AD8611ARZ Analog Devices Inc, AD8611ARZ Datasheet - Page 10

• Manufacturer Part Number: AD8611ARZ
• Description: Comparator Single 5V 8-Pin SOIC N
• Manufacturer: Analog Devices Inc
• Type: with Latchr

Specifications of AD8611ARZ

• Package: 8SOIC N
• Typical Response Time Range: 0.0003 to 0.05 us
• Typical Voltage Gain Range: 40 to 70 dB
• Output Type: Complementary
• Number Of Channels Per Chip: 1
• Minimum Single Supply Voltage: 3 V
• Power Supply Type: Single
• Number Of Elements: 1
• Voltage - Supply: 2.7 V ~ 6 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Amplifier Type: Comparator
• Common Mode Rejection Ratio: 85
• Current, Input Bias: -4 μA
• Current, Input Offset: ±4 μA
• Current, Supply: -2.2 to +5.7 mA
• Impedance, Thermal: 158 °C/W
• Number Of Amplifiers: Quad
• Package Type: SOIC-8
• Propagation Delay: 4 ns
• Temperature, Operating, Range: -40 to +85 °C
• Time, Fall: 1.1 ns
• Time, Rise: 2.5 ns
• Voltage, Gain: 3000 V/V
• Voltage, Input: ±4 V
• Voltage, Input Offset: 1 mV
• Voltage, Supply: 3 to 5 V
• Comparator Type: High Speed
• No. Of Comparators: 1
• Response Time: 4ns
• Ic Output Type: CMOS, MOS, Open-Collector / Drain, TTL
• Supply Current: 5.7mA
• Rohs Compliant: Yes
• Output Compatibility: TTL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD8611/AD8612
APPLICATIONS
OPTIMIZING HIGH SPEED PERFORMANCE
As with any high speed comparator or amplifier, proper design
and layout of the AD8611/AD8612 should be used to ensure
optimal performance. Excess stray capacitance or improper
grounding can limit the maximum performance of high speed
circuitry.
Minimizing resistance from the source to the comparator’s
input is necessary to minimize the propagation delay of the
circuit. Source resistance in combination with the equivalent
input capacitance of the AD8611/AD8612 creates an R-C filter
that could cause a lagged voltage rise at the input to the
comparator. The input capacitance of the AD8611/AD8612 in
combination with stray capacitance from an input pin to
ground results in several picofarads of equivalent capacitance.
Using a surface-mount package and a minimum of input trace
length, this capacitance is typically around 3 pF to 5 pF. A
combination of 3 kΩ source resistance and 3 pF of input
capacitance yields a time constant of 9 ns, which is slower than
the 4 ns propagation delay of the AD8611/AD8612. Source
impedances should be less than 1 kΩ for best performance.
Another important consideration is the proper use of power-
supply-bypass capacitors around the comparator. A 1 μF bypass
capacitor should be placed within 0.5 inches of the device
between each power supply pin and ground. Another 10 nF
ceramic capacitor should be placed as close as possible to the
device in parallel with the 1 μF bypass capacitor. The 1 μF
capacitor reduces any potential voltage ripples from the power
supply, and the 10 nF capacitor acts as a charge reservoir for the
comparator during high frequency switching.
A continuous ground plane on the PC board is also
recommended to maximize circuit performance. A ground
plane can be created by using a continuous conductive plane
over the surface of the circuit board, only allowing breaks in the
plane for necessary traces and vias. The ground plane provides a
low inductive current return path for the power supply, thus
eliminating any potential differences at various ground points
throughout the circuit board caused from ground bounce. A
proper ground plane can also minimize the effects of stray
capacitance on the circuit board.
UPGRADING THE LT1394 AND LT1016
The AD8611 single comparator is pin-for-pin compatible with
the LT1394 and LT1016 and offers an improvement in propagation
delay over both comparators. These devices can easily be replaced
with the higher performance AD8611; however, there are differ-
ences, so it is useful to ensure that the system still operates properly.
The five major differences between the AD8611 and the LT1016
include input voltage range, input bias currents, propagation
delay, output voltage swing, and power consumption. Input
common-mode voltage is found by taking the average of the
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two voltages at the inputs to the comparator. The LT1016 has an
input voltage range from 1.25 V above the negative supply to
1.5 V below the positive supply. The AD8611 input voltage
range extends down to the negative supply voltage to within 2 V
of V+. If the input common-mode voltage is exceeded, input
signals should be shifted or attenuated to bring them into range,
keeping in mind the note about source resistance in the
Optimizing High Speed Performance section.
For example, an AD8611 powered from a 5 V single supply has
its noninverting input connected to a 1 V peak-to-peak, high
frequency signal centered around 2.3 V and its inverting input
connected to a fixed 2.5 V reference voltage. The worst-case
input common-mode voltage to the AD8611 is 2.65 V. This is
well below the 3.0 V input common-mode voltage range to the
comparator. Note that signals much greater than 3.0 V result in
increased input currents and may cause the comparator to
operate more slowly.
The input bias current to the AD8611 is 7 μA maximum over
temperature (−40°C to +85°C). This is identical to the
maximum input bias current for the LT1394, and half of the
maximum I
and LT1394 flow out from the comparator’s inputs, as opposed
to the LT1016 whose input bias current flows into its inputs.
Using low value resistors around the comparator and low
impedance sources will minimize any potential voltage shifts
due to bias currents.
The AD8611 is able to swing within 200 mV of ground and
within 1.5 V of positive supply voltage. This is slightly more
output voltage swing than the LT1016. The AD8611 also uses
less current than the LT1016—5 mA as compared to 25 mA of
typical supply current.
The AD8611 has a typical propagation delay of 4 ns, compared
with the LT1394 and LT1016, whose propagation delays are
typically 7 ns and 10 ns, respectively.
MAXIMUM INPUT FREQUENCY AND OVERDRIVE
The AD8611 can accurately compare input signals up to
100 MHz with less than 10 mV of overdrive. The level of
overdrive required increases with ambient temperature, with up
to 50 mV of overdrive recommended for a 100 MHz input
signal and an ambient temperature of +85°C.
It is not recommend to use an input signal with a fundamental
frequency above 100 MHz because the AD8611 could draw up
to 20 mA of supply current and the outputs may not settle to a
definite state. The device returns to its specified performance
once the fundamental input frequency returns to below 100 MHz.
B
for the LT1016. Input bias currents to the AD8611