Rainbow Electronics MAX934 User Manual

Page 1

19-0194; Rev 1; 2/97

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

_______________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.

PART

INTERNAL

REFERENCE

COMPARATORS

PER

PACKAGE

INTERNAL

HYSTERESIS

Yes1YesMAX931

Yes2YesMAX932

Yes2YesMAX933

No4YesMAX934

PACK-

AGE

8-Pin DIP/SO/ µMAX

16-Pin DIP/SO

____________________________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

______________Ordering Information

PIN-PACKAGETEMP. RANGEPART

MAX931CPA

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.

8 Plastic DIP0°C to +70°C 8 SO0°C to +70°CMAX931CSA 8 µMAX0°C to +70°CMAX931CUA 8 Plastic DIP-40°C to +85°CMAX931EPA 8 SO-40°C to +85°CMAX931ESA

__________Typical Operating Circuit

IN+

3

IN-

4

V+

OUT

MAX931-MAX934

________________________Applications

Battery-Powered Systems Threshold Detectors Window Comparators Oscillator Circuits Alarm Circuits

________________________________________________________________

HYST

5

REF

THRESHOLD DETECTOR

MAX931

V-

Maxim Integrated Products

GND

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

Page 2

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

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

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.

MAX931-MAX934

ELECTRICAL CHARACTERISTICS—5V Operation

(V+ = 5V, V- = GND = 0V, TA= T

MIN

to T

, unless otherwise noted.)

MAX

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

PARAMETER

POWER REQUIREMENTS

Supply Voltage Range

Supply Current IN+ = IN- + 100mV µA

COMPARATOR

Input Offset Voltage

Input Leakage Current (HYST) Input Common-Mode Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range REF – 0.05 REF V

(Note 1)

VCM= 2.5V IN+ = IN- = 2.5V, C/E temp. ranges MAX931, MAX932, MAX933

V- to (V+ – 1.3V) V+ = 2.5V to 11V 100Hz to 100kHz MAX931, MAX932, MAX933

TA= +25°C, 100pF load

CONDITIONS

MAX931, HYST = REF

MAX932, HYST = REF

MAX933, HYST = REF

MAX934

TA= +25°C C/E temp. ranges 4 TA= +25°C C/E temp. ranges 6 TA= +25°C C/E temp. ranges 6 TA= +25°C C/E temp. ranges 8.5

Overdrive = 10mV Overdrive = 100mV

MIN TYP MAX UNITS

2.5 11 V

2.5 3.2

3.1 4.5

5.5 6.5

±10 mV ±0.01 ±5 ±0.02 nA

0.1 1.0 mV/V

0.1 1.0 mV/V 20 µV

nAInput Leakage Current (IN-, IN+)

µsResponse Time

VV- V+ – 1.3

RMS

2 _______________________________________________________________________________________

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Ultra Low-Power, Low-Cost

Comparators with 2% Reference

ELECTRICAL CHARACTERISTICS—5V Operation (continued)

(V+ = 5V, V- = GND = 0V, TA= T

PARAMETER

Output Low Voltage

REFERENCE

Sink Current

Voltage Noise

Note 1: MAX934 comparators work below 2.5V, see

MIN

to T

, unless otherwise noted.)

MAX

CONDITIONS

C/E temp. ranges, I

= 1.8mA

OUT

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

100Hz to 100kHz 100 µV

Low-Voltage Operation

OUT

= 17mA

MAX932,

MAX933

MAX931,

MAX934

section for more details.

MAX931-MAX934

MIN TYP MAX UNITS

VOutput High Voltage V+ – 0.4

V- + 0.4

GND + 0.4

1.158 1.182 1.206 VReference Voltage

15 25

µASource Current

815

µA

RMS

ELECTRICAL CHARACTERISTICS—3V Operation

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

PARAMETER

POWER REQUIREMENTS

Supply Current IN+ = (IN- + 100mV)

COMPARATOR

Input Offset Voltage

Input Leakage Current (HYST)

MIN

to T

, unless otherwise noted.)

MAX

CONDITIONS

MAX931,

HYST = REF

MAX932,

HYST = REF

MAX933,

HYST = REF

MAX934

VCM= 1.5V IN+ = IN- = 1.5V, C/E temp. ranges MAX931, MAX932, MAX933

MIN TYP MAX UNITS

TA= +25°C C/E temp. ranges 3.8 TA= +25°C C/E temp. ranges 5.8 TA= +25°C C/E temp. ranges TA= +25°C C/E temp. ranges

2.4 3.0

3.4 4.3

5.8

5.2 6.2

8.0

±10 mV ±0.01 ±1 nAInput Leakage Current (IN-, IN+) ±0.02 nA

µA

_______________________________________________________________________________________ 3

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

ELECTRICAL CHARACTERISTICS—3V Operation (continued)

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

MIN

to T

, unless otherwise noted.)

MAX

PARAMETER

Input Common-Mode Voltage Range VV- V+ – 1.3 Common-Mode Rejection Ratio 0.2 1 mV/V Power-Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range REF – 0.05 REF V

V- to (V+ – 1.3V) V+ = 2.5V to 11V 100Hz to 100kHz MAX931, MAX932, MAX933

TA= +25°C, 100pF load

C/E temp. ranges, I

MAX931-MAX934

Output Low Voltage

REFERENCE

Reference Voltage

Voltage Noise

C/E temp. ranges, I

C temp. range E temp. range 1.147 1.217 TA= +25°C C/E temp. ranges TA= +25°C C/E temp. ranges

100Hz to 100kHz 100 µV

CONDITIONS

= 10mA

OUT

= 0.8mA

OUT

Overdrive = 10mV Overdrive = 100mV

MAX932,

MAX933 MAX931

MIN TYP MAX UNITS

0.1 1 mV/V 20 µV

V- + 0.4

GND + 0.4

1.158 1.182 1.206

15 25

6 815 4

RMS

µsResponse Time

VOutput High Voltage V+ – 0.4

µASource Current

µASink Current

RMS

4 _______________________________________________________________________________________

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Ultra Low-Power, Low-Cost

Comparators with 2% Reference

__________________________________________Typical Operating Characteristics

(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.)

OUTPUT VOLTAGE LOW

OUTPUT VOLTAGE HIGH vs.

vs. LOAD CURRENT

2.5

2.0

V+ = 3V

020

48 16

LOAD CURRENT (mA)

(V)

1.5

1.0

0.5

0.0

V+ = 5V

MAX921/4-TOC1

(V)

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

V+ = 5V

010 30 50

REFERENCE VOLTAGE 

vs. TEMPERATURE

1.22

1.21

1.20

1.19

1.18

1.17

1.16

REFERENCE VOLTAGE (V)

1.15

1.14

EXTENDED TEMP. RANGE

COMMERCIAL 

TEMP. RANGE

-60 -20 60 140

-40 0 8040 120

20 100

TEMPERATURE (°C)

MAX921/924-TOC4

SUPPLY CURRENT vs. TEMPERATURE

4.5 IN+ = IN- + 100mV

4.0

V+ = 5V, V- = -5V

3.5

3.0

SUPPLY CURRENT (µA)

2.5

2.0

V+ = 5V, V- = 0V

-60 140

MAX933

SUPPLY CURRENT vs. TEMPERATURE

5.0

IN+ = IN- +100mV

4.5

4.0

3.5

3.0

SUPPLY CURRENT (µA)

2.5

2.0

-60 140

V+ = 5V, V- = 0V

V+ = 3V, V- = 0V

-20 20 100 TEMPERATURE (°C)

MAX921/924-TOC7

SUPPLY CURRENT vs. TEMPERATURE

IN+ = (IN- + 100mV)

V+ = 5V, V- = -5V

SUPPLY CURRENT (µA)

-60 140

LOAD CURRENT

V+ = 3V

20 40

LOAD CURRENT (mA)

MAX931

V+ = 3V, V- = 0V

-20 20 100 TEMPERATURE (°C)

MAX934 

V+ = 5V, V- = 0V

V+ = 3V, V- = 0V

-20 20 100

TEMPERATURE (°C)

MAX921/924-TOC2

REFERENCE OUTPUT VOLTAGE (V)

MAX921/924-TOC5

SUPPLY CURRENT (µA)

MAX921/924-TOC8

SUPPLY CURRENT (µA)

REFERENCE OUTPUT VOLTAGE vs.

OUTPUT LOAD CURRENT

1.190

1.185

1.180

1.175

1.170

1.165

1.160

1.155

V+ = 5V  V+ = 3V

0 5 15 25

SINK

SOURCE

OR

10 20

OUTPUT LOAD CURRENT (µA)

MAX932 

SUPPLY CURRENT vs. TEMPERATURE

5.0

IN+ = IN- +100mV

4.5

4.0

3.5

3.0

2.5

2.0

V+ = 5V, V- = 0V

V+ = 3V, V- = 0V

-20 20 100

-60 140 TEMPERATURE (°C)

MAX934

SUPPLY CURRENT vs. 

LOW SUPPLY VOLTAGES

IN+ = IN- +100mV

0.1

0.01

1.0 2.0 2.5

1.5

SINGLE-SUPPLY VOLTAGE (V)

MAX931-MAX934

MAX921/924-TOC3

MAX921/924-TOC6

MAX921/924-TOC9

_______________________________________________________________________________________

Page 6

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

____________________________Typical Operating Characteristics (continued)

(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.)

HYSTERESIS CONTROL



80 60

OUTPUT HIGH

40 20

IN+ – IN- (V)

-20

-40 OUTPUT LOW

-60

MAX931-MAX934

-80

010 30 50

NO CHANGE

20 40

-V

(mV)

REF

HYST

RESPONSE TIME FOR VARIOUS

INPUT OVERDRIVES

5 4

100mV

3 2

50mV

OUTPUT VOLTAGE (V)

20mV

10mV

100

-2 2 10 18

INPUT VOLTAGE (mV)

614

RESPONSE TIME (µs)

MAX934 OUTPUT DRIVE

AT LOW SUPPLY VOLTAGES

100

SOURCE CURRENT INTO 0.75V LOAD

CURRENT (mA)

SINK CURRENT AT V

0.1

1.0 2.0 2.5

1.5

SINGLE-SUPPLY VOLTAGE (V)

OUT

= 0.4V

5.0

4.5

MAX921/924 TOC10

4.0

3.5

3.0

2.5

2.0

1.5

OUTPUT VOLTAGE (V)

1.0

0.5 0

-0.3 -0.1 0.3

MAX921/924-TOC13

100mV

OUTPUT VOLTAGE (V)

50mV

100

-2 2 10 18

INPUT VOLTAGE (mV)

SHORT-CIRCUIT SOURCE CURRENT 

200 180

OUT CONNECTED TO V-

160

MAX921/924-TOC16

140 120 100

80 60

SOURCE CURRENT (mA)

40 20

0 1.0 3.0 5.0

TRANSFER FUNCTION



100k

10µF

0.1

-0.2 0 IN+ INPUT VOLTAGE (mV)

0.2

RESPONSE TIME FOR VARIOUS

INPUT OVERDRIVES

10mV

20mV

614

RESPONSE TIME (µs)

vs. SUPPLY VOLTAGE

2.0 4.0

TOTAL SUPPLY VOLTAGE (V)

18 16

MAX921/924-TOC11

14 12

RESPONSE TIME (µs)

6 4

0 20 60 100

MAX921/924-TOC14

0.1

RESPONSE TIME (ms)

0.01

1.0 2.0 2.5



MAX121/124-TOC17



SINK CURRENT (mA)

010

RESPONSE TIME vs. LOAD CAPACITANCE

OHL

OLH

40 80

LOAD CAPACITANCE (nF)

MAX934 RESPONSE TIME 

AT LOW SUPPLY VOLTAGES

±20mV OVERDRIVE

±100mV 

OVERDRIVE

1.5

SINGLE-SUPPLY VOLTAGE (V)

SHORT-CIRCUIT SINK CURRENT 

vs. SUPPLY VOLTAGE

OUT CONNECTED TO V+

GND CONNECTED TO V-

TOTAL SUPPLY VOLTAGE (V)

MAX921/924 TOC12

MAX921/924-TOC15

MAX121/124-TOC18

6 _______________________________________________________________________________________

Page 7

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

____________________________________________________________Pin Descriptions

MAX931 MAX932 MAX933

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 – – IN+ Noninverting comparator input – 3 3 INA+ Noninverting input of comparator A 4 – – IN- Inverting comparator input – 4 – INB+ Noninverting input of comparator B – – 4 INB- Inverting input of comparator B

5 5 HYST 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

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.

NAME FUNCTION

Ground. Connect to V- for single-supply operation. Output swings from V+ to GND.

Hysteresis input. Connect to REF if not used. Input voltage range is from V

to V

REF

- 50mV.

REF

MAX931-MAX934

_______________________________________________________________________________________ 7

Page 8

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

_______________Detailed Description

The MAX931-MAX934 comprise various combinations of a micropower 1.182V reference and a micropower comparator. 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

MAX931-MAX934

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

Figure 1a. MAX932 Functional Diagram

Typical Operating Circuit

OUTA

V-

INA+

INB+

MAX932

V-

OUTB

REF

HYST

V+

shows the

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

MAX934

OUTB

OUTA

V+

INA-

INA+

OUTC

OUTD

GND

IND+

IND-

OUTA

V-

INA+

INB-

MAX933

V-

Figure 1b. MAX933 Functional Diagram

8 _______________________________________________________________________________________

OUTB

REF

HYST

V+

INB-

INB+

REF

Figure 1c. MAX934 Functional Diagram

INC+

INC-

V-

Page 9

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

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

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.

). The useful input

Comparator Output

With 100mV of overdrive, propagation delay is typically 3µs. 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.

Typical Operating Characteristics

show the

As the input voltage approaches the comparator's offset, the output begins to bounce back and forth; this peaks when V 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.

= VOS. (The lowpass filter shown on

__________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

IN+

THRESHOLDS

MAX931-MAX934

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

_______________________________________________________________________________________ 9

IN-

VREF - VHYST

OUT

Figure 2. Threshold Hysteresis Band

HYSTERESIS

BAND

Page 10

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

maximum difference between REF and HYST (50mV) will therefore produce a 100mV max hysteresis band. Use the following equations to determine R1 and R2:

R1 =

R2 =

Where I

REF

2 I

()

REF

 





1.182 –

 

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

values between 0.1µA and 4µA are

REF

usually appropriate. If 2.4MΩ is chosen for R2 (I

MAX931-MAX934

approximated as:

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

REF

R1 (k ) = V (mV)

Ω

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

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

/R3,

2. Choose the hysteresis voltage (V

), the voltage

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

3. Calculate R1.

R1 = R3

10M

=×

100k

=Ω

4. Choose the threshold voltage for VINrising (V this example, choose V

0.05 5

THR

= 3V.

5. Calculate R2.

THR



1R11

−−

 

 



 





−−

  



R2 =























(1.182 100k)1100k110M







65.44k

REF R1)

Ω

A 1% preferred value is 64.9kΩ.

6. Verify the threshold voltages with these formulas:

V rising:

=××++

V V R1

THR REF

V falling:

V V

=−

THF THR

 



R1 V

×+

()

). In

 



2.5V TO 11V

REF



Figure 3. Programming the HYST Pin

10 ______________________________________________________________________________________

REF

HYST

V+

MAX931 MAX932 MAX933

V-

Figure 4. External Hysteresis

MAX934

GND

REF

V+

OUT

V+ V-

Page 11

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

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

- 0.12V), but draws only 3.5µA quiescent current.

BATT

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)

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

section.

MAX931-MAX934

MOMENTARY SWITCH

4.5V TO 6.0V

REF

47k

HYST

1.1M 4

IN-

100k

Figure 5. Auto-off power switch operates on 2.5µA quiescent current.

V+

MAX931

V-

______________________________________________________________________________________ 11

GND

IN+

OUT

VBATT -0.15V

10mA

= 5.5V

OTH

= 4.5V

UTH

INA+

R5

10k

R4

2.4M

HYST

REF

INB-

Figure 6. Window Detector

+5V

V+

OUTA

OUTB

MAX933

V-

UNDERVOLTAGE

POWER GOOD

OVERVOLTAGE

Page 12

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

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:

R2 R3 R1

+=×

294k

=×

1.068M

=Ω



OTH

 

V V

REF H

 



5.5

(1.182 0.005)

−

 



−

 



4. Calculate R2. The undervoltage threshold should be 4.5V when VINis falling. The design equation is

MAX931-MAX934

as follows:

(V V )

−

R2 (R1 + R2 + R3)

=×

(294k + 1.068M)

Ω

62.2k

Choose R2 61.9k (1% standard value).

Ω

REF H

UTH

(1.182 0.005)

−

4.5

5. Calculate R3.

R3 (R2 + R3) R2

=−

.068M 6 k

=−

119 .

1.006M

Choose R3 1M (1% standard value).

Ω

The full-scale threshold (all LEDs on) is given by V

= (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.

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.

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.

−

294k

Level Shifter

Two-Stage Low-Voltage Detector

V-

330Ω

182k

1.182V

+5V

V+

REF

INA+

INA-

MAX934

OUTA

V

6. Verify the resistor values. The equations are as follows, evaluated for the above example.

Overvoltage threshold:

V (V V )

5.474V.

=+×

OTH REF H

(R1 R2 R3)

Undervoltage threshold:

V (V V )

4.484V,

=−×

UTH REF H

where the hysteresis voltage V V

(R1 R2 R3)

(R1 + R2)

=×.

H REF

R5 R4

Bar-Graph Level Gauge

250k

750mV

250k

500mV

250k

250mV

250k

INB+

OUTB

INB-

INC+

OUTC

INC-

IND+

OUTD

IND-

GND

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.

12 ______________________________________________________________________________________

Figure 7. Bar-Graph Level Gauge

330Ω

Page 13

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

+5V

V+

10k

INA

10k

INB

10k

INC

10k

IND

INA+

INA-

INB+

INB-

INC+

INC-

IND+

IND-

GND

MAX934

OUTA

OUTB

OUTC

OUTD

V-

REF

0 FOR V 1 FOR V

N.C.

< 0V

INA

> 0V

INB

INA+

REF

HYST

INB+

+5V

V+

INPUT VOLTAGE FAIL

INPUT VOLTAGE LOW

MAX932

V-

MAX931-MAX934

-5V

Figure 8. Level Shifter: ±5V Input to CMOS Output Figure 9. Two-Stage Low-Voltage Detector

______________________________________________________________________________________ 13

Page 14

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

_________________Pin Configurations _Ordering Information (continued)

TOP VIEW

GND

IN+

IN-

1 2

V-

MAX931

3 4

8 7 6 5

DIP/SO/µMAX

OUTA

INA+ INB+

V-

MAX932

3 4

MAX931-MAX934

8 7 6 5

OUT V+

REF HYST

OUTB V+

REF HYST

MAX932CPA

MAX933CPA

MAX934CPE

PIN-PACKAGETEMP. RANGEPART

8 Plastic DIP0°C to +70°C 8 SO0°C to +70°CMAX932CSA 8 µMAX0°C to +70°CMAX932CUA 8 Plastic DIP-40°C to +85°CMAX932EPA 8 SO-40°C to +85°CMAX932ESA 8 Plastic DIP0°C to +70°C 8 SO0°C to +70°CMAX933CSA 8 µMAX0°C to +70°CMAX933CUA 8 Plastic DIP-40°C to +85°CMAX933EPA 8 SO-40°C to +85°CMAX933ESA 16 Plastic DIP0°C to +70°C 16 Narrow SO0°C to +70°CMAX934CSE 16 Plastic DIP-40°C to +85°CMAX934EPE 16 Narrow SO-40°C to +85°CMAX934ESE

OUTA

INA+ INB-

OUTB OUTA

INAINA+ INB-

INB+

REF

V-

1 2

V+

3 4 5 6 7 8

DIP/SO/µMAX

1 2

MAX933

3 4

DIP/SO/µMAX

MAX934

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

OUTB

V+

REF

HYST

OUTC

OUTD

GND

IND+

IND-

INC+

INC-

V-

MAX922 are not pin-compatible.

14 ______________________________________________________________________________________

Page 15

Ultra Low-Power, Low-Cost

Comparators with 2% Reference

________________________________________________________Package Information

PDIPN.EPS

MAX931-MAX934

SOICN.EPS

______________________________________________________________________________________ 15

Page 16

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

__________________________________________Package Information (continued)

8LUMAXD.EPS

MAX931-MAX934

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.

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600