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PDF MAX975 Data sheet ( Hoja de datos )
| Número de pieza | MAX975 | |
| Descripción | Single/Dual / +3V/+5V Dual-Speed Comparators with Auto-Standby | |
| Fabricantes | Maxim Integrated | |
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19-1141; Rev 2; 2/07
Single/Dual, +3V/+5V Dual-Speed
Comparators with Auto-Standby
General Description
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.
The auto-standby feature allows the comparator 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.
The MAX975/MAX977’s inputs have a common-mode
voltage range of -0.2V to (VCC - 1.2V). The differential
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.
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.
____________________________Features
♦ 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
♦ +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)
Ordering Information
PART
MAX975ESA
MAX975EUA-T
MAX977ESD
MAX977EEE
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
8 µMAX-8
14 SO
16 QSOP
PKG
CODE
S8-2
U8-1
S14-1
E16-1
Functional Diagram
________________________Applications
Battery-Powered Systems
RF ID Tags
Keyless Entry
Threshold Detectors/Discriminators
3V Systems
IR Receivers
Digital-Line Receivers
VCC
IN+
MAX975
HIGH SPEED
ENABLE
LOW POWER
ENABLE
IN-
LP
OUT
TRANSITION
MONITOR
GND
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
STAT
TIMING
CIRCUIT
STO
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Single/Dual, +3V/+5V Dual-Speed
Comparators with Auto-Standby
__________________________________________Typical Operating Characteristics
(VCC = 3.0V, TA = +25°C, unless otherwise noted.)
LOW-POWER OFFSET VOLTAGE
vs. TEMPERATURE
-0.60
-0.65
-0.70
VCC = 3V
-0.75
-0.80
-0.85
-0.90
-0.95
-1.00
-1.05
-1.10
-1.15
-1.20
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
SUPPLY CURRENT PER COMPARATOR
vs. OUTPUT TRANSITION FREQUENCY
10000
1000
HIGH-SPEED MODE
100
10 LOW-POWER MODE
1
0.01k 0.1k 1k 10k 100k 1M 10M 100M
TRANSITION FREQUENCY (kHz)
HIGH-SPEED INPUT BIAS CURRENT
vs. TEMPERATURE
-50
-70
VCC = 3V
-90
-110
VCC = 5V
-130
-150
-170
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
LOW-POWER INPUT BIAS CURRENT
vs. TEMPERATURE
7.0
6.5
6.0
5.5
VCC = 5V
5.0
4.5
VCC = 3V
4.0
3.5
3.0
-60 -40 -20 0 20 40 60
TEMPERATURE (°C)
80 100
LOW-POWER PROPAGATION DELAY
vs. CAPACITIVE LOAD
600
550
VCC = 5V
500 tPD+
450
400
350
300
250
200
0
VCC = 3V
VCC = 3V
VCC = 5V
tPD-
50mV OVERDRIVE
50 100 150 200
CAPACITIVE LOAD (pF)
250
HIGH-SPEED VOLTAGE TRIP POINTS/INPUT
OFFSET VOLTAGE vs. TEMPERATURE
1.0
0.8 VCC = 5V
0.6 VTRIP+
0.4
0.2
0 VOS
-0.2
-0.4 VTRIP-
-0.6
-0.8
-1.0
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
LOW-POWER PROPAGATION DELAY
vs. INPUT OVERDRIVE
700
650 CLOAD =15pF
600
550 VCC = 5V
500 tPD+
450
400 VCC = 3V
350
300 VCC = 3V
250 tPD-
200 VCC = 5V
150
0
40 80 120 160 200 240
INPUT OVERDRIVE (mV)
HIGH-SPEED VOLTAGE TRIP POINTS/INPUT
OFFSET VOLTAGE vs. TEMPERATURE
1.2
1.0 VCC = 3V
0.8
0.6
VTRIP+
0.4
0.2
0 VOS
-0.2
-0.4
-0.6 VTRIP-
-0.8
-1.0
-1.2
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
AUTO-STANDBY TIMEOUT
vs. TEMPERATURE
10.2
10.1
10.0
9.9
VCC = 3V
9.8
9.7
9.6
VCC = 5V
9.5
9.4
9.3
-60 -40 -20 0 20 40 60
TEMPERATURE (°C)
80 100
_______________________________________________________________________________________ 5
5 Page 
Single/Dual, +3V/+5V Dual-Speed
Comparators with Auto-Standby
Table 1. Programming
INPUTS
LP STO_
L tASB = CSTO x 10µs/pF
L
↓
(falling edge)
H
tASB = CSTO x 10µs/pF
L
X
IDLE TIME
<tASB
≥tASB
X
X
MODE
High speed
(Auto-standby enabled)
Auto-standby
High speed
(Auto-standby mode disabled)
Low power
STAT
OUTPUT
L
H
L
H
_______________Detailed Description
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
feature switches into low-power standby for each
comparator with unchanging outputs in high-speed
mode. The timeout period, or the time that OUT_
must be idle (unchanged state) 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.
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.
Hysteresis (High-Speed Mode Only)
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
VHYST
VTRIP+
VIN+
VTRIP-
VOS = VTRIP+ + VTRIP-
2
VIN- = 0
COMPARATOR
OUTPUT
VOH
VOL
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-
age applied and IN+ is varied. If the inputs were
reversed, the figure would be the same, except with an
inverted output.
Auto-Standby Mode
The MAX975/MAX977’s auto-standby function operates
only in high-speed mode. The device enters auto-
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
state and sink/source capabilities of OUT_ remain
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-
parator for a transition. When an output transition
occurs (OUT_ changes state), the timing circuitry is
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX975.PDF ] | |
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