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19-3241; Rev 0; 5/04
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference
General Description
The MAX9025-MAX9028 nanopower comparators in space-saving chip-scale (UCSPTM) packages feature Beyond-the-RailsTM inputs and are guaranteed to operate down to +1.8V. The MAX9025/MAX9026 feature an on-board 1.236V 1% reference and draw an ultra-low supply current of only 1A, while the MAX9027/ MAX9028 (without reference) require just 0.6A of supply current. These features make the MAX9025-MAX9028 family of comparators ideal for all 2-cell batterymonitoring/management applications. The unique design of the output stage limits supplycurrent 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.
Features
Space-Saving UCSP Package (1mm x 1.52mm) Ultra-Low Supply Current 0.6A (MAX9027/MAX9028) 1A 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
MAX9025-MAX9028
Ordering Information
PART MAX9025EBT-T TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C BUMPPACKAGE 6 UCSP-6 6 UCSP-6 6 UCSP-6 6 UCSP-6 TOP MARK ADB ADC ADD ADE
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
MAX9026EBT-T MAX9027EBT-T MAX9028EBT-T
Pin Configurations
TOP VIEW (BUMPS ON BOTTOM) B 1 A VCC
IN+
Selector Guide
PART MAX9025 MAX9026 MAX9027 MAX9028 INTERNAL REFERENCE Yes Yes No No OUTPUT TYPE Push-Pull Open-Drain Push-Pull Open-Drain SUPPLY CURRENT (A) 1.0 1.0 0.6 0.6
3 INREF (VEE)
MAX9025- MAX9028
2 OUT
Typical Application Circuit appears at end of data sheet. Beyond-the-Rails and UCSP are trademarks of Maxim Integrated Products, Inc.
VEE
( ) MAX9027/MAX9028 PINS
UCSP
________________________________________________________________ Maxim Integrated Products
1
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
ABSOLUTE MAXIMUM RATINGS
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 = +70C) 6-Bump UCSP (derate 3.9mW/C above +70C)........308mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Bump Temperature (soldering) Reflow............................+235C
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)
(VCC = +5V, VEE = 0V, VIN+ = VREF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Supply Voltage Range Supply Current SYMBOL VCC ICC VCC = 1.8V VCC = 5V TA = +25C TA = TMIN to TMAX VEE 0.2 0.3 4 0.15 0.1 TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX 0.001 35 3 33 3 7 6 s mA VCC = 5V VCC = 1.8V VCC = 5V VCC = 1.8V 57 250 56 250 1 2 1 350 450 200 300 350 450 200 300 1 A mV mV CONDITIONS Inferred from the PSRR test MIN 1.8 0.8 1.0 TYP MAX 5.5 1.5 1.7 2.2 VCC + 0.2 5 10 V mV mV nA mV/V A UNITS V
IN+ Voltage Range Input Offset Voltage Input-Referred Hysteresis Input Bias Current Power-Supply Rejection Ratio
VIN+ VOS VHB IB PSRR VCC VOH
Inferred from output swing test (Note 2) (Note 3) TA = +25C TA = TMIN to TMAX VCC = 1.8V to 5.5V MAX9025, VCC = 5V, ISOURCE = 6mA MAX9025, VCC = 1.8V, ISOURCE = 1mA VCC = 5V, ISINK = 6mA VCC = 1.8V, ISINK = 1mA TA = +25C TA = TMIN to TMAX
Output Voltage Swing High
Output Voltage Swing Low
VOL
Output Leakage Current
ILEAK
MAX9026 only, VO = 5.5V Sourcing, VO = VEE
Output Short-Circuit Current
ISC Sinking, VO = VCC
High-to-Low Propagation Delay (Note 4)
tPD-
VCC = 1.8V VCC = 5V
2
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference
ELECTRICAL CHARACTERISTICS--MAX9025/MAX9026 (WITH REF) (continued)
(VCC = +5V, VEE = 0V, VIN+ = VREF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MAX9025 only Low-to-High Propagation Delay (Note 4) tPD+ MAX9026 only, RPULLUP = 100k CL = 15pF TA = +25C TA = TMIN to TMAX 1.224 1.205 40 CREF = 1nF BW = 10Hz to 100kHz BW = 10Hz to 6kHz 29 60 0.5 0.03 VCC = 1.8V VCC = 5V VCC = 1.8V VCC = 5V MIN TYP 11 28 12 31 1.6 0.2 1.2 1.236 1.248 1.267 s s ms V ppm/ C VRMS mV/V mV/ nA s MAX UNITS
MAX9025-MAX9028
Rise Time Fall Time Power-Up Time Reference Voltage Reference Voltage Temperature Coefficient Reference Output Voltage Noise Reference Line Regulation Reference Load Regulation
tRISE tFALL tON VREF TCREF EN VREF/ VCC VREF/ IOUT
MAX9025 only, CL = 15pF
VCC = 1.8V to 5.5V IOUT = 0nA to 100nA
ELECTRICAL CHARACTERISTICS--MAX9027/MAX9028 (WITHOUT REF)
(VCC = +5V, VEE = 0V, VCM = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Supply Voltage Range Supply Current Input Common-Mode Voltage Range Input Offset Voltage Input-Referred Hysteresis Input Bias Current Power-Supply Rejection Ratio Common-Mode Rejection Ratio SYMBOL VCC ICC VCC = 1.8V VCC = 5V TA = +25C TA = TMIN to TMAX VEE 0.2 0.3 CONDITIONS Inferred from the PSRR test MIN 1.8 0.45 0.6 TYP MAX 5.5 0.75 1.0 1.25 VCC + 0.2 5 mV TA = TMIN to TMAX 4 0.15 0.1 0.5 1 2 1 3 10 mV nA mV/V mV/V V A UNITS V
VCM
Inferred from the CMRR test -0.2V VCM (VCC + 0.2V) (Note 2) TA = +25C
VOS VHB IB PSRR CMRR
-0.2V VCM (VCC + 0.2V) (Note 3) TA = +25C TA = TMIN to TMAX VCC = 1.8V to 5.5V (VEE - 0.2V) VCM (VCC + 0.2V)
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3
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
ELECTRICAL CHARACTERISTICS--MAX9027/MAX9028 (WITHOUT REF) (continued)
(VCC = +5V, VEE = 0V, VCM = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MAX9027 only, VCC = 5V, ISOURCE = 5mA MAX9028 only, VCC = 1.8V, ISOURCE = 1mA VCC = 5V, ISINK = 5mA VCC = 1.8V, ISINK = 1mA TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX 0.001 35 3 33 3 16 14 15 40 16 45 1.6 0.2 1.2 s s ms s s mA VCC = 5V VCC = 1.8V VCC = 5V VCC = 1.8V VCC = 1.8V VCC = 5V MAX9027 only Low-to-High Propagation Delay (Note 4) tPD+ MAX9028 only VCC = 1.8V VCC = 5V VCC = 1.8V, RPULLUP = 100k VCC = 5V, RPULLUP = 100k Rise Time Fall Time Power-Up Time tRISE tFALL tON MAX9027 only, CL = 15pF CL = 15pF 56 191 58 MIN TYP 191 MAX 400 500 200 300 400 500 200 300 1 A mV mV UNITS
Output Voltage Swing High
VCC - VOH
Output Voltage Swing Low
VOL
Output Leakage Current
ILEAK
MAX9028 only, VO = 5.5V Sourcing, VO = VEE
Output Short-Circuit Current
ISC Sourcing, VO = VCC
High-to-Low Propagation Delay (Note 4)
tPD-
Note 1: All specifications are 100% tested at TA = +25C. 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 MAX9025/MAX9026, reference voltage error should also be added.
4
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
Typical Operating Characteristics
(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25C, unless otherwise noted.)
MAX9025/MAX9026 SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9025-28 toc01
MAX9027/MAX9028 SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9025-28 toc02
MAX9025/MAX9026 SUPPLY CURRENT vs. TEMPERATURE
MAX9025-28 toc03
1200 TA = +85C SUPPLY CURRENT (nA) 1000
800
1200
700 SUPPLY CURRENT (nA) TA = +85C 600
SUPPLY CURRENT (nA)
VCC = 5V 1000 VCC = 3V 800 VCC = 1.8V
TA = +25C
TA = -40C 800
500
TA = +25C TA = -40C
400
600 1.5 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
300 1.5 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
600 -40 -15 10 35 60 85 TEMPERATURE (C)
MAX9027/MAX9028 SUPPLY CURRENT vs. TEMPERATURE
MAX9025-28 toc04
MAX9025/MAX9026 SUPPLY CURRENT vs. OUTPUT TRANSITION FREQUENCY
MAX9025-28 toc05
MAX9027/MAX9028 SUPPLY CURRENT vs. OUTPUT TRANSITION FREQUENCY
35 SUPPLY CURRENT (A) 30 25 20 15 10 VCC = 5V VCC = 1.8V 0.1 1 10 100 VCC = 3V
MAX9025-28 toc06
800
40 35 SUPPLY CURRENT (A) 30 25 20 15 10 VCC = 5V VCC = 1.8V VCC = 3V
40
700 SUPPLY CURRENT (nA) VCC = 5V 600 VCC = 3V
500
400 VCC = 1.8V 300 -40 -15 10 35 60 85 TEMPERATURE (C)
5 0 0.1 1 10
5 0 100
TRANSITION FREQUENCY (kHz)
TRANSITION FREQUENCY (kHz)
OUTPUT VOLTAGE LOW vs. SINK CURRENT
MAX9025-28 toc07
OUTPUT VOLTAGE LOW vs. SINK CURRENT
MAX9025-28 toc08
MAX9025/MAX9027 OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
OUTPUT VOLTAGE HIGH (VCC - VOH, mV)
MAX9025-28 toc09
800
800
800
OUTPUT VOLTAGE LOW (mV)
OUTPUT VOLTAGE LOW (mV)
600 VCC = 3V VCC = 1.8V 400
600 TA = +25C 400 TA = +85C 200
600 VCC = 1.8V 400 VCC = 3V
200
VCC = 5V
TA = -40C
200 VCC = 5V 0
0 0 2 4 6 8 10 SINK CURRENT (mA)
0 0 2 4 6 8 10 SINK CURRENT (mA)
0
2
4
6
8
10
SOURCE CURRENT (mA)
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5
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25C, unless otherwise noted.)
MAX9025/MAX9027 OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
MAX9025-28 toc10
SHORT-CIRCUIT SINK CURRENT vs. TEMPERATURE
MAX9025-28 toc11
MAX9025/MAX9027 SHORT-CIRCUIT SOURCE CURRENT vs. TEMPERATURE
VOUT = VEE SHORT-CIRCUIT SINK CURRENT (mA) 30 VCC = 5V 20 VCC = 3V 10
MAX9025-28 toc12 MAX9025-28 toc18
MAX9025-28 toc15
800 OUTPUT VOLTAGE HIGH (VCC - VOH, mV)
40 VOUT = VCC SHORT-CIRCUIT SINK CURRENT (mA) 30 VCC = 5V 20 VCC = 3V 10
40
600
400 TA = +85C 200 TA = +25C 0 0 2 4 6 8 10 SOURCE CURRENT (mA) TA = -40C
VCC = 1.8V
VCC = 1.8V
0 -40 -15 10 35 60 85 TEMPERATURE (C)
0 -40 -15 10 35 60 85 TEMPERATURE (C)
OFFSET VOLTAGE vs. TEMPERATURE
MAX9025-28 toc13
HYSTERESIS VOLTAGE vs. TEMPERATURE
MAX9025-28 toc14
INPUT BIAS CURRENT vs. INPUT BIAS VOLTAGE
1.000 IN+ = 2.5V
1.0
4.0 VCC = 3V
OFFSET VOLTAGE (mV)
0.8
3.5
VCC = 1.8V
INPUT BIAS CURRENT (IN-) (nA)
HYSTERESIS VOLTAGE (mV)
0.600
0.200
0.5
VCC = 3V
VCC = 1.8V
3.0 VCC = 5V 2.5
-0.200
0.3 VCC = 5V 0 -40 -15 10 35 60 85 TEMPERATURE (C)
-0.600
2.0 -40 -15 10 35 60 85 TEMPERATURE (C)
-1.000 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 INPUT BIAS VOLTAGE (IN-) (V)
MAX9025/MAX9026 REFERENCE VOLTAGE vs. TEMPERATURE
MAX9025-28 toc16
MAX9025/MAX9026 REFERENCE VOLTAGE vs. TEMPERATURE
5 DEVICES REFERENCE VOLTAGE (V) 1.237
MAX9025-28 toc17
MAX9025/MAX9026 REFERENCE VOLTAGE vs. SUPPLY VOLTAGE
1.238
1.2370 VCC = 3V VCC = 1.8V REFERENCE VOLTAGE (V) 1.2360 VCC = 5V 1.2350
1.239
REFERENCE VOLTAGE (V)
1.237
1.235
1.236
1.2340
1.233
1.235
1.2330 -40 -15 10 35 60 85 TEMPERATURE (C)
1.231 -40 -15 10 35 60 85 TEMPERATURE (C)
1.234 1.5 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
6
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25C, unless otherwise noted.)
MAX9025/MAX9026 REFERENCE VOLTAGE vs. REFERENCE CURRENT
MAX9025-28 toc19
PROPAGATION DELAY (tPD-) vs. TEMPERATURE
MAX9025-28 toc20
MAX9025/MAX9027 PROPAGATION DELAY (tPD+) vs. TEMPERATURE
MAX9025-28 toc21
1.240 VCC = 3V REFERENCE VOLTAGE (V) 1.238 VCC = 1.8V 1.236 VCC = 5V 1.234
20 VCC = 1.8V 15 VCC = 3V tPD- (s)
50
40 VCC = 5V tPD+ (s) 30 VCC = 3V 20
10 VCC = 5V 5
10 VCC = 1.8V
1.232 -100 -50 0 50 100 REFERENCE CURRENT (nA)
0 -40 -15 10 35 60 85 TEMPERATURE (C)
0 -40 -15 10 35 60 85 TEMPERATURE (C)
PROPAGATION DELAY (tPD-) vs. CAPACITIVE LOAD
MAX9025-28 toc22
MAX9025/MAX9027 PROPAGATION DELAY (tPD+) vs. CAPACITIVE LOAD
MAX9025-28 toc23
PROPAGATION DELAY (tPD-) vs. INPUT OVERDRIVE
70 60 tPD- (s) 50 40 30 VCC = 1.8V
MAX9025-28 toc24
20
40
80
15 tPD- (s)
VCC = 1.8V
30 VCC = 5V VCC = 3V tPD+ (s)
10 VCC = 3V VCC = 5V 5
20
VCC = 3V
10 VCC = 1.8V
20 10 0 0.01 0.1 1 10 100 0 10 20 30 40 50 CAPACITIVE LOAD (nF) INPUT OVERDRIVE (mV) VCC = 5V
0 0.01 0.1 1 10 100 CAPACITIVE LOAD (nF)
0
MAX9025/MAX9027 PROPAGATION DELAY (tPD+) vs. INPUT OVERDRIVE
MAX9025-28 toc25
MAX9026/MAX9028 PROPAGATION DELAY (tPD+) vs. PULLUP RESISTANCE
MAX9025-28 toc26
PROPAGATION DELAY (VCC = 5V)
MAX9025 toc27
60 50 40 tPD+ (s) 30 VCC = 3V 20 10 VCC = 1.8V 0 0 10 20 30 40 VCC = 5V
200 175 150 tPD+ (s) 125 100 75 50 25 0 VCC = 5V VCC = 3V
+100mV IN+ -100mV
OUT 2V/div 0V VCC = 1.8V 100 1000 10000 20s/div
50
10
INPUT OVERDRIVE (mV)
PULLUP RESISTANCE (k)
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7
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = 0V, CL = 15pF, VOVERDRIVE = 100mV, TA = +25C, unless otherwise noted.)
1kHz FREQUENCY RESPONSE (VCC = 5V)
+100mV IN+ -100mV
PROPAGATION DELAY (VCC = 3V)
MAX9025 toc28
PROPAGATION DELAY (VCC = 1.8V)
MAX9025 toc29
MAX9025 toc30
+100mV IN+ -100mV
+100mV IN+ -100mV
OUT 1V/div 0V
OUT 1V/div 0V 20s/div
OUT 2V/div 0V
20s/div
200s/div
10kHz FREQUENCY RESPONSE (VCC = 1.8V)
MAX9025 toc31
REFERENCE RESPONSE TO SUPPLY VOLTAGE TRANSIENT (CREF = 10nF)
+100mV IN+ -100mV
MAX9025 toc32
POWER-UP/POWER-DOWN RESPONSE
MAX9025 toc33
REF 200mV/div 5V VCC 1V/div
VCC 2V/div 0V OUT 2V/div 0V
OUT 1V/div 0V
1.8V
20s/div
1ms/div
40s/div
8
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference
Functional Diagrams
VCC
MAX9025-MAX9028
VCC
IN+ OUT IN-
IN+ OUT IN-
REF REF 1.236V VEE
MAX9025 MAX9026
MAX9027 MAX9028
VEE
Pin Description
PIN MAX9025/ MAX9026 A2 A3 B1 B2 A1 B3 MAX9027/ MAX9028 A2 A3, B2 B1 -- A1 B3 NAME OUT VEE IN+ REF VCC INFUNCTION Comparator Output Negative Supply Voltage Comparator Noninverting Input 1.236V Reference Output Positive Supply Voltage Comparator Inverting Input
MAX9026/MAX9028 have an open-drain output stage that can be pulled beyond VCC to a maximum of 5.5V above V EE. 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 supply rails, these ESD protection diodes become forward biased and begin to conduct.
Output Stage Circuitry
Detailed Description
The MAX9025/MAX9026 feature an on-board 1.236V 1% reference, yet draw an ultra-low supply current of 1.0A. The MAX9027/MAX9028 (without reference) consume just 0.6A 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 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
The MAX9025-MAX9028 contain a unique breakbefore-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 during 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 applications, this characteristic results in a substantial increase in battery life.
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9
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
Reference (MAX9025/MAX9026)
The MAX9025-MAX9028s' internal +1.236V reference has a typical temperature coefficient of 40ppm/C over the full -40C to +85C temperature range. The reference is a very-low-power bandgap cell, with a typical 35k 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.
VCC
BANDGAP
REF
VEE
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.
Figure 1. MAX9025/MAX9026 Voltage Reference Output Equivalent Circuit
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 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 hysteresis 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 dissipation in the additional circuitry. Regardless of which approach is taken, the external hysteresis 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.
Table 1. Battery Applications Using MAX9025-MAX9028
BATTERY TYPE Alkaline (2 Cells) NickelCadmium (2 Cells) Lithium-Ion (1 Cell) Nickel-MetalHydride (2 Cells) RECHARGEABLE VFRESH (V) VEND-OF-LIFE (V) CAPACITY, AA SIZE (mA-H) 2000 MAX9025/MAX9026 OPERATING TIME (hr) 1.8 x 106 MAX9027/MAX9028 OPERATING TIME (hr) 2.8 x 106
No
3.0
1.8
Yes
2.4
1.8
750
680,000
1.07 x 106
Yes
3.5
2.7
1000
0.9 x 106
1.4 x 106
Yes
2.4
1.8
1000
0.9 x 106
1.4 x 106
10
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
IN+ VTHR INVHB VTHF HYSTERESIS BAND THRESHOLDS
RS VIN VCC
RFB
MAX9027
VCC/2
OUT
OUT
Figure 2. Threshold Hysteresis Band
Figure 3. MAX9025/MAX9027 External Hysteresis
Simplest Circuit The simplest circuit for adding external hysteresis is shown in Figure 3. In this example, the hysteresis is defined by: Hysteresis = RS x VCC RFB
Asymmetrical Hysteresis When the input threshold is not set at 1/2 VCC, the hysteresis added to the input threshold will not be symmetrical. 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.
where RS is the source resistance and RFB is the feedback 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 hysteresis 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 10M gives RS as 100k. The total impedance seen at IN+ is therefore 10M || 100k, or 99k. The maximum IB of the MAX9025-MAX9028 is 2nA; therefore, the error due to source impedance is less than 400V.
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 surfacemount components 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 resistor 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 supply voltage to the pullup resistor.
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11
UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference MAX9025-MAX9028
VCC
Typical Application Circuit
+5V (+3V)
100mVP-P IN+
VCC
+3V (+5V)
OUT
2M IN-
VCC
IN-
RPULLUP 3V (5V) LOGIC OUT
MAX9027
2M
VEE
OUT IN+
MAX9028 Figure 4. Zero-Crossing Detector
VEE 5V (3V) LOGIC IN LOGIC-LEVEL TRANSLATOR
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 Maxim's web site at www.maxim-ic.com/ucsp to find the Application Note: UCSP--A Wafer-Level Chip-Scale Package.
Chip Information
TRANSISTOR COUNT: 209 PROCESS: BiCMOS
12
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UCSP, 1.8V, Nanopower, Beyond-the-Rails Comparators With/Without Reference
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
6L, UCSP.EPS
MAX9025-MAX9028
PACKAGE OUTLINE, 3x2 UCSP 21-0097 G
1 1
Note: The MAX9025EBT-MAX9028EBT use Package Code B6-1.
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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