MAX977ESD-T [MAXIM]
Comparator, 2 Func, 3000uV Offset-Max, 28ns Response Time, CMOS, PDSO14, SOP-14;
| 型号： | MAX977ESD-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Comparator, 2 Func, 3000uV Offset-Max, 28ns Response Time, CMOS, PDSO14, SOP-14 放大器 光电二极管 |
| 文件： | 总16页 (文件大小：261K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1141; Rev 1; 11/98
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX975/MAX977 single/dual comparators feature
three different operating modes, and are optimized for
+3V and +5V single-supply applications. The operating
modes are as follows: high speed, high speed with
auto-standby, and low power. Propagation delay is 28ns
in high-speed mode, while supply current is only 250µA.
Supply current is reduced to 3µA in low-power mode.
♦ Three Operating Modes:
High Speed
High Speed with Auto-Standby
Low Power
♦ 28ns Propagation Delay (high-speed mode)
♦ 5µA Max Supply Current in Low-Power/
Auto-Standby Modes
The a uto-sta ndb y fe a ture a llows the c omp a ra tor to
automatically change from low-power mode to high-
speed mode upon receipt of an input signal. In the
absence of an input signal, the comparator reverts
back to low-power mode after an adjustable timeout
period. The timeout period for the MAX975 to enter
standby is set by a single capacitor. The dual MAX977
features independently adjustable timeout periods for
each comparator using separate capacitors.
♦ +3V/+5V Single-Supply Operation
♦ Rail-to-Rail Outputs
♦ Ground-Sensing Input
♦ Internal Hysteresis (high-speed mode)
♦ Adjustable Timeout Period
♦ µMAX Package (MAX975)
QSOP-16 Package (MAX977)
The MAX975/MAX977’s inputs have a common-mode
voltage range of -0.2V to (V
- 1.2V). The differential
CC
input voltage range extends rail to rail. The outputs are
capable of rail-to-rail 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
comparator’s internal hysteresis in high-speed mode
ensures clean output switching, even with slow-moving
input signals.
Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO
MAX975ESA
MAX975EUA
MAX977ESD
MAX977EEE
8 µMAX
14 SO
16 QSOP
The single MAX975 is available in 8-pin SO and 8-pin
µMAX packages, while the dual MAX977 is available in
14-pin SO and 16-pin QSOP packages.
Fu n c t io n a l Dia g ra m
V
CC
________________________Ap p lic a t io n s
MAX975
IN+
Battery-Powered Systems
RF ID Tags
LP
HIGH SPEED
ENABLE
OUT
Keyless Entry
Threshold Detectors/Discriminators
3V Systems
TRANSITION
MONITOR
IR Receivers
Digital-Line Receivers
GND
LOW POWER
ENABLE
IN-
TIMING
CIRCUIT
STAT
STO
Pin Configurations appear at end of data sheet.
________________________________________________________________ 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 1-800-835-8769.
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V ) ............................................................+6V
14-Pin SO (derate 8.33mW/°C above +70°C)................667mW
16-Pin QSOP (derate 8.33mW/°C above +70°C)...........667mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
All Other Pins ..............................................-0.3V to (V + 0.3V)
CC
Duration of Output Short Circuit to GND_ or V ......Continuous
CC
Continuous Power Dissipation (T = +70°C)
A
8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW
8-Pin µMAX (derate 4.10mW/°C above +70°C) .............330mW
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
(V = +2.7V to +5.25V, specifications are for high-speed mode, T = -40°C to +85°C, unless otherwise noted. Typical values are at
CC
A
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
5/MAX97
POWER SUPPLY
Supply-Voltage
Operating Range
V
CC
2.7
5.25
High-speed mode
Auto-standby/low-power modes
250
3
500
5
Supply Current
Per Comparator
I
CC
SO
µA
µMAX/QSOP
3
6
High-speed mode
Low-power mode
63
90
77
Power-Supply
Rejection Ratio
V
= 1V,
CM
PSRR
dB
2.7V ≤ V ≤ 5.25V
CC
COMPARATOR INPUTS
Common-Mode
Voltage Range
V
CMR
(Note 2)
-0.2
V
CC
- 1.2
V
High-speed mode, T = +25°C
+0.2
±2
±3
A
High-speed mode, T = T
to T
MAX
A
MIN
Input Offset Voltage
(Note 3)
V
V
CC
= 1V,
= 5V
CM
V
OS
mV
Auto-standby/
low-power modes,
SO
±1
±1
±5
±7
µMAX/QSOP
T
A
= T to T
MIN MAX
SO
0.5
0.3
2
2
4
Input-Referred Hysteresis
Input Bias Current
V
V
= 1V, V = 5V (Note 4)
mV
nA
HYS
CM
CC
µMAX/QSOP
SO
4
-100
-100
-5
-300
-400
High-speed mode
Auto-standby/low-power modes
I
µMAX/QSOP
B
Input Offset Current
Input Capacitance
I
±20
3
±100
nA
pF
OS
C
IN
SO
66
54
90
High-speed mode
Low-power mode
Common-Mode
Rejection Ratio
-0.2V ≤ V
CM
CMRR
µMAX/QSOP
dB
≤ V - 1.2V
CC
82
2
_______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
ELECTRICAL CHARACTERISTICS (continued)
(V = +2.7V to +5.25V, specifications are for high-speed mode, T = -40°C to +85°C, unless otherwise noted. Typical values are at
CC
A
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL INPUTS
LP Input Voltage High
LP Input Voltage Low
LP Fall Time
V
0.7 xV
V / 2
CC
V
V
LPIH
CC
V
LPIL
V
/ 2 0.3 x V
CC CC
t
(Note 5)
10
µs
µA
V
LP
LP Input Current
I
0.01
±1
LPB
STO_ Input Voltage Low
STO_ Source Current
DIGITAL OUTPUTS
OUT_ Output Voltage High
OUT_ Output Voltage Low
V
V
/ 2 0.3 x V
CIL
CC CC
I
V
CC
= 3V
0.15
µA
STO
V
I
= 2mA, all modes
= 2mA, all modes
SINK
V
- 0.4
V - 0.1
CC
V
V
OH
CC
SOURCE
V
I
0.1
0.4
50
OL
High-speed mode,
overdrive = 5mV
28
0.82
28
ns
µs
ns
µs
Propagation Delay, Low to High
(Note 6)
C
= 10pF,
LOAD
t
PD+
V
CC
= 5V
Low-power mode,
overdrive = 10mV
1.6
50
High-speed mode,
overdrive = 5mV
Propagation Delay, High to Low
(Note 6)
C
V
CC
= 10pF,
= 10pF
LOAD
t
PD-
= 5V
Low-power mode,
overdrive = 10mV
0.48
1.6
Propagation-Delay Skew (Note 6)
Propagation-Delay Matching
t
C
2
1
ns
ns
SKEW
LOAD
∆t
MAX977 only, C
= 10pF
PD
LOAD
High-speed mode
Low-power mode
1.6
1.6
C
V
CC
= 10pF,
= 5.0V
LOAD
Rise/Fall Time
ns
STAT_ Output Voltage High
STAT_ Output Voltage Low
V
I
= 3mA, all modes
V
CC
- 0.4
V
V
SH
SOURCE
V
SL
I
= 400µA, all modes
0.4
SINK
Note 1: The MAX975EUA is 100% production tested at T = +25°C; all temperature specifications are guaranteed by design.
A
Note 2: Inferred by CMRR. Either input can be driven to the absolute maximum limit without false output inversion, as long as the
other input is within the specified common-mode input voltage range.
Note 3: V is defined as the mean of trip points. The trip points are the extremities of the differential input voltage required to make
OS
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: Guaranteed by design. The LP pin is sensitive to noise. If fall times larger than 10µs are expected, bypass LP to ground
using a 0.1µF capacitor.
Note 6: Propagation delay is guaranteed by design. For low-overdrive conditions, V is added to the overdrive. The following
OS
equation defines propagation-delay skew: t
= t
- t
SKEW
PD+ PD-.
_______________________________________________________________________________________
3
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
ELECTRICAL CHARACTERISTICS (continued)
(V = +2.7V to +5.25V, specifications are for high-speed mode, T = -40°C to +85°C, unless otherwise noted. Typical values are at
CC
A
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
16
UNITS
AUTO-STANDBY/LOW-POWER TIMING (Note 7; Figure 2)
Auto-Standby Timeout
t
(Note 8)
(Note 9)
5
10
3
ms
µs
µs
ASB
Auto-Standby Enable Time
Auto-Standby Wake-Up Time
t
ASBE
t
10mV overdrive (Note 10)
2
4
ASD
Auto-Standby Wake-Up Input
or LP Pulse Width
t
10mV overdrive (Note 11)
1.6
µs
µs
PWD
Auto-Standby Comparator
Disable
t
(Note 12)
0.8
ASCD
Low-Power Enable Time
High-Speed Enable Time
Low-Power Comparator Disable
Low-Power STAT_ High
t
(Note 13)
(Note 14)
(Note 15)
(Note 16)
3
µs
µs
µs
ns
LPE
X
t
1.1
0.7
20
4
HSE
t
LPCD
t
LPSH
Note 7: Timing specifications are guaranteed by design.
Note 8: Set by 1000pF external capacitor at the STO_ pin. t
is defined as the time from last input transition to STAT_ = high.
ASB
Does not include time to go into standby condition (t
.
ASBE)
Note 9:
t
is defined as the time from when STAT_ goes high to when the supply current drops to 5µA.
ASBE
Note 10: t
is defined as the time from the last input transition to when STAT_ goes low. The comparator is in high-speed mode
ASD
before STAT_ is low.
Note 11: t
is defined as the minimum input or LP pulse width to trigger fast-mode operation from auto-standby.
PWD
Note 12: t
Note 13: t
Note 14: t
is defined as the time from the last input transition to when the supply current increases to 300µA.
is defined as the time from when LP is driven high to when the supply current drops to 5µA.
is defined as the time from when LP goes low to when STAT goes low. The comparator is in high-speed mode before
ASCD
LPE
HSE
STAT_ is low.
Note 15: t
Note 16: t
is defined as the time from when LP goes low to when the supply current increases to 300µA.
is defined as the time from when LP goes high to when STAT_ goes high.
LPCD
LPSH
4
_______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = 3.0V, T = +25°C, unless otherwise noted.)
CC
A
LOW-POWER OFFSET VOLTAGE
vs. TEMPERATURE
HIGH-SPEED INPUT BIAS CURRENT
vs. TEMPERATURE
SUPPLY CURRENT PER COMPARATOR
vs. OUTPUT TRANSITION FREQUENCY
-0.60
-50
-70
-90
10000
1000
100
V
CC
= 3V
-0.65
-0.70
-0.75
-0.80
HIGH-SPEED MODE
V
= 3V
= 5V
CC
-0.85
-0.90
-0.95
-1.00
-1.05
-1.10
-1.15
-1.20
-110
-130
V
CC
LOW-POWER MODE
10
1
-150
-170
-60 -40 -20
0
20 40 60 80 100
0.01k 0.1k 1k 10k 100k 1M 10M 100M
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TRANSITION FREQUENCY (kHz)
TEMPERATURE (°C)
LOW-POWER INPUT BIAS CURRENT
vs. TEMPERATURE
HIGH-SPEED VOLTAGE TRIP POINTS/INPUT
OFFSET VOLTAGE vs. TEMPERATURE
HIGH-SPEED VOLTAGE TRIP POINTS/INPUT
OFFSET VOLTAGE vs. TEMPERATURE
7.0
6.5
1.0
1.2
1.0
0.8
0.6
0.4
V
CC
= 5V
V
CC
= 3V
0.8
0.6
V
TRIP+
V
TRIP+
6.0
5.5
0.4
0.2
0
0.2
0
V
= 5V
CC
V
OS
V
OS
5.0
4.5
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
-0.2
V
TRIP-
V
CC
= 3V
-0.4
-0.6
-0.8
-1.0
4.0
3.5
3.0
V
TRIP-
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
LOW-POWER PROPAGATION DELAY
vs. CAPACITIVE LOAD
LOW-POWER PROPAGATION DELAY
vs. INPUT OVERDRIVE
AUTO-STANDBY TIMEOUT
vs. TEMPERATURE
600
550
500
700
650
600
550
500
450
400
350
300
250
200
150
10.2
10.1
C
LOAD
=15pF
V
= 5V
= 3V
CC
10.0
9.9
t
+
PD
V
= 5V
= 3V
CC
450
400
350
300
t
V
CC
= 3V
PD+
V
CC
9.8
V
CC
9.7
9.6
V
CC
= 3V
= 5V
V
CC
= 5V
V
CC
= 3V
= 5V
t
PD-
9.5
9.4
t
V
CC
PD-
250
200
V
CC
50mV OVERDRIVE
9.3
0
50
100
150
200
250
0
40
80
120
160
200
240
-60 -40 -20
0
20 40 60 80 100
CAPACITIVE LOAD (pF)
INPUT OVERDRIVE (mV)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = 3.0V, T = +25°C, unless otherwise noted.)
CC
A
OUTPUT HIGH VOLTAGE
vs. OUTPUT SOURCE CURRENT
OUTPUT LOW VOLTAGE
vs. OUTPUT SINK CURRENT
AUTO-STANDBY TIMEOUT
vs. TIMEOUT CAPACITOR
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
100000
V
CC
= 3V
V
= 3V
CC
T = +25°C
A
T = +85°C
A
10000
1000
100
T = -40°C
A
T = -40°C
A
T = +85°C
A
10
5/MAX97
T = +25°C
A
1
1
10
100
1000
10000
0
5
10
15
20
25 30
35
0
5
10 15 20 25 30 35 40
SINK CURRENT (mA)
CAPACITANCE (pF)
SOURCE CURRENT (mA)
HIGH-SPEED SUPPLY CURRENT
PER COMPARATOR
vs. TEMPERATURE (V = 5V)
CC
HIGH-SPEED PROPAGATION DELAY
vs. TEMPERATURE (V = 5V)
HIGH-SPEED PROPAGATION DELAY
vs. TEMPERATURE (V = 3V)
CC
CC
30
26
35
400
C
V
OD
= 15pF
= 50mV
LOAD
C
V
OD
= 15pF
= 50mV
375
350
325
300
LOAD
33
31
t
PD-
29
27
25
23
OUT_ = HIGH
OUT_ = LOW
22
18
275
250
225
200
175
150
125
100
t
PD+
t
PD-
t
PD+
21
19
17
15
14
10
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
STANDBY/LOW-POWER SUPPLY
CURRENT PER COMPARATOR
STANDBY/LOW POWER-SUPPLY
CURRENT PER COMPARATOR
HIGH-SPEED SUPPLY CURRENT
PER COMPARATOR
vs. TEMPERATURE (V = 5V)
CC
vs. TEMPERATURE (V = 3V)
CC
vs. TEMPERATURE (V = 3V)
CC
4.5
4.0
3.5
3.8
300
3.6
3.4
3.2
280
260
OUT_ = LOW
OUT_ = HIGH
240
220
200
180
3.0
2.8
2.6
OUT = LOW
3.0
2.5
OUT_ = HIGH
OUT_ = LOW
2.4
2.2
2.0
1.8
160
140
120
100
2.0
1.5
OUT = HIGH
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = 3.0V, T = +25°C, unless otherwise noted.)
CC
A
HIGH-SPEED PROPAGATION DELAY
vs. CAPACITIVE LOAD
HIGH-SPEED PROPAGATION DELAY
vs. INPUT OVERDRIVE
LOW-POWER PROPAGATION DELAY
vs. TEMPERATURE (V = 3V)
CC
30
25
20
15
10
5
600
560
520
480
440
400
360
320
280
240
200
45.0
t
42.5
40.0
37.5
35.0
C
V
OD
= 15pF
= 50mV
C
V
OD
= 15pF
= 50mV
PD-
LOAD
LOAD
V
= +3V
CC
V
= +3V
= +5V
CC
t
PD-
t
PD+
32.5
30.0
27.5
25.0
t
V
CC
= +5V
PD+
t
PD+
t
PD-
t
V
CC
t
PD-
PD+
22.5
20.0
17.5
15.0
C
LOAD
= 15pF
0
0
50
100
150
200
250
0
20 40 60 80 100 120 140 160 180 200
INPUT OVERDRIVE (mV)
-60 -40 -20
0
20 40 60 80 100
CAPACITIVE LOAD (pF)
TEMPERATURE (°C)
PROPAGATION DELAY t
+
PD
LOW-POWER PROPAGATION DELAY
vs. TEMPERATURE (V = 5V)
HIGH-SPEED MODE (V = +3V)
CC
CC
750
700
650
600
550
C
V
OD
= 15pF
= 50mV
LOAD
INPUT
5mV/div
V
OS
V
CC
t
500
450
400
350
300
250
200
150
PD+
V
/2
CC
OUTPUT
1V/div
t
PD-
GND
MAX975/977 TOC23
5ns/div
t
-60 -40 -20
0
20 40 60 80 100
PD+
TEMPERATURE (°C)
PROPAGATION DELAY t
PROPAGATION DELAY t
PD-
PD-
HIGH-SPEED MODE (V = +3V)
HIGH-SPEED MODE (V = +5V)
CC
CC
INPUT
V
OS
INPUT
V
OS
5mV/div
5mV/div
V
CC
V
/2
CC
V
CC
OUTPUT
1V/div
OUTPUT
2V/div
V
/2
GND
CC
GND
MAX975/977 TOC24
MAX975/977 TOC25
5ns/div
t
5ns/div
t
PD-
PD-
_______________________________________________________________________________________
7
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = 3.0V, T = +25°C, unless otherwise noted.)
CC
A
PROPAGATION DELAY t
PROPAGATION DELAY t
PD-
PD+
LOW-POWER MODE (V = +3V)
HIGH-SPEED MODE (V = +5V)
CC
CC
INPUT
5mV/div
INPUT
5mV/div
V
OS
V
OS
V
CC
V
/2
CC
V
CC
OUTPUT
1V/div
OUTPUT
2V/div
V
/2
CC
GND
GND
5/MAX97
MAX975/977 TOC27
MAX975/977 TOC26
100ns/div
5ns/div
t
t
PD-
PD+
PROPAGATION DELAY t
PD+
LOW-POWER MODE (V = +3V)
CC
INPUT
V
OS
5mV/div
V
CC
V
/2
CC
OUTPUT
1V/div
GND
MAX975/977 TOC28
100ns/div
t
PD+
PROPAGATION DELAY t
PROPAGATION DELAY t
PD+
PD-
LOW-POWER MODE (V = +5V)
LOW-POWER MODE (V = +3V)
CC
CC
INPUT
5mV/div
INPUT
5mV/div
V
OS
V
OS
V
CC
V
CC
OUTPUT
2V/div
OUTPUT
2V/div
V
/2
V
/2
CC
CC
GND
GND
MAX975/977 TOC29
MAX975/977 TOC30
100ns/div
100ns/div
t
t
PD+
PD-
8
_______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = 3.0V, T = +25°C, unless otherwise noted.)
CC
A
100kHz RESPONSE
LOW-POWER MODE (V = +3V)
100kHz RESPONSE
LOW-POWER MODE (V = +5V)
CC
CC
INPUT
5mV/div
V
OS
INPUT
5mV/div
V
OS
V
CC
V
CC
OUTPUT
2V/div
OUTPUT
1V/div
GND
GND
MAX975/977 TOC32
2µs/div
MAX975/977 TOC31
2µs/div
10MHz RESPONSE
HIGH-SPEED MODE (V = +5V)
CC
INPUT
V
OS
5mV/div
V
CC
OUTPUT
2V/div
GND
MAX975/977 TOC34
20ns/div
MAX975
10MHz RESPONSE
AUTO-STANDBY OPERATION
HIGH-SPEED MODE (V = +3V)
CC
+100mV
INPUT
5mV/div
V
OS
I
np
V
CC
-100mV
3V
OUTPUT
1V/div
OUT
0V
250µA
GND
I
CC
0µA
MAX975/977 TOC35
MAX975/977 TOC33
1ms/div
= 100pF
20ns/div
C
STO_
_______________________________________________________________________________________
9
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
_____________________________________________________________P in De s c rip t io n s
MAX975
PIN
1
NAME
FUNCTION
V
CC
Positive Supply Voltage, +2.7V to +5.25V
Noninverting Comparator Input
Inverting Comparator Input
2
IN+
IN-
3
Mode Status Pin. Indicates the operating mode. STAT is high for auto-standby mode or low-power
mode, and during the transition to high-speed mode. STAT = low indicates that the comparator is in
high-speed mode. STAT can source 3mA to power additional circuitry.
4
5
STAT
STO
Set Timeout Input. Connect a capacitor from STO to GND to program the time the comparator may
remain idle before entering standby mode. Connect STO to GND to disable the auto-standby fea-
ture. Calculate timeout with the following relationship: tASB = 10 x C µs, where C is in pF.
5/MAX97
6
7
GND
OUT
Ground
Comparator Output
Low Power Mode Input. Drive LP high for low-power mode. Drive LP low for high-speed mode
(STO = GND) or for high-speed mode with auto-standby. Connect to GND if low-power mode will
8
LP
not be used. Connect to V if high-speed mode will not be used.
CC
MAX977
SO
QSOP
NAME
FUNCTION
Set Idle Timeout Input A/B. Connect a capacitor from STOA/STOB to GND to program
the time in which comparator A/B may remain idle before entering standby mode.
Connect STOA/STOB to GND to disable the auto-standby feature for comparator A/B.
STOA,
STOB
1, 8
1, 9
Calculate timeout with the following relationship: t
= 10 x C µs, where C is in pF.
ASB
2, 9
3, 10
4
2, 10
3, 11
4, 5
GNDA, GNDB Ground for Comparator A/B
OUTA, OUTB Output for Comparator A/B
V
Positive Supply Voltage, +2.7V to +5.25V. For QSOP, connect pin 4 to pin 5.
Noninverting Input for Comparator B/A
CC
5, 12
6, 13
6, 14
7, 15
INB+, INA+
INB-, INA-
Inverting Input for Comparator B/A
Mode Status Pin B/A. Indicates the operating mode of comparator B/A.
STATB/STATA is high for auto-standby mode or for low-power mode, and during
the transition to high-speed mode. STATB/STATA = low indicates that comparator
B/A is in high-speed mode. STATB/STATA can source 3mA to power additional
circuitry.
STATB,
STATA
7, 14
8, 16
—
11
12
13
N.C.
LP
No connection. Not internally connected.
Low Power Mode Input for both comparators. Drive LP high for low-power mode.
Drive LP low for high-speed mode (STO_ = GND) or for high-speed mode with auto-
standby. Connect to GND if low-power mode will not be used. Connect to V if
CC
high-speed mode will not be used.
10 ______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
Table 1. Programming
INPUTS
STO_
STAT
OUTPUT
MODE
LP
L
IDLE TIME
High speed
(Auto-standby enabled)
t
t
= C
= C
x 10µs/pF
<t
L
H
L
ASB
STO
ASB
L
x 10µs/pF
≥t
ASB
Auto-standby
ASB
STO
L
High speed
(Auto-standby mode disabled)
↓
X
(falling edge)
H
X
X
Low power
H
_______________De t a ile d De s c rip t io n
V
HYST
The MAX975/MAX977 single/dual comparators have
three operating modes, and use a +2.7V to +5.25V
single supply. The operating modes are as follows:
high speed, high speed with auto-standby, and low
power. Propagation delay is typically 28ns in high-
speed mode, while typical supply current is 250µA. In
low-power mode, propagation delay is typically 480ns
and power consumption is only 3µA. The auto-standby
fe a ture s witc he s into low-p owe r s ta nd b y for e a c h
comparator with unchanging outputs in high-speed
mod e . The time out p e riod , or the time tha t OUT_
mus t b e id le (unc ha ng e d s ta te ) for the MAX975/
MAX977 to enter auto-standby, is adjustable by means
of an external capacitor. All inputs and outputs can tol-
erate a continuous short-circuit fault condition to either
rail. Internal hysteresis in high-speed mode ensures
clean output switching, even with slow-moving input
signals.
V
TRIP+
V
+ V
TRIP-
TRIP+
V
=
OS
V
IN+
2
V
TRIP-
V = 0
IN-
V
OH
COMPARATOR
OUTPUT
V
OL
Figure 1. Input and Output Waveforms, Noninverting Input
Varied
input voltage (Figure 1). The difference between the trip
points is the hysteresis. When the comparators’ 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 oscilla-
tion occurs.
Figure 1 illustrates the case where IN- has a fixed volt-
a g e a p p lie d a nd IN+ is va rie d . If the inp uts we re
reversed, the figure would be the same, except with an
inverted output.
The MAX975 functional diagram shows two paralleled
comparators, a timing circuit, a transition detector, and
logic gates. The upper comparator is high speed, while
the lower comparator is a slower low-power compara-
tor. The dual MAX977 features independent timeout
adjustment. The following sections discuss the details
of operation.
Au t o -S t a n d b y Mo d e
The MAX975/MAX977’s auto-standby function operates
only in hig h-s p e e d mod e . The d e vic e e nte rs a uto-
standby when OUT_ remains unchanged for a prepro-
grammed timeout period. In auto-standby mode, the
low-power comparator is enabled while the high-speed
comparator is disabled and STAT_ goes high. The logic
s ta te a nd s ink/s ourc e c a p a b ilitie s of OUT_ re ma in
unchanged, but propagation delay increases to 480ns.
In this mode, the timing circuitry is powered down, and
the transition detector monitors the low-power com-
p a ra tor for a tra ns ition. Whe n a n outp ut tra ns ition
occurs (OUT_ changes state), the timing circuitry is
Hys t e re s is (Hig h -S p e e d Mo d e On ly)
Most high-speed comparators can oscillate in the linear
operating region because of noise or undesired para-
sitic 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 MAX975/MAX977 have internal hys-
teresis 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
______________________________________________________________________________________ 11
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
t
t
PWD
ASB
V
OS
DIFFERENTIAL
INPUT
VOLTAGE
V
CC
V
OH
A
V
OL
OUT_
t
LPSH
t
t
PD-
t
PD+
ASD
V
CC
STAT_
0V
t
ASCD
300µA
3µA
I
CC (TYP)
t
5/MAX97
LPCD
t
ASBE
LP
t
t
LPE
HSE
Figure 2. Timing Diagram
powered up, the high-speed comparator is enabled,
the low-power comparator is disabled, and STAT goes
high, placing the MAX975 back into high-speed mode
(Figure 2).
Lo w -P o w e r Mo d e
Driving LP high switches the MAX975/MAX977 to low-
power mode. In this mode, the supply current drops to
a maximum of 5µA, and propagation delay increases
typically to 480ns. The high-speed comparator is dis-
abled and the low-power comparator is enabled for
continuous operation. Return to high-speed mode by
driving LP low. The LP pin is sensitive to noise. If fall
times larger than 10µs are expected, bypass LP with a
0.1µF c a p a c itor to GND. The log ic s ta te a nd s ink/
source capabilities of OUT_ remain unchanged in low-
power mode.
Use an external capacitor, C
, to program the timeout
STO
p e riod re q uire d for the c omp a ra tor to e nte r a uto-
standby mode. Determine the capacitor required for a
particular timeout period by the relationship t
=
ASB
10 x Cµs, where C is in pF. For example, connecting a
0.1µF capacitor to STO_ results in a timeout period of
1sec. The propagation delay of OUT_ when exiting auto
standby mode is equivalent to the low-power-mode
propagation delay. When STAT_ goes low, the low-
power comparator is disabled and the high-speed com-
parator is ready for operation. To bring the comparator
out of auto-standby mode without a transition occurring
on OUT_, toggle LP low-high-low. The LP pin is sensitive
to noise. If fall times larger than 10µs are expected,
bypass LP with a 0.1µF capacitor to GND. To disable
auto-standby mode, drive STO_ low or connect it to
g round . Note tha t d riving STO_ low while in a uto-
standby mode will not bring the comparator out of auto-
standby mode. Also, if driving STO_ with an open drain,
le a ka g e mus t b e le s s tha n 1nA. On p owe r-up , the
device is in high-speed mode unless LP is high. The
MAX977 operates in the same manner as the MAX975.
In p u t -S t a g e Circ u it ry
The MAX975/MAX977 input common-mode range is
from -0.2V to (V
- 1.2V). But the voltage range for
CC
each comparator input extends to both V
and GND
CC
rails. The output remains in the correct logic state while
one or both of the inputs are within the common-mode
range. If both input levels are out of the common-mode
range, input-stage current saturation occurs and the
output becomes unpredictable.
12 ______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
__________Ap p lic a t io n s In fo rm a t io n
P o w e rin g Circ u it ry w it h S TAT
STAT’s function is to indicate the comparator’s operat-
ing mode. When STAT is low, the comparator is in high-
speed mode and will meet the guaranteed propagation
delay. When STAT is high, the comparator is in auto-
standby mode, in low-power mode, or in transition to
high-speed mode. An additional feature of this pin is
that it can source 3mA of current. When STAT is high,
additional circuitry can be powered. This circuitry can
b e a utoma tic a lly p owe re d up or p owe re d d own,
depending on the input signal or lack of input signal
received by the MAX975/MAX977.
CMOS
LOGIC
STO_
Figure 3. Driving STO_ with CMOS Logic
V
CC
R3
V
CC
V
CC
OUT
S TO_ Co n s id e ra t io n s
The charge currents for the capacitor connected to
STO_ are on the order of 100nA. This necessitates cau-
tion in c a p a c itor typ e s e le c tion a nd b oa rd la yout.
Capacitor leakage currents must be less than 1nA to
prevent timing errors. Ceramic capacitors are available
in values up to 1µF, and are an excellent choice for this
application. If a larger capacitance value is needed,
use parallel ceramic capacitors to get the required
c a p a c ita nc e . Aluminum a nd ta nta lum e le c trolytic
capacitors are not recommended due to their higher
leakage currents.
R
D
STAT
LOSS OF SIGNAL
GND
R1
R2
MAX975
V
CC
Figure 4. IR Receiver
1) Use a printed circuit board with an unbroken, low-
inductance ground plane.
Board layout can create timing errors due to parasitic
effects. Make the STO_ traces as short as possible to
reduce capacitance and coupling effects. When driving
STO_ to disa b le a uto-sta nd by mod e , use sta nda rd
CMOS logic isolated with a low-leakage (<1nA) diode,
such as National’s FJT1100 (Figure 3). 15nA leakage
typically results in 10% error.
2) Pla c e a d e c oup ling c a p a c itor (a 0.1µF c e ra mic
capacitor is a good choice) as close to V as pos-
CC
sible.
3) Keep lead lengths short on the inputs and outputs, to
avoid unwanted parasitic feedback around the com-
parators.
The MAX977 has separate timing inputs (STOA and
STOB). These pins must have separate capacitors. The
timing c irc uits will not op e ra te c orre c tly if a s ing le
capacitor is used with STOA and STOB connected
together.
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.
The relationship between the timeout period and the
STO_ capacitor is t
= 10 x C
_ µs, where C
_
ASB
STO
STO
IR Re c e ive r
Figure 4 shows an application using the MAX975 as an
infrared receiver. The infrared photodiode creates a
current relative to the amount of infrared light present.
is in pF. This equation is for larger capacitance values,
and does not take into account variations due to board
capacitance and board leakage. If less than 1ms is
desired, subtract the ~3pF STO_ parasitic capacitance
from the calculated value.
This current creates a voltage across R . When this
D
voltage level crosses the voltage applied by the voltage
divider to the inverting input, the output transitions. If
the photodiode is not receiving enough signal to cause
transitions on the MAX975’s output, STAT is used as a
loss-of-signal indicator. R3 adds additional hysteresis
for noise immunity.
Circ u it La yo u t a n d Byp a s s in g
The MAX975/MAX977’s high gain bandwidth requires
design precautions to realize the comparator’s full high-
speed capability. The following precautions are recom-
mended:
______________________________________________________________________________________ 13
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
V
CC
R3
14
15
3V
0.1µF
V
IN
0.1µF
4
82.1k, 1%
UNDERVOLTAGE
1/2
MAX977
3
1
V
CC
WAKE-UP IRQ
2
STAT
LP
C
STOA
V
CC
I/0
µP
R2
MAX975
STO
POWER GOOD
24.9k, 1%
1
I/0
V
CC
50Ω
6
7
2
MAX6120
3
5
C
STO
11
OVERVOLTAGE
1/2
GND
MAX977
X-BAND
DETECTOR
9
5/MAX97
3V
C
STOB
10
R1
100k, 1%
4.7k
1M
0.1µF
(PIN NUMBERS SHOWN ARE FOR QSOP PACKAGE)
Figure 5. Window Comparator
Figure 6. Toll-Tag Reader
4) Calculate R3 with the following formula:
R3 = (R2 + R3) - R2
Win d o w Co m p a ra t o r
The MAX977 is ideal for making a window detector
(undervoltage/overvoltage detector). The schematic
shown in Figure 5 uses a MAX6120 reference and com-
ponent values selected for a 2.0V undervoltage thresh-
old 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 outp uts p rovid e s a n a c tive -hig h,
power-good signal. The design procedure is as follows:
5) Verify the resistor values. The equations are as
follows:
V
OTH
= (V
+ V ) x (R1 + R2 + R3) / R1
REF H
V
UTH
= (V
- V ) x (R1 + R2 + R3) / (R1 + R2)
REF H
To ll-Ta g Circ u it
The circuit shown in Figure 6 uses a MAX975 in a very
low standby-power AM demodulator circuit that wakes
up a toll ta g (p a rt of a n a utoma te d roa d wa y toll-
collection system). This application requires very long
standby times with brief and infrequent interrogations.
In the awake state, it is capable of demodulating the
typical 600kHz AM carrier riding on the 2.4GHz RF sig-
nal. In this state, the comparator draws its 250µA high-
speed current. After communications have ceased, or
when instructed by the microcontroller, the comparator
returns to its low-power state. The comparator draws
only 3µA in this state, while monitoring for RF activity.
Typically, this application requires two comparators
a nd a d is c re te p owe r-ma na g e me nt a nd s ig na l-
switchover circuit. The MAX975 circuit is smaller, sim-
pler, less costly, and saves design time.
1) Select R1. The leakage current into INB- is normally
100nA, so the current through R1 should exceed
10µA for the thresholds to be accurate. R1 values in
the 50kΩ to 100kΩ range are typical.
2) Choose the overvoltage threshold (V ) when V
OTH IN
is rising, and calculate R2 and R3 with the following
formula:
R2 + R3 = R1 x [V
/ (V
+ V ) - 1]
OTH
REF H
where V = 1/2V
.
H
HYST
3) Choose the undervoltage threshold (V ) when V is
UTH IN
falling, and calculate R2 with the following formula:
R2 = (R1 + R2 + R3) x [(V - V ) / V ] - R1
REF
H
UTH
where V = 1/2V
.
H
HYST
14 ______________________________________________________________________________________
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
5/MAX97
__________________________________________________________P in Co n fig u ra t io n s
TOP VIEW
STOA
GNDA
OUTA
1
2
3
4
5
6
7
8
STATA
16
1
2
3
4
5
6
7
14 STATA
STOA
GNDA
OUTA
15 INA-
14 INA+
13 LP
13
12
11
10
9
INA-
V
1
2
3
4
8
7
6
5
LP
CC
INA+
LP
V
CC
MAX977
IN+
IN-
OUT
GND
STO
MAX975
V
CC
MAX977
V
CC
12 N.C.
11 OUTB
STAT
INB+
INB-
OUTB
GNDB
STOB
INB+
INB-
10
9
GNDB
STOB
STATB
8
STATB
SO/µMAX
SO
QSOP
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 522 (MAX975)
1044 (MAX977)
______________________________________________________________________________________ 15
S in g le /Du a l, +3 V/+5 V Du a l-S p e e d
Co m p a ra t o rs w it h Au t o -S t a n d b y
________________________________________________________P a c k a g e In fo rm a t io n
5/MAX97
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.
16 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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