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PDF MAX971 Data sheet ( Hoja de datos )
| Número de pieza | MAX971 | |
| Descripción | Ultra-Low-Power / Open-Drain / Single/Dual-Supply Comparators | |
| Fabricantes | Maxim Integrated | |
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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 4µA 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 open-
drain 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 single-
ended converters. For similar devices with complementary
output stages, see the MAX921–MAX924 (1% reference)
and the MAX931–MAX934 (2% reference).
____________________________Features
o µMAX Package—Smallest 8-Pin SO
(MAX9_1/MAX9_2/MAX9_3)
o Ultra-Low 4µA 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 12µs Propagation Delay (10mV Overdrive)
o Output Has Separate GND Pin (MAX9_1/MAX9_4)
________________________Applications
Battery-Powered Systems
Level Translators
Threshold Detectors
Oscillator Circuits
Window Comparators
______________Ordering Information
PART
MAX971CPA
MAX971CSA
MAX971CUA
MAX971C/D
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 µMAX
Dice*
Ordering Information continued at end of data sheet.
* Dice are tested at TA = +25°C, DC parameters only.
__________Typical Operating Circuit
MAX971
1%
1
Yes
8-Pin
DIP/SO/µMAX
MAX972 None
2
No
8-Pin
DIP/SO/µMAX
MAX973
1%
2
Yes
8-Pin
DIP/SO/µMAX
MAX974
1%
4
No 16-Pin DIP/SO
VIN
7
V+
3 IN+
4 IN-
OUT 8
MAX981
MAX982
MAX983
2%
2%
2%
1
Yes
8-Pin
DIP/SO/µMAX
2
Yes
8-Pin
DIP/SO/µMAX
2
Yes
8-Pin
DIP/SO/µMAX
5 HYST
6 REF
V-
2
MAX971
MAX981
GND
1
MAX984
2%
4
No 16-Pin DIP/SO
THRESHOLD DETECTOR
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
1 page  
Ultra-Low-Power, Open-Drain,
Single/Dual-Supply Comparators
____________________________Typical Operating Characteristics (continued)
(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted.)
MAX9_1
SUPPLY CURRENT vs.
TEMPERATURE
4.5
IN+ = IN- + 100mV
4.0
MAX972
SUPPLY CURRENT vs. TEMPERATURE
4.5
IN+ = (IN- + 100mV)
4.0
MAX982/MAX9_3
SUPPLY CURRENT vs. TEMPERATURE
5.0
4.5
V+ = 5V, V- = - 5V
3.5
3.0
V+ = 3V, V- = 0V
2.5
2.0
-60
V+ = 5V, V- = 0V
-20 20 60 100
TEMPERATURE (°C)
140
MAX9_4
SUPPLY CURRENT vs. TEMPERATURE
10
IN+ = (IN- + 100mV)
9
8
7
V+ = 5V, V- = -5V
6
5 V+ = 5V, V- = 0V
4 V+ = 3V, V- = 0V
3
-60
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
-0.3
-20 20 60 100
TEMPERATURE (°C)
MAX9_1/MAX972/MAX9_4
TRANSFER FUNCTION
+5V
10k 100k
10µF
V0
-0.2 -0.1 0 0.1 0.2
IN+ INPUT VOLTAGE (mV)
140
0.3
3.5
V+ = 10V, V- = 0V
3.0
2.5
2.0
1.5
-60
10
V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
-20 20 60 100
TEMPERATURE (°C)
MAX9_4
SUPPLY CURRENT vs.
LOW SUPPLY VOLTAGES
140
1
0.1
0.01
1.0
1.5 2.0
SINGLE-SUPPLY VOLTAGE (V)
RESPONSE TIME vs.
LOAD CAPACITANCE
18
V- = 0V
16
14
VOHL
12
10
8
6
4
2
0
20 40 60 80
LOAD CAPACITANCE (nF)
2.5
100
4.0
V+ = 5V, V- = 0V
3.5
3.0
2.5
2.0
-60
V+ = 3V, V- = 0V
-20 20 60 100
TEMPERATURE (°C)
140
MAX9_1/MAX982/MAX9_3
HYSTERESIS CONTROL
80
60
OUTPUT HIGH
40
20
0 NO CHANGE
-20
-40
OUTPUT LOW
-60
-80
0
10 20 30 40
VREF -VHYST (mV)
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES (VOHL)
50
5
4
3
100mV
2
1
0 50mV
100
0
10mV
20mV
-2 2 6 10 14 18
RESPONSE TIME (µs)
_______________________________________________________________________________________ 5
5 Page 
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 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 VIN is rising. The design
equation is as follows:
R2
+
R3
=
R1
×
VOTH
VREF +
VH
−
1
=
294k
×
5.5
(1.182 + 0.005)
−
1
= 1.068MΩ
4) Calculate R2. The undervoltage threshold should be
4.5V when VIN is falling. The design equation is as
follows:
R2 = (R1 + R2 + R3) × (VREF − VH) − R1
VUTH
= (294k + 1.068M) × (1.182 − 0.005) − 294k
4.5
= 62.2kΩ
Choose R2 = 61.9kΩ (1% standard value).
5) Calculate R3:
R3 = (R2 + R3) − R2
= 1.068M − 61.9k
= 1.006MΩ
Choose R3 = 1MΩ (1% standard value)
6) Verify the resistor values. The equations are as
follows, evaluated for the above example:
Overvoltage Threshold :
VOTH
=
(VREF
+ VH) ×
(R1 + R2 + R3)
R1
= 5.474V
Undervoltage Threshold :
VUTH
=
(VREF
− VH) ×
(R1 + R2 + R3)
(R1 + R2)
= 4.484V
where the hysteresis voltage VH
=
VREF ×
R5 .
R4
VIN
R3
1M
VOTH = 5.5V
VUTH = 4.5V
3 INA+
R2
62.2k
R1
294k
5 HYST
R5
10k
R4 6 REF
2.4M
4 INB-
V-
2
+5V
7
V+
OUTA 1
1M
OUTB 8
POWER GOOD
MAX9_3
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 10kΩ resistors
protect the comparator inputs, and do not materially
affect the circuit’s operation.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX971.PDF ] | |
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