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Teilenummer | MAX923 |
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Beschreibung | Ultra Low-Power / Single/Dual-Supply Comparators | |
Hersteller | Maxim Integrated | |
Logo | ||
Gesamt 16 Seiten 19-0115; Rev 3; 3/95
Ultra Low-Power,
Single/Dual-Supply Comparators
_______________General Description
The MAX921–MAX924 single, dual, and quad micro-
power, low-voltage comparators feature the lowest
power consumption available. These comparators draw
less than 4µA supply current over temperature
(MAX921/MAX922), and include an internal 1.182V
±1% voltage reference, programmable hysteresis, and
TTL/CMOS outputs that sink and source current.
Ideal for 3V or 5V single-supply applications, the
MAX921–MAX924 operate from a single +2.5V to +11V
supply (or a ±1.25V to ±5V dual supply), and each
comparator’s input voltage range swings from the
negative supply rail to within 1.3V of the positive
supply.
The MAX921–MAX924’s unique output stage con-
tinuously sources as much as 40mA. And by eliminating
power-supply glitches that commonly occur when com-
parators change logic states, the MAX921–MAX924
minimize parasitic feedback, which makes them easier to
use.
The single MAX921 and dual MAX923 provide a unique
and simple method for adding hysteresis without
feedback and complicated equations, simply by using
the HYST pin and two resistors.
MAX921
MAX922
MAX923
MAX924
Yes
No
Yes
Yes
1
Yes
8-Pin
DIP/SO/µMAX
2
No
8-Pin
DIP/SO/µMAX
2
Yes
8-Pin
DIP/SO/µMAX
4
No
16-Pin
DIP/SO/µMAX
________________________Applications
Battery-Powered Systems
Threshold Detectors
Window Comparators
Oscillator Circuits
____________________________Features
o µMAX Package—Smallest 8-Pin SO
(MAX921/MAX922/MAX923)
o Ultra-Low 4µA Max Quiescent Current
Over Extended Temp. Range (MAX921)
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 Adjustable Hysteresis
o TTL/CMOS-Compatible Outputs
o 12µs Propagation Delay (10mV Overdrive)
o No Switching Crowbar Current
o 40mA Continuous Source Current
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX921CPA
0°C to +70°C
8 Plastic DIP
MAX921CSA
0°C to +70°C
8 SO
MAX921CUA
0°C to +70°C
8 µMAX
MAX921C/D
0°C to +70°C
Dice*
MAX921EPA
-40°C to +85°C
8 Plastic DIP
MAX921ESA
-40°C to +85°C
8 SO
MAX921MJA
-55°C to +125°C 8 CERDIP**
Ordering Information continued at end of data sheet.
* Dice are tested at TA = +25°C, DC parameters only.
** Contact factory for availability and processing to MIL-STD-883.
__________Typical Operating Circuit
VIN
7
V+
3 IN+
4 IN-
OUT 8
5 HYST
6 REF
V-
2
MAX921
GND
1
THRESHOLD DETECTOR
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
Ultra Low-Power,
Single/Dual-Supply Comparators
__________________________________________Typical Operating Characteristics
(V+ = 5V, V- = GND, TA = +25°C, unless otherwise noted).
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
5
4
100mV
3
2
1 50mV
0
20mV
10mV
0
100
-2
2 6 10 14
RESPONSE TIME (µs)
18
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
5
4
3
100mV
2
1
50mV
0
100
0
10mV
20mV
-2 2 6 10 14 18
RESPONSE TIME (µs)
MAX924 RESPONSE TIME
AT LOW SUPPLY VOLTAGES
10
1
±20mV OVERDRIVE
0.1
±100mV
OVERDRIVE
0.01
1.0
1.5 2.0
SINGLE-SUPPLY VOLTAGE (V)
2.5
MAX924 RESPONSE TIME
AT LOW SUPPLY VOLTAGES
100
SOURCE CURRENT INTO 0.75V LOAD
10
1
SINK CURRENT AT VOUT = 0.4V
0.1
1.0 1.5 2.0
SINGLE-SUPPLY VOLTAGE (V)
2.5
SHORT-CIRCUIT SOURCE CURRENT
vs. SUPPLY VOLTAGE
200
180 OUT CONNECTED TO V-
160
140
120
100
80
60
40
20
0
0
1.0 2.0 3.0 4.0 5.0
TOTAL SUPPLY VOLTAGE (V)
SHORT-CIRCUIT SINK CURRENT
vs. SUPPLY VOLTAGE
OUT CONNECTED TO V+
GND CONNECTED TO V-
20
10
0
0
5
TOTAL SUPPLY VOLTAGE (V)
10
____________________________________________________________Pin Descriptions
PIN
MAX921 MAX922 MAX923
1––
–11
222
3––
–33
4––
–4–
NAME
GND
OUTA
V-
IN+
INA+
IN-
INA-
FUNCTION
Ground. Connect to V- for single-supply operation. Output swings from V+ to GND.
Comparator A output. Sinks and sources current. Swings from V+ to V-.
Negative supply. Connect to ground for single-supply operation (MAX921).
Noninverting comparator input
Noninverting input of comparator A
Inverting comparator input
Inverting input of comparator A
6 _______________________________________________________________________________________
6 Page Ultra Low-Power,
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
VOTH = 5.5V
VUTH = 4.5V
INA+
HYST
10k
R2 R5
REF
R4
2.4M
INB-
V-
R1
+5V
V+
OUTA
OUTB
MAX923
UNDERVOLTAGE
POWER GOOD
OVERVOLTAGE
Figure 6. Window Detector
Bar-Graph Level Gauge
The high output source capability of the MAX921 series
is useful for driving LEDs. An example of this is the
simple four-stage level detector shown in Figure 7.
The full-scale threshold (all LEDs on) is given by VIN =
(R1 + R2)/R1 volts. The other thresholds are at 3/4 full
scale, 1/2 full scale, and 1/4 full scale. The output
resistors limit the current into the LEDs.
Level Shifter
Figure 8 shows a circuit to shift from bipolar ±5V inputs
to TTL signals. The 10kΩ resistors protect the
comparator inputs, and do not materially affect the
operation of the circuit.
12 ______________________________________________________________________________________
12 Page | ||
Seiten | Gesamt 16 Seiten | |
PDF Download | [ MAX923 Schematic.PDF ] |
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