The MAX907/MAX908/MAX909 dual, quad, and single
high-speed, ultra low-power voltage comparators are
designed for use in systems powered from a single
+5V supply; the MAX909 also accepts dual ±5V supplies. Their 40ns propagation delay (with 5mV input
overdrive) is achieved with a power consumption of
only 3.5mW per comparator. The wide input commonmode range extends from 200mV below ground (below
the negative supply rail for the MAX909) to within 1.5V
of the positive supply rail.
Because they are micropower, high-speed comparators that operate from a single +5V supply and include
built-in hysteresis, these devices replace a variety of
older comparators in a wide range of applications.
MAX907/MAX908/MAX909 outputs are TTL compatible, requiring no external pull-up circuitry. All inputs
and outputs can be continuously shorted to either supply rail without damage. These easy-to-use comparators incorporate internal hysteresis to ensure clean output switching even when the devices are driven by a
slow-moving input signal.
The MAX909 features complementary outputs and an
output latch. A separate supply pin for extending the
analog input range down to -5V is also provided.
The dual MAX907 and single MAX909 are available in
8-pin DIP and small-outline packages, and the quad
MAX908 is available in 14-pin DIP and small-outline
packages. These comparators are ideal for single
+5V-supply applications that require the combination
of high speed, precision, and ultra-low power
dissipation.
_______________________Applications
Battery-Powered Systems
High-Speed A/D Converters
High-Speed V/F Converters
Line Receivers
Threshold Detectors/Discriminators
High-Speed Sampling Circuits
Zero Crossing Detectors
___________________________Features
♦ 40ns Propagation Delay
♦ 700µA (3.5mW) Supply Current per Comparator
♦ Single 4.5V to 5.5V Supply Operation
MAX90_C_ _ ...................................... 0°C to +70°C
MAX90_E_ _ ...................................-40°C to +85°C
MAX90_MJ_ ..................................-55°C to +125°C
Storage Temperature Range ...................-65°C to +160°C
Lead Temperature (soldering, 10sec)....................+300°C
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+ = 5V, TA= +25°C; MAX909 only: V- = 0V, V
MAX907/MAX908/MAX909
PARAMETERCONDITIONSMINTYPMAXUNITS
Positive Trip Point
Negative Trip Point
Input Offset Voltage
Input Bias Current
Input Offset Current
Input Voltage Range
SYMBOL
V
TRIP+
V
TRIP-
V
OS
I
B
I
OS
V
CMR
Common-Mode Rejection RatioCMRR(Notes 4, 5)50100µV/V
Power-Supply Rejection RatioPSRR(Notes 4, 6)50100µV/V
Output High Voltage
Positive Supply Current per
Comparator
V
OH
V
OL
I+(Note 7)
Negative Supply CurrentI-MAX909 only: V- = -5V60100µA
Power Dissipation per
Comparator
Output Rise Time
Output Fall Time
PD(Note 8)
t
r
t
f
= 0V; unless otherwise noted.)
LATCH
(Note 1)24 mV
(Note 1)-2-4mV
(Note 2)0.52.0mV
VCM= 0V, VIN= V
VCM= 0V, VIN= V
Latch Input Voltage Low
Latch Input Current
Latch Setup Time
Latch Hold Time
Note 1: Trip Point is defined as the input voltage required to make the comparator output change state. The difference
Note 2: Input Offset Voltage is defined as the center of the input-referred hysteresis zone. Specified for V
Note 3: Inferred from the CMRR test. Note that a correct logic result is obtained at the output, provided that at least one input is
MAX907/MAX908/MAX909
Note 4: Tested with V+ = 5.5V (and V- = 0V for MAX909). MAX909 also tested over the full analog input range (i.e., with
Note 5: Tested over the full input voltage range (V
Note 6: Specified over the full tolerance of operating supply voltage: MAX907/MAX908 tested with 4.5V < V+ < 5.5V. MAX909
Note 7: Positive Supply Current specified with the worst-case condition of all outputs at logic low (MAX907/MAX908), and
Note 8: Typical power specified with V+ = 5V; maximum with V+ = 5.5V (and with V- = -5.5V for MAX909).
Note 9: Due to difficulties in measuring propagation delay with 5mV of overdrive in automatic test equipment, the
Note 10: Differential Propagation Delay is specified as the difference between any two channels in the MAX907/MAX908 (both out-
Note 11: Propagation Delay Skew is specified as the difference between any single channel’s output low-to-high transition (t
Note 12: Latch specifications apply to MAX909 only. See Figure 2.
to T
MIN
PARAMETER
; MAX909 only: V- = 0V, V
MAX
SYMBOLCONDITIONSMINTYPMAXUNITS
t
PD+,tPD-
∆t
PD
tPDskew
V
IH
V
IL
IIH, I
IL
t
s
t
h
between upper (V
+) and lower (V
TRIP
TRIP
Specified for an input common-mode voltage (V
within the V
limits. Note also that either or both inputs can be driven to the upper or lower absolute maximum limit with-
-) trip points is equal to the width of the input-referred hysteresis zone (V
) of 0V. See Figure 1.
CM
= 0V. See Figure 1.
CM
out damage to the part.
V- = -5.5V).
).
CMR
tested with 4.5V < V+ < 5.5V and with -5.5V < V- < 0V.
with V+ = 5.5V.
MAX907/MAX908/MAX909 are sample tested to 0.1% AQL with 100mV input overdrive. Correlation tests show that the
specification can be guaranteed if all other DC parameters are within the specified limits. V
must be added to the over-
OS
drive voltage for low values of overdrive.
puts making either a low-to-high or a high-to-low transition).
and high-to-low transition (t
-), and also between the QOUT and QOUT transition on the MAX909.
11OUTAComparator A Output
22INA-Comparator A Inverting Input
33INA+Comparator A Noninverting Input
841V+Positive Supply
55INB+Comparator B Noninverting Input
66INB-Comparator B Inverting Input
77OUTBComparator B Output
8OUTCComparator C Output
9INC-Comparator C Inverting Input
10INC+Comparator C Noninverting Input
4116GNDGround
12IND+Comparator D Noninverting Input
13IND-Comparator D Inverting Input
14OUTDComparator D Output
2IN+Noninverting Input
3IN-Inverting Input
MAX907/MAX908/MAX909
4V-Negative Supply or Ground
5LE
7QOUTComparator Output
8
NAMEFUNCTION
The latch is transparent when LE is low. The comparator output is
stored when LE is high.
QOUT
Inverted Comparator Output
_______________Detailed Description
Timing
Noise or undesired parasitic AC feedback cause most
high-speed comparators to oscillate in the linear region
(i.e., when the voltage on one input is at or near the
voltage on the other input). The MAX907/MAX908/
MAX909 eliminate this problem by incorporating internal hysteresis. When the two comparator input voltages are equal, hysteresis effectively causes one comparator input voltage to move quickly past the other,
thus taking the input out of the region where oscillation
occurs. Standard comparators require that hysteresis
be added through the use of external resistors. The
MAX907/MAX908/MAX909’s fixed internal hysteresis
eliminates these resistors (and the equations required
to determine appropriate values).
Adding hysteresis to a comparator creates two trip
points: one for the input voltage rising and one for the
input voltage falling (Figure 1). The difference between
these two input-referred trip points is the hysteresis.
Figure 1 illustrates the case where IN- is fixed and IN+
is varied. If the inputs were reversed, the figure would
look the same, except the output would be inverted.
The MAX909 includes an internal latch, allowing the
result of a comparison to be stored. If LE is low, the
latch is transparent (i.e., the comparator operates as
though the latch is not present). The state of the comparator output is stored when LE is high. See Figure 2.
Note that the MAX909 can be operated with V- connected to ground or to a negative supply voltage. The
MAX909’s input range extends from (V- - 0.2V) to
(V+ - 1.5V).
Single/Dual/Quad High-Speed, Ultra Low-Power,
Single-Supply TTL Comparators
V
TRIP+
V
V
HYST
V
TRIP-
COMPARATOR
OUTPUT
IN+
V
+ V
TRIP+
V
=
OS
V
= 0V
IN-
V
V
TRIP-
2
OH
OL
Figure 1. Input and Output Waveforms, Noninverting Input
Varied
__________Applications Information
Circuit Layout
Because of the MAX907/MAX908/MAX909’s high gain
bandwidth, special precautions must be taken to realize the full high-speed capability. A printed circuit
board with a good, low-inductance ground plane is
mandatory. Place the decoupling capacitor (a 0.1µF
ceramic capacitor is a good choice) as close to V+ as
possible. Pay close attention to the decoupling capacitor’s bandwidth, keeping leads short. Short lead
lengths on the inputs and outputs are also essential to
avoid unwanted parasitic feedback around the comparators. Solder the device directly to the printed circuit board instead of using a socket.
Overdriving the Inputs
The inputs to the MAX907/MAX908/MAX909 may be
driven beyond the voltage limits given in the
Maximum Ratings
, as long as the current flowing into
the device is limited to 25mA. However, if the inputs
are overdriven, the output may be inverted. The addition of an external diode prevents this inversion by limiting the input voltage to 200mV to 300mV below ground
(see Figure 3).
Absolute
3V
LE
1.4V
COMPARE
0
V
INPUT
VOLTAGE
OUTPUT
(QOUT)
OUTPUT
Q
OUT)
(
V
1.4V
V
V
1.4V
V
OS
OH
OL
OH
OL
DIFFERENTIAL
Figure 2. MAX909 Timing Diagram
Battery-Operated Infrared Data Link
Figure 4's circuit allows reception of infrared data. The
MAX403 converts the photodiode current to a voltage,
and the MAX907 determines whether the amplifier output
is high enough to be called a “1”. The current consumption of this circuit is minimal: The MAX403 and MAX907
require typically 250µA and 700µA, respectively.
____Pin Configurations (continued)_Ordering Information (continued)
PARTTEMP. RANGEPIN-PACKAGE
TOP VIEW
IN+
IN-
MAX908CPD
V+
1
MAX909
2
3
4
V-
DIP/SO
8
QOUT
QOUT
7
GND
6
5
LE
MAX908CSD0°C to +70°C14 SO
MAX908EPD-40°C to +85°C14 Plastic DIP
MAX908ESD-40°C to +85°C14 SO
MAX908MJD-55°C to +125°C14 CERDIP
MAX909CPA
MAX909CSA0°C to +70°C8 SO
MAX909C/D0°C to +70°CDice*
MAX909EPA-40°C to +85°C8 Plastic DIP
MAX909ESA-40°C to +85°C8 SO
MAX909MJA-55°C to +125°C8 CERDIP
* Dice are specified at +25°C, DC parameters only.
TRANSISTOR COUNT: 95;
SUBSTRATE CONNECTED TO V-.
QOUT
QOUT
GND
LE
0.051"
(1.30mm)
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.
12
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