MAX922C/D [MAXIM]
Ultra Low-Power, Single/Dual-Supply Comparators; 超低功耗，单/双电源比较器
| 型号： | MAX922C/D |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Ultra Low-Power, Single/Dual-Supply Comparators |
| 文件： | 总16页 (文件大小：141K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0115; Rev 3; 3/95
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX921–MAX924 single, dual, and quad micro-
p owe r, low-volta g e c omp a ra tors fe a ture the lowe s t
power consumption available. These comparators draw
le s s tha n 4µA s up p ly c urre nt ove r te mp e ra ture
(MAX921/MAX922), a nd inc lud e a n inte rna l 1.182V
±1% voltage reference, programmable hysteresis, and
TTL/CMOS outputs that sink and source current.
♦ µMAX Package—Smallest 8-Pin SO
(MAX921/MAX922/MAX923)
♦ Ultra-Low 4µA Max Quiescent Current
Over Extended Temp. Range (MAX921)
♦ Power Supplies:
Single +2.5V to +11V
Dual ±1.25V to ±5.5V
Id e a l for 3V or 5V s ing le -s up p ly a p p lic a tions , the
MAX921–MAX924 operate from a single +2.5V to +11V
supply (or a ±1.25V to ±5V dual supply), and each
c omp a ra tor’s inp ut volta g e ra ng e s wing s from the
ne g a tive s up p ly ra il to within 1.3V of the p os itive
supply.
♦ Input Voltage Range Includes Negative Supply
♦ Internal 1.182V ±1% Bandgap Reference
♦ Adjustable Hysteresis
The MAX921–MAX924’s uniq ue outp ut s ta g e c on-
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.
♦ TTL/CMOS-Compatible Outputs
♦ 12µs Propagation Delay (10mV Overdrive)
♦ No Switching Crowbar Current
♦ 40mA Continuous Source Current
The single MAX921 and dual MAX923 provide a unique
a nd s imp le me thod for a d d ing hys te re s is without
feedback and complicated equations, simply by using
the HYST pin and two resistors.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
MAX921CPA
MAX921CSA
MAX921CUA
MAX921C/D
MAX921EPA
MAX921ESA
MAX921MJA
8 µMAX
Dice*
8 Plastic DIP
8 SO
8 CERDIP**
Ordering Information continued at end of data sheet.
Dice are tested at T = +25°C, DC parameters only.
** Contact factory for availability and processing to MIL-STD-883.
*
A
8-Pin
DIP/SO/µMAX
MAX921
MAX922
MAX923
MAX924
Yes
No
1
2
2
4
Yes
No
__________Typ ic a l Op e ra t in g Circ u it
8-Pin
DIP/SO/µMAX
V
IN
8-Pin
DIP/SO/µMAX
Yes
Yes
Yes
No
7
V+
16-Pin
DIP/SO/µMAX
3
IN+
OUT 8
4 IN-
________________________Ap p lic a t io n s
HYST
5
Battery-Powered Systems
Threshold Detectors
Window Comparators
Oscillator Circuits
MAX921
6 REF
GND
1
V-
2
THRESHOLD DETECTOR
________________________________________________________________ Maxim Integrated Products
1
Ca ll t o ll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 fo r fre e s a m p le s o r lit e ra t u re .
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
ABSOLUTE MAXIMUM RATINGS
V+ to V-, V+ to GND, GND to V-................................-0.3V, +12V
Inputs
Continuous Power Dissipation (T = +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ...727mW
A
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_ (MAX921/924) .....(V+ + 0.3V) to (GND – 0.3V)
Voltage OUT_ (MAX922/923)...........(V+ + 0.3V) to (V- – 0.3V)
OUT_ Short-Circuit Duration (V+ ≤ 5.5V) ...............Continuous
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)........640mW
16-Pin Plastic DIP (derate 10.53mW/°C above +70°C)..842mW
16-Pin SO (derate 8.70mW/°C above +70°C) ................696mW
16-Pin CERDIP (derate 10.00mW/°C above +70°C)......800mW
Operating Temperature Ranges:
MAX92_C_ _ .......................................................0°C to +70°C
MAX92_E_ _.....................................................-40°C to +85°C
MAX92_MJ_ ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
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.
1–MAX924
ELECTRICAL CHARACTERISTICS: 5V OPERATION
(V+ = 5V, V- = GND = 0V, T = T
A
to T , unless otherwise noted.)
MAX
MIN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
POWER REQUIREMENTS
Supply Voltage Range
(Note 1)
2.5
11
3.2
4
V
T
= +25°C
2.5
2.5
3.1
5.5
A
MAX921,
HYST = REF
C/E temp. ranges
M temp. range
5
T
A
= +25°C
3.2
4
MAX922
C/E temp. ranges
M temp. range
5
Supply Current
IN+ = IN- + 100mV
µA
T
A
= +25°C
4.5
6
MAX923,
HYST = REF
C/E temp. ranges
M temp. range
7.5
6.5
8.5
11
T
A
= +25°C
MAX924
C/E temp. ranges
M temp. range
COMPARATOR
Input Offset Voltage
V
= 2.5V
±10
±5
mV
nA
CM
C/E temp. ranges
M temp. range
±0.01
±0.02
Input Leakage Current (IN-, IN+)
Input Leakage Current (HYST)
IN+ = IN- = 2.5V
MAX921, MAX923
±40
nA
V
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
Voltage Noise
V-
V+ – 1.3
1.0
V- to (V+ – 1.3V)
V+ = 2.5V to 11V
100Hz to 100kHz
MAX921, MAX923
0.1
0.1
20
mV/V
mV/V
1.0
µV
RMS
Hysteresis Input Voltage Range
REF- 0.05V
REF
V
Overdrive = 10mV
Overdrive = 100mV
12
4
Response Time
T
A
= +25°C, 100pF load
µs
2
_______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
ELECTRICAL CHARACTERISTICS: 5V OPERATION (continued)
(V+ = 5V, V- = GND = 0V, T = T
A
to T , unless otherwise noted.)
MAX
MIN
PARAMETER
CONDITIONS
C/E temp. ranges: I
MIN
TYP
MAX
UNITS
= 17mA;
= 10mA
OUT
OUT
OUT
Output High Voltage
MAX92_
V+ – 0.4
V
M temp. range: I
OUT
MAX922/ C/E temp. ranges: I
= 1.8mA;
= 1.2mA
V- + 0.4
MAX923 M temp. range: I
OUT
Output Low Voltage
V
MAX921/ C/E temp. ranges: I
MAX924 M temp. range: I
= 1.8mA;
= 1.2mA
GND + 0.4
OUT
REFERENCE (MAX921/MAX923/MAX924 ONLY)
C temp. range
E temp. range
M temp. range
1.170
1.182
25
1.194
1.206
1.217
Reference Voltage
1.158
V
1.147
T
A
= +25°C
15
6
Source Current
Sink Current
C/E temp. ranges
M temp. range
µA
µA
4
T
A
= +25°C
8
15
C/E temp. ranges
M temp. range
4
2
Voltage Noise
100Hz to 100kHz
100
µV
RMS
Note 1: MAX924 comparators work below 2.5V, see Low-Voltage Operation section for more details.
ELECTRICAL CHARACTERISTICS: 3V OPERATION
(V+ = 3V, V- = GND = 0V, T = T
A
to T , unless otherwise noted.)
MAX
MIN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
POWER REQUIREMENTS
T
= +25°C
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
A
MAX921 C/E temp. ranges
M temp. range
T
A
= +25°C
2.4
3.4
5.2
MAX922 C/E temp. ranges
M temp. range
HYST = REF,
IN+ = (IN- + 100mV)
Supply Current
µA
T
A
= +25°C
MAX923
C/E temp. ranges
M temp. range
T
A
= +25°C
MAX924 C/E temp. ranges
M temp. range
COMPARATOR
Input Offset Voltage
V
= 1.5V
±10
±5
mV
nA
nA
CM
C/E temp. ranges
M temp. range
±0.01
±0.02
Input Leakage Current (IN-, IN+)
Input Leakage Current (HYST)
IN+ = IN- = 1.5V
MAX921, MAX923
±40
_______________________________________________________________________________________
3
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
ELECTRICAL CHARACTERISTICS: 3V OPERATION (continued)
(V+ = 3V, V- = GND = 0V, T = T
A
to T , unless otherwise noted.)
MAX
MIN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
Voltage Noise
V-
V+ – 1.3
V
V- to (V+ – 1.3V)
V+ = 2.5V to 11V
100Hz to 100kHz
MAX921, MAX923
0.2
0.1
20
1
1
mV/V
mV/V
µV
RMS
Hysteresis Input Voltage Range
REF- 0.05V
V+ – 0.4
REF
V
Overdrive = 10mV
Overdrive = 100mV
14
5
Response Time
T
A
= +25°C, 100pF load
µs
C/E temp. ranges: I
M temp. range: I
= 10mA;
= 6mA
OUT
OUT
OUT
Output High Voltage
MAX92_
V
V
OUT
MAX922/ C/E temp. ranges: I
MAX923 M temp. range: I
= 0.8mA;
= 0.6mA
V- + 0.4
OUT
1–MAX924
Output Low Voltage
MAX921/ C/E temp. ranges: I
MAX924 M temp. range: I
= 0.8mA;
GND + 0.4
= 0.6mA
OUT
REFERENCE
C temp. range
E temp. range
M temp. range
1.170
1.182
25
1.194
1.206
1.217
Reference Voltage
1.158
V
1.147
T
A
= +25°C
15
6
Source Current
C/E temp. ranges
M temp. range
µA
µA
4
T
A
= +25°C
8
15
Sink Current
C/E temp. ranges
M temp. range
4
2
Voltage Noise
100Hz to 100kHz
100
µV
RMS
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V+ = 5V, V- = GND, T = +25°C, unless otherwise noted).
A
OUTPUT VOLTAGE LOW
vs. LOAD CURRENT
OUTPUT VOLTAGE HIGH vs.
LOAD CURRENT
REFERENCE OUTPUT VOLTAGE vs.
OUTPUT LOAD CURRENT
2.5
2.0
5.0
1.190
V+ = 5V
SINK
V+ = 5V
4.5
4.0
1.185
1.180
V+ = 3V
SOURCE
1.5
1.0
3.5
3.0
2.5
2.0
1.5
1.175
1.170
1.165
1.160
1.155
V+ = 3V
V+ = 5V
OR
0.5
0.0
V+ = 3V
0
4
8
12
16
20
0
10
20
30
40
50
0
5
10
15
20
25
30
LOAD CURRENT (mA)
LOAD CURRENT (mA)
OUTPUT LOAD CURRENT (µA)
4
_______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1-MAX924
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V+ = 5V, V- = GND, T = +25°C, unless otherwise noted).
A
MAX921
REFERENCE VOLTAGE
vs. TEMPERATURE
MAX922
SUPPLY CURRENT vs.
TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
1.22
1.21
4.5
4.0
4.5
4.0
IN+ = (IN- + 100mV)
V+ = 10V, V- = 0V
IN+ = IN- + 100mV
MILITARY TEMP. RANGE
EXTENDED TEMP. RANGE
1.20
1.19
3.5
3.0
2.5
2.0
1.5
V+ = 5V, V- = - 5V
COMMERCIAL
TEMP. RANGE
3.5
3.0
1.18
1.17
V+ = 3V, V- = 0V
V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
1.16
1.15
2.5
2.0
V+ = 5V, V- = 0V
1.14
-60 -40 -20
0
20 40 60 80 100 120 140
-60
-20
20
60
100
140
-60
-20
20
60
100
140
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX924
SUPPLY CURRENT vs.
LOW SUPPLY VOLTAGES
MAX924
MAX923
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
10
9
5.0
10
IN+ = (IN- + 100mV)
4.5
4.0
8
1
V+ = 5V, V- = 0V
7
V+ = 5V, V- = -5V
3.5
3.0
2.5
2.0
6
0.1
V+ = 5V, V- = 0V
V+ = 3V, V- = 0V
5
4
V+ = 3V, V- = 0V
3
0.01
-60
-20
20
60
100
140
-60
-20
20
60
100
140
1.0
1.5
2.0
2.5
TEMPERATURE (°C)
TEMPERATURE (°C)
SINGLE-SUPPLY VOLTAGE (V)
RESPONSE TIME vs.
LOAD CAPACITANCE
TRANSFER FUNCTION
HYSTERESIS CONTROL
5.0
4.5
80
60
18
16
V- = 0V
100k
V
0
OUTPUT HIGH
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
10µF
40
20
14
12
V
OHL
0
NO CHANGE
10
8
-20
V
OLH
-40
-60
6
4
OUTPUT LOW
10
-80
2
-0.3
-0.1
0.1
0.2
0.3
0
20
-V
30
(mV)
40
50
-0.2
0
0
20
40
60
80
100
IN+ INPUT VOLTAGE (mV)
V
LOAD CAPACITANCE (nF)
REF HYST
_______________________________________________________________________________________
5
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V+ = 5V, V- = GND, T = +25°C, unless otherwise noted).
A
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
RESPONSE TIME FOR VARIOUS
INPUT OVERDRIVES
MAX924 RESPONSE TIME
AT LOW SUPPLY VOLTAGES
10
5
5
4
3
4
3
100mV
50mV
10mV
1
20mV
100mV
2
1
2
1
20mV
50mV
10mV
0
100
0
0
±20mV OVERDRIVE
0.1
±100mV
OVERDRIVE
0
100
1–MAX924
0.01
-2
2
6
10
14
18
1.0
1.5
2.0
2.5
-2
2
6
10
14
18
RESPONSE TIME (µs)
SINGLE-SUPPLY VOLTAGE (V)
RESPONSE TIME (µs)
SHORT-CIRCUIT SOURCE CURRENT
vs. SUPPLY VOLTAGE
SHORT-CIRCUIT SINK CURRENT
vs. SUPPLY VOLTAGE
MAX924 RESPONSE TIME
AT LOW SUPPLY VOLTAGES
200
100
OUT CONNECTED TO V+
GND CONNECTED TO V-
180
160
140
120
100
80
OUT CONNECTED TO V-
SOURCE CURRENT INTO 0.75V LOAD
20
10
1
10
0
60
40
20
SINK CURRENT AT V
OUT
= 0.4V
2.0
0
0.1
0
1.0
2.0
3.0
4.0
5.0
0
5
10
1.0
1.5
2.5
TOTAL SUPPLY VOLTAGE (V)
TOTAL SUPPLY VOLTAGE (V)
SINGLE-SUPPLY VOLTAGE (V)
____________________________________________________________P in De s c rip t io n s
PIN
NAME
FUNCTION
MAX921 MAX922 MAX923
1
–
2
3
–
4
–
–
1
2
–
3
–
4
–
1
2
–
3
–
–
GND
OUTA
V-
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
IN+
INA+
IN-
Noninverting input of comparator A
Inverting comparator input
INA-
Inverting input of comparator A
6
_______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
_______________________________________________P in De s c rip t io n s (c o n t in u e d )
PIN
NAME
FUNCTION
MAX921 MAX922 MAX923
–
5
5
–
4
5
INB-
Inverting input of comparator B
Hysteresis input. Connect to REF if not used. Input voltage range is from
HYST
V
to V - 50mV.
REF
REF
6
–
7
8
–
–
6
7
–
8
6
–
7
–
8
REF
INB+
V+
Reference output. 1.182V with respect to V-.
Noninverting input of comparator B
Positive supply
OUT
OUTB
Comparator output. Sinks and sources current. Swings from V+ to GND.
Comparator B output. Sinks and sources current. Swings from V+ to V-.
PIN
MAX924
NAME
FUNCTION
1
2
OUTB
OUTA
V+
Comparator B output. Sinks and sources current. Swings from V+ to GND.
Comparator A output. Sinks and sources current. Swings from V+ to GND.
Positive supply
3
4
INA-
INA+
INB-
INB+
REF
Inverting input of comparator A
5
Noninverting input of comparator A
6
Inverting input of comparator B
7
Noninverting input of comparator B
8
Reference output. 1.182V with respect to V-.
Negative supply. Connect to ground for single-supply operation.
Inverting input of comparator C
9
V-
10
11
12
13
14
15
16
INC-
INC+
IND-
IND+
GND
OUTD
OUTC
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 output. Sinks and sources current. Swings from V+ to GND.
Comparator C output. Sinks and sources current. Swings from V+ to GND.
_______________________________________________________________________________________
7
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
s e p a ra te g round for the outp ut d rive r, a llowing
_______________De t a ile d De s c rip t io n
operation with dual supplies ranging from ±1.25V to
± 5.5V. Conne c t V- to GND whe n op e ra ting the
MAX921 and the MAX924 from a single supply. The
maximum supply voltage in this case is still 11V.
The MAX921–MAX924 comprise various combinations
of a micropower 1.182V reference and a micropower
comparator. The Typical Operating Circuit shows the
MAX921 configuration, and Figures 1a-1c show the
MAX922–MAX924 configurations.
For proper comparator operation, the input signal can
swing from the negative supply (V-) to within one volt of
the p os itive s up p ly (V+ – 1V). The g ua ra nte e d
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.
Each comparator continuously sources up to 40mA,
a nd the uniq ue outp ut s ta g e e limina te s c rowb a r
glitches during output transitions. This makes them
immune to p a ra s itic fe e d b a c k (whic h c a n c a us e
instability) and provides excellent performance, even
when circuit-board layout is not optimal.
Operating the MAX921 and MAX924 at ±5V provides
TTL/CMOS compatibility when monitoring bipolar input
signals. TTL compatibility for the MAX922 and MAX923
is achieved by operation from a single +5V supply.
Internal hysteresis in the MAX921 and MAX923 provides
the easiest method for implementing hysteresis. It also
produces faster hysteresis action and consumes much
less current than circuits using external positive feedback.
1–MAX924
Low-Voltage Operation: V+ = 1V (MAX924 Only)
The guaranteed minimum operating voltage is 2.5V (or
±1.25V). As the total supply voltage is reduced below
2.5V, the p e rforma nc e d e g ra d e s a nd the s up p ly
current falls. The reference will not function below
P o w e r-S u p p ly a n d In p u t S ig n a l Ra n g e s
This family of devices operates from a single +2.5V to
+11V power supply. The MAX921 and MAX924 have a
MAX922
OUTA
OUTB 8
1
2
3
V-
V+ 7
MAX924
1
2
3
4
OUTC 16
OUTD 15
OUTB
OUTA
INA+
INB+ 6
4 INA-
INB-
5
V+
GND 14
IND+ 13
IND- 12
INA-
Figure 1a. MAX922 Functional Diagram
5 INA+
INB-
6
INC+ 11
INC- 10
V- 9
MAX923
OUTA
OUTB 8
1
2
3
7 INB+
V-
V+ 7
REF 6
8
REF
INA+
4 INB-
HYST 5
V-
Figure 1c. MAX924 Functional Diagram
Figure 1b. MAX923 Functional Diagram
8
_______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
The MAX921–MAX924’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
ma ximum p owe r d is s ip a tion is not e xc e e d e d . The
outp ut s ta g e d oe s not g e ne ra te c rowb a r s witc hing
currents during transitions, which minimizes feedback
through the supplies and helps ensure stability without
bypassing.
THRESHOLDS
IN+
HYSTERESIS
BAND
IN-
VREF - VHYST
V
HB
Vo lt a g e Re fe re n c e
The internal bandgap voltage reference has an output
of 1.182V a b ove V-. Note tha t the REF volta g e is
referenced to V-, not to GND. Its accuracy is ±1% 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.
OUT
Figure 2. Threshold Hysteresis Band
No is e Co n s id e ra t io n s
Although the comparators have a very high gain, useful
gain is limited by noise. This is shown in the Transfer
about 2.2V, although the comparators will continue to
operate with a total supply voltage as low as 1V. While
the MAX924 has comparators that may be used at
supply voltages below 2V, the MAX921, MAX922, and
MAX923 may not be used with supply voltages sig-
nificantly below 2.5V.
Function graph (see Typical Operating Characteristics).
As the inp ut volta g e a p p roa c he s the c omp a ra tor's
offset, the output begins to bounce back and forth; this
peaks when
V
= V . (The lowpass filter shown on
IN OS
the g ra p h a ve ra g e s out the b ounc ing , ma king the
transfer function easy to observe.) Consequently, the
comparator has an effective wideband peak-to-peak
nois e of a round 0.3mV. The volta g e re fe re nc e ha s
peak-to peak noise approaching 1mV. Thus, when a
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 und e r 1V b e low the p os itive s up p ly, whic h is
s lig htly c los e r to the p os itive ra il tha n the d e vic e
op e ra ting from hig he r s up p ly volta g e s . Te s t your
prototype over the full temperature and supply-voltage
range if operation below 2.5V is anticipated.
2.5V TO 11V
7
I
REF
6
5
V+
REF
Co m p a ra t o r Ou t p u t
With 100mV of overdrive, propagation delay is typically
3µs. The Typical Operating Characteristics show the
propagation delay for various overdrive levels.
R1
R2
MAX921
MAX923
HYST
V-
2
The MAX921 and MAX924 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 MAX922 and MAX923 have no GND pin, and their
outputs swing from V+ to V-. Connect V- to ground and
V+ to a +5V supply to achieve TTL compatibility.
Figure 3. Programming the HYST Pin
_______________________________________________________________________________________
9
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
comparator is used with the reference, the combined
peak-to-peak noise is about 1mV. This, of course, is
muc h hig he r tha n the RMS nois e of the ind ivid ua l
components. Care should be taken in the layout to
a void c a p a c itive c oup ling from a ny outp ut to the
reference pin. Crosstalk can significantly increase the
actual noise of the reference.
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 /R3,
REF
or 100nA for R3 = 11.8MΩ. 10MΩ is a g ood
practical value.
__________Ap p lic a t io n s In fo rm a t io n
2. Choose the hysteresis voltage (V ), the voltage
between the upper and lower thresholds. In this
example, choose V = 50mV.
HB
Hys t e re s is
Hysteresis increases the comparators’ noise margin by
increasing the upper threshold and decreasing the
lower threshold (see Figure 2).
HB
3. Calculate R1.
V
HB
R1 = R3 ×
Hysteresis (MAX921/MAX923)
To add hysteresis to the MAX921 or MAX923, connect
re s is tor R1 b e twe e n REF a nd HYST, a nd c onne c t
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
V +
0.05
= 10M ×
= 100kΩ
1–MAX924
5
4. Choose the threshold voltage for V rising (V ).
In this example, choose V
IN
THR
= 3V.
THR
5. Calculate R2.
and lower thresholds, V ) is approximately equal to
HB
1
twice the voltage between REF and HYST. The HYST
input can be adjusted to a maximum voltage of REF
a nd to a minimum volta g e 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:
R2 =
V
1
1
THR
−
−
(V
R1 R3
REF × R1)
1
=
3
1
1
−
−
V
HB
R1 =
(1.182 × 100k)
100k 10M
2 × I
(
)
REF
= 65.44kΩ
A 1% preferred value is 64.9kΩ.
V
HB
1.182 –
2
R2 =
I
REF
V+
Whe re I
(the c urre nt s ourc e d b y the re fe re nc e )
REF
R3
s hould not e xc e e d the REF s ourc e c a p a b ility, a nd
s hould b e s ig nific a ntly la rg e r tha n the HYST inp ut
R1
c urre nt.
I
va lue s b e twe e n 0.1µA a nd 4µA a re
REF
V
IN
usually appropriate. If 2.4MΩ is chosen for R2 (I
=
REF
0.5µA), the e q ua tion for R1 a nd
approximated as:
V
HB
c a n b e
V+ OUT
V-
R2
MAX924
GND
R1 (kΩ) = V (mV)
HB
Whe n hys te re s is is ob ta ine d in this ma nne r for the
MAX923, the same hysteresis applies to both comparators.
V
REF
Hysteresis (MAX922/MAX924)
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
p in on the MAX921 a nd MAX923, a nd the hig h
Figure 4. External Hysteresis
10 ______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
_______________Typ ic a l Ap p lic a t io n s
MOMENTARY
SWITCH
Au t o -Off P o w e r S o u rc e
Figure 5 shows the schematic for a 40mA power supply
tha t ha s a time d a uto p owe r-off func tion. The
c omp a ra tor outp ut is the s witc he d p owe r-s up p ly
outp ut. With a 10mA loa d , it typ ic a lly p rovid e s a
4.5V TO 6.0V
7
V+
volta g e of (V
– 0.12V), b ut d ra ws only 3.5µA
BATT
quiescent current. This circuit takes advantage of the
four key features of the MAX921: 2.5µA supply current,
a n inte rna l re fe re nc e , hys te re s is , a nd hig h c urre nt
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.
MAX921
IN+ 3
6
REF
47k
R
C
5
HYST
1.1M
100k
OUT 8
VBATT -0.15V
10mA
4 IN-
The RC time constant determines the maximum power-
on time of the OUT pin before power-down occurs.
This period can be approximated by:
V-
GND
1
2
R x C x 4.6sec
For example: 2MΩ x 10µF x 4.6 = 92sec. The actual
time will va ry with b oth the le a ka g e c urre nt of the
capacitor and the voltage applied to the circuit.
Figure 5. Auto-off power switch operates on 2.5µA quiescent
current.
Win d o w De t e c t o r
The MAX923 is id e a l for ma king wind ow d e te c tors
(undervoltage/overvoltage detectors). The schematic
is shown in Figure 6, with component values selected
for a n 4.5V und e rvolta g e thre s hold , a nd 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 active-
high, power-good signal.
6. Verify the threshold voltages with these formulas:
V
rising :
IN
1
1
1
V
= V
× R1 ×
+
+
THR
REF
R1
R2
R3
V
falling :
IN
R1 × V +
(
−
THR
)
V
= V
THF
R3
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 (MAX921/MAX923) section. In this
example, ±5mV of hysteresis has been added at the
Bo a rd La yo u t a n d Byp a s s in g
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.
comparator input (V = V /2). This means that the
H
HB
hysteresis apparent at V will be larger because of
IN
the input resistor divider.
______________________________________________________________________________________ 11
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
2. Select R1. The leakage current into INB- is normally
und e r 1nA, s o the c urre nt throug h R1 s hould
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.
V
V
UTH
= 5.5V
= 4.5V
V
IN
OTH
+5V
V+
R3
INA+
3. Ca lc ula te R2 + R3. The ove rvolta g e thre s hold
OUTA
s hould b e 5.5V whe n V is ris ing . The d e s ig n
equation is as follows:
UNDERVOLTAGE
POWER GOOD
IN
HYST
REF
V
OTH
+ V
H
R2 + R3 = R1 ×
− 1
10k
R5
V
R2
REF
5.5
(1.182 + 0.005)
= 294k ×
− 1
R4
2.4M
OUTB
OVERVOLTAGE
= 1.068MΩ
INB-
1–MAX924
V-
4. Calculate R2. The undervoltage threshold should
MAX923
R1
be 4.5V when V is falling. The design equation is
IN
as follows:
(V
− V )
H
REF
R2 = (R1 + R2 + R3) ×
− R1
V
UTH
(1.182 − 0.005)
= (294k + 1.068M) ×
= 62.2kΩ
− 294k
Figure 6. Window Detector
4.5
Choose R2 = 61.9kΩ (1% standard value).
Ba r-Gra p h Le ve l Ga u g e
5. Calculate R3.
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.
R3 = (R2 + R3) − R2
= 1.068M − 61.9k
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.
= 1.006MΩ
Choose R3 = 1MΩ (1% standard value)
6. Verify the resistor values. The equations are as
follows, evaluated for the above example.
Le ve l S h ift e r
Figure 8 shows a circuit to shift from bipolar ±5V inputs
to TTL s ig na ls . The 10kΩ re s is tors p rote c t the
comparator inputs, and do not materially affect the
operation of the circuit.
Overvoltage threshold :
(R1 + R2 + R3)
V
= (V
+ V ) ×
OTH
REF H
R1
= 5.474V.
Undervoltage threshold :
(R1 + R2 + R3)
V
= (V
− V ) ×
UTH
REF H
(R1 + R2)
= 4.484V,
R5
R4
where the hysteresis voltage V = V
×
REF
.
H
12 ______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
R2
R1
V
IN
+5V
+5V
3
V+
V+
MAX924
10k
10k
MAX924
INA+
1.182V
8
5
4
7
6
REF
V
INA
OUTA
0 FOR V < 0V
INA
V-
9
1 FOR V > 0V
INB
INA-
INB+
INB-
INA+
182k
250k
250k
OUTA 2
330Ω
330Ω
330Ω
330Ω
1V
INA-
INB+
INB-
V
INB
OUTB
OUTC
1
OUTB
OUTC
OUTD
10k
10k
INC+
INC-
IND+
IND-
750mV
V
INC
11 INC+
16
15
500mV 10 INC-
V
IND
OUTD
REF
13
IND+
250k
250k
N.C.
250mV 12 IND-
V-
GND
GND
14
-5V
Figure 7. Bar-Graph Level Gauge
Figure 8. Level Shifter: ±5V Input to CMOS Output
______________________________________________________________________________________ 13
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
_________________P in Co n fig u ra t io n s
_Ord e rin g In fo rm a t io n (c o n t in u e d )
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
TOP VIEW
MAX922CPA
MAX922CSA
MAX922CUA
MAX922C/D
MAX922EPA
MAX922ESA
MAX922MJA
MAX923CPA
MAX923CSA
MAX923CUA
MAX923C/D
MAX923EPA
MAX923ESA
MAX923MJA
MAX924CPE
MAX924CSE
MAX924C/D
MAX924EPE
MAX924ESE
MAX924MJE
1
2
3
4
8
7
6
5
GND
V-
OUT
V+
8 µMAX
Dice*
MAX921
REF
IN+
IN-
8 Plastic DIP
8 SO
HYST
8 CERDIP**
8 Plastic DIP
8 SO
DIP/SO/µMAX
8 µMAX
1
2
3
4
8
7
6
5
OUTA
V-
OUTB
V+
Dice*
8 Plastic DIP
8 SO
MAX922
1–MAX924
INB+
INB-
INA+
INA-
8 CERDIP**
16 Plastic DIP
16 Narrow SO
Dice*
DIP/SO/µMAX
16 Plastic DIP
16 Narrow SO
16 CERDIP**
1
2
3
4
8
7
6
5
OUTA
V-
OUTB
V+
MAX923
REF
*
Dice are tested at T = +25°C, DC parameters only.
A
** Contact factory for availability and processing to MIL-STD-883.
INA+
INB-
HYST
DIP/SO/µMAX
OUTB
OUTA
V+
OUTC
OUTD
GND
IND+
IND-
INC+
INC-
V-
1
16
15
14
13
12
11
10
9
2
3
4
5
6
7
8
INA-
MAX924
INA+
INB-
INB+
REF
DIP/Narrow SO
14 ______________________________________________________________________________________
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
1–MAX924
__________________________________________________________Ch ip To p o g ra p h ie s
MAX921/MAX922/MAX923
MAX924
OUTB OUTC
OUTA
OUTD
10
V+
1
9
8
2
3
GND
0. 075"
(1. 91mm)
4
5
7
6
0. 108"
(2. 74mm)
IND+
INA-
IND-
INC+
INA+
0. 059"
INB-
(1. 50mm)
INB+ REF V- INC-
DIE PAD
MAX921
GND
V-
MAX922
OUTA
V-
MAX923
OUTA
V-
0. 069"
1
2
(1. 75mm)
3
V-
V-
V-
4
IN+
INA+
INA-
INB-
INB+
V+
INA+
INB-
HYST
REF
TRANSISTOR COUNT: 267
SUBSTRATE CONNECTED TO V+
5
IN-
6
HYST
REF
V+
7
8
V+
9
V+
V+
V+
10
OUT
OUTB
OUTB
TRANSISTOR COUNT: 164
SUBSTRATE CONNECTED TO V+
______________________________________________________________________________________ 15
Ult ra Lo w -P o w e r,
S in g le /Du a l-S u p p ly Co m p a ra t o rs
_______________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.036
MAX
0.044
0.008
0.014
0.007
0.120
0.120
MIN
0.91
0.10
0.25
0.13
2.95
2.95
MAX
1.11
0.20
0.36
0.18
3.05
3.05
A
C
A1 0.004
α
A
B
C
D
E
e
0.010
0.005
0.116
0.116
0.101mm
0.004 in
e
B
A1
L
0.0256
0.65
H
L
0.188
0.016
0°
0.198
0.026
6°
4.78
0.41
0°
5.03
0.66
6°
α
21-0036D
1–MAX924
E
H
8-PIN µMAX
MICROMAX SMALL-OUTLINE
PACKAGE
D
INCHES
MILLIMETERS
DIM
MIN
MAX
0.069
0.010
0.019
0.010
0.157
MIN
1.35
0.10
0.35
0.19
3.80
MAX
1.75
0.25
0.49
0.25
4.00
A
0.053
D
A1 0.004
B
C
E
e
0.014
0.007
0.150
0°-8°
A
0.101mm
0.004in.
0.050
1.27
e
H
L
0.228
0.016
0.244
0.050
5.80
0.40
6.20
1.27
A1
C
B
L
INCHES
MILLIMETERS
DIM PINS
Narrow SO
SMALL-OUTLINE
PACKAGE
MIN MAX
MIN
MAX
5.00
8.75
8
0.189 0.197 4.80
D
D
D
E
H
14 0.337 0.344 8.55
16 0.386 0.394 9.80 10.00
21-0041A
(0.150 in.)
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 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1995 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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