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General Description
The MAX917–MAX920 nanopower comparators in
space-saving SOT23 packages feature Beyond-theRails™ 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 (without 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-current 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 suitable 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
PART
MAX917EUK-T
MAX917ESA -40°C to +85°C
-40°C to +85°C
TEMP.
RANGE
PIN-
PACKAGE
5 SOT23-5
8 SO
Pin Configurations continue at end of data sheet.
Typical Application Circuit appears at end of data sheet.
Pin Configurations
Selector Guide
Ordering Information
SOT
TOP MARK
ADIQ
—
MAX918EUK-T
MAX918ESA
ADIR
-40°C to +85°C
-40°C to +85°C 5 SOT23-5
8 SO —
MAX919EUK-T
MAX919ESA
ADIS
-40°C to +85°C
-40°C to +85°C 5 SOT23-5
8 SO —
MAX920EUK-T
MAX920ESA
ADIT
-40°C to +85°C
-40°C to +85°C 5 SOT23-5
8 SO —
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.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
19-1512; Rev 0; 7/99
TOP VIEW
1
OUT
MAX917
2
V
EE
IN+
( ) ARE FOR MAX917/MAX918.
MAX918
MAX919
MAX920
3
SOT23-5
5
4
V
CC
IN- (REF)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS—MAX917/MAX918
(VCC= +5V, VEE= 0, V
IN+
= V
REF
, 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 (VCCto VEE)..................................................+6V
Voltage Inputs (IN+, IN-, REF) .........(VEE- 0.3V) to (VCC+ 0.3V)
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, 10sec) .............................+300°C
V
CC
= 1.8V
VCC= 1.8V
VCC= 5V
VCC= 1.8V
VCC= 5V
Output Voltage Swing Low V
OL
190 400
mV
500
55 200
TA= T
MIN
to T
MAX
TA= +25°C
300
VCC= 5V,
I
SINK
= 8mA
TA= T
MIN
to T
MAX
VCC= 1.8V,
I
SINK
= 1mA
TA= +25°C
TA= T
MIN
to T
MAX
TA= +25°C
TA= T
MIN
to T
MAX
TA= +25°C
TA= T
MIN
to T
MAX
TA= +25°C
TA= T
MIN
to T
MAX
TA= +25°C
TA= T
MIN
to T
MAX
TA= +25°C
PARAMETER SYMBOL MIN TYP MAX UNITS
10
Input Offset Voltage V
OS
15
mV
IN+ Voltage Range V
IN+
VEE- 0.2 V
CC
+ 0.2 V
1.60
Input-Referred Hysteresis V
HB
4 mV
Input Bias Current I
B
0.15 1
nA
2
Power-Supply Rejection Ratio PSRR 0.1 1 mV/V
Supply Current
Supply Voltage Range V
CC
1.8 5.5 V
I
CC
0.75
µA
0.80 1.30
Output Voltage Swing High VCC- V
OH
190 400
mV
500
55 200
300
Output Leakage Current I
LEAK
0.001 1 µA
Output Short-Circuit Current I
SC
95
mA
8
98
10
CONDITIONS
MAX917 only, VCC=
5V, I
SOURCE
= 8mA
(Note 2)
Inferred from the output swing test
(Note 3)
MAX917 only, VCC=
1.8V, I
SOURCE
= 1mA
V
CC
= 1.8V to 5.5V
MAX918 only, VO= 5.5V
Sourcing, VO= V
EE
Inferred from the PSRR test
Sinking, VO= V
CC
VCC= 5V
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS—MAX919/MAX920
(VCC= +5V, VEE= 0, VCM= 0, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
V
CC
= 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= T
MIN
to T
MAX
0.45 0.80
µA
0.38
I
CC
V1.8 5.5V
CC
Supply Voltage Range
Supply Current
nA
0.15 1
I
B
Input Bias Current
mV4V
HB
Input-Referred Hysteresis
1.2
TA= +25°C
VVEE- 0.2 V
CC
+ 0.2V
CM
Input Common-Mode
Voltage Range
mV
15
V
OS
Input Offset Voltage
10
UNITSMIN TYP MAXSYMBOLPARAMETER
TA= T
MIN
to T
MAX
2TA= T
MIN
to T
MAX
V
CC
= 5V,
R
PULL-UP
= 100kΩ
V
CC
= 1.8V,
R
PULL-UP
= 100kΩ
V
CC
= 5V
V
CC
= 1.8V
V
CC
= 1.8V
MAX917 only
95
µs
30
t
PD+
Low-to-High Propagation Delay
(Note 4)
35
MAX918 only
120
µs
95
CONDITIONS
TA = +25°C
ms1.2
22
17
t
PD-
High-to-Low Propagation Delay
(Note 4)
t
ON
Power-Up Time
∆I
OUT
= 10nA mV/nA±0.2
∆V
REF
/
∆I
OUT
Reference Load Regulation
UNITS
MIN TYP MAXSYMBOL
PARAMETER
CL= 15pF
1.8V ≤ VCC≤ 5.5V
BW = 10Hz to 100kHz, C
REF
= 1nF
MAX917 only, CL= 15pF
V
CC
= 5V
BW = 10Hz to 100kHz
TA = T
MIN
to T
MAX
mV/V0.1
∆V
REF
/
∆V
CC
Reference Line Regulation
215
µV
RMS
e
n
Reference Output
Voltage Noise
1.200 1.290
V
1.227 1.245 1.263
V
REF
Reference Voltage
µs4t
FALL
Fall Time
µs6t
RISE
Rise Time
ppm/°CTC
REF
Reference Voltage Temperature
Coefficient
600
ELECTRICAL CHARACTERISTICS—MAX917/MAX918 (continued)
(VCC= +5V, VEE= 0, V
IN+
= V
REF
, 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= 0, VCM= 0, 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 T
A
= +25°C. Specification limits over temperature (TA= T
MIN
to T
MAX
) are guaranteed
by design, not production tested.
Note 2: V
OS
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., V
OS
) (Figure 2).
Note 4: Specified with an input overdrive (V
OVERDRIVE
) of 100mV, and load capacitance of CL= 15pF. V
OVERDRIVE
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= V
CC
Sourcing, VO= V
EE
MAX920 only, VO= 5.5V
TA= +25°C
TA= +25°C
MAX919 only, VCC=
1.8V, I
SOURCE
= 1mA
TA= T
MIN
to T
MAX
VCC= 1.8V,
I
SINK
= 1mA
MAX919 only, VCC=
5V, I
SOURCE
= 8mA
CONDITIONS
ms1.2
10
t
ON
Power-Up Time
98
8
mA
95
I
SC
Output Short-Circuit Current
µA0.001 1I
LEAK
Output Leakage Current
TA= T
MIN
to T
MAX
300
TA= +25°C
TA= T
MIN
to T
MAX
VCC= 5V,
I
SINK
= 8mA
55 200
300
TA= +25°C
TA= T
MIN
to T
MAX
500
55 200
500
mV
190 400
VCC- V
OH
Output Voltage Swing High,
pA10I
OS
Input Offset Current
mV
190 400
V
OL
Output Voltage Swing Low
VCC= 5V
VCC= 1.8V
VCC= 5V
VCC= 1.8V
UNITSMIN TYP MAXSYMBOLPARAMETER
MAX919 only, CL= 15pF µs6t
RISE
High-to-Low Propagation Delay
(Note 4)
Rise Time
µs
17
t
PD-
V
CC
= 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
t
PD+
VCC= 5V
VCC= 1.8V
95
MAX920 only
VCC= 1.8V
R
PULL-UP
= 100kΩ
35
VCC= 5V
R
PULL-UP
= 100kΩ
120
CL= 15pF µs4t
FALL
Fall Time
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________
5
Typical Operating Characteristics
(VCC= +5V, V
EE
= 0, CL= 15pF, V
OVERDRIVE
= 100mV, TA= +25°C, unless otherwise noted.)
MAX917/MAX918
SUPPLY CURRENT vs.
SUPPLY VOLTAGE AND TEMPERATURE
900
TA = +85°C
800
TA = +25°C
700
SUPPLY CURRENT (nA)
TA = -40°C
600
500
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
SUPPLY VOLTAGE (V)
MAX919/MAX920
SUPPLY CURRENT vs. TEMPERATURE
550
500
450
400
SUPPLY CURRENT (nA)
350
300
VCC = 5V
VCC = 3V
VCC = 1.8V
-40 -15 10 35 60 85
TEMPERATURE (°C)
MAX917-920 toc01
MAX917-920 toc04
SUPPLY VOLTAGE AND TEMPERATURE
600
500
400
SUPPLY CURRENT (nA)
300
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
16
14
12
10
8
6
SUPPLY CURRENT (µA)
4
2
0
1 10 100 1k 10k 100k
MAX919/MAX920
SUPPLY CURRENT vs.
TA = +85°C
TA = +25°C
TA = -40°C
SUPPLY VOLTAGE (V)
MAX917/MAX918
SUPPLY CURRENT vs.
OUTPUT TRANSITION FREQUENCY
VCC = 5V
VCC = 3V
VCC = 1.8V
OUTPUT TRANSITION FREQUENCY (Hz)
MAX917-920 toc02
MAX917-920 toc05
SUPPLY CURRENT vs. TEMPERATURE
MAX917/MAX918
900
850
800
750
700
650
SUPPLY CURRENT (nA)
600
550
500
-40 -15 10 35 60 85
VCC = 5V
VCC = 3V
VCC = 1.8V
TEMPERATURE (°C)
MAX919/MAX920
SUPPLY CURRENT vs.
OUTPUT TRANSITION FREQUENCY
14
12
10
8
6
SUPPLY CURRENT (µA)
4
2
0
1 10 100 1k 10k 100k
OUTPUT TRANSITION FREQUENCY (Hz)
VCC = 5V
MAX917-920 toc03
MAX917-920 toc06
VCC = 3V
VCC = 1.8V
OUTPUT VOLTAGE LOW vs. SINK CURRENT
450
400
350
300
250
(mV)
OL
V
200
150
100
50
VCC = 1.8V
0
0682 4 10 12 14 16
VCC = 3V
SINK CURRENT (mA)
VCC = 5V
MAX917-920 toc07
OUTPUT VOLTAGE LOW vs. SINK CURRENT
AND TEMPERATURE
600
500
400
(mV)
300
OL
V
TA = +85°C
200
100
0
0682 4 10 12 14 16
TA = +25°C
SINK CURRENT (mA)
TA = -40°C
MAX917-920 toc08
OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
MAX917/MAX919
(V)
- V
V
0.6
0.5
0.4
OH
0.3
CC
0.2
0.1
0
VCC = 1.8V
VCC = 3V
0862 4 10 12 14 16 18 20
SOURCE CURRENT (mA)
VCC = 5V
MAX917-920 toc09
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC= +5V, V
EE
= 0, CL= 15pF, V
OVERDRIVE
= 100mV, TA= +25°C, unless otherwise noted.)
SOURCE CURRENT AND TEMPERATURE
0.6
0.5
0.4
(V)
OH
0.3
- V
CC
V
0.2
0.1
0
0862 4 10 12 14 16 18 20
OFFSET VOLTAGE vs. TEMPERATURE
0.10
0.09
0.08
0.07
(mV)
OS
V
0.06
0.05
0.04
0.03
-40 10-15 35 60 85
MAX917/MAX919
OUTPUT VOLTAGE HIGH vs.
TA = +25°C
TA = +85°C
TA = -40°C
SOURCE CURRENT (mA)
VCC = 1.8V
VCC = 3V
VCC = 5V
TEMPERATURE (°C)
MAX917-920 toc10
MAX917-920 toc13
SHORT-CIRCUIT SINK CURRENT
vs. TEMPERATURE
120
100
80
60
40
SINK CURRENT (mA)
20
VCC = 1.8V
0
-40 10-15 35 60 85
VCC = 5V
MAX917-920 toc11
VCC = 3V
TEMPERATURE (°C)
HYSTERESIS VOLTAGE vs. TEMPERATURE
5.0
4.5
4.0
(mV)
HB
V
3.5
3.0
2.5
-40 10-15 35 60 85
TEMPERATURE (°C)
MAX917-920 toc14
MAX917/MAX919
SHORT-CIRCUIT SOURCE CURRENT
vs. TEMPERATURE
140
120
100
80
60
SOURCE CURRENT (mA)
40
20
0
-40 10-15 35 60 85
TEMPERATURE (°C)
MAX917/MAX918
REFERENCE VOLTAGE vs. TEMPERATURE
1.246
1.245
1.244
1.243
REFERENCE VOLTAGE (V)
1.242
1.241
-40 10-15 35 60 85
VCC = 5V
VCC = 3V
VCC = 1.8V
TEMPERATURE (°C)
VCC = 5V
VCC = 3V
VCC = 1.8V
MAX917-920 toc12
MAX917-920 toc15
MAX917/MAX918
REFERENCE VOLTAGE vs.
SUPPLY VOLTAGE
1.2460
1.2455
1.2450
REFERENCE VOLTAGE (V)
1.2445
1.2440
1.5 2.5 3.5 4.52.0 3.0 4.0 5.0 5.5
SUPPLY VOLTAGE (V)
MAX917-920 toc16
1.2440
1.2435
1.2430
(V)
REF
V
1.2425
1.2420
1.2415
045231 678910
MAX917/MAX918
REFERENCE OUTPUT VOLTAGE vs.
REFERENCE SOURCE CURRENT
VCC = 3V
VCC = 1.8V
VCC = 5V
SOURCE CURRENT (nA)
1.2460
1.2455
MAX917-920 toc17
1.2450
(V)
REF
V
1.2445
1.2440
1.2435
MAX917/MAX918
REFERENCE OUTPUT VOLTAGE vs.
REFERENCE SINK CURRENT
VCC = 3V
045231 678910
SINK CURRENT (nA)
VCC = 1.8V
MAX917-920 toc18
VCC = 5V
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
_______________________________________________________________________________________
7
Typical Operating Characteristics (continued)
(VCC= +5V, V
EE
= 0, CL= 15pF, V
OVERDRIVE
= 100mV, TA= +25°C, unless otherwise noted.)
PROPAGATION DELAY (t
vs. TEMPERATURE
30
25
20
(µs)
VCC = 3V
15
PD-
t
10
5
0
-40 10-15 35 60 85
VCC = 1.8V
TEMPERATURE (°C)
MAX917/MAX919
PROPAGATION DELAY (t
vs. CAPACITIVE LOAD
160
140
120
VCC = 5V
100
(µs)
80
PD+
t
60
VCC = 3V
40
VCC = 1.8V
20
0
0.01 10.1 10 100 1000
CAPACITIVE LOAD (nF)
MAX918/MAX920
PROPAGATION DELAY (t
PULL-UP RESISTANCE
20
19
18
(µs)
17
PD-
t
16
15
14
10 100 1k 10k
VCC = 1.8V
VCC = 3V
VCC = 5V
R
PULL-UP
(kΩ)
PD-
PD+
PD-
)
VCC = 5V
) vs.
MAX917-920 toc19
)
MAX917-920 toc22
MAX917-920 toc25
140
120
100
80
(µs)
PD+
t
60
40
20
0
-40 10-15 35 60 85
70
VCC = 3V
60
50
(µs)
40
PD-
t
30
VCC = 5V
20
10
02010 30 40 50
250
200
150
(µs)
PD-
t
100
50
0
10 100 1k 10k
MAX917/MAX919
PROPAGATION DELAY (t
vs. TEMPERATURE
VCC = 5V
VCC = 3V
VCC = 1.8V
TEMPERATURE (°C)
PROPAGATION DELAY (t
vs. INPUT OVERDRIVE
VCC = 1.8V
INPUT OVERDRIVE (mV)
MAX918/MAX920
PROPAGATION DELAY (t
PULL-UP RESISTANCE
VCC = 5V
VCC = 3V
VCC = 1.8V
R
PULL-UP
(kΩ)
PD+
PD+
PD-
)
)
) vs.
MAX917-920 toc20
MAX917-920 toc23
MAX917-920 toc26
PROPAGATION DELAY (t
vs. CAPACITIVE LOAD
120
100
80
(µs)
60
PD-
t
40
20
0
0.01 10.1 10 100 1000
CAPACITIVE LOAD (nF)
VCC = 1.8V
VCC = 3V
MAX917/MAX919
PROPAGATION DELAY (t
100
90
80
70
60
(µs)
50
PD+
t
40
30
20
10
0
vs. INPUT OVERDRIVE
VCC = 5V
VCC = 3V
VCC = 1.8V
02010 30 40 50
INPUT OVERDRIVE (mV)
PROPAGATION DELAY (t
(V
= 5V)
CC
20µs/div
)
PD-
VCC = 5V
)
PD+
)
PD-
MAX917-920 toc27
MAX917-920 toc21
MAX917-920 toc24
IN+
(50mV/
div)
OUT
(2V/div)
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC= +5V, V
EE
= 0, CL= 15pF, V
OVERDRIVE
= 100mV, TA= +25°C, unless otherwise noted.)
IN+
(50mV/
div)
OUT
(2V/div)
MAX917/MAX919
PROPAGATION DELAY (t
PD+
)
(V
CC
= 5V)
20µs/div
MAX917-920 toc28
IN+
(50mV/
div)
OUT
(2V/div)
PROPAGATION DELAY (t
PD-
)
(V
CC
= 3V)
20µs/div
MAX917-920 toc29
IN+
(50mV/
div)
OUT
(2V/div)
MAX917/MAX919
PROPAGATION DELAY (t
PD+
)
(V
CC
= 3V)
20µs/div
MAX917-920 toc30
IN+
(50mV/
div)
OUT
(1V/div)
PROPAGATION DELAY (t
PD-
)
(V
CC
= 1.8V)
20µs/div
MAX917-920 toc31
IN+
(50mV/div)
OUT
(2V/div)
MAX917/MAX919
1kHz RESPONSE (V
CC
= 5V)
200µs/div
MAX917-920 toc34
IN+
(50mV/
div)
OUT
(1V/div)
MAX917/MAX919
PROPAGATION DELAY (t
PD+
)
(V
CC
= 1.8V)
20µs/div
MAX917-920 toc32
IN+
(50mV/
div)
OUT
(1V/div)
MAX917/MAX919
10kHz RESPONSE (V
CC
= 1.8V)
20µs/div
MAX917-920 toc33
V
CC
(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
SO
PIN
SOT23-5
MAX919/MAX920
SOT23-5
SO
N.C.
V
CC
V
EE
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 common-mode input voltage range extends 200mV
beyond-the-rails. Internal hysteresis ensures clean output 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 minimizes 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 VCCto an absolute maximum of
6V above VEE. These open-drain versions are ideal for
implementing wire-Or output logic functions.
Input Stage Circuitry
The input common-mode voltage range extends from
V
EE
- 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 protected from overvoltage by internal ESD protection
diodes connected to the supply rails. As the input voltage exceeds the supply rails, these ESD protection
diodes become forward biased and begin to conduct.
V
CC
IN+
OUT
REF
MAX917
MAX918
REF
1.245V
V
EE
V
CC
IN+
OUT
IN-
MAX919
MAX920
V
EE
Output Stage Circuitry
The MAX917–MAX920 contain a unique break-beforemake output stage capable of rail-to-rail operation with
up to ±8mA loads. Many comparators consume orders
of magnitude more current during switching than during steady-state operation. However, with this family of
comparators, the supply-current change during an output transition is extremely small. In the
Typical Oper-
ating Characteristics
, the Supply Current vs. Output
Transition Frequency graphs show the minimal supplycurrent 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 batterypowered 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 typical 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 reference 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 operation because of noise or undesired parasitic feedback. 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 (V
THR
) and one for the
falling input voltage (V
THF
) (Figure 2). The difference
between the trip points is the hysteresis (VHB). When
the comparator’s input voltages are equal, the hysteresis 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 ______________________________________________________________________________________
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
V
END-OF-LIFE
(V)
V
FRESH
(V)
BATTERY
TYPE
RECHARGEABLE
2000
1000
1000
750
2.5 x 10
6
1.25 x 10
6
1.25 x 10
6
937,500
5 x 10
6
2.5 x 10
6
2.5 x 10
6
1.875 x 10
6
MAX919/MAX920
OPERATING TIME
(hr)
MAX917/MAX918
OPERATING TIME
(hr)
CAPACITY,
AA SIZE
(mA-h)
Table 1. Battery Applications Using MAX917–MAX920
V
120nA
CC
V
EE
REF
MAX917–MAX920
SOT23, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
______________________________________________________________________________________ 11
IN+
Figure 2. Threshold Hysteresis Band
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 response 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 current through R3 at the trip point is (V
REF
- V
OUT
)/R3.
Considering the two possible output states in solving
for R3 yields two formulas: R3 = V
REF/IR3
or R3 =
(VCC- V
REF
)/IR3. Use the smaller of the two resulting
resistor values. For example, when using the
MAX917 (V
REF
= 1.245V) and VCC= 5V, and if we
choose IR3= 1µA, then the two resistor values are
1.2MΩ and 3.8MΩ. Choose a 1.2MΩ standard 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 V
IN
rising (V
THR
) such that
V
THR
> V
REF
· (R1 + R3)/R3 (V
THF
is the trip point for
VINfalling). This is the threshold voltage at which the
comparator switches its output from low to high as
VINrises above the trip point. For this example,
choose 3V.
5) Calculate R2 as follows:
R2 = 1/[V
THR
/(V
REF
· R1) - (1 / R1) - (1 / R3)]
R2 = 1/[3.0V/(1.2V · 12kΩ) - (1 / 12kΩ) -
(1/1.2MΩ)] = 8.05kΩ
For this example, choose an 8.2kΩ standard value.
6) Verify the trip voltages and hysteresis as follows:
V
IN
rising: V
THR
= V
REF
· R1 [(1 / R1) + (1 / R2)
+ (1 / R3)]
VINfalling: V
THF
= V
THR
- (R1 · VCC/ R3)
Hysteresis = V
THR
- V
THF
Additional Hysteresis (MAX918/MAX920)
The MAX918/MAX920 have a 4mV internal hysteresis
band. They have open-drain outputs and require an
external pull-up resistor (Figure 4). Additional hysteresis can be generated using positive feedback, but the
formulas differ slightly from those of the MAX917/
MAX919. Use the following procedure to calculate
resistor values.
1) Select R3 according to the formulas R3 = V
REF
/ 1µA
or R3 = (VCC- V
REF
)/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 VINrising (V
THR
) (V
THF
is
the trip point for VINfalling). This is the threshold
voltage at which the comparator switches its output
from low to high as VINrises above the trip point.
5) Calculate R2 as follows:
IN-
OUT
V
THRESHOLDS
V
THR
HYSTERESIS
V
HB
V
THF
BAND
V
R1
IN
R2
V
REF
CC
R3
V
CC
OUT
V
EE
MAX917
MAX919
R2 1/ V / V R1
THR REF
=
()
1
−
−
⋅
R11R3
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.
12
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Figure 4. MAX918/MAX920 Additional Hysteresis
Figure 5. Zero-Crossing Detector
Typical Application Circuit
OUT
N.C.
( ) ARE FOR MAX917/MAX918.
V
EE
1
2
87N.C.
V
CC
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 = V
THR
- V
THF
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 surface-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 pull-up
resistor for the MAX920’s open-drain output is connected 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 VCCand the
+5V supply voltage to the pull-up resistor.
V rising: V V R1
1R11R21
R3
V falling: V
IN THR REF
IN THF
=++
=
⋅
V R1
1R11
R21R3 R4R1R3 R4
V
REF CC
++
+
−
+
⋅⋅
V
CC
R3
R1
V
IN
R2
V
REF
V
CC
V
EE
OUT
MAX918
MAX920
R4
100mVp-p
IN+
IN-
V
CC
V
CC
OUT
MAX919
V
EE
100k
100k
5V (3V) LOGIC IN
IN-
IN+
+5V (+3V)
V
CC
V
EE
MAX920
OUT
LOGIC LEVEL
TRANSLATOR
+3V (+5V)
R
PULL-UP
3V (5V)
LOGIC OUT
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