For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
General Description
The MAX917–MAX920 nanopower comparators in
space-saving SOT23 packages feature Beyond-the-
Rails™ inputs and are guaranteed to operate down to
+1.8V. The MAX917/MAX918 feature an on-board
1.245V ±1.5% reference and draw an ultra-low supply
current of only 750nA, while the MAX919/MAX920 (with-
out reference) require just 380nA of supply current.
These features make the MAX917–MAX920 family of
comparators ideal for all 2-cell battery applications,
including monitoring/management.
The unique design of the output stage limits supply-cur-
rent surges while switching, virtually eliminating the
supply glitches typical of many other comparators. This
design also minimizes overall power consumption
under dynamic conditions. The MAX917/MAX919 have
a push-pull output stage that sinks and sources current.
Large internal output drivers allow rail-to-rail output
swing with loads up to 8mA. The MAX918/MAX920
have an open-drain output stage that makes them suit-
able for mixed-voltage system design.
Applications
2-Cell Battery Monitoring/Management
Ultra-Low-Power Systems
Mobile Communications
Notebooks and PDAs
Threshold Detectors/Discriminators
Sensing at Ground or Supply Line
Telemetry and Remote Systems
Medical Instruments
Features
♦Ultra-Low Supply Current
380nA per Comparator (MAX919/MAX920)
750nA per Comparator with Reference
(MAX917/MAX918)
♦Guaranteed to Operate Down to +1.8V
♦Internal 1.245V ±1.5% Reference
(MAX917/MAX918)
♦Input Voltage Range Extends 200mV
Beyond-the-Rails
♦CMOS Push-Pull Output with ±8mA Drive
Capability (MAX917/MAX919)
♦Open-Drain Output Versions Available
(MAX918/MAX920)
♦Crowbar-Current-Free Switching
♦Internal Hysteresis for Clean Switching
♦No Phase Reversal for Overdriven Inputs
♦Space-Saving SOT23 Package
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
________________________________________________________________ Maxim Integrated Products 1
VEE
IN- (REF)
IN+
15VCC
OUT
MAX917
MAX918
MAX919
MAX920
SOT23
TOP VIEW
2
34
( ) ARE FOR MAX917/MAX918.
PART PIN-PACKAGE TOP
MARK
PKG
CODE
MAX917EUK+T 5 SOT23 ADIQ U5+1
MAX917ESA+ 8 SO —S8+2
MAX918EUK+T 5 SOT23 ADIR U5+1
MAX918ESA+ 8 SO —S8+2
MAX919EUK+T 5 SOT23 ADIS U5+1
MAX919EUK/V+T 5 SOT23 AFGP U5+1
MAX919ESA+ 8 SO —S8+2
MAX920EUK+T 5 SOT23 ADIT U5+1
MAX920ESA+ 8 SO —S8+2
Pin Configurations continue at end of data sheet.
Typical Application Circuit appears at end of data sheet.
Pin Configurations
Selector Guide
Ordering Information
Open-DrainYesMAX918 750
380
380
750
SUPPLY
CURRENT
(nA)
Open-DrainNoMAX920
PART
Push-PullNoMAX919
Push-PullYesMAX917
OUTPUT
TYPE
INTERNAL
REFERENCE
Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc.
19-1512; Rev 2; 10/10
Note: All devices are specified over the -40°C to +85°C operating
temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS—MAX917/MAX918
(VCC = +5V, VEE = 0V, VIN+ = VREF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
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.
Supply Voltage (VCC to VEE)..................................................+6V
Voltage Inputs (IN+, IN-, REF) .........(VEE - 0.3V) to (VCC + 0.3V)
Current Into Input Pins......................................................±20mA
Output Voltage
MAX917/MAX919 ........................(VEE - 0.3V) to (VCC + 0.3V)
MAX918/MAX920 ......................................(VEE - 0.3V) to +6V
Output Current..................................................................±50mA
Output Short-Circuit Duration .............................................10sec
Continuous Power Dissipation (TA= +70°C)
5-Pin SOT23 (derate 7.31mW/°C above +70°C).........571mW
8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
VCC = 1.8V
VCC = 1.8V
VCC = 5V
VCC = 1.8V
VCC = 5V
Output-Voltage Swing Low VOL
190 400
mV
500
55 200
TA= TMIN to TMAX
TA= +25°C
300
VCC = 5V,
ISINK = 8mA TA= TMIN to TMAX
VCC = 1.8V,
ISINK = 1mA
TA= +25°C
TA= TMIN to TMAX
TA= +25°C
TA= TMIN to TMAX
TA= +25°C
TA= TMIN to TMAX
TA= +25°C
TA= TMIN to TMAX
TA= +25°C
TA= TMIN to TMAX
TA= +25°C
PARAMETER SYMBOL MIN TYP MAX UNITS
10
Input Offset Voltage VOS
15
mV
IN+ Voltage Range VIN+ VEE - 0.2 VCC + 0.2 V
1.60
Input-Referred Hysteresis VHB 4mV
Input Bias Current IB
0.15 1 nA
2
Power-Supply Rejection Ratio PSRR 0.1 1 mV/V
Supply Current
Supply Voltage Range VCC 1.8 5.5 V
ICC
0.75
µA
0.80 1.30
Output-Voltage Swing High VCC - VOH
190 400
mV
500
55 200
300
Output Leakage Current ILEAK 0.001 1 µA
Output Short-Circuit Current ISC
95
mA
8
98
10
CONDITIONS
MAX917 only, VCC =
5V, ISOURCE = 8mA
(Note 2)
Inferred from the output swing test
(Note 3)
MAX917 only, VCC =
1.8V, ISOURCE = 1mA
VCC = 1.8V to 5.5V
MAX918 only, VO= 5.5V
Sourcing, VO= VEE
Inferred from the PSRR test
Sinking, VO= VCC
VCC = 5V
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS—MAX919/MAX920
(VCC = +5V, VEE = 0V, VCM = 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
VCC = 1.8V
VCC = 5V
Inferred from the PSRR test
-0.2V ≤VCM ≤(VCC + 0.2V) (Note 3)
TA= +25°C
Inferred from the CMRR test
-0.2V ≤VCM ≤
(VCC + 0.2V) (Note 2)
TA= +25°C
CONDITIONS
TA= TMIN to TMAX
0.45 0.80 µA
0.38
ICC
V1.8 5.5VCC
Supply Voltage Range
Supply Current
nA
0.15 1
IB
Input Bias Current
mV4VHB
Input-Referred Hysteresis
1.2
TA= +25°C
VVEE - 0.2 VCC + 0.2VCM
Input Common-Mode
Voltage Range
mV
15
VOS
Input Offset Voltage 10
UNITSMIN TYP MAXSYMBOLPARAMETER
TA= TMIN to TMAX
2TA= TMIN to TMAX
VCC = 5V,
RPULLUP = 100kΩ
VCC = 1.8V,
RPULLUP = 100kΩ
VCC = 5V
VCC = 1.8V
VCC = 1.8V
MAX917 only 95
µs
30
tPD+
Low-to-High Propagation Delay
(Note 4) 35
MAX918 only
120
µs
95
CONDITIONS
TA = +25°C
ms1.2
22
17
tPD-
High-to-Low Propagation Delay
(Note 4)
tON
Power-Up Time
ΔIOUT = 10nA mV/nA±0.2
ΔVREF/
ΔIOUT
Reference Load Regulation
UNITS
MIN TYP MAXSYMBOL
PARAMETER
CL= 15pF
1.8V ≤VCC ≤5.5V
BW = 10Hz to 100kHz, CREF = 1nF
MAX917 only, CL= 15pF
VCC = 5V
BW = 10Hz to 100kHz
TA = TMIN to TMAX
mV/V0.1
ΔVREF/
ΔVCC
Reference Line Regulation
215 µVRMS
en
Reference Output
Voltage Noise
1.200 1.290 V
1.227 1.245 1.263
VREF
Reference Voltage
µs4tFALL
Fall Time
µs6tRISE
Rise Time
ppm/°CTCREF
Reference Voltage Temperature
Coefficient
600
ELECTRICAL CHARACTERISTICS—MAX917/MAX918 (continued)
(VCC = +5V, VEE = 0V, VIN+ = VREF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS—MAX919/MAX920 (continued)
(VCC = +5V, VEE = 0V, VCM = 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1: All specifications are 100% tested at TA= +25°C. Specification limits over temperature (TA= TMIN to TMAX) are guaranteed
by design, not production tested.
Note 2: VOS is defined as the center of the hysteresis band at the input.
Note 3: The hysteresis-related trip points are defined as the edges of the hysteresis band, measured with respect to the center of
the band (i.e., VOS) (Figure 2).
Note 4: Specified with an input overdrive (VOVERDRIVE) of 100mV, and load capacitance of CL= 15pF. VOVERDRIVE is defined
above and beyond the offset voltage and hysteresis of the comparator input. For the MAX917/MAX918, reference voltage
error should also be added.
Sinking, VO= VCC
Sourcing, VO= VEE
MAX920 only, VO= 5.5V
TA= +25°C
TA= +25°C
MAX919 only, VCC =
1.8V, ISOURCE = 1mA
TA= TMIN to TMAX
VCC = 1.8V,
ISINK = 1mA
MAX919 only, VCC =
5V, ISOURCE = 8mA
CONDITIONS
ms1.2
10
tON
Power-Up Time
98
8mA
95
ISC
Output Short-Circuit Current
µA0.001 1ILEAK
Output Leakage Current
TA= TMIN to TMAX
300
TA= +25°C
TA= TMIN to TMAX
VCC = 5V,
ISINK = 8mA
55 200
300
TA= +25°C
TA= TMIN to TMAX
500
55 200
500
mV
190 400
VCC - VOH
Output-Voltage Swing High
pA10IOS
Input Offset Current
mV
190 400
VOL
Output-Voltage Swing Low
VCC = 5V
VCC = 1.8V
VCC = 5V
VCC = 1.8V
UNITSMIN TYP MAXSYMBOLPARAMETER
MAX919 only, CL= 15pF µs6tRISE
High-to-Low Propagation Delay
(Note 4)
Rise Time
µs
17
tPD-
VCC = 1.8V to 5.5V mV/V0.1 1PSRRPower-Supply Rejection Ratio
(VEE - 0.2V) ≤VCM ≤(VCC + 0.2V) mV/V0.5 3CMRRCommon-Mode Rejection Ratio
22
VCC = 1.8V
VCC = 5V
MAX919 only
Low-to-High Propagation Delay
(Note 4) µs
30
tPD+
VCC = 5V
VCC = 1.8V
95
MAX920 only
VCC = 1.8V
RPULLUP = 100kΩ35
VCC = 5V
RPULLUP = 100kΩ120
CL= 15pF µs4tFALL
Fall Time
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________ 5
500
600
700
800
900
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
MAX917/MAX918
SUPPLY CURRENT vs.
SUPPLY VOLTAGE AND TEMPERATURE
MAX917-920 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
TA = +85°C
TA = +25°C
TA = -40°C
300
400
500
600
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
MAX919/MAX920
SUPPLY CURRENT vs.
SUPPLY VOLTAGE AND TEMPERATURE
MAX917-920 toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
TA = +85°C
TA = +25°C
TA = -40°C
500
550
600
650
700
750
800
850
900
-40 -15 10 35 60 85
MAX917/MAX918
SUPPLY CURRENT vs. TEMPERATURE
MAX917-920 toc03
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
VCC = 3V
VCC = 5V
VCC = 1.8V
300
350
400
450
500
550
-40 -15 10 35 60 85
MAX919/MAX920
SUPPLY CURRENT vs. TEMPERATURE
MAX917-920 toc04
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
VCC = 3V
VCC = 5V
VCC = 1.8V
0
100
50
250
200
150
400
350
300
450
0682 4 10 12 14 16
OUTPUT-VOLTAGE LOW vs. SINK CURRENT
MAX917-920 toc07
SINK CURRENT (mA)
VOL (mV)
VCC = 1.8V VCC = 3V
VCC = 5V
10
12
14
16
0
1 10 100 1k 10k 100k
MAX917/MAX918
SUPPLY CURRENT vs.
OUTPUT TRANSITION FREQUENCY
2
MAX917-920 toc05
OUTPUT TRANSITION FREQUENCY (Hz)
SUPPLY CURRENT (μA)
4
6
8
VCC = 1.8V
VCC = 3V
VCC = 5V
10
12
14
0
1 10 100 1k 10k 100k
MAX919/MAX920
SUPPLY CURRENT vs.
OUTPUT TRANSITION FREQUENCY
2
MAX917-920 toc06
OUTPUT TRANSITION FREQUENCY (Hz)
SUPPLY CURRENT (μA)
4
6
8
VCC = 1.8V
VCC = 3V
VCC = 5V
0
100
200
500
400
300
600
0682 4 10 12 14 16
OUTPUT-VOLTAGE LOW vs. SINK CURRENT
AND TEMPERATURE
MAX917-920 toc08
SINK CURRENT (mA)
VOL (mV)
TA = +25°C
TA = -40°C
TA = +85°C
0
0.3
0.2
0.1
0.4
0.5
0.6
0862 4 10 12 14 16 18 20
MAX917/MAX919
OUTPUT-VOLTAGE HIGH vs. SOURCE CURRENT
MAX917-920 toc09
SOURCE CURRENT (mA)
VCC - VOH (V)
VCC = 1.8V
VCC = 3V VCC = 5V
Typical Operating Characteristics
(VCC = +5V, VEE = 0V, CL= 15pF, VOVERDRIVE = 100mV, TA= +25°C, unless otherwise noted.)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
6 _______________________________________________________________________________________
0
0.3
0.2
0.1
0.4
0.5
0.6
0862 4 10 12 14 16 18 20
MAX917/MAX919
OUTPUT-VOLTAGE HIGH vs.
SOURCE CURRENT AND TEMPERATURE
MAX917-920 toc10
SOURCE CURRENT (mA)
VCC - VOH (V)
TA = +25°C
TA = -40°C
TA = +85°C
0
40
20
80
60
100
120
-40 10-15 356085
SHORT-CIRCUIT SINK CURRENT
vs. TEMPERATURE
MAX917-920 toc11
TEMPERATURE (°C)
SINK CURRENT (mA)
VCC = 3V
VCC = 5V
VCC = 1.8V
0
40
20
80
60
120
100
140
-40 10-15 356085
MAX917/MAX919
SHORT-CIRCUIT SOURCE CURRENT
vs. TEMPERATURE
MAX917-920 toc12
TEMPERATURE (°C)
SOURCE CURRENT (mA)
VCC = 3V
VCC = 5V
VCC = 1.8V
0.03
0.05
0.04
0.07
0.06
0.09
0.08
0.10
-40 10-15 356085
OFFSET VOLTAGE vs. TEMPERATURE
MAX917-920 toc13
TEMPERATURE (°C)
VOS (mV)
VCC = 3V
VCC = 5V
VCC = 1.8V
1.2440
1.2445
1.2450
1.2455
1.2460
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
MAX917/MAX918
REFERENCE VOLTAGE vs.
SUPPLY VOLTAGE
MAX917-920 toc16
SUPPLY VOLTAGE (V)
REFERENCE VOLTAGE (V)
2.5
3.5
3.0
4.5
4.0
5.0
-40 10-15 35 60 85
HYSTERESIS VOLTAGE vs. TEMPERATURE
MAX917-920 toc14
TEMPERATURE (°C)
VHB (mV)
1.241
1.243
1.242
1.245
1.244
1.246
-40 10-15 356085
MAX917/MAX918
REFERENCE VOLTAGE vs. TEMPERATURE
MAX917-920 toc15
TEMPERATURE (°C)
REFERENCE VOLTAGE (V)
VCC = 3V
VCC = 5V
VCC = 1.8V
1.2415
1.2420
1.2425
1.2430
1.2435
1.2440
045231 678910
MAX917/MAX918
REFERENCE OUTPUT VOLTAGE vs.
REFERENCE SOURCE CURRENT
MAX917-920 toc17
SOURCE CURRENT (nA)
VREF (V)
VCC = 3V
VCC = 5V
VCC = 1.8V
1.2435
1.2440
1.2445
1.2450
1.2455
1.2460
045231 678910
MAX917/MAX918
REFERENCE OUTPUT VOLTAGE vs.
REFERENCE SINK CURRENT
MAX917-920 toc18
SINK CURRENT (nA)
VREF (V)
VCC = 3V
VCC = 5V
VCC = 1.8V
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL= 15pF, VOVERDRIVE = 100mV, TA= +25°C, unless otherwise noted.)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________ 7
0
10
5
20
15
25
30
-40 10-15 356085
PROPAGATION DELAY (tPD-)
vs. TEMPERATURE
MAX917-920 toc19
TEMPERATURE (°C)
tPD- (μs)
VCC = 5V
VCC = 1.8V
VCC = 3V
0
40
20
80
60
100
120
140
-40 10-15 356085
MAX917/MAX919
PROPAGATION DELAY (tPD+)
vs. TEMPERATURE
MAX917-920 toc20
TEMPERATURE (°C)
tPD+ (μs)
VCC = 5V
VCC = 1.8V
VCC = 3V
0
40
20
80
60
100
120
0.01 10.1 10 100 1000
PROPAGATION DELAY (tPD-)
vs. CAPACITIVE LOAD
MAX917-920 toc21
CAPACITIVE LOAD (nF)
tPD- (μs)
VCC = 5V
VCC = 1.8V
VCC = 3V
0
40
20
80
60
100
120
140
160
0.01 10.1 10 100 1000
MAX917/MAX919
PROPAGATION DELAY (tPD+)
vs. CAPACITIVE LOAD
MAX917-920 toc22
CAPACITIVE LOAD (nF)
tPD+ (μs)
VCC = 5V
VCC = 1.8V
VCC = 3V
10
30
20
50
40
60
70
02010 30 40 50
PROPAGATION DELAY (tPD-)
vs. INPUT OVERDRIVE
MAX917-920 toc23
INPUT OVERDRIVE (mV)
tPD- (μs)
VCC = 5V
VCC = 1.8V
VCC = 3V
0
30
20
10
40
50
60
70
80
90
100
02010 30 40 50
MAX917/MAX919
PROPAGATION DELAY (tPD+)
vs. INPUT OVERDRIVE
MAX917-920 toc24
INPUT OVERDRIVE (mV)
tPD+ (μs)
VCC = 5V
VCC = 3V
VCC = 1.8V
10 100 1k 10k
MAX918/MAX920
PROPAGATION DELAY (tPD-) vs.
PULLUP RESISTANCE
MAX917-920 toc25
RPULLUP (kΩ)
tPD- (μs)
20
14
15
16
17
18
19
VCC = 5V
VCC = 1.8V
VCC = 3V
10 100 1k 10k
MAX918/MAX920
PROPAGATION DELAY (tPD+) vs.
PULLUP RESISTANCE
MAX917-920 toc26
RPULLUP (kΩ)
tPD- (μs)
250
0
50
100
150
200
VCC = 5V
VCC = 1.8V
VCC = 3V
IN+
(50mV/
div)
OUT
(2V/div)
PROPAGATION DELAY (tPD-)
(VCC = 5V)
20μs/div
MAX917-920 toc27
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL= 15pF, VOVERDRIVE = 100mV, TA= +25°C, unless otherwise noted.)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL= 15pF, VOVERDRIVE = 100mV, TA= +25°C, unless otherwise noted.)
IN+
(50mV/
div)
OUT
(2V/div)
MAX917/MAX919
PROPAGATION DELAY (tPD+)
(VCC = 5V)
20μs/div
MAX917-920 toc28
IN+
(50mV/
div)
OUT
(2V/div)
PROPAGATION DELAY (tPD-)
(VCC = 3V)
20μs/div
MAX917-920 toc29
IN+
(50mV/
div)
OUT
(2V/div)
MAX917/MAX919
PROPAGATION DELAY (tPD+)
(VCC = 3V)
20μs/div
MAX917-920 toc30
IN+
(50mV/
div)
OUT
(1V/div)
PROPAGATION DELAY (tPD-)
(VCC = 1.8V)
20μs/div
MAX917-920 toc31
IN+
(50mV/div)
OUT
(2V/div)
MAX917/MAX919
1kHz RESPONSE (VCC = 5V)
200μs/div
MAX917-920 toc34
IN+
(50mV/
div)
OUT
(1V/div)
MAX917/MAX919
PROPAGATION DELAY (tPD+)
(VCC = 1.8V)
20μs/div
MAX917-920 toc32
IN+
(50mV/
div)
OUT
(1V/div)
MAX917/MAX919
10kHz RESPONSE (VCC = 1.8V)
20μs/div
MAX917-920 toc33
VCC
(2V/div)
OUT
(2V/div)
POWER-UP/DOWN RESPONSE
40μs/div
MAX917-920 toc35
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________ 9
Pin Description
Functional Diagrams
MAX917
MAX918
IN+
OUT
VCC
VEE
REF
REF
1.245V
MAX919
MAX920
IN+
OUT
VCC
VEE
IN-
MAX917/MAX918
SO
PIN
SOT23-5
MAX919/MAX920
SOT23-5 SO
N.C.
VCC
VEE
IN-
REF
IN+
OUT
1, 5, 8
7
4
2
—
3
6
—
5
2
4
—
3
1
—1, 5, 8 No Connection. Not internally connected.
5 7 Positive Supply Voltage
2 4 Negative Supply Voltage
— — Comparator Inverting Input
4 2 1.245V Reference Output and Comparator Inverting Input
3 3 Comparator Noninverting Input
1 6 Comparator Output
NAME FUNCTION
Detailed Description
The MAX917/MAX918 feature an on-board 1.245V
±1.5% reference, yet draw an ultra-low supply current
of 750nA. The MAX919/MAX920 (without reference)
consume just 380nA of supply current. All four devices
are guaranteed to operate down to +1.8V. Their com-
mon-mode input voltage range extends 200mV
beyond-the-rails. Internal hysteresis ensures clean out-
put switching, even with slow-moving input signals.
Large internal output drivers allow rail-to-rail output
swing with up to ±8mA loads.
The output stage employs a unique design that mini-
mizes supply-current surges while switching, virtually
eliminating the supply glitches typical of many other
comparators. The MAX917/MAX919 have a push-pull
output stage that sinks as well as sources current. The
MAX918/MAX920 have an open-drain output stage that
can be pulled beyond VCC to an absolute maximum of
6V above VEE. These open-drain versions are ideal for
implementing wire-ORed output logic functions.
Input Stage Circuitry
The input common-mode voltage range extends from
VEE - 0.2V to VCC + 0.2V. These comparators operate
at any differential input voltage within these limits. Input
bias current is typically ±0.15nA if the input voltage is
between the supply rails. Comparator inputs are pro-
tected from overvoltage by internal ESD protection
diodes connected to the supply rails. As the input volt-
age exceeds the supply rails, these ESD protection
diodes become forward biased and begin to conduct.
Output Stage Circuitry
The MAX917–MAX920 contain a unique break-before-
make output stage capable of rail-to-rail operation with
up to ±8mA loads. Many comparators consume orders
of magnitude more current during switching than dur-
ing steady-state operation. However, with this family of
comparators, the supply-current change during an out-
put transition is extremely small. In the Typical Oper-
ating Characteristics, the Supply Current vs. Output
Transition Frequency graphs show the minimal supply-
current increase as the output switching frequency
approaches 1kHz. This characteristic reduces the need
for power-supply filter capacitors to reduce glitches
created by comparator switching currents. In battery-
powered applications, this characteristic results in a
substantial increase in battery life.
Reference (MAX917/MAX918)
The internal reference in the MAX917/MAX918 has an
output voltage of +1.245V with respect to VEE. Its typi-
cal temperature coefficient is 95ppm/°C over the full
-40°C to +85°C temperature range. The reference is a
PNP emitter-follower driven by a 120nA current source
(Figure 1). The output impedance of the voltage refer-
ence is typically 200kΩ, preventing the reference from
driving large loads. The reference can be bypassed
with a low-leakage capacitor. The reference is stable
for any capacitive load. For applications requiring a
lower output impedance, buffer the reference with a
low-input-leakage op amp, such as the MAX406.
Applications Information
Low-Voltage, Low-Power Operation
The MAX917–MAX920 are ideally suited for use with most
battery-powered systems. Table 1 lists a variety of battery
types, capacities, and approximate operating times for
the MAX917–MAX920, assuming nominal conditions.
Internal Hysteresis
Many comparators oscillate in the linear region of oper-
ation because of noise or undesired parasitic feed-
back. This tends to occur when the voltage on one
input is equal or very close to the voltage on the other
input. The MAX917–MAX920 have internal hysteresis to
counter parasitic effects and noise.
The hysteresis in a comparator creates two trip points:
one for the rising input voltage (VTHR) and one for the
falling input voltage (VTHF) (Figure 2). The difference
between the trip points is the hysteresis (VHB). When
the comparator’s input voltages are equal, the hystere-
sis effectively causes one comparator input to move
quickly past the other, thus taking the input out of the
region where oscillation occurs. Figure 2 illustrates the
case in which IN- has a fixed voltage applied, and IN+
is varied. If the inputs were reversed, the figure would
be the same, except with an inverted output.
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
10 ______________________________________________________________________________________
120nA
REF
VCC
VEE
Figure 1. MAX917/MAX918 Voltage Reference Output
Equivalent Circuit
No
Alkaline
(2 Cells)
Yes
Lithium-Ion
(1 Cell)
Yes
Nickel-Metal-
Hydride
(2 Cells)
Yes
Nickel-Cadmium
(2 Cells)
3.0
3.5
2.4
2.4
1.8
2.7
1.8
1.8
VEND-OF-LIFE
(V)
VFRESH
(V)
BATTERY
TYPE RECHARGEABLE
2000
1000
1000
750
2.5 x 106
1.25 x 106
1.25 x 106
937,500
5 x 106
2.5 x 106
2.5 x 106
1.875 x 106
MAX919/MAX920
OPERATING TIME
(hr)
MAX917/MAX918
OPERATING TIME
(hr)
CAPACITY,
AA SIZE
(mA-h)
Table 1. Battery Applications Using MAX917–MAX920
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
______________________________________________________________________________________ 11
THRESHOLDS
OUT
IN+
IN-
VHB
HYSTERESIS
BAND
VTHF
VTHR
Figure 2. Threshold Hysteresis Band
VCC
MAX917
MAX919
OUT
R3
R1
R2
VREF
VEE
VIN
VCC
Figure 3. MAX917/MAX919 Additional Hysteresis
Additional Hysteresis (MAX917/MAX919)
The MAX917/MAX919 have a 4mV internal hysteresis
band (VHB). Additional hysteresis can be generated
with three resistors using positive feedback (Figure 3).
Unfortunately, this method also slows hysteresis re-
sponse time. Use the following procedure to calculate
resistor values.
1) Select R3. Leakage current at IN is under 2nA, so
the current through R3 should be at least 0.2µA to
minimize errors caused by leakage current. The cur-
rent through R3 at the trip point is (VREF - VOUT)/R3.
Considering the two possible output states in solving
for R3 yields two formulas: R3 = VREF/IR3 or R3 =
(VCC - VREF)/IR3. Use the smaller of the two resulting
resistor values. For example, when using the
MAX917 (VREF = 1.245V) and VCC = 5V, and if we
choose IR3 = 1µA, then the two resistor values are
1.2MΩand 3.8MΩ. Choose a 1.2MΩstandard value
for R3.
2) Choose the hysteresis band required (VHB). For this
example, choose 50mV.
3) Calculate R1 according to the following equation:
R1 = R3 (VHB / VCC)
For this example, insert the values
R1 = 1.2MΩ(50mV/5V) = 12kΩ
4) Choose the trip point for VIN rising (VTHR) such that
VTHR > VREF ·(R1 + R3)/R3 (VTHF is the trip point for
VIN falling). This is the threshold voltage at which the
comparator switches its output from low to high as
VIN rises above the trip point. For this example,
choose 3V.
5) Calculate R2 as follows:
R2 = 1/[VTHR/(VREF ·R1) - (1 / R1) - (1 / R3)]
R2 = 1/[3.0V/(1.2V ·12kΩ) - (1 / 12kΩ) -
(1/1.2MΩ)] = 8.05kΩ
For this example, choose an 8.2kΩstandard value.
6) Verify the trip voltages and hysteresis as follows:
VIN rising: VTHR = VREF ·R1 [(1 / R1) + (1 / R2)
+ (1 / R3)]
VIN falling: VTHF = VTHR - (R1 ·VCC / R3)
Hysteresis = VTHR - VTHF
Additional Hysteresis (MAX918/MAX920)
The MAX918/MAX920 have a 4mV internal hysteresis
band. They have open-drain outputs and require an
external pullup resistor (Figure 4). Additional hysteresis
can be generated using positive feedback, but the for-
mulas differ slightly from those of the MAX917/
MAX919. Use the following procedure to calculate
resistor values.
1) Select R3 according to the formulas R3 = VREF / 1µA
or R3 = (VCC - VREF)/1µA - R4. Use the smaller of
the two resulting resistor values.
2) Choose the hysteresis band required (VHB).
3) Calculate R1 according to the following equation:
R1 = (R3 + R4) (VHB/VCC)
4) Choose the trip point for VIN rising (VTHR) (VTHF is
the trip point for VIN falling). This is the threshold
voltage at which the comparator switches its output
from low to high as VIN rises above the trip point.
5) Calculate R2 as follows:
R2 1/ V / V R1 1
R1
1
R3
THR REF =
()
−⎛
⎝
⎜⎞
⎠
⎟−
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
⋅
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
12 ______________________________________________________________________________________
MAX920
IN-
100kΩ
100kΩ
RPULLUP
3V (5V)
LOGIC OUT
OUT
VCC
+5V (+3V)
+3V (+5V)
VEE
5V (3V) LOGIC IN
IN+
LOGIC-LEVEL
TRANSLATOR
VEE
VCC OUT
R3
R2
R1 R4
VREF
VIN
VCC
MAX918
MAX920
Figure 4. MAX918/MAX920 Additional Hysteresis
MAX919
IN+
OUT
VCC
100mVP-P
VCC
VEE
IN-
Figure 5. Zero-Crossing Detector
Typical Application Circuit
OUT
N.C.
( ) ARE FOR MAX917/MAX918.
VEE
1
2
8
7
N.C.
VCC
IN- (REF)
IN+
N.C.
SO
TOP VIEW
3
4
6
5
MAX917
MAX918
MAX919
MAX920
Pin Configurations (continued)
6) Verify the trip voltages and hysteresis as follows:
Hysteresis = VTHR - VTHF
Board Layout and Bypassing
Power-supply bypass capacitors are not typically
needed, but use 100nF bypass capacitors close to the
device’s supply pins when supply impedance is high,
supply leads are long, or excessive noise is expected
on the supply lines. Minimize signal trace lengths to
reduce stray capacitance. A ground plane and sur-
face-mount components are recommended.
Zero-Crossing Detector
Figure 5 shows a zero-crossing detector application.
The MAX919’s inverting input is connected to ground,
and its noninverting input is connected to a 100mVP-P
signal source. As the signal at the noninverting input
crosses 0V, the comparator’s output changes state.
Logic-Level Translator
The Typical Application Circuit shows an application
that converts 5V logic to 3V logic levels. The MAX920 is
powered by the +5V supply voltage, and the pullup
resistor for the MAX920’s open-drain output is connect-
ed to the +3V supply voltage. This configuration allows
the full 5V logic swing without creating overvoltage on
the 3V logic inputs. For 3V to 5V logic-level translations,
simply connect the +3V supply voltage to VCC and the
+5V supply voltage to the pullup resistor.
V R1
1
R1
1
R2
1
R3 R4
R1
R3 R4 V
REF CC
=× ++
+
⎛
⎝
⎜⎞
⎠
⎟−+×
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
______________________________________________________________________________________ 13
SOT-23 5L .EPS
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the
package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
8 SO S8+2 21-0041 90-0096
SOT23 U5+1 21-0057 90-0174
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
14 ______________________________________________________________________________________
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the
package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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.
15 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
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