General Description
The MAX9025/MAX9028 nanopower comparators in
space-saving chip-scale (UCSP™) packages feature
Beyond-the-Rails™ inputs and are guaranteed to oper-
ate down to +1.8V. The MAX9025/MAX9026 feature
an on-board 1.236V ±1% reference and draw an ultra-
low supply current of only 1µA, while the MAX9027−
MAX9028 (without reference) require just 0.6µA of
supply current. These features make the MAX9025−
MAX9028 family of comparators ideal for all 2-cell battery-
monitoring/management applications.
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 MAX9025/MAX9027 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 5mA. The MAX9026/MAX9028 have an
open-drain output stage that makes them suitable for
mixed-voltage system design. All devices are available in
the miniature 6-bump UCSP packages.
Refer to the MAX9117 data sheet for similar comparators
in 5-pin SC70 packages and the MAX9017 data sheet for
similar dual comparators in 8-pin SOT23 packages.
Applications
●2-Cell Battery Monitoring/Management
●Ultra-Low-Power Systems
●Mobile Communications
●Notebooks and PDAs
●Sensing at Ground or Supply Line
●Telemetry and Remote Systems
●Medical Instruments
Features
●Space-Saving UCSP Package (1mm x 1.52mm)
●Ultra-Low Supply Current
• 0.6µA (MAX9027/MAX9028)
• 1µA with Reference (MAX9025/MAX9026)
●Guaranteed to Operate Down to +1.8V
●Internal 1.236V ±1% Reference (MAX9025/
MAX9026)
●Input Voltage Range Extends 200mV
Beyond-the-Rails
●CMOS Push-Pull Output with ±5mA Drive Capability
(MAX9025/MAX9027)
●Open-Drain Output Versions Available (MAX9026/
MAX9028)
●Crowbar-Current-Free Switching
●Internal Hysteresis for Clean Switching
●No Phase Reversal for Overdriven Inputs
19-3241; Rev 1; 6/11
Typical Application Circuit appears at end of data sheet.
Beyond-the-Rails and UCSP are trademarks of Maxim
Integrated Products, Inc.
+Denotes lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
PART INTERNAL
REFERENCE
OUTPUT
TYPE
SUPPLY
CURRENT (µA)
MAX9025 Yes Push-Pull 1.0
MAX9026 Yes Open-Drain 1.0
MAX9027 No Push-Pull 0.6
MAX9028 No Open-Drain 0.6
PART TEMP
RANGE
BUMP-
PACKAGE
TOP
MARK
MAX9025EBT+T -40°C to +85°C 6 UCSP ADB
MAX9026EBT+T -40°C to +85°C 6 UCSP ADC
MAX9027EBT+T -40°C to +85°C 6 UCSP ADD
MAX9028EBT+T -40°C to +85°C 6 UCSP ADE
TOP VIEW
(BUMPS ON BOTTOM)
UCSP
MAX9025–
MAX9028
1
2
3
VCC
A
B
OUT
VEE
IN+
REF
(VEE)
IN-
( ) MAX9027/MAX9028 PINS
Selector Guide
Ordering Information
Pin Congurations
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
EVALUATION KIT AVAILABLE
Supply Voltage (VCC to VEE) ................................................+6V
Voltage Inputs (IN+, IN-, REF) ......(VEE - 0.3V) to (VCC + 0.3V)
Output Voltage
MAX9025/MAX9027 ................(VEE - 0.3V) to (VCC + 0.3V)
MAX9026/MAX9028 ...............................(VEE - 0.3V) to +6V
Current into Input Pins .......................................................20mA
Output Current ..................................................................±50mA
Output Short-Circuit Duration ................................................ 10s
Continuous Power Dissipation (TA = +70°C)
6-Bump UCSP (derate 3.9mW/°C above +70°C) ........308mW
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Bump Temperature (soldering) Reflow ............................ +235°C
(VCC = +5V, VEE = 0V, VIN+ = VREF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VCC Inferred from the PSRR test 1.8 5.5 V
Supply Current ICC
VCC = 1.8V 0.8 1.5
µA
VCC = 5V TA = +25°C 1.0 1.7
TA = TMIN to TMAX 2.2
IN+ Voltage Range VIN+ Inferred from output swing test VEE -
0.2
VCC +
0.2 V
Input O󰀨set Voltage VOS (Note 2) TA = +25°C 0.3 5 mV
TA = TMIN to TMAX 10
Input-Referred Hysteresis VHB (Note 3) 4 mV
Input Bias Current IB
TA = +25°C 0.15 1 nA
TA = TMIN to TMAX 2
Power-Supply Rejection Ratio PSRR VCC = 1.8V to 5.5V 0.1 1 mV/V
Output Voltage Swing High VCC -
VOH
MAX9025, VCC = 5V,
ISOURCE = 6mA
TA = +25°C 250 350
mV
TA = TMIN to TMAX 450
MAX9025, VCC = 1.8V,
ISOURCE = 1mA
TA = +25°C 56 200
TA = TMIN to TMAX 300
Output Voltage Swing Low VOL
VCC = 5V,
ISINK = 6mA
TA = +25°C 250 350
mV
TA = TMIN to TMAX 450
VCC = 1.8V,
ISINK = 1mA
TA = +25°C 57 200
TA = TMIN to TMAX 300
Output Leakage Current ILEAK MAX9026 only, VO = 5.5V 0.001 1 µA
Output Short-Circuit Current ISC
Sourcing, VO = VEE
VCC = 5V 35
mA
VCC = 1.8V 3
Sinking, VO = VCC
VCC = 5V 33
VCC = 1.8V 3
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.
Electrical Characteristics-MAX9025/MAX9026 (with REF)
Absolute Maximum Ratings
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(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 = +5V, VEE = 0V, VIN+ = VREF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
High-to-Low Propagation
Delay (Note 4) tPD-
VCC = 1.8V 7 µs
VCC = 5V 6
Low-to-High Propagation
Delay (Note 4) tPD+
MAX9025 only VCC = 1.8V 11
µs
VCC = 5V 28
MAX9026 only,
RPULLUP = 100kΩ
VCC = 1.8V 12
VCC = 5V 31
Rise Time tRISE MAX9025 only, CL = 15pF 1.6 µs
Fall Time tFALL CL = 15pF 0.2 µs
Power-Up Time tON 1.2 ms
Reference Voltage VREF
TA = +25°C 1.224 1.236 1.248 V
TA = TMIN to TMAX 1.205 1.267
Reference Voltage
Temperature Coe󰀩cient TCREF 40 ppm/
°C
Reference Output Voltage
Noise EN CREF = 1nF BW = 10Hz to 100kHz 29 µVRMS
BW = 10Hz to 6kHz 60
Reference Line Regulation DVREF/
DVCC
VCC = 1.8V to 5.5V 0.5 mV/V
Reference Load Regulation DVREF/
DIOUT
DIOUT = 0nA to 100nA 0.03 mV/
nA
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VCC Inferred from the PSRR test 1.8 5.5 V
Supply Current ICC
VCC = 1.8V 0.45 0.75
µA
VCC = 5V TA = +25°C 0.6 1.0
TA = TMIN to TMAX 1.25
Input Common-Mode
Voltage Range VCM Inferred from the CMRR test VEE -
0.2
VCC +
0.2 V
Input O󰀨set Voltage VOS
-0.2V ≤ VCM ≤
(VCC + 0.2V)
(Note 2)
TA = +25°C 0.3 5
mV
TA = TMIN to TMAX 10
Input-Referred Hysteresis VHB -0.2V ≤ VCM ≤ (VCC + 0.2V) (Note 3) 4 mV
Input Bias Current IB
TA = +25°C 0.15 1 nA
TA = TMIN to TMAX 2
Power-Supply Rejection Ratio PSRR VCC = 1.8V to 5.5V 0.1 1 mV/V
Common-Mode Rejection Ratio CMRR (VEE - 0.2V) ≤ VCM ≤ (VCC + 0.2V) 0.5 3 mV/V
Electrical Characteristics-MAX9025/MAX9026 (with REF) (continued)
Electrical Characteristics-MAX9027/MAX9028 (without REF)
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(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 guaran-
teed 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 MAX9025/MAX9026, reference volt-
age error should also be added.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Output Voltage Swing High VCC - VOH
MAX9027 only, VCC =
5V, ISOURCE = 5mA
TA = +25°C 191 400
mV
TA = TMIN to TMAX 500
MAX9028 only, VCC =
1.8V, ISOURCE = 1mA
TA = +25°C 58 200
TA = TMIN to TMAX 300
Output Voltage Swing Low VOL
VCC = 5V,
ISINK = 5mA
TA = +25°C 191 400
mV
TA = TMIN to TMAX 500
VCC = 1.8V,
ISINK = 1mA
TA = +25°C 56 200
TA = TMIN to TMAX 300
Output Leakage Current ILEAK MAX9028 only, VO = 5.5V 0.001 1 µA
Output Short-Circuit Current ISC
Sourcing, VO = VEE
VCC = 5V 35
mA
VCC = 1.8V 3
Sourcing, VO = VCC
VCC = 5V 33
VCC = 1.8V 3
High-to-Low Propagation Delay
(Note 4) tPD-
VCC = 1.8V 16 µs
VCC = 5V 14
Low-to-High Propagation Delay
(Note 4) tPD+
MAX9027 only VCC = 1.8V 15
µs
VCC = 5V 40
MAX9028 only
VCC = 1.8V,
RPULLUP = 100kΩ 16
VCC = 5V,
RPULLUP = 100kΩ 45
Rise Time tRISE MAX9027 only, CL = 15pF 1.6 µs
Fall Time tFALL CL = 15pF 0.2 µs
Power-Up Time tON 1.2 ms
Electrical Characteristics-MAX9027/MAX9028 (without REF) (continued)
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25°C, unless otherwise noted.)
MAX9025/MAX9026
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9025-28 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
4.53.52.5
800
1000
1200
600
1.5 5.5
TA = +85ºC
TA = +25ºC
TA = -40ºC
MAX9025-28 toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
4.53.52.5
400
500
600
700
800
300
1.5 5.5
MAX9027/MAX9028
SUPPLY CURRENT vs. SUPPLY VOLTAGE
TA = +85°C
TA = +25°C
TA = -40°C
MAX9025-28 toc03
TEMPERATURE (ºC)
SUPPLY CURRENT (nA)
603510-15
800
1000
1200
600
-40 85
MAX9025/MAX9026
SUPPLY CURRENT vs. TEMPERATURE
VCC = 5V
VCC = 1.8V
VCC = 3V
MAX9025-28 toc04
TEMPERATURE (ºC)
SUPPLY CURRENT (nA)
603510-15
400
500
600
700
800
300
-40 85
VCC = 5V
VCC = 3V
MAX9027/MAX9028
SUPPLY CURRENT vs. TEMPERATURE
VCC = 1.8V
MAX9025-28 toc05
TRANSITION FREQUENCY (kHz)
SUPPLY CURRENT (µA)
101
5
10
15
20
25
30
35
40
0
0.1 100
MAX9025/MAX9026
SUPPLY CURRENT vs. OUTPUT
TRANSITION FREQUENCY
VCC = 5V
VCC = 3V
VCC = 1.8V
MAX9025-28 toc06
TRANSITION FREQUENCY (kHz)
SUPPLY CURRENT (µA)
101
5
10
15
20
25
30
35
40
0
0.1 100
MAX9027/MAX9028
SUPPLY CURRENT vs. OUTPUT
TRANSITION FREQUENCY
VCC = 5V
VCC = 3V
VCC = 1.8V
OUTPUT VOLTAGE LOW
vs. SINK CURRENT
MAX9025-28 toc07
SINK CURRENT (mA)
OUTPUT VOLTAGE LOW (mV)
8642
200
400
600
800
0
0 10
VCC = 5V
VCC = 3V
VCC = 1.8V
OUTPUT VOLTAGE LOW
vs. SINK CURRENT
MAX9025-28 toc08
SINK CURRENT (mA)
OUTPUT VOLTAGE LOW (mV)
8642
200
400
600
800
0
0 10
TA = +85°C
TA = +25°C
TA = -40°C
MAX9025/MAX9027
OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
MAX9025-28 toc09
SOURCE CURRENT (mA)
OUTPUT VOLTAGE HIGH (V
CC - VOH, mV)
8642
200
400
600
800
0
0 10
VCC = 5V
VCC = 3V
VCC = 1.8V
Typical Operating Characteristics
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25°C, unless otherwise noted.)
MAX9025/MAX9027
OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
MAX9025-28 toc10
SOURCE CURRENT (mA)
CC - VOH, mV)
8642
200
400
600
800
0
0 10
TA = +85°C
TA = +25°C
TA = -40°C
SHORT-CIRCUIT SINK
CURRENT vs. TEMPERATURE
MAX9025-28 toc11
TEMPERATURE (ºC)
SHORT-CIRCUIT SINK CURRENT (mA)
603510-15
10
20
30
40
0
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
VOUT = VCC
MAX9025/MAX9027 SHORT-CIRCUIT SOURCE
CURRENT vs. TEMPERATURE
MAX9025-28 toc12
TEMPERATURE (ºC)
SHORT-CIRCUIT SINK CURRENT (mA)
603510-15
10
20
30
40
0
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
VOUT = VEE
OFFSET VOLTAGE
vs. TEMPERATURE
MAX9025-28 toc13
TEMPERATURE (ºC)
OFFSET VOLTAGE (mV)
603510-15
0.3
0.5
0.8
1.0
0
-40 85
VCC = 5V
VCC = 3V VCC = 1.8V
HYSTERESIS VOLTAGE
vs. TEMPERATURE
MAX9025-28 toc14
TEMPERATURE (ºC)
HYSTERESIS VOLTAGE (mV)
603510-15
2.5
3.0
3.5
4.0
2.0
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
-1.000
-0.600
0.200
-0.200
0.600
1.000
-0.5 1.50.5 2.5 3.5 4.5 5.5
INPUT BIAS CURRENT
vs. INPUT BIAS VOLTAGE
MAX9025-28 toc15
INPUT BIAS VOLTAGE (IN-) (V)
INPUT BIAS CURRENT (IN-) (nA)
IN+ = 2.5V
MAX9025/MAX9026
REFERENCE VOLTAGE vs. TEMPERATURE
MAX9025-28 toc16
TEMPERATURE (ºC)
REFERENCE VOLTAGE (V)
603510-15
1.2340
1.2350
1.2360
1.2370
1.2330
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
MAX9025/MAX9026
REFERENCE VOLTAGE vs. TEMPERATURE
MAX9025-28 toc17
TEMPERATURE (ºC)
REFERENCE VOLTAGE (V)
603510-15
1.233
1.235
1.237
1.239
1.231
-40 85
5 DEVICES
MAX9025/MAX9026
REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
MAX9025-28 toc18
SUPPLY VOLTAGE (V)
REFERENCE VOLTAGE (V)
4.53.52.5
1.235
1.236
1.237
1.238
1.234
1.5 5.5
Typical Operating Characteristics (continued)
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25°C, unless otherwise noted.)
MAX9025/MAX9026
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
MAX9025-28 toc19
REFERENCE CURRENT (nA)
REFERENCE VOLTAGE (V)
500-50
1.234
1.236
1.238
1.240
1.232
-100 100
VCC = 5V
VCC = 3V
VCC = 1.8V
PROPAGATION DELAY (tPD-)
vs. TEMPERATURE
MAX9025-28 toc20
TEMPERATURE (°C)
tPD- (µs)
603510-15
5
10
15
20
0
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
MAX9025/MAX9027
PROPAGATION DELAY (tPD+)
vs. TEMPERATURE
MAX9025-28 toc21
TEMPERATURE (ºC)
tPD+ (µs)
603510-15
10
20
30
40
50
0
-40 85
VCC = 5V
VCC = 3V
VCC = 1.8V
20
15
10
5
0
0.01 10.1 10 100
PROPAGATION DELAY (tPD-)
vs. CAPACITIVE LOAD
MAX9025-28 toc22
CAPACITIVE LOAD (nF)
tPD- (µs)
VCC = 5V
VCC = 3V
VCC = 1.8V
40
30
20
10
0
0.01 10.1 10 100
MAX9025/MAX9027
PROPAGATION DELAY (tPD+)
vs. CAPACITIVE LOAD
MAX9025-28 toc23
CAPACITIVE LOAD (nF)
tPD+ (µs)
VCC = 5V VCC = 3V
VCC = 1.8V
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50
PROPAGATION DELAY (tPD-)
vs. INPUT OVERDRIVE
MAX9025-28 toc24
INPUT OVERDRIVE (mV)
tPD- (µs)
VCC = 5V
VCC = 3V
VCC = 1.8V
0
20
10
40
30
50
60
0 2010 30 40 50
MAX9025/MAX9027
PROPAGATION DELAY (tPD+)
vs. INPUT OVERDRIVE
MAX9025-28 toc25
INPUT OVERDRIVE (mV)
tPD+ (µs)
VCC = 5V
VCC = 3V
VCC = 1.8V
MAX9026/MAX9028
PROPAGATION DELAY (tPD+)
vs. PULLUP RESISTANCE
MAX9025-28 toc26
PULLUP RESISTANCE (kΩ)
t
PD+
(
µ
s)
1000100
25
50
75
100
125
150
175
200
0
10 10000
VCC = 5V
VCC = 3V
VCC = 1.8V
20µs/div
PROPAGATION DELAY (VCC = 5V)
+100mV
MAX9025 toc27
-100mV
OUT
2V/div
0V
IN+
Typical Operating Characteristics (continued)
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25°C, unless otherwise noted.)
20µs/div
PROPAGATION DELAY (VCC = 3V)
+100mV
MAX9025 toc28
-100mV
OUT
1V/div
0V
IN+
20µs/div
PROPAGATION DELAY (VCC = 1.8V)
+100mV
MAX9025 toc29
-100mV
OUT
1V/div
0V
IN+
200µs/div
1kHz FREQUENCY RESPONSE
(VCC = 5V)
+100mV
MAX9025 toc30
-100mV
OUT
2V/div
0V
IN+
20µs/div
10kHz FREQUENCY RESPONSE
(VCC = 1.8V)
+100mV
MAX9025 toc31
-100mV
OUT
1V/div
0V
IN+
1ms/div
REFERENCE RESPONSE TO SUPPLY
VOLTAGE TRANSIENT (CREF = 10nF)
REF
200mV/div
MAX9025 toc32
VCC
1V/div
1.8V
5V
40µs/div
POWER-UP/POWER-DOWN RESPONSE
VCC
MAX9025 toc33
0V
OUT
2V/div
0V
2V/div
Typical Operating Characteristics (continued)
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
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Detailed Description
The MAX9025/MAX9026 feature an on-board 1.236V ±1%
reference, yet draw an ultra-low supply current of 1.0µA.
The MAX9027/MAX9028 (without reference) consume just
0.6µA 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 hystere-
sis ensures clean output switching, even with slow-moving
input signals. Large internal output drivers allow rail-to-rail
output swing with up to ±5mA 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 MAX9025/MAX9027 have a push-pull output stage
that sinks as well as sources current. The MAX9026/
MAX9028 have an open-drain output stage that can be
pulled beyond VCC to a maximum of 5.5V 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
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 protected from
overvoltage by internal ESD protection diodes connected
to the supply rails. As the input voltage exceeds the sup-
ply rails, these ESD protection diodes become forward
biased and begin to conduct.
Output Stage Circuitry
The MAX9025–MAX9028 contain a unique break-before-
make output stage capable of rail-to-rail operation with
up to ±5mA 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 output
transition is extremely small. In the Typical Operating
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 appli-
cations, this characteristic results in a substantial increase
in battery life.
PIN
NAME FUNCTION
MAX9025/
MAX9026
MAX9027/
MAX9028
A2 A2 OUT Comparator Output
A3 A3, B2 VEE Negative Supply Voltage
B1 B1 IN+ Comparator Noninverting
Input
B2 — REF 1.236V Reference Output
A1 A1 VCC Positive Supply Voltage
B3 B3 IN- Comparator Inverting
Input
MAX9025
MAX9026
IN+
OUT
VCC
VEE
IN-
REF
1.236V
MAX9027
MAX9028
IN+
OUT
VCC
VEE
IN-
REF
Functional Diagrams
Pin Description
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Reference (MAX9025/MAX9026)
The MAX9025−MAX9028s’ internal +1.236V reference
has a typical temperature coefficient of 40ppm/ºC over
the full -40ºC to +85ºC temperature range. The reference
is a very-low-power bandgap cell, with a typical 35kΩ
output impedance. REF can source and sink up to 100nA
to external circuitry. For applications needing increased
drive, buffer REF with a low input-bias current op amp
such as the MAX4162. Most applications require no REF
bypass capacitor. For noisy environments or fast VCC
transients, connect a 1nF to 10nF ceramic capacitor from
REF to GND.
Applications Information
Low-Voltage, Low-Power Operation
The MAX9025−MAX9028 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 MAX9025−MAX9028, assuming nominal conditions.
Internal Hysteresis
Many comparators oscillate in the linear region of opera-
tion 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
MAX9025−MAX9028 have internal 4mV 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 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.
Adding External Hysteresis
In applications requiring more than the internal 4mV hys-
teresis of the MAX9025−MAX9028, additional hysteresis
can be added with external components. Because the
MAX9025−MAX9028 are intended for very low-power
systems, care should be taken to minimize power dissipa-
tion in the additional circuitry.
Regardless of which approach is taken, the external hys-
teresis will be VCC dependent. Over the full discharge
range of battery-powered systems, the hysteresis can
change as much as 40%. This must be considered
during design.
Figure 1. MAX9025/MAX9026 Voltage Reference Output
Equivalent Circuit
Table 1. Battery Applications Using MAX9025−MAX9028
BATTERY
TYPE RECHARGEABLE VFRESH
(V)
VEND-OF-LIFE
(V)
CAPACITY,
AA SIZE
(mA-h)
MAX9025/MAX9026
OPERATING TIME
(hr)
MAX9027/MAX9028
OPERATING TIME
(hr)
Alkaline
(2 Cells) No 3.0 1.8 2000 1.8 x 1062.8 x 106
Nickel-
Cadmium
(2 Cells)
Yes 2.4 1.8 750 680,000 1.07 x 106
Lithium-Ion
(1 Cell) Yes 3.5 2.7 1000 0.9 x 1061.4 x 106
Nickel-Metal-
Hydride
(2 Cells)
Yes 2.4 1.8 1000 0.9 x 1061.4 x 106
BANDGAP REF
VEE
VCC
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Simplest Circuit
The simplest circuit for adding external hysteresis is
shown in Figure 3. In this example, the hysteresis is
defined by:
SCC
FB
R
Hysteresis V
R
= ×
where RS is the source resistance and RFB is the feed-
back resistance. Because the comparison threshold is 1/2
VCC, the MAX9027 was chosen for its push-pull output
and lack of reference. This provides symmetrical hyster-
esis around the threshold.
Output Considerations
In most cases, the push-pull outputs of the MAX9025/
MAX9027 are best for external hysteresis. The open-
drain output of the MAX9026/MAX9028 can be used, but
the effect of the feedback network on the actual output
high voltage must be considered.
Component Selection
Because the MAX9025−MAX9028 are intended for very
low power-supply systems, the highest impedance circuits
should be used wherever possible. The offset error due
to input-bias current is proportional to the total impedance
seen at the input. For example, selecting components for
Figure 3, with a target of 50mV hysteresis, a 5V supply,
and choosing an RFB of 10MΩ gives RS as 100kΩ. The
total impedance seen at IN+ is therefore 10MΩ || 100kΩ,
or 99kΩ. The maximum IB of the MAX9025−MAX9028 is
2nA; therefore, the error due to source impedance is less
than 400µV.
Asymmetrical Hysteresis
When the input threshold is not set at 1/2 VCC, the hys-
teresis added to the input threshold will not be symmetri-
cal. This is typical of the MAX9025/MAX9026 where the
internal reference is usually used as the threshold. If the
asymmetry is unacceptable, it can be corrected by adding
resistors to the circuit.
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 sup-
ply lines. Minimize signal trace lengths to reduce stray
capacitance. A ground plane and surface-mount compo-
nents are recommended. If the REF pin is decoupled, use
a new low-leakage capacitor.
Zero-Crossing Detector
Figure 4 shows a zero-crossing detector application. The
MAX9027’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 MAX9028 is
powered by the +5V supply voltage, and the pullup resis-
tor for the MAX9028’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 VCC and the +5V sup-
ply voltage to the pullup resistor.
Figure 2. Threshold Hysteresis Band Figure 3. MAX9025/MAX9027 External Hysteresis
THRESHOLDS
OUT
IN+
IN-
VHB
HYSTERESIS
BAND
VTHF
VTHR
VCC
MAX9027 OUT
RSRFB
VCC/2
VIN
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UCSP Applications Information
For the latest application details on UCSP construction,
dimensions, tape carrier information, printed circuit board
techniques, bump-pad layout, and recommended reflow
temperature profiles, as well as the latest information
on reliability testing results, go to Application Note 1891:
Wafer-Level Packaging (WLP) and its Applications.
Figure 4. Zero-Crossing Detector
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
6 UCSP B6+1 21-0097
Refer to
Application
Note 1891
MAX9028
IN-
2MΩ
2MΩ
RPULLUP
3V (5V)
LOGIC OUT
OUT
VCC
+5V (+3V)
+3V (+5V)
VEE
5V (3V) LOGIC IN
IN+
LOGIC-LEVEL
TRANSLATOR
MAX9027
IN+
OUT
VCC
100mVP-P
VCC
VEE
IN-
Chip Information
PROCESS: BiCMOS
Typical Application Circuit
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.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.
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REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 5/04 Initial release —
1 6/11 Added information for lead-free versions 1
Revision History
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX9025–MAX9028 UCSP, 1.8V, Nanopower, Beyond-the-Rails
Comparators With/Without Reference
© 2011 Maxim Integrated Products, Inc.
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