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19-0450; Rev 0; 11/95
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
_______________General Description
The MAX971-MAX974 and MAX981-MAX984 single/ dual/quad low-voltage comparators feature the lowest power consumption available. These micropower devices draw less than 4A supply current over temperature (MAX971/MAX972, MAX981/MAX982), and include an internal 1.182V 1% (MAX971/MAX973/ MAX974) or 2% (MAX981-MAX984) voltage reference and programmable hysteresis. Ideal for 3V or 5V single-supply applications, these devices operate from a single +2.5V to +11V supply (or 1.25V to 5.5V dual supplies), and each comparator's input voltage ranges from the negative supply rail to within 1.3V of the positive supply. The single MAX971 and MAX981 and the dual MAX973 and MAX982/MAX983 provide a unique, simple method for adding hysteresis without feedback or complicated equations, simply by using the HYST pin plus two resistors. The MAX971-MAX974 and MAX981-MAX984's opendrain outputs permit wire-ORed configurations. Thanks to an 11V output range and separate GND pin for the output transistor (MAX971/MAX974, MAX981/MAX984), these devices are ideal for level translators and bipolar to singleended converters. For similar devices with complementary output stages, see the MAX921-MAX924 (1% reference) and the MAX931-MAX934 (2% reference).
COMPARATORS PER PACKAGE
____________________________Features
o MAX Package--Smallest 8-Pin SO (MAX9_1/MAX9_2/MAX9_3) o Ultra-Low 4A Max Quiescent Current Over Extended Temp. Range (MAX971/MAX981) o Power Supplies: Single +2.5V to +11V Dual 1.25V to 5.5V o Input Voltage Range Includes Negative Supply o Internal 1.182V 1% Bandgap Reference o 12s Propagation Delay (10mV Overdrive) o Output Has Separate GND Pin (MAX9_1/MAX9_4)
MAX971-MAX974/MAX981-MAX984
________________________Applications
Battery-Powered Systems Threshold Detectors Window Comparators Level Translators Oscillator Circuits
______________Ordering Information
PART MAX971CPA MAX971CSA MAX971CUA MAX971C/D TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C 0C to +70C PIN-PACKAGE 8 Plastic DIP 8 SO 8 MAX Dice*
INTERNAL HYSTERESIS
INTERNAL PRECISION REFERENCE
PACKAGE
Ordering Information continued at end of data sheet. * Dice are tested at TA = +25C, DC parameters only.
PART
__________Typical Operating Circuit
VIN 7 V+ 3 IN+ OUT 8 4 IN-
MAX971 MAX972 MAX973 MAX974 MAX981 MAX982 MAX983 MAX984
1% None 1% 1% 2% 2% 2% 2%
1 2 2 4 1 2 2 4
Yes No Yes No Yes Yes Yes No
8-Pin DIP/SO/MAX 8-Pin DIP/SO/MAX 8-Pin DIP/SO/MAX 16-Pin DIP/SO 8-Pin DIP/SO/MAX 8-Pin DIP/SO/MAX 8-Pin DIP/SO/MAX 16-Pin DIP/SO
5 HYST
6 REF V2
MAX971 MAX981
GND 1
THRESHOLD DETECTOR 1
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
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 OUT_ ................................................................50mA Voltage: REF ....................................(V+ + 0.3V) to (V- - 0.3V) OUT_ (MAX9_1/9_4) ...............+12V to (GND - 0.3V) (MAX9_2/9_3) ....................+12V to (V- - 0.3V) OUT_ Short-Circuit Duration ..................................Continuous Continuous Power Dissipation (TA = +70C) 8-Pin Plastic DIP (derate 9.09mW/C above +70C) ...727mW 8-Pin SO (derate 5.88mW/C above +70C)................471mW 8-Pin MAX (derate 4.1mW/C above +70C) .............330mW 8-Pin CERDIP (derate 8.00mW/C above +70C)........640mW 16-Pin Plastic DIP (derate 10.53mW/C above +70C)..842mW 16-Pin SO (derate 8.70mW/C above +70C) ................696mW 16-Pin CERDIP (derate 10.00mW/C above +70C) ......800mW Operating Temperature Ranges MAX97_C_ _/MAX98_C_ _ ..................................0C to +70C MAX97_E_ _/MAX98_E_ _ ...............................-40C to +85C MAX97_MJ_/MAX98_MJ_ .............................-55C to +125C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS: 5V OPERATION
(V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER POWER REQUIREMENTS Supply Voltage Range Output Voltage Range MAX9_1, C/E temp. ranges HYST = REF M temp. range TA = +25C MAX972 Supply Current IN+ = IN- + 100mV C/E temp. ranges M temp. range TA = +25C MAX982/ MAX9_3, C/E temp. ranges HYST = REF M temp. range TA = +25C C/E temp. ranges MAX9_4 M temp. range 3.1 2.5 TA = +25C (Note 1) 2.5 0 2.5 11 11 3.2 4 5 3.2 4 5 4.5 6 7.5 6.5 8.5 11 10 5 40 V+ - 1.3 1.0 1.0 REF 12 4 300 mV nA nA V mV/V mV/V VRMS V s s A V V CONDITIONS MIN TYP MAX UNITS
5.5
COMPARATOR Input Offset Voltage Input Leakage Current (IN-, IN+) Input Leakage Current (HYST) Input Common-Mode Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range Response Time (high-to-low transition) Response Time (low-to-high transition) (Note 2) 2
VCM = 2.5V IN+ = IN- = 2.5V MAX9_1/MAX982/MAX9_3 VV- to (V+ - 1.3V) V+ = 2.5V to 11V 100Hz to 100kHz MAX9_1/MAX982/MAX9_3 TA = +25C, 100pF load, 1M pull-up to V+ Overdrive = 10mV Overdrive = 100mV 0.1 0.1 20 REF - 0.05 C/E temp. ranges M temp. range 0.01 0.02
TA = +25C, 100pF load, 1M pull-up to V+
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Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
ELECTRICAL CHARACTERISTICS: 5V OPERATION (continued)
(V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MAX9_2/MAX9_3, IOUT = 1.8mA for C/E temp. ranges, IOUT = 1.2mA for M temp. range MAX9_1/MAX9_4, IOUT = 1.8mA for C/E temp. ranges, IOUT = 1.2mA for M temp. range VOUT = 11V 1.170 1.158 1.147 15 6 4 8 4 2 1.182 MIN TYP MAX V- + 0.4 V GND + 0.4 100 1.194 1.206 1.217 nA UNITS
MAX971-MAX974/MAX981-MAX984
Output Low Voltage
Output Leakage Current
REFERENCE (MAX9_1/MAX982/MAX9_3/MAX9_4 ONLY) X C temp. range E temp. range Reference Voltage M temp. range TA = +25C C/E temp. ranges Source Current M temp. range TA = +25C Sink Current C/E temp. ranges M temp. range Voltage Noise 100Hz to 100kHz
V
25 A 15 A 100 VRMS
ELECTRICAL CHARACTERISTICS: 3V OPERATION
(V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER POWER REQUIREMENTS TA = +25C MAX9_1 C/E temp. ranges M temp. range TA = +25C MAX972 Supply Current HYST = REF, IN+ = (IN- + 100mV) MAX982/ MAX9_3 C/E temp. ranges M temp. range TA = +25C C/E temp. ranges M temp. range TA = +25C C/E temp. ranges M temp. range 3.4 2.4 2.4 3.0 3.8 4.8 3.0 3.8 4.8 4.3 5.8 7.2 6.2 8.0 10.5 10 5 40 V+ - 1.3 1 1 mV nA nA V mV/V mV/V A CONDITIONS MIN TYP MAX UNITS
5.2
MAX9_4 COMPARATOR Input Offset Voltage Input Leakage Current (IN-, IN+) Input Leakage Current (HYST) Input Common-Mode Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio
VCM = 1.5V IN+ = IN- = 1.5V MAX9_1/MAX982/MAX9_3 VV- to (V+ - 1.3V) V+ = 2.5V to 11V 0.2 0.1 C/E temp. ranges M temp. range 0.01 0.02
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3
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
ELECTRICAL CHARACTERISTICS: 3V OPERATION (continued)
(V+ = 5V, V- = GND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Voltage Noise Hysteresis Input Voltage Range Response Time (high-to-low transition) Response Time (low-to-high transition) (Note 2) CONDITIONS 100Hz to 100kHz MAX9_1/MAX982/MAX9_3 TA = +25C, 100pF load, 1M pull-up to V+ Overdrive = 10mV Overdrive = 100mV MIN REF - 0.05 12 4 300 V- + 0.4 V GND + 0.4 100 1.170 1.158 1.147 15 6 4 8 4 2 1.182 1.194 1.206 1.217 nA TYP 20 REF MAX UNITS VRMS V s s
TA = +25C, 100pF load, 1M pull-up to V+ MAX9_2/MAX9_3, IOUT = 0.8mA for C/E temp. ranges, IOUT = 0.6mA for M temp. range MAX9_1/MAX9_4, IOUT = 0.8mA for C/E temp. ranges, IOUT = 0.6mA for M temp. range VOUT = 11V C temp. range E temp. range M temp. range TA = +25C C/E temp. ranges M temp. range TA = +25C C/E temp. ranges M temp. range 100Hz to 100kHz
Output Low Voltage
Output Leakage Current REFERENCE Reference Voltage
V
25 A 15 A 100 VRMS
Source Current
Sink Current Voltage Noise
Note 1: MAX974/MAX984 comparators work below 2.5V; see Low-Voltage Operation section for more details. Note 2: Low-to-high response time is the result of the 1M pull-up and the 100pF capacitive load, based on three time constants. A faster response time is achieved with a smaller RC.
__________________________________________Typical Operating Characteristics
(V+ = 5V, V- = GND, TA = +25C, unless otherwise noted.)
OUTPUT VOLTAGE LOW vs. LOAD CURRENT
MAX971/4-TOC1
REFERENCE OUTPUT VOLTAGE vs. OUTPUT LOAD CURRENT
MAX971/4-TOC2
MAX971/MAX973/MAX974 REFERENCE VOLTAGE vs. TEMPERATURE
1.21 REFERENCE VOLTAGE (V) 1.20 1.19 1.18 1.17 1.16 1.15 1.14 MILITARY TEMP. RANGE EXTENDED TEMP. RANGE COMMERCIAL TEMP. RANGE
MAX971/4-TOC3
2.5
V+ = 5V
1.190 REFERENCE OUTPUT VOLTAGE (V) SINK 1.185 1.180 SOURCE 1.175 1.170 1.165 1.160 1.155 V+ = 5V OR V+ = 3V 0 5 10 15 20 25
1.22
2.0 V+ = 3V VOL (V) 1.5
1.0
0.5
0 0 4 8 12 16 20 LOAD CURRENT (mA)
30
-60 -40 -20 0
20 40 60 80 100 120 140
OUTPUT LOAD CURRENT (A)
TEMPERATURE (C)
4
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Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
____________________________Typical Operating Characteristics (continued)
(V+ = 5V, V- = GND, TA = +25C, unless otherwise noted.)
MAX9_1 SUPPLY CURRENT vs. TEMPERATURE
MAX971/4-TOC4
MAX971-MAX974/MAX981-MAX984
MAX972 SUPPLY CURRENT vs. TEMPERATURE
MAX971/4-TOC5
MAX982/MAX9_3 SUPPLY CURRENT vs. TEMPERATURE
MAX971/4-TOC6
4.5 IN+ = IN- + 100mV SUPPLY CURRENT (A) 4.0 V+ = 5V, V- = - 5V
4.5 IN+ = (IN- + 100mV) 4.0 SUPPLY CURRENT (A) 3.5 V+ = 10V, V- = 0V 3.0 2.5 V+ = 5V, V- = 0V 2.0 V+ = 3V, V- = 0V 1.5
5.0 4.5 SUPPLY CURRENT (A) 4.0 V+ = 5V, V- = 0V 3.5 3.0 2.5 V+ = 3V, V- = 0V 2.0
3.5
3.0 V+ = 3V, V- = 0V 2.5 V+ = 5V, V- = 0V 2.0 -60 -20 20 60 100 140 TEMPERATURE (C)
-60
-20
20
60
100
140
-60
-20
20
60
100
140
TEMPERATURE (C)
TEMPERATURE (C)
MAX9_4 SUPPLY CURRENT vs. TEMPERATURE
IN+ = (IN- + 100mV) 9 SUPPLY CURRENT (A) 8 7 6 5 4 3 -60 -20 20 60 100 140 TEMPERATURE (C) V+ = 5V, V- = 0V V+ = 3V, V- = 0V 0.01 1.0 V+ = 5V, V- = -5V
MAX971/4-TOC7
MAX9_4 SUPPLY CURRENT vs. LOW SUPPLY VOLTAGES
MAX971/4-TOC8
MAX9_1/MAX982/MAX9_3 HYSTERESIS CONTROL
60 40 IN+ - IN- (V)
MAX971/4 TOC9
10
10
80 OUTPUT HIGH
SUPPLY CURRENT (A)
1
20 0 -20 -40 OUTPUT LOW -60 -80 NO CHANGE
0.1
1.5
2.0
2.5
0
10
20
30
40
50
SINGLE-SUPPLY VOLTAGE (V)
VREF -VHYST (mV)
MAX9_1/MAX972/MAX9_4 TRANSFER FUNCTION
+5V 10k 100k 10F V0
MAX971/4-TOC10
RESPONSE TIME vs. LOAD CAPACITANCE
16 RESPONSE TIME (s) 14 12 10 8 6 4 2 VIN (mV) V- = 0V
MAX971/4 TOC11
RESPONSE TIME FOR VARIOUS INPUT OVERDRIVES (VOHL)
5 VOUT (V) 4 3 2 1 0 100 0 50mV 100mV 20mV 10mV
MAX971/4-TOC12
5.0 4.5 4.0 OUTPUT VOLTAGE (V) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -0.3
18
VOHL
0.2 0.1 -0.2 -0.1 0 IN+ INPUT VOLTAGE (mV)
0.3
0
20
40
60
80
100
-2
2
6
10
14
18
LOAD CAPACITANCE (nF)
RESPONSE TIME (s)
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5
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
____________________________Typical Operating Characteristics (continued)
(V+ = 5V, V- = GND, TA = +25C, unless otherwise noted.)
RESPONSE TIME AT LOW SUPPLY VOLTAGES (VOHL)
MAX971/4-TOC13
MAX924 RESPONSE TIME AT LOW SUPPLY VOLTAGES
MAX971/4-TOC14
SHORT-CIRCUIT SINK CURRENT vs. SUPPLY VOLTAGE
OUT CONNECTED TO V+ GND CONNECTED TO V20 SINK CURRENT (mA)
MAX971/4-TOC15
1000 RPULL-UP = 10k
100
25
RESPONSE TIME (s)
100
CURRENT (mA)
10
15
10 -100mV
-20mV
10
1
5 SINK CURRENT AT VOUT = 0.4V 1 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 SINGLE-SUPPLY VOLTAGE (V) 0.1 1.0 1.5 2.0 2.5 SINGLE-SUPPLY VOLTAGE (V) 0 0 5 TOTAL SUPPLY VOLTAGE (V) 10
____________________________________________________________Pin Descriptions
PIN MAX971 MAX981 1 -- 2 3 -- 4 -- -- -- 5 6 7 8 -- MAX972 -- 1 2 -- 3 -- 4 5 6 -- -- 7 -- 8 MAX982 -- 1 2 -- 3 -- -- -- 4 5 6 7 -- 8 MAX973 MAX983 -- 1 2 -- 3 -- -- 4 -- 5 6 7 -- 8 NAME FUNCTION
GND OUTA VIN+ INA+ ININAINBINB+ HYST REF V+ OUT OUTB
Ground. Connect to V- for single-supply operation. Output transistor pulls to GND. Comparator A Open-Drain Output. Sinks current to V-. Negative Supply. Connect to ground for single-supply operation (MAX9_1). Noninverting Comparator Input Noninverting Input of Comparator A Inverting Comparator Input Inverting Input of Comparator A Inverting Input of Comparator B Noninverting Input of Comparator B Hysteresis Input. Connect to REF if not used. Input voltage range is from VREF to VREF - 50mV. Reference Output. 1.182V with respect to V-. Positive Supply Comparator Output. Sinks current to GND. Comparator B Open-Drain Output. Sinks current to V-.
6
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Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
_______________________________________________Pin Descriptions (continued)
PIN MAX974 MAX984 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 NAME FUNCTION
MAX971-MAX974/MAX981-MAX984
OUTB OUTA V+ INAINA+ INBINB+ REF VINCINC+ INDIND+ GND OUTD OUTC
Comparator B Open-Drain Output. Sinks current to GND. Comparator A Open-Drain Output. Sinks current to GND. Positive Supply Inverting Input of Comparator A Noninverting Input of Comparator A Inverting Input of Comparator B Noninverting Input of Comparator B Reference Output. 1.182V with respect to V-. Negative Supply. Connect to ground for single-supply operation. Inverting Input of Comparator C Noninverting Input of Comparator C Inverting Input of Comparator D Noninverting Input of Comparator D Ground. Connect to V- for single-supply operation. Comparator D Open-Drain Output. Sinks current to GND. Comparator C Open-Drain Output. Sinks current to GND.
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7
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
_______________Detailed Description
The MAX971-MAX974 and MAX981-MAX984 comprise various combinations of a micropower 1.182V reference and micropower comparators. The Typical Operating Circuit shows the MAX971/MAX981 configuration, and Figures 1a-1d show the MAX9_2-MAX9_4 configurations. Internal hysteresis in the MAX9_1, MAX982, and MAX9_3 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 MAX9_1 and MAX9_4 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 MAX9_1 or MAX9_4 from a single supply. The maximum total supply voltage in this case is still 11V. For proper comparator operation, the input signal can range 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.
1 OUTA 1 OUTA 2 V3 INA+ 4 INA-
MAX9_3
OUTB 8 V+ 7 REF 6 HYST 5
MAX972
OUTB 8 V+ 7 INB+ 6 INB- 5
2 V3 INA+ 4 INBV-
Figure 1c. MAX973/MAX983 Functional Diagram (Window Comparator) Figure 1a. MAX972 Functional Diagram
1 OUTB 2 OUTA 3 V+ 4 INAOUTB 8 5 INA+ 2 V3 INA+ 4 INB+ VV+ 7 REF 6 6 INBHYST 5 7 INB+ 8 REF INC- 10 V- 9 INC+ 11 IND- 12
MAX9_4
OUTC 16 OUTD 15 GND 14 IND+ 13
1 OUTA
MAX982
Figure 1b. MAX982 Functional Diagram
8
Figure 1d. MAX974/MAX984 Functional Diagram
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Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
The negative supply does not affect the output sink current. The positive supply provides gate drive for the output N-channel MOSFET and heavily influences the output current capability, especially at low supply voltages (see Typical Operating Characteristics section). The MAX9_2 and MAX9_3 have no GND pin, and their outputs sink current to V-.
MAX971-MAX974/MAX981-MAX984
IN+
THRESHOLDS
INVREF - VHYST
HYSTERESIS VHB BAND
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 1% (MAX971/MAX973/MAX974) or 2% (MAX981-MAX984) in the 0C to +70C range. The REF output is typically capable of sourcing 25A and sinking 15A. Do not bypass the REF output.
OUT
Noise Considerations
Figure 2. Threshold Hysteresis Band
Low-Voltage Operation: V+ = 1V (MAX9_4 Only) The guaranteed minimum operating voltage is 2.5V (or 1.25V). As the total supply voltage falls below 2.5V, performance degrades and the supply 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 MAX9_4 has comparators that may be used at supply voltages below 2V, the MAX9_1/MAX9_2/MAX9_3 may not be used with supply voltages below 2.5V. At low supply voltages, the comparators' output sink capability 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 when the device operates from higher supply voltages. Test your prototype over the full temperature and supply-voltage range if you anticipate operation below 2.5V.
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 300V. 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. Take care in your layout to avoid capacitive coupling from any output to the reference pin. Crosstalk can significantly increase the actual noise of the reference.
Comparator Output
With 100mV of overdrive, propagation delay is typically 3s. The Typical Operating Characteristics show the propagation delay for various overdrive levels. The open-drain outputs are intended for wire-ORed and level-shifting applications. The maximum output voltage is 11V above V-, and may be applied even when no supply voltage is present (V+ = V-). The MAX9_1 and MAX9_4 outputs sink current to GND, making these devices ideal for bipolar to single-ended conversion and level-shifting applications.
R1
IREF
6 REF
2.5V TO 11V 7 V+
MAX9_1 MAX982 MAX9_3
5 HYST V2
R2
Figure 3. Programming the HYST Pin
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9
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
__________Applications Information
Hysteresis
Hysteresis increases the comparators' noise margin by increasing the upper threshold and decreasing the lower threshold (Figure 2).
RH V+
Hysteresis (MAX9_1/MAX982/MAX9_3) To add hysteresis to the MAX9_1, MAX982, or MAX9_3, 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 maximum difference between REF and HYST (50mV) will therefore produce a 100mV max hysteresis band. Use the following equations to determine R1 and R2: VHB R1 = (2 x IREF )
VHB 1.182 - 2 R2 = IREF 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 0.1A and 4A are usually appropriate. If 2.4M is chosen for R2 (IREF = 0.5A), the equation for R1 and V HB can be approximated as: R1 (k) = VHB (mV) When hysteresis is obtained in this manner for the MAX982/MAX9_3, the same hysteresis applies to both comparators.
VIN
RPULL-UP V+ OUT
MAX9_4 VGND VREF
Figure 4. External Hysteresis
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.
Window Detector
The MAX9_3 is ideal for making window detectors (undervoltage/overvoltage detectors). The schematic is shown in Figure 5, with component values selected for a 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. Taken alone, OUTA would provide an active-low undervoltage indication, and OUTB would give an active-low overvoltage indication. Wired-ORing 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 (MAX9_1/MAX982/MAX9_3) section. In this example, 5mV of hysteresis has been added at the comparator input (VH = VHB / 2). This means that the hysteresis apparent at V IN will be larger because of the input resistor divider.
Hysteresis (MAX972/MAX9_4) Hysteresis can be implemented with any comparator using positive feedback, as shown in Figure 4. This approach generally draws more current than circuits using the HYST pin on the MAX9_1/MAX982/MAX9_3, and the high feedback impedance slows hysteresis. In addition, because the output does not source current, any increase in the upper threshold is dependent on the load or pull-up resistor on the output.
10
______________________________________________________________________________________
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
2) Select R1. The leakage current into INB- is normally under 1nA, so the current through R1 should exceed 100nA for the thresholds to be accurate. R1 values up to about 10M can be used, but values in the 100k to 1M range are usually easier to deal with. In this example, choose R1 = 294k. 3) Calculate R2 + R3. The overvoltage threshold should be 5.5V when V IN is rising. The design equation is as follows: VOTH R2 + R3 = R1 x - 1 VREF + VH 5.5 = 294k x - 1 (1.182 + 0.005) = 1.068M 4) Calculate R2. The undervoltage threshold should be 4.5V when VIN is falling. The design equation is as follows: (VREF - VH ) R2 = (R1 + R2 + R3) x - R1 VUTH = (294k + 1.068M) x (1.182 - 0.005) - 294k 4.5
R1 294k
MAX971-MAX974/MAX981-MAX984
VIN R3 1M
VOTH = 5.5V VUTH = 4.5V
+5V 7 V+ OUTA 1
3 INA+
1M
5 HYST R2 62.2k R5 10k R4 2.4M 6 REF OUTB 8 4 INBV2 POWER GOOD
MAX9_3
= 62.2k Choose R2 = 61.9k (1% standard value). 5) Calculate R3: R3 = (R2 + R3) - R2 = 1.068M - 61.9k = 1.006M Choose R3 = 1M (1% standard value) 6) Verify the resistor values. The equations are as follows, evaluated for the above example: Overvoltage Threshold : (R1 + R2 + R3) VOTH = (VREF + VH ) x R1 = 5.474V Undervoltage Threshold : (R1 + R2 + R3) VUTH = (VREF - VH ) x (R1 + R2) = 4.484V where the hysteresis voltage VH = VREF x R5 . R4
Figure 5. Window Detector
Battery Switchover Circuit
The switchover from line-powered DC to a backup battery is often accomplished with diodes. But this simple method is sometimes unacceptable, due to the voltage drop and associated power loss across the diode in series with the battery. Figure 6's circuit replaces the diode with a P-channel MOSFET controlled by one of the MAX9_3 comparator outputs. When the DC wall adapter drops below 4V (determined by R1 and R2), OUTA goes low, turning on Q1. Comparator B is used to measure the battery voltage, and gives a "low-battery" indication when the battery drops below 3.6V.
Level Shifter
Figure 7 shows a circuit to shift from bipolar 5V inputs to single-ended +5V outputs. The 10k resistors protect the comparator inputs, and do not materially affect the circuit's operation.
______________________________________________________________________________________
11
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
+5V WALL ADAPTER +9V DC Q1 STEP-DOWN REGULATOR 10k +3.3V LOGIC SUPPLY VINA 5 INA+ 3 V+ +3.3V
MAX974 MAX984
OUTA 2
4 1M 7 V+ 10k VINB
INA-
7 INB+ OUTB 1
BATTERY (4 CELLS) 953k 4 INB-
MAX973 MAX983
OUTB 8
10k 10k VINC LOW BATT
6 INB-
11 INC+ OUTC 16 10 INC-
470k
1 OUTA R1 110k DC OK 10k VIND 3 INA+ REF 6 R2 47k V2 20k HYST 5 2.4M
13 IND+ OUTD 15 12 INDREF GND 14 V9 -5V 8
N.C.
Figure 6. Battery Switchover Circuit
Figure 7. Level Shifter: 5V Input to Single-Ended +3.3V Output
__________________________________________________________Pin Configurations
TOP VIEW
GND
1
8 7
OUT V+ REF HYST
OUTA
1
8 7
OUTB V+ INB+ INB-
OUTA
1
8 7
OUTB V+ REF HYST
V- 2 IN+ 3 IN- 4
V- 2 INA+ 3 INA- 4
V- 2 INA+ 3 INB+ 4
MAX971 MAX981
6 5
MAX972
6 5
MAX982
6 5
DIP/SO/MAX
DIP/SO/MAX
DIP/SO/MAX
12
______________________________________________________________________________________
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
_____________________________________________Pin Configurations (continued)
TOP VIEW
OUTB 1 OUTA 1 8 7 OUTA 2 OUTB V+ REF HYST V+ 3 INA- 4 INA+ 5 INB- 6 14 GND 16 OUTC 15 OUTD
MAX971-MAX974/MAX981-MAX984
V- 2 INA+ 3 INB- 4
MAX973 MAX983
6 5
MAX974 MAX984
13 IND+ 12 IND11 INC+ 10 INC9 V-
DIP/SO/MAX
INB+ 7 REF 8
DIP/Narrow SO
__________________________________________Ordering Information (continued)
PART MAX971EPA MAX971ESA MAX971MJA MAX972CPA MAX972CSA MAX972CUA MAX972C/D MAX972EPA MAX972ESA MAX972MJA MAX973CPA MAX973CSA MAX973CUA MAX973C/D MAX973EPA MAX973ESA MAX973MJA MAX974CPE MAX974CSE MAX974C/D MAX974EPE MAX974ESE MAX974MJE TEMP. RANGE -40C to +85C -40C to +85C -55C to +125C 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -55C to +125C 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -55C to +125C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -55C to +125C PIN-PACKAGE 8 Plastic DIP 8 SO 8 CERDIP** 8 Plastic DIP 8 SO 8 MAX Dice* 8 Plastic DIP 8 SO 8 CERDIP** 8 Plastic DIP 8 SO 8 MAX Dice* 8 Plastic DIP 8 SO 8 CERDIP** 16 Plastic DIP 16 Narrow SO Dice* 16 Plastic DIP 16 Narrow SO 16 CERDIP** PART MAX981CPA MAX981CSA MAX981CUA MAX981EPA MAX981ESA MAX982CPA MAX982CSA MAX982CUA MAX982EPA MAX982ESA MAX983CPA MAX983CSA MAX983CUA MAX983EPA MAX983ESA MAX984CPE MAX984CSE MAX984EPE MAX984ESE TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C 0C to +70C 0C to +70C -40C to +85C -40C to +85C PIN-PACKAGE 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO 16 Plastic DIP 16 Narrow SO 16 Plastic DIP 16 Narrow SO
* Dice are tested at TA = +25C, DC parameters only. ** Contact factory for availability and processing to MIL-STD-883.
______________________________________________________________________________________
13
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
___________________Chip Information
MAX971/MAX972/MAX973
TRANSISTOR COUNT: 164 SUBSTRATE CONNECTED TO V+
MAX974
TRANSISTOR COUNT: 267 SUBSTRATE CONNECTED TO V+
14
______________________________________________________________________________________
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators
_______________________________________________________Package Information
DIM
C A 0.101mm 0.004 in B A1 L
MAX971-MAX974/MAX981-MAX984
e
A A1 B C D E e H L
INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6 0
MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0 6
21-0036D
E
H
8-PIN MAX MICROMAX SMALL-OUTLINE PACKAGE
D
DIM
D A e B
0.101mm 0.004in.
0-8
A1
C
L
A A1 B C E e H L
INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.157 0.150 0.050 0.244 0.228 0.050 0.016
MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 3.80 4.00 1.27 5.80 6.20 0.40 1.27
E
H
Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.)
DIM PINS D D D 8 14 16
INCHES MILLIMETERS MIN MAX MIN MAX 0.189 0.197 4.80 5.00 0.337 0.344 8.55 8.75 0.386 0.394 9.80 10.00
21-0041A
______________________________________________________________________________________
15
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators MAX971-MAX974/MAX981-MAX984
__________________________________________Package Information (continued)
E D A3 A A2 E1
DIM A A1 A2 A3 B B1 C D1 E E1 e eA eB L INCHES MAX MIN 0.200 - - 0.015 0.175 0.125 0.080 0.055 0.022 0.016 0.065 0.045 0.012 0.008 0.080 0.005 0.325 0.300 0.310 0.240 - 0.100 - 0.300 0.400 - 0.150 0.115 INCHES MIN MAX 0.348 0.390 0.735 0.765 0.745 0.765 0.885 0.915 1.015 1.045 1.14 1.265 MILLIMETERS MIN MAX - 5.08 0.38 - 3.18 4.45 1.40 2.03 0.41 0.56 1.14 1.65 0.20 0.30 0.13 2.03 7.62 8.26 6.10 7.87 2.54 - 7.62 - - 10.16 2.92 3.81 MILLIMETERS MIN MAX 8.84 9.91 18.67 19.43 18.92 19.43 22.48 23.24 25.78 26.54 28.96 32.13
21-0043A
L A1 e B D1
0 - 15 C B1 eA eB
Plastic DIP PLASTIC DUAL-IN-LINE PACKAGE (0.300 in.)
PKG. DIM PINS P P P P P N D D D D D D 8 14 16 18 20 24
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 (c) 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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