/E temp. ranges 8.5
POWER REQUIREMENTS
COMPARATOR
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
_______________________________________________________________________________________ 3
PARAMETER
Voltage Noise
C/E temp. ranges, IOUT = 17mA
MIN TYP MAX UNITS
100Hz to 100kHz 100 µVRMS
CONDITIONS
VOutput High Voltage V+ – 0.4
V- + 0.4 V
15 25 µASource Current
GND + 0.4
Output Low Voltage
µA
X
815
Sink Current
1.158 1.182 1.206 VReference Voltage
ELECTRICAL CHARACTERISTICS—5V Operation (continued)
(V+ = 5V, V- = GND = 0V, TA= TMIN to TMAX, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS—3V Operation
(V+ = 3V, V- = GND = 0V, TA= TMIN to TMAX, unless otherwise noted.)
PARAMETER
MAX933,
HYST = REF
MIN TYP MAX UNITS
MAX934
MAX931,
HYST = REF
5.2 6.2
Supply Current IN+ = (IN- + 100mV)
IN+ = IN- = 1.5V, C/E temp. ranges
µA
MAX932,
HYST = REF
2.4 3.0
Input Offset Voltage
CONDITIONS
±10 mV
TA= +25°C
±0.01 ±1 nAInput Leakage Current (IN-, IN+)
Input Leakage Current (HYST)
TA= +25°C
±0.02 nA
VCM = 1.5V
MAX931, MAX932, MAX933
TA= +25°C
TA= +25°C
3.4 4.3
3.4 4.3
Note 1: MAX934 comparators work below 2.5V, see
Low-Voltage Operation
section for more details.
C temp. range
E temp. range 1.147 1.217
TA= +25°C
C/E temp. ranges 6
TA= +25°C
C/E temp. ranges 4
C/E temp. ranges 3.8
C/E temp. ranges 5.8
5.8
C/E temp. ranges
C/E temp. ranges
8.0
C/E temp. ranges,
IOUT = 1.8mA
MAX932,
MAX933
MAX931,
MAX934
POWER REQUIREMENTS
COMPARATOR
REFERENCE
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS—3V Operation (continued)
(V+ = 3V, V- = GND = 0V, TA= TMIN to TMAX, unless otherwise noted.)
PARAMETER
Voltage Noise
C/E temp. ranges, IOUT = 10mA
MIN TYP MAX UNITS
100Hz to 100kHz 100 µVRMS
Input Common-Mode Voltage Range VV- V+ – 1.3
C/E temp. ranges, IOUT = 0.8mA
TA= +25°C, 100pF load
MAX931
CONDITIONS
Common-Mode Rejection Ratio 0.2 1 mV/V
Power-Supply Rejection Ratio V- to (V+ – 1.3V)
V+ = 2.5V to 11V
100Hz to 100kHz 0.1 1 mV/V
Voltage Noise MAX931, MAX932, MAX933 Overdrive = 10mV
Overdrive = 100mV
20 µVRMS
Hysteresis Input Voltage Range REF – 0.05 REF V
14 µsResponse Time 5
VOutput High Voltage V+ – 0.4
V- + 0.4 V
15 25 µASource Current TA= +25°C
GND + 0.4
Output Low Voltage
815 µASink Current
1.158 1.182 1.206 V
TA= +25°C
Reference Voltage C temp. range
E temp. range 1.147 1.217
C/E temp. ranges
C/E temp. ranges
6
4
MAX932,
MAX933
REFERENCE
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
_______________________________________________________________________________________
5
1.22
1.14 -60 -20 60 140
REFERENCE VOLTAGE
vs. TEMPERATURE
1.16
1.20
MAX921/924-TOC4
TEMPERATURE (°C)
REFERENCE VOLTAGE (V)
20 100
1.18
1.21
1.15
1.19
1.17
-40 0 8040 120
EXTENDED TEMP. RANGE
COMMERCIAL
TEMP. RANGE
2.0 -60 140
MAX931
SUPPLY CURRENT vs. TEMPERATURE
2.5
4.5
MAX921/924-TOC5
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
60
3.5
3.0
-20 20 100
4.0
V+ = 5V, V- = -5V
V+ = 3V, V- = 0V
V+ = 5V, V- = 0V
IN+ = IN- + 100mV 5.0
2.0 -60 140
MAX932
SUPPLY CURRENT vs. TEMPERATURE
2.5
4.5
MAX921/924-TOC6
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
60
3.5
3.0
-20 20 100
4.0
V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
IN+ = IN- +100mV
4.5
5.0
-60 140
MAX933
SUPPLY CURRENT vs. TEMPERATURE
2.0
4.0
MAX921/924-TOC7
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
60
3.0
2.5
-20 20 100
3.5 V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
IN+ = IN- +100mV
10
3-60 140
MAX934
SUPPLY CURRENT vs. TEMPERATURE
4
8
MAX921/924-TOC8
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
60
6
5
-20 20 100
7
9IN+ = (IN- + 100mV)
V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
V+ = 5V, V- = -5V
10
0.01 1.0 2.0 2.5
MAX934
SUPPLY CURRENT vs.
LOW SUPPLY VOLTAGES
0.1
1
MAX921/924-TOC9
SINGLE-SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
1.5
IN+ = IN- +100mV
__________________________________________Typical Operating Characteristics
(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.)
0.0 020
OUTPUT VOLTAGE LOW
vs. LOAD CURRENT
0.5
2.5
MAX921/4-TOC1
LOAD CURRENT (mA)
VOL (V)
12
1.5
1.0
48 16
2.0
V+ = 5V
V+ = 3V
1.5 010 30 50
OUTPUT VOLTAGE HIGH vs.
LOAD CURRENT
2.5
4.5
MAX921/924-TOC2
LOAD CURRENT (mA)
VOH (V)
20 40
3.5
5.0
2.0
4.0
3.0
V+ = 5V
V+ = 3V
1.155 0 5 15 25
REFERENCE OUTPUT VOLTAGE vs.
OUTPUT LOAD CURRENT
1.165
1.185
MAX921/924-TOC3
OUTPUT LOAD CURRENT (µA)
REFERENCE OUTPUT VOLTAGE (V)
10 20
1.175
1.190
1.160
1.180
1.170
V+ = 5V
OR
V+ = 3V
30
SINK
SOURCE
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
6 _______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.)
-2 2 10 18
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
0
4
MAX921/924-TOC13
RESPONSE TIME (µs)
OUTPUT VOLTAGE (V)
614
2
0
5
100
3
150mV
100mV
20mV
10mV
INPUT VOLTAGE (mV)
-2 2 10 18
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
0
4
MAX921/924-TOC14
RESPONSE TIME (µs)
OUTPUT VOLTAGE (V)
614
2
0
5
100
3
150mV
100mV 20mV
10mV
INPUT VOLTAGE (mV)
10
0.01 1.0 2.0 2.5
MAX934 RESPONSE TIME
AT LOW SUPPLY VOLTAGES
0.1
1
MAX921/924-TOC15
SINGLE-SUPPLY VOLTAGE (V)
RESPONSE TIME (ms)
1.5
±20mV OVERDRIVE
±100mV
OVERDRIVE
100
0.1 1.0 2.0 2.5
MAX934 OUTPUT DRIVE
AT LOW SUPPLY VOLTAGES
1
10
MAX921/924-TOC16
SINGLE-SUPPLY VOLTAGE (V)
CURRENT (mA)
1.5
SINK CURRENT AT VOUT = 0.4V
SOURCE CURRENT INTO 0.75V LOAD
200
00 1.0 3.0 5.0
SHORT-CIRCUIT SOURCE CURRENT
vs. SUPPLY VOLTAGE
40
160
MAX121/124-TOC17
TOTAL SUPPLY VOLTAGE (V)
SOURCE CURRENT (mA)
2.0 4.0
120
80
20
60
180
140
100
OUT CONNECTED TO V-
20
0010
SHORT-CIRCUIT SINK CURRENT
vs. SUPPLY VOLTAGE
MAX121/124-TOC18
TOTAL SUPPLY VOLTAGE (V)
SINK CURRENT (mA)
5
10
OUT CONNECTED TO V+
GND CONNECTED TO V-
80
-80 010 30 50
HYSTERESIS CONTROL
-40
40
MAX921/924 TOC10
VREF -VHYST (mV)
IN+ – IN- (V)
20 40
0
60
-60
20
-20
NO CHANGE
OUTPUT LOW
OUTPUT HIGH
5.0
0-0.3 -0.1 0.3
TRANSFER FUNCTION
1.0
4.0
MAX921/924-TOC11
IN+ INPUT VOLTAGE (mV)
OUTPUT VOLTAGE (V)
0.1
3.0
2.0
4.5
0.5
3.5
2.5
1.5
-0.2 0 0.2
100k V0
10µF
18
20 20 60 100
RESPONSE TIME vs.
LOAD CAPACITANCE
6
14
MAX921/924 TOC12
LOAD CAPACITANCE (nF)
RESPONSE TIME (µs)
40 80
10
16
4
12
8VOLH
VOHL
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
_______________________________________________________________________________________ 7
____________________________________________________________Pin Descriptions
PIN
5
MAX931 MAX932 MAX933 NAME FUNCTION
– 4 – INB+ Noninverting input of comparator B
5 5 HYST Hysteresis input. Connect to REF if not used. Input voltage range is from
VREF to VREF - 50mV.
6 6 6 REF Reference output. 1.182V with respect to V-.
7 7 7 V+ Positive supply
8 – – OUT Comparator output. Sinks and sources current. Swings from V+ to GND.
– 8 8 OUTB Comparator B output. Sinks and sources current. Swings from V+ to V-.
MAX934 NAME FUNCTION
1 OUTB Comparator B output. Sinks and sources current. Swings from V+ to GND.
2 OUTA Comparator A output. Sinks and sources current. Swings from V+ to GND.
3 V+ Positive supply
4 INA- Inverting input of comparator A
5 INA+ Noninverting input of comparator A
6 INB- Inverting input of comparator B
7 INB+ Noninverting input of comparator B
8 REF Reference output. 1.182V with respect to V-.
9 V- Negative supply. Connect to ground for single-supply operation.
10 INC- Inverting input of comparator C
11 INC+ Noninverting input of comparator C
12 IND- Inverting input of comparator D
13 IND+ Noninverting input of comparator D
14 GND Ground. Connect to V- for single-supply operation.
15 OUTD Comparator D output. Sinks and sources current. Swings from V+ to GND.
16 OUTC Comparator C output. Sinks and sources current. Swings from V+ to GND.
– – 4 INB- Inverting input of comparator B
1 – – GND
– 1 1 OUTA Comparator A output. Sinks and sources current. Swings from V+ to V-.
2 2 2 V- Negative supply. Connect to ground for single-supply operation (MAX931).
– 3 3 INA+ Noninverting input of comparator A
3 – – IN+ Noninverting comparator input
4 – – IN- Inverting comparator input
Ground. Connect to V- for single-supply operation. Output swings from V+ to GND.
PIN
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
8 _______________________________________________________________________________________
_______________Detailed Description
The MAX931-MAX934 comprise various combinations
of a micropower 1.182V reference and a micropower
comparator. The
Typical Operating Circuit
shows the
MAX931 configuration, and Figures 1a-1c show the
MAX932/MAX933/MAX934 configurations.
Each comparator continuously sources up to 40mA, and
the unique output stage eliminates crowbar glitches
during output transitions. This makes them immune to
parasitic feedback (which can cause instability) and
provides excellent performance, even when circuit-
board layout is not optimal.
Internal hysteresis in the MAX931/MAX932/MAX933
provides the easiest method for implementing
hysteresis. It also produces faster hysteresis action
and consumes much less current than circuits using
external positive feedback.
Power-Supply and Input Signal Ranges
This family of devices operates from a single +2.5V to
+11V power supply. The MAX931 and MAX934 have
a separate ground for the output driver, allowing
operation with dual supplies ranging from ±1.25V to
±5.5V. Connect V- to GND when operating the
MAX931 and the MAX934 from a single supply. The
maximum supply voltage in this case is still 11V.
For proper comparator operation, the input signal can
be driven from the negative supply (V-) to within one
volt of the positive supply (V+ - 1V). The guaranteed
common-mode input voltage range extends from
V- to (V+ - 1.3V). The inputs can be taken above and
below the supply rails by up to 300mV without damage.
Operating the MAX931 and MAX934 at ±5V provides
TTL/CMOS compatibility when monitoring bipolar input
signals. TTL compatibility for the MAX932 and MAX933
is achieved by operation from a single +5V supply.
Low-Voltage Operation: V+ = 1V
(MAX934 Only)
The guaranteed minimum operating voltage is 2.5V (or
±1.25V). As the total supply voltage is reduced below
2.5V, the performance degrades and the supply
OUTA
V-
INA+
INB+
OUTB
V+
REF
HYST
MAX932
1
2
3
4
8
7
6
5
V-
Figure 1a. MAX932 Functional Diagram
OUTA
V-
INA+
INB-
OUTB
V+
REF
HYST
MAX933
1
2
3
4
8
7
6
5
V-
Figure 1b. MAX933 Functional Diagram
OUTA
V+
INA-
INA+
OUTD
GND
IND+
IND-
MAX934
2
3
4
5
15
14
13
12
16
11
10
9
1
6
7
8
OUTB
INB-
INB+
REF
OUTC
INC+
INC-
V-
AD
BC
Figure 1c. MAX934 Functional Diagram
current falls. The reference will not function below
about 2.2V, although the comparators will continue to
operate with a total supply voltage as low as 1V. While
the MAX934 has comparators that may be used at
supply voltages below 2V, the MAX931, MAX932, and
MAX933 may not be used with supply voltages
significantly below 2.5V.
At low supply voltages, the comparators’ output drive is
reduced and the propagation delay increases (see
Typical Operating Characteristics
). The useful input
voltage range extends from the negative supply to a
little under 1V below the positive supply, which is
slightly closer to the positive rail than the device
operating from higher supply voltages. Test your
prototype over the full temperature and supply-voltage
range if operation below 2.5V is anticipated.
Comparator Output
With 100mV of overdrive, propagation delay is typically
3µs. The
Typical Operating Characteristics
show the
propagation delay for various overdrive levels.
The MAX931 and MAX934 output swings from V+ to
GND, so TTL compatibility is assured by using a
+5V ±10% supply. The negative supply does not affect
the output swing, and can range from 0V to -5V ±10%.
The MAX932 and MAX933 do not have a GND pin, and
their outputs swing from V+ to V-. Connect V- to ground
and V+ to a +5V supply to achieve TTL compatibility.
The MAX931-MAX934’s unique design achieves an
output source current of more than 40mA and a
sink current of over 5mA, while keeping quiescent
currents in the microampere range. The output can
source 100mA (at V+ = 5V) for short pulses, as long as
the package's maximum power dissipation is not
exceeded. The output stage does not generate crowbar
switching currents during transitions, which minimizes
feedback through the supplies and helps ensure stability
without bypassing.
Voltage Reference
The internal bandgap voltage reference has an output
of 1.182V above V-. Note that the REF voltage is
referenced to V-, not to GND. Its accuracy is ±2% in
the range 0°C to +70°C. The REF output is typically
capable of sourcing 15µA and sinking 8µA. Do not
bypass the REF output. For applications that require a
1% precision reference, see the MAX921-MAX924
data sheet.
Noise Considerations
Although the comparators have a very high gain, useful
gain is limited by noise. This is shown in the Transfer
Function graph (see
Typical Operating Characteristics
).
As the input voltage approaches the comparator's
offset, the output begins to bounce back and forth; this
peaks when VIN = VOS. (The lowpass filter shown on
the graph averages out the bouncing, making the
transfer function easy to observe.) Consequently, the
comparator has an effective wideband peak-to-peak
noise of around 0.3mV. The voltage reference has
peak-to peak noise approaching 1mV. Thus, when a
comparator is used with the reference, the combined
peak-to-peak noise is about 1mV. This, of course, is
much higher than the RMS noise of the individual
components. Care should be taken in the layout to
avoid capacitive coupling from any output to the
reference pin. Crosstalk can significantly increase the
actual noise of the reference.
__________Applications Information
Hysteresis
Hysteresis increases the comparators’ noise margin by
increasing the upper threshold and decreasing the
lower threshold (see Figure 2).
Hysteresis (MAX931/MAX932/MAX933)
To add hysteresis to the MAX931/MAX932/MAX933,
connect resistor R1 between REF and HYST, and
connect resistor R2 between HYST and V- (Figure 3). If
no hysteresis is required, connect HYST to REF. When
hysteresis is added, the upper threshold increases by
the same amount that the lower threshold decreases.
The hysteresis band (the difference between the upper
and lower thresholds, VHB) is approximately equal to
twice the voltage between REF and HYST. The HYST
input can be adjusted to a maximum voltage of REF
and to a minimum voltage of (REF - 50mV). The
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
_______________________________________________________________________________________ 9
THRESHOLDS
OUT
IN-
IN+
VHB
HYSTERESIS
BAND
VREF - VHYST
Figure 2. Threshold Hysteresis Band
MAX931-MAX934
maximum difference between REF and HYST (50mV)
will therefore produce a 100mV max hysteresis band.
Use the following equations to determine R1 and R2:
Where IREF (the current sourced by the reference)
should not exceed the REF source capability, and
should be significantly larger than the HYST input
current. IREF values between 0.1µA and 4µA are
usually appropriate. If 2.4MΩis chosen for
R2 (IREF = 0.5µA), the equation for R1 and VHB can be
approximated as:
When hysteresis is obtained in this manner for
the MAX932/MAX933, the same hysteresis applies to
both comparators.
Hysteresis (MAX934)
Hysteresis can be set with two resistors using positive
feedback, as shown in Figure 4. This circuit generally
draws more current than the circuits using the HYST
pin on the MAX931/MAX932/MAX933, and the high
feedback impedance slows hysteresis. The design
procedure is as follows:
1. Choose R3. The leakage current of IN+ is under 1nA
(up to +85°C), so the current through R3 can be
around 100nA and still maintain good accuracy.
The current through R3 at the trip point is VREF/R3,
or 100nA for R3 = 11.8MΩ. 10MΩis a good
practical value.
2. Choose the hysteresis voltage (VHB), the voltage
between the upper and lower thresholds. In this
example, choose VHB = 50mV.
3. Calculate R1.
4. Choose the threshold voltage for VIN rising (VTHR). In
this example, choose VTHR = 3V.
5. Calculate R2.
A 1% preferred value is 64.9kΩ.
6. Verify the threshold voltages with these formulas:
V rising:
V V R1 1
R1
1
R2
1
R3
V falling:
V V R1 V
R3
IN
THR REF
IN
THF THR
=××++
=−
×+
()
R2 = V
(V 1
R1 1
R3
3
(1.182 100k) 1
100k 1
10M
65.44k
THR
REF R1)
1
1
×
−−
=
×
−−
=
Ω
R1 = R3 V
V
10M
0.05
5
100k
HB
×+
=×
=Ω
R1 (k ) = V (mV)
HB
Ω
R1 = V
2 I
R2 = 1.182 – V2
I
HB
REF
HB
REF
×
()
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10 ______________________________________________________________________________________
GND V-
V+
MAX934
OUT
R3
R1
R2
VREF
VIN
V+
Figure 4. External Hysteresis
7
2
5
6
HYST
REF
V-
V+
R1
R2
MAX931
MAX932
MAX933
2.5V TO 11V
IREF
Figure 3. Programming the HYST Pin
Board Layout and Bypassing
Power-supply bypass capacitors are not needed if the
supply impedance is low, but 100nF bypass capacitors
should be used when the supply impedance is high or
when the supply leads are long. Minimize signal lead
lengths to reduce stray capacitance between the input
and output that might cause instability. Do not bypass
the reference output.
_______________Typical Applications
Auto-Off Power Source
Figure 5 shows the schematic for a 40mA power supply
that has a timed auto power-off function. The
comparator output is the switched power-supply output.
With a 10mA load, it typically provides a voltage of
(VBATT - 0.12V), but draws only 3.5µA quiescent current.
This circuit takes advantage of the four key features of
the MAX931: 2.5µA supply current, an internal
reference, hysteresis, and high current output. Using
the component values shown, the three-resistor voltage
divider programs the maximum ±50mV of hysteresis
and sets the IN- voltage at 100mV. This gives an IN+
trip threshold of approximately 50mV for IN+ falling.
The RC time constant determines the maximum power-
on time of the OUT pin before power-down occurs.
This period can be approximated by:
R x C x 4.6sec
For example: 2MΩx 10µF x 4.6 = 92sec. The actual
time will vary with both the leakage current of the
capacitor and the voltage applied to the circuit.
Window Detector
The MAX933 is ideal for making window detectors
(undervoltage/overvoltage detectors). The schematic
is shown in Figure 6, with component values selected
for an 4.5V undervoltage threshold, and a 5.5V
overvoltage threshold. Choose different thresholds by
changing the values of R1, R2, and R3. To prevent
chatter at the output when the supply voltage is close
to a threshold, hysteresis has been added using R4
and R5. OUTA provides an active-low undervoltage
indication, and OUTB gives an active-low overvoltage
indication. ANDing the two outputs provides an active-
high, power-good signal.
The design procedure is as follows:
1. Choose the required hysteresis level and calculate
values for R4 and R5 according to the formulas in
the
Hysteresis (MAX931/MAX932/MAX933)
section.
In this example, ±5mV of hysteresis has been added
at the comparator input
(VH= VHB/2). This means
that the hysteresis apparent at VIN will be larger
because of the input resistor divider.
2. Select R1. The leakage current into INB- is normally
under 1nA, so the current through R1 should exceed
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
______________________________________________________________________________________ 11
IN+
MAX931
OUT
IN-
HYST
REF
V-
V+
VBATT -0.15V
10mA
21
4
5
6
8
3
100k
1.1M
47k
4.5V TO 6.0V
MOMENTARY SWITCH
7
R
C
GND
Figure 5. Auto-off power switch operates on 2.5µA quiescent
current.
MAX933
INB-
REF
HYST
INA+
V-
V+
OUTA
OUTB
R5
10k
R1
R2
R3
UNDERVOLTAGE
VIN VOTH = 5.5V
VUTH = 4.5V +5V
POWER GOOD
OVERVOLTAGE
R4
2.4M
Figure 6. Window Detector
100nA for the thresholds to be accurate. R1 values
up to about 10MΩcan be used, but values in the
100kΩto 1MΩrange are usually easier to deal with.
In this example, choose R1 = 294kΩ.
3. Calculate R2 + R3. The overvoltage threshold
should be 5.5V when VIN is rising. The design
equation is as follows:
4. Calculate R2. The undervoltage threshold should
be 4.5V when VIN is falling. The design equation is
as follows:
5. Calculate R3.
6. Verify the resistor values. The equations are as
follows, evaluated for the above example.
Bar-Graph Level Gauge
The high output source capability of the MAX931 series
is useful for driving LEDs. An example of this is the
simple four-stage level detector shown in Figure 7.
The full-scale threshold (all LEDs on) is given by
VIN = (R1 + R2)/R1 volts. The other thresholds are at
3/4 full scale, 1/2 full scale, and 1/4 full scale. The
output resistors limit the current into the LEDs.
Level Shifter
Figure 8 shows a circuit to shift from bipolar ±5V inputs
to TTL signals. The 10kΩresistors protect the
comparator inputs, and do not materially affect the
operation of the circuit.
Two-Stage Low-Voltage Detector
Figure 9 shows the MAX932 monitoring an input
voltage in two steps. When VIN is higher than the
LOW and FAIL thresholds, outputs are high. Threshold
calculations are similar to those for the window-
detector application.
Overvoltage threshold:
V (V V ) (R1 R2 R3)
R1
5.474V.
Undervoltage threshold:
V (V V ) (R1 R2 R3)
(R1 + R2)
4.484V,
where the hysteresis voltage V V R5
R4
OTH REF H
UTH REF H
H REF
=+×
++
=
=−×
++
=
=×.
R3 (R2 + R3) R2
.068M 6 k
1.006M
Choose R3 1M (1% standard value).
=−
=−
=
=
119 .
Ω
Ω
R2 (R1 + R2 + R3) (V V )
V R1
(294k + 1.068M) (1.182 0.005)
4.5 294k
62.2k
Choose R2 61.9k (1% standard value).
REF H
UTH
=×
−
−
=×
−
−
=
=
ΩΩ
R2 R3 R1 V
V V
1
294k 5.5
(1.182 0.005) 1
1.068M
OTH
REF H
+=× +−
=× +−
=Ω
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
12 ______________________________________________________________________________________
INB+
INB-
INC+
INC-
IND+
IND-
INA+
INA-
OUTA
OUTB
OUTC
OUTD
5
4
7
6
11
10
13
12
750mV
1V
500mV
250mV
250k
250k
250k
250k
182k
9
2
1
16
15
REF
8
V-
V+
GND
14
MAX934
3
+5V V IN
R1 R2
1.182V
330Ω
330Ω
330Ω
330Ω
Figure 7. Bar-Graph Level Gauge
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
______________________________________________________________________________________ 13
INB+
INB-
INC+
INC-
IND+
IND-
INA+
INA-
OUTA
OUTB
OUTC
OUTD
10k
V+
GND
MAX934
+5V
10k
10k
10k
REF
V-
N.C.
-5V
0 FOR VINA < 0V
1 FOR VINB > 0V
VINA
VINB
VINC
VIND
Figure 8. Level Shifter: ±5V Input to CMOS Output Figure 9. Two-Stage Low-Voltage Detector
INA+
REF
R5
R3
R2
R1
HYST
INB+
V-
V+
+5V
VIN
MAX932
INPUT VOLTAGE FAIL
INPUT VOLTAGE LOW
R4
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
14 ______________________________________________________________________________________
1
2
3
4
8
7
6
5
OUT
V+
REF
HYST
IN-
IN+
V-
GND
MAX931
DIP/SO/µMAX
TOP VIEW
1
2
3
4
8
7
6
5
OUTB
V+
REF
HYST
INB+
INA+
V-
OUTA
MAX932
DIP/SO/µMAX
1
2
3
4
8
7
6
5
OUTB
V+
REF
HYST
INB-
INA+
V-
OUTA
MAX933
DIP/SO/µMAX
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
OUTC
OUTD
GND
IND+
INA-
V+
OUTA
OUTB
MAX934
IND-
INC+
INC-
V-
REF
INB+
INB-
INA+
DIP/Narrow SO
For similar devices guaranteed over the military temp. range, see
the MAX921-MAX924 data sheet. The MAX931, MAX933, and
MAX934 are pin-compatible with the 1% accurate MAX921,
MAX923, and MAX924, respectively. The MAX932 and
MAX922 are not pin-compatible.
16 Narrow SO-40°C to +85°CMAX934ESE 16 Plastic DIP-40°C to +85°CMAX934EPE 16 Narrow SO0°C to +70°CMAX934CSE 16 Plastic DIP0°C to +70°C
MAX934CPE 8 SO-40°C to +85°CMAX933ESA
8 µMAX0°C to +70°CMAX933CUA 8 SO0°C to +70°CMAX933CSA 8 Plastic DIP0°C to +70°C
MAX933CPA 8 SO-40°C to +85°CMAX932ESA
8 µMAX0°C to +70°CMAX932CUA 8 SO0°C to +70°CMAX932CSA 8 Plastic DIP0°C to +70°C
MAX932CPA PIN-PACKAGETEMP. RANGEPART
8 Plastic DIP-40°C to +85°CMAX932EPA
8 Plastic DIP-40°C to +85°CMAX933EPA
_________________Pin Configurations _Ordering Information (continued)
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
______________________________________________________________________________________ 15
________________________________________________________Package Information
PDIPN.EPS
SOICN.EPS
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.
16
__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX931-MAX934
Ultra Low-Power, Low-Cost
Comparators with 2% Reference
__________________________________________Package Information (continued)
8LUMAXD.EPS
