AD8611AR Analog Devices Inc, AD8611AR Datasheet - Page 12

• Manufacturer Part Number: AD8611AR
• Description: IC COMPARATOR SNGL 4NS HS 8-SOIC
• Manufacturer: Analog Devices Inc
• Type: with Latchr

Specifications of AD8611AR

• Rohs Status: RoHS non-compliant
• Number Of Elements: 1
• Output Type: Complementary, TTL
• Voltage - Supply: 2.7 V ~ 6 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Comparator Type: High Speed
• No. Of Comparators: 1
• Response Time: 4ns
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Single Supply Voltage Min (+v): 3V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD8611/AD8612
voltage is greater than V
the input voltage is less than V
where V+ is the positive supply voltage.
The capacitor C
pole into the feedback network. This has the effect of increasing
the amount of hysteresis at high frequencies, which is useful
when comparing relatively slow signals in high frequency noise
environments. At frequencies greater than f
window approaches V
frequencies less than f
Equation 1.
CLOCK TIMING RECOVERY
Comparators are often used in digital systems to recover clock
timing signals. High speed square waves transmitted over any
distance, even tens of centimeters, can become distorted due to
stray capacitance and inductance. Poor layout or improper
termination can also cause reflections on the transmission line,
further distorting the signal waveform. A high speed
comparator can be used to recover the distorted waveform
while maintaining a minimum of delay.
Figure 25 shows V
65 MHz, 100 mV peak-to-peak distorted clock signal into a 4 V
peak-to-peak square wave. The lower trace is the input to the
AD8611, and the upper trace is the QA or QB output from the
comparator. The AD8611 is powered from a 5 V single supply.
V
V
V
OUT
V
LO
HI
Figure 25. Using the AD8611 to Recover a Noisy Clock Signal
IN
=
=
(
V
V
REF
+
F
−
×
is optional and can be added to introduce a
1
OUT
R
5 .
1
R
V
P
vs. V
+
HI
, the threshold voltages remain as in
2
REF
HI
R
= V+ − 1.5 V and V
, and does not switch high again until
2
TIME (10ns/DIV)
)
IN
R
20mV/DIV
1
as the AD8611 is used to recover a
LO
R
+
2V/DIV
1
, as given in Equation 1:
R
2
+
V
REF
P
, the hysteresis
LO
= 0 V. For
Rev. A | Page 12 of 20
(1)
A 5 V, HIGH SPEED WINDOW COMPARATOR
A window comparator circuit is used to detect when a signal is
between two fixed voltages. The AD8612 can be used to create a
high speed window comparator, as shown in Figure 26. In this
example, the reference window voltages are set as:
The output of the A1 comparator goes high when the input
signal exceeds V
V
and V
and Q2, thus driving V
goes outside of the reference voltage window, V
To ensure a minimum of switching delay, the use of high speed
transistors is recommended for Q1 and Q2. Using the AD8612
with 2N3960 transistors provides a total propagation delay from
V
Table 8. Window Comparator Output States
V
≈ 200 mV
+5 V
≈ 200 mV
OUT
IN
IN
NOTES
1. Q1, Q2 = 2N3960.
2. PINS 2 AND 13 ARE NO CONNECTS.
R1
R2
R3
R4
V
drops below V
to V
IN
5V
5V
V
LO
HI
, both comparator outputs are low, turning off both Q1
OUT
V
V
=
HI
LO
R
of less than 10 ns.
Figure 26. A High Speed Window Comparator
1
6
R
7
8
9
+
2
5
HI
4
R
A1
A2
5V
, and the output of A2 goes high only when
11
LO
2
AD8612
10
. When the input voltage is between V
3
AD8612
12
1
OUT
14
V
LO
1kΩ
to a high state. If the input signal
1kΩ
Input Voltage
V
V
V
=
IN
LO
IN
< V
> V
< V
R
3
500Ω
R
LO
HI
IN
+
4
500Ω
< V
R
4
Q1
HI
5V
Q2
OUT
1kΩ
goes low.
V
OUT
HI