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19-1299; Rev 1; 1/98
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators
________________General Description
The MAX976/MAX978/MAX998 dual/quad/single, highspeed, low-power comparators are optimized for +3V/+5V single-supply applications. They achieve a 20ns propagation delay while consuming only 225A supply current per comparator. The MAX998 features a low-power shutdown mode that places the output in a high-impedance state and reduces supply current to 1nA. The MAX976/MAX978/MAX998 inputs have a commonmode voltage range that extends 200mV below ground. Their outputs are capable of Rail-to-Rail(R) operation without external pull-up circuitry, making these devices ideal for interface with CMOS/TTL logic. All inputs and outputs can tolerate a continuous short-circuit fault condition to either rail. The comparators' internal hysteresis ensures clean output switching, even with slow-moving input signals. For space-critical applications, the single MAX998 is available in a 6-pin SOT23 package, the dual MAX976 is available in an 8-pin MAX package, and the quad MAX978 is available in a 16-pin QSOP package.
____________________________Features
o Single-Supply Operation Down to 2.7V o 20ns Propagation Delay o 225A Supply Current o 1nA Shutdown Supply Current o Rail-to-Rail Outputs o Ground-Sensing Inputs o Internal Hysteresis Ensures Clean Switching o Available in Space-Saving Packages: SOT23-6 (MAX998) MAX (MAX976) QSOP-16 (MAX978)
MAX976/MAX978/MAX998
_______________Ordering Information
PART MAX976ESA MAX976EUA MAX978ESE MAX978EEE MAX998ESA MAX998EUT-T TEMP. RANGE PIN-PACKAGE -40C to +85C 8 SO -40C to +85C 8 MAX -40C to +85C 16 Narrow SO -40C to +85C 16 QSOP -40C to +85C 8 SO -40C to +85C 6 SOT23-6 SOT TOP MARK -- -- -- -- -- AAAO
________________________Applications
Battery-Powered Systems Threshold Detectors/Discriminators 3V Systems IR Receivers Digital Line Receivers
___________Typical Operating Circuit
VCC VCC 0.1F VCC RD GND SHDN VCC R1 VCC R2 OUT
__________________Pin Configurations
TOP VIEW
OUT 1
MAX998
6
VCC
GND 2
5
SHDN
+-
MAX998
IN+ 3
4
IN-
SOT23-6
IR RECEIVER
Pin Configurations continued at end of data sheet
Rail-to-Rail is a registered trademark of Nippon Motorola Ltd.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators MAX976/MAX978/MAX998
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC).............................................................+6V SHDN (MAX998) .........................................................-0.3V to 6V All Other Pins..............................................-0.3V to (VCC + 0.3V) Duration of Output Short Circuit to GND or VCC ........Continuous Continuous Power Dissipation (TA = +70C) 6-Pin SOT23-6 (derate 7.1mW/C above +70C) .........571mW 8-Pin MAX (derate 4.10mW/C above +70C) ............330mW 8-Pin SO (derate 5.88mW/C above +70C).................471mW 16-Pin Narrow SO (derate 8.70mW/C above +70C) ..696mW 16-Pin QSOP (derate 8.33mW/C above +70C)..........667mW Operating Temperature Range ..........................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
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
(VCC = +2.7V to +5.5V, VCM = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Supply Voltage Range Supply Current per Comparator Shutdown Supply Current Power-Supply Rejection Ratio Common-Mode Voltage Range Common-Mode Rejection Ratio Input Offset Voltage Input-Referred Hysteresis Input Bias Current Input Offset Current OUT Output Voltage High OUT Output Voltage Low OUT Short-Circuit Current Input Capacitance SHDN Input Voltage High SHDN Input Voltage Low OUT Leakage Current SHDN Input Current Propagation Delay Propagation-Delay Skew Propagation-Delay Matching Between Channels Output Rise/Fall Time Shutdown Delay Time SYMBOL VCC ICC ISD PSRR VCMR CMRR VOS VHYS IB IOS VOH VOL ISH CIN VIH VIL IOUT I SHDN tPD tSKEW tPD tR/tF tSD MAX998 only MAX998 only MAX998 only, SHDN = GND, VOUT = 0V to VCC MAX998 only CLOAD =10pF, VCC = 5V (Note 5) Overdrive = 5mV Overdrive = 50mV 1 1 28 20 2 1 1.6 5 40 0.65 x VCC 0.2 x VCC 200 200 ISOURCE = 2mA, VCC - VOH ISINK = 2mA VCC = 5.5V Sinking Sourcing VCC = 5.5V VCC = 2.7V MAX998 only, SHDN = GND 2.7V < VCC < 5.5V (Note 2) -0.2V VCM (VCC - 1.2V) VCC = 5V (Note 3) VCC = 5V (Note 4) TA = +25C TA = TMIN to TMAX MAX976EUA, MAX998EUT All others 0.3 0.5 1.5 1.5 75 5 0.1 0.1 74 90 3 63 -0.2 66 95 0.2 2 3 5 4 300 100 0.4 0.4 CONDITIONS Inferred from PSRR test MIN 2.7 300 225 1 100 VCC - 1.2 500 TYP MAX 5.5 650 UNITS V A nA dB V dB mV mV mV nA nA V V mA pF V V nA nA ns ns ns ns s
CLOAD =10pF (Note 6) MAX976/MAX978 only CLOAD =10pF MAX998 only, VCC = 5V, ICC = 10% of typical
2
_______________________________________________________________________________________
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +2.7V to +5.5V, VCM = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Wake-Up from Shutdown Power-Up Delay SYMBOL tEN tPU CONDITIONS MAX998 only, VCC = 5V, ICC = 90% of typical (Note 7) VCC = 0V to 5V step, output valid MIN TYP 15 3 MAX UNITS s s
MAX976/MAX978/MAX998
Note 1: The MAX998EUT specifications are 100% tested at TA = +25C. Limits over the extended temperature range are guaranteed by design, not production tested. Note 2: Inferred from CMRR test. Either input can be driven to the absolute maximum limit without false output inversion, as long as the other input is within the common-mode voltage range. Note 3: VOS is defined as the mean of trip points. The trip points are the extremities of the differential input voltage required to make the comparator output change state (Figure 1). Note 4: The difference between the upper and lower trip points is equal to the width of the input-referred hysteresis zone (Figure 1). Note 5: Propagation Delay is guaranteed by design. For low overdrive conditions, VTRIP (Figure 1) is added to the overdrive. Note 6: Propagation-Delay Skew is the difference between the positive-going and the negative-going propagation delay. Note 7: For design purposes, the tEN can be as high as 60s.
__________________________________________Typical Operating Characteristics
(VCC = +5V, VCM = 0V, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT PER COMPARATOR vs. TEMPERATURE
MAX976 TOC01
SHORT-CIRCUIT OUTPUT CURRENT vs. TEMPERATURE
MAZX976 TOC2
OUTPUT LOW VOLTAGE vs. OUTPUT SINK CURRENT
1.4 OUTPUT LOW VOLTAGE (V) 1.2 1.0 0.8 0.6 0.4 0.2 VCC = 5.5V VCC = 2.7V
MAX976 TOC03
375 SUPPLY CURRENT PER COMPARATOR (A) VCC = 5.5V, VOUT = HIGH VCC = 2.7V, VOUT = HIGH
110 100 90 OUTPUT CURRENT (mA) 80 70 60 50 40 30 20 10 -60 VCC = 2.7V, SINKING -40 -20 0 20 40 60 80 VCC = 2.7V, SOURCING VCC = 5.5V, SINKING VCC = 5.5V, SOURCING
1.6
325
275
225
175
125 -60 -40 -20 0
VCC = 5.5V, VCC = 2.7V, VOUT = LOW VOUT = LOW 20 40 60 80 100 TEMPERATURE (C)
0 100 0.1 1 10 100 OUTPUT CURRENT (mA)
TEMPERATURE (C)
OUTPUT HIGH VOLTAGE vs. OUTPUT SOURCE CURRENT
MAX976 TOC04
PROPAGATION DELAY vs. TEMPERATURE
MAZX976 TOC5
PROPAGATION DELAY vs. CAPACITIVE LOAD
VOD = 50mV 35 PROPAGATION DELAY (ns) 30 25 20 15 10
MAX976 TOC06
6 VCC = 5.5V 5 OUTPUT HIGH VOLTAGE (V) 4 3 2 1 0 0.1 1 10 VCC = 2.7V
27 26 PROPAGATION DELAY (ns) 25 24 23 22 21 20 19 18 17 VCC = 5.5V VOD = 50mV CLOAD = 15pF VCC = 2.7V
40
100
-60
-40
-20
0
20
40
60
80
100
10
100 CAPACITIVE LOAD (pF)
1000
OUTPUT CURRENT (mA)
TEMPERATURE (C)
_______________________________________________________________________________________
3
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators MAX976/MAX978/MAX998
______________________________Typical Operating Characteristics (continued)
(VCC = +5V, VCM = 0V, TA = +25C, unless otherwise noted.)
PROPAGATION DELAY vs. INPUT OVERDRIVE
MAX976 TOC07
TRIP POINTS AND OFFSET VOLTAGE vs. TEMPERATURE
1.5 1.0 0.5 0 -0.5 VTRIP-1.0 -1.5 -2.0 VTRIP+ VOS
MAX976 TOC08
INPUT BIAS CURRENT vs. TEMPERATURE
MAX976 TOC09
90 80 PROPAGATION DELAY (ns) 70 60 50 40 30 20 10 0 1 10 INPUT OVERDRIVE (mV) CLOAD = 15pF
2.0 TRIP POINTS/OFFSET VOLTAGE (V)
100 90 INPUT BIAS CURRENT (nA) 80 VCC = 5.5V 70 60 VCC = 2.7V 50 40
100
-60
-40
-20
0
20
40
60
80
100
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (C)
TEMPERATURE (C)
INPUT BIAS CURRENT vs. INPUT COMMON-MODE VOLTAGE
MAX976 TOC10
PROPAGATION DELAY (tPD+, VCC = 3V)
MAX976 TOC11
PROPAGATION DELAY (tPD-, VCC = 3V)
MAX976 TOC12
100 VCC = 2.7V INPUT BIAS CURRENT (nA) 10 VCC = 5.5V
VOD = 50mV CLOAD = 15pF VIN+ 50mV/div VIN+ 50mV/div
1
0.1
VOUT 1V/div
VOUT 1V/div
CLOAD = 15pF VOD = 50mV 10ns/div
0.01 -1 0 1 2 3 4 5 6 10ns/div INPUT COMMON-MODE VOLTAGE (V)
PROPAGATION DELAY (tPD+, VCC = 5V)
MAX976 TOC13
PROPAGATION DELAY (tPD-, VCC = 5V)
MAX976 TOC14
10MHz RESPONSE
MAX976 TOC15
VOD = 50mV CLOAD = 15pF VIN+ 50mV/div VOS VIN+ 50mV/div VCC OUTPUT 2V/div VOUT 2V/div VOUT 2V/div GND VOD = 50mV CLOAD = 15pF 10ns/div 20ns/div INPUT 50mV/div
10ns/div
4
_______________________________________________________________________________________
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators MAX976/MAX978/MAX998
______________________________Typical Operating Characteristics (continued)
(VCC = +5V, VCM = 0V, TA = +25C, unless otherwise noted.)
SHUTDOWN DELAY TIME
MAX976 TOC16
WAKE-UP FROM SHUTDOWN
MAX976 TOC17
VIN+ > VINSHDN 2V/div SHDN 2V/div
VIN+ > VIN-
VOUT 2V/div
VOUT 2V/div
200ns/div
5s/div
______________________________________________________________Pin Description
PIN MAX976 SO/MAX 1, 3 2, 4 5 6, 7 8 -- -- MAX978 SO/QSOP 1, 3, 5, 7 2, 4, 6, 8 9, 13 10, 11, 14, 15 12, 16 -- -- 3 4 2 1 6 -- 5 MAX998 SOT23-6 SO 3 2 4 6 7 1, 5 8 IN_+ IN_GND OUT_ VCC N.C. SHDN Comparator Noninverting Input Comparator Inverting Input Ground Comparator Output Supply Voltage, +2.7V to +5.5V No Connection. Not internally connected. Shutdown Input. Drive low for shutdown mode. Drive high or connect to VCC for normal operation. NAME FUNCTION
__________________Detailed Description
The MAX976/MAX978/MAX998 dual/quad/single comparators operate from a single +2.7V to +5.5V supply. They achieve a 20ns propagation delay while consuming only 225A of supply current per comparator. The MAX998 features a low-power shutdown mode that places the output in a high-impedance state and reduces supply current to 1nA. Activate shutdown mode by driving SHDN low. The MAX976/MAX978/MAX998 comparator inputs have a common-mode voltage range of -0.2V to (VCC - 1.2V).
Either input can be driven to the Absolute Maximum Ratings limit without false output inversion, as long as the other input is within the Common-Mode Voltage Range. Their push/pull output structure is capable of rail-to-rail operation without external pull-up circuitry, making these devices ideal for interfacing with CMOS/TTL logic. All inputs and outputs can tolerate a continuous short-circuit fault condition to either supply. The comparator's internal hysteresis ensures clean output switching, even with slow-moving input signals.
_______________________________________________________________________________________
5
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators MAX976/MAX978/MAX998
Hysteresis
High-speed comparators can oscillate in the linear operating region because of noise or undesired parasitic feedback. This tends to occur when the voltage on one input is equal to or very close to the voltage on the other input. The MAX976/MAX978/MAX998 have internal hysteresis to counter parasitic effects and noise. The hysteresis in a comparator creates two trip points: one for the rising input voltage and one for the falling input voltage (Figure 1). The difference between the trip points is the hysteresis. When the comparator input voltages are equal, the hysteresis effectively causes one comparator input voltage to move quickly past the other, taking the input out of the region where oscillation occurs. Figure 1 illustrates the case where 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. affecting comparator operation. Likewise, do not threestate SHDN. Due to the output leakage currents of three-state devices and the small internal current for SHDN, three-stating this pin could also result in indeterminate logic levels. The maximum input voltage for SHDN is 6V, referred to GND, and is not limited by VCC. This allows the use of 5V logic to drive SHDN while VCC operates at a lower voltage, such as 3V. The logic threshold limits for SHDN are proportional to V CC (see Electrical Characteristics).
_____________Applications Information
Circuit Layout and Bypassing
The MAX976/MAX978/MAX998 have a high-gain bandwidth and require careful board layout. We recommend the following design guidelines: 1) Use a printed circuit board with an unbroken, lowinductance ground plane. Surface-mount components are recommended. 2) Place a decoupling capacitor (a 0.1F ceramic capacitor is a good choice) between V CC and ground as close to the pins as possible. 3) Keep lead lengths short on the inputs and outputs to avoid unwanted parasitic feedback around the comparators. 4) Solder the devices directly to the printed circuit board instead of using a socket. 5) Minimize input impedance. 6) For slowly varying inputs, use a small capacitor (~1000pF) across the inputs to improve stability.
Input-Stage Circuitry
The MAX976/MAX978/MAX998 input common-mode voltage range is from -0.2V to (VCC - 1.2V). The voltage range for each comparator input extends to both VCC and GND. The output remains in the correct logic state while one or both of the inputs are within the commonmode range. If both input levels are out of the commonmode range, input-stage current saturation occurs, and the output becomes unpredictable.
Shutdown Mode
The MAX998 features a low-power shutdown mode, which is activated by forcing SHDN low. Shutdown mode reduces the supply current to 1nA (typical), disables the comparator, and places the output in a highimpedance state. Drive SHDN high to enable the comparator. Do not leave SHDN unconnected. Since it is a high-impedance input, leaving SHDN unconnected could result in indeterminate logic levels, adversely
Additional Hysteresis
Generate additional hysteresis with three resistors using positive feedback, as shown in Figure 2. This positive feedback method slows the hysteresis response time. Calculate resistor values as follows: 1) Select R3. The leakage current of IN+ is typically 75nA, so the current through R3 should be at least 1.0A to minimize errors caused by leakage current. The current through R3 at the trip point is (VREF VOUT) / R3. Consider the two possible output states when solving for R3. The two formulas are: R3 = VREF / 1.0A or R3 = (VCC - VREF) / 1.0A Use the smaller of the two resulting resistor values. For example, if VREF = 1.2V and VCC = 5.0V, the two resistor values are 1.2M and 3.8M. Choose a standard value for R3 of 1.2M.
VHYST VTRIP+ VIN+ VTRIP-
VOS = VTRIP+ + VTRIP2 VIN- = 0
COMPARATOR OUTPUT
VOH VOL
Figure 1. Input and Output Waveforms, Noninverting Input Varied
6
_______________________________________________________________________________________
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators
R3 VCC
Window Comparator
The MAX976 is ideal for making a window detector (undervoltage/overvoltage detector). The schematic shown in Figure 3 uses a MAX6120 reference and component values selected for a 2.0V undervoltage threshold and a 2.5V overvoltage threshold. Choose different thresholds by changing the values of R1, R2, and R3. OUTA provides an active-low undervoltage indication, and OUTB gives an active-low overvoltage indication. ANDing the two outputs provides an active-high, power-good signal. The design procedure is as follows: 1) Select R1. The leakage current into INB- is normally 75nA, so the current through R1 should exceed 1.0A for the thresholds to be accurate. R1 values in the 50k to 100k range are typical. 2) Choose the overvoltage threshold (VOTH) when VIN is rising, and calculate R2 and R3 with the following formula: RSUM = R2 + R3 = R1 x [VOTH / (VREF + VH) - 1] where VH = 1/2VHYST. 3) Choose the undervoltage threshold (VUTH) when VIN is falling, and calculate R2 with the following formula: R2 = (R1 + RSUM) x [(VREF - VH) / VUTH] - R1 where VH = 1/2VHYST. 4) Calculate R3 with the following formula: R3 = (RSUM) - R2 5) Verify the resistor values. The equations are as follows: = 16.2k VOTH = (VREF + VH) x (R1 + R2 + R3) / R1 VUTH = (VREF - VH) x (R1 + R2 + R3) / (R1 + R2)
VCC 1 8 7 0.1F UNDERVOLTAGE 5
MAX976/MAX978/MAX998
R1 VIN VCC R2 GND VREF
0.1F OUT
MAX976 MAX978 MAX998
Figure 2. Additional Hysteresis
2) Choose the hysteresis band required (VHB). For this example, choose 100mV. 3) Calculate R1. R1 = R3 x (VHB / VCC). Plugging in the values for this example, R1 = 1.2M x (100mV / 5.0V) = 24k 4) Choose the trip point for V IN rising. This is the threshold voltage at which the comparator switches from low to high as VIN rises above the trip point. In this example, choose 3.0V. 5) Calculate R2 as follows: R2 = 1 VTHR 1 1 V - R1 - R3 REF x R1 1 3.0V 1 1 - - 24k 1.2M 1.2 x 24k
R2 =
Choose a standard value for R2 of 16k. 6) Verify the trip voltage and hysteresis as follows: 1 1 1 VIN rising: VTHR = VREF x R1 x + + R2 R3 R1 R1 x VCC VIN falling : VTHF = VTHR - R3 Hysteresis = VTHR - VTHF
R3 82.1k, 1% VIN R2 24.9k, 1%
1/2
VCC 1 2
MAX976
POWER GOOD 2 3
MAX6120
1/2
6
OVERVOLTAGE
IR Receiver
The Typical Operating Circuit shows an application using the MAX998 as an infrared receiver. The infrared photodiode creates a current relative to the amount of infrared light present. This current creates a voltage across RD. When this voltage level crosses the voltage applied by the voltage divider to the inverting input, the output transitions.
3 R1 100k, 1%
4
MAX976
Figure 3. Window Comparator
7
_______________________________________________________________________________________
Single/Dual/Quad, SOT23, Single-Supply, High-Speed, Low-Power Comparators MAX976/MAX978/MAX998
______________________________________________Pin Configurations (continued)
TOP VIEW
MAX978 MAX998
N.C. 1 IN- 2 IN+ 3 8 7 SHDN VCC OUT N.C. INA+ 1 INA- 2 INB+ 3
MAX976
+ + 8 7 6 5 VCC OUTA OUTB
INA+ 1 INA- 2 INB+ 3 INB- 4 INC+ 5 GND INC- 6 IND+ 7
+ + + + -
16 VCC 15 OUTA 14 OUTB 13 GND 12 VCC 11 OUTC 10 OUTD 9 GND
+
6 5
GND 4
INB- 4
SO
SO/MAX
IND- 8
SO/QSOP
___________________Chip Information
TRANSISTOR COUNT: 415 (MAX976) 830 (MAX978) 300 (MAX998)
________________________________________________________Package Information
6LSOT.EPS
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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