Maxim MAX933CSA, MAX933CPA, MAX932ESA, MAX932EPA, MAX932CUA Datasheet

_______________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 power­supply 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

V

IN

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 [phone]

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= T

MIN

to T

MAX

, 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 µV

RMS

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, I

OUT

= 17mA

MIN TYP MAX UNITS

100Hz to 100kHz 100 µV

RMS

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= T

MIN

to T

MAX

, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS—3V Operation

(V+ = 3V, V- = GND = 0V, TA= T

MIN

to T

MAX

, 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,
I

OUT

= 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= T

MIN

to T

MAX

, unless otherwise noted.)

PARAMETER

Voltage Noise

C/E temp. ranges, I

OUT

= 10mA

MIN TYP MAX UNITS

100Hz to 100kHz 100 µV

RMS

Input Common-Mode Voltage Range VV- V+ – 1.3

C/E temp. ranges, I

OUT

= 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 µV

RMS

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

9

IN+ = (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)

V

OL

(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)

V

OH

(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

1

50mV

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

1

50mV

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 V

OUT

= 0.4V

SOURCE CURRENT INTO 0.75V LOAD

200

0

0 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

0

010

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

V

REF

-V

HYST

(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

V

0

10µF

18

2

0 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

8

V

OLH

V

OHL

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
V

REF

to V

REF

- 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 circuit­board 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-

A

D

B

C

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 V

IN

= 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+

V

HB

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 I

REF

(the current sourced by the reference)
should not exceed the REF source capability, and
should be significantly larger than the HYST input
current. I

REF

values between 0.1µA and 4µA are
usually appropriate. If 2.4MΩ is chosen for
R2 (I

REF

= 0.5µA), the equation for R1 and VHBcan 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 V

REF

/R3,
or 100nA for R3 = 11.8MΩ. 10MΩ is a good
practical value.

2. Choose the hysteresis voltage (V

HB

), the voltage
between the upper and lower thresholds. In this
example, choose VHB= 50mV.

3. Calculate R1.

4. Choose the threshold voltage for VINrising (V

THR

). In

this example, choose V

THR

= 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

1R11

R3

3

(1.182 100k)1100k110M

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 –

V

2

I

HB

REF

HB

REF

×

()











Ultra Low-Power, Low-Cost
Comparators with 2% Reference

10 ______________________________________________________________________________________

GND

V-

V+

MAX934

OUT

R3

R1

R2

V

REF

V

IN

V+

Figure 4. External Hysteresis

7

2

5

6

HYST

REF

V-

V+

R1

R2

MAX931
MAX932
MAX933

2.5V TO 11V

I

REF



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
(V

BATT

- 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 power­on time of the OUT pin before power-down occurs.
This period can be approximated by:

R x C x 4.6sec

For example: 2MΩ x 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 active­high, 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 VINwill 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

V

IN

V

OTH

= 5.5V

V

UTH

= 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 10MΩ can be used, but values in the
100kΩ to 1MΩ range are usually easier to deal with.
In this example, choose R1 = 294kΩ.

3. Calculate R2 + R3. The overvoltage threshold
should be 5.5V when VINis rising. The design
equation is as follows:

4. Calculate R2. The undervoltage threshold should
be 4.5V when VINis 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
V

IN

= (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 10kΩ resistors 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 VINis higher than the
LOW and FAIL thresholds, outputs are high. Threshold
calculations are similar to those for the window­detector 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

=×

−

−

=×

−

−

=

=

Ω

Ω

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 V

INA

< 0V

1 FOR V

INB

> 0V

V

INA

V

INB

V

INC

V

IND

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

V

IN

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

IND­INC+
INC­V-

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 [phone]

© 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