a
Ultrafast
TTL Comparators
AD9696/AD9698
FEATURES
4.5 ns Propagation Delay
200 ps Maximum Propagation Delay Dispersion
Single +5 V or 65 V Supply Operation
Complementary Matched TTL Outputs
Both devices allow the use of either a single +5 V supply or
± 5 V supplies. The choice of supplies determines the common
mode input voltage range available: –2.2 V to +3.7 V for ± 5 V
operation, +1.4 V to +3.7 V for single +5 V supply operation.
The differential input stage features high precision, with offset
voltages that are less than 2 mV and offset currents less than
1 µA. A latch enable input is provided to allow operation in either sample-and-hold or track-and-hold applications.
APPLICATIONS
High Speed Line Receivers
Peak Detectors
Window Comparators
High Speed Triggers
Ultrafast Pulse Width Discriminators
The AD9696 and AD9698 are both available as commercial
temperature range devices operating from ambient temperatures
of 0°C to +70°C, and as extended temperature range devices for
ambient temperatures from –55°C to +125°C. Both versions are
available qualified to MIL-STD-883 class B.
GENERAL DESCRIPTION
The AD9696 and AD9698 are ultrafast TTL-compatible voltage comparators able to achieve propagation delays previously
possible only in high performance ECL devices. The AD9696 is
a single comparator providing 4.5 ns propagation delay, 200 ps
maximum delay dispersion and 1.7 ns setup time. The AD9698
is a dual comparator with equally high performance; both devices are ideal for critical timing circuits in such applications as
ATE, communications receivers and test instruments.
Package options for the AD9696 include a 10-pin TO-100 metal
can, an 8-pin ceramic DIP, an 8-pin plastic DIP, and an 8-lead
small outline plastic package. The AD9698 is available in a
16-pin ceramic DIP, a 16-lead ceramic gullwing, a 16-pin plastic
DIP and a 16-lead small outline plastic package. Military qualified versions of the AD9696 come in the TO-100 can and
ceramic DIP; the dual AD9698 comes in ceramic DIP.
FUNCTIONAL BLOCK DIAGRAM
AD9696
AD9696/AD9698 Architecture
INPUT
LATCH
GAIN
LEVEL
SHIFT
OUTPUT
NONINVERTING
INPUT
Q OUTPUT
INVERTING
INPUT
Q OUTPUT
LATCH
ENABLE
AD9698
NONINVERTING
INPUT
INVERTING
INPUT
Q OUTPUT
Q OUTPUT
#1
#2
Q OUTPUT
LATCH
ENABLE
Q OUTPUT
NONINVERTING
INPUT
INVERTING
INPUT
LATCH
ENABLE
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997
AD9696/AD9698–SPECIFICATIONS
Operating Temperature Range2
AD9696/AD9698KN/KQ/KR . . . . . . . . . . . . 0°C to +70°C
AD9696/AD9698TQ . . . . . . . . . . . . . . . . –55°C to +125°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature
KQ/TQ Suffixes . . . . . . . . . . . . . . . . . . . . . . . . . . . +175°C
KN/KR Suffixes . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
Lead Soldering Temperature (10 sec) . . . . . . . . . . . . +300°C
ABSOLUTE MAXIMUM RATINGS 1
Supply Voltage (+VS/–VS) . . . . . . . . . . . . . . . . . . . . +7 V/–7 V
Input Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 5 V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . 5.4 V
Latch Enable Voltage . . . . . . . . . . . . . . . . . . . . . –0.5 V to +VS
Output Current (Continuous) . . . . . . . . . . . . . . . . . . . 20 mA
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 mW
ELECTRICAL CHARACTERISTICS
(Supply Voltages = –5.2 V and +5.0 V; load as specified in Note 4,
unless otherwise noted)
08C to +708C
AD9696/AD9698
KN/KQ/KR
Min
Typ
Max
Temp
Test
Level
+25°C
Full
Full
+25°C
Full
+25°C
Full
+25°C
I
VI
V
I
VI
I
VI
V
Full
Full
VI
VI
–2.2
+1.4
Full
Full
VI
VI
80
57
LATCH ENABLE INPUT
Logic “1” Voltage Threshold
Logic “0” Voltage Threshold
Logic “1” Current
Logic “0” Current
Full
Full
Full
Full
VI
VI
VI
VI
2.0
DIGITAL OUTPUTS
Logic “1” Voltage (Source 4 mA)
Logic “0” Voltage (Sink 10 mA)
Full
Full
VI
VI
2.7
Full
Full
+25°C
+25°C
+25°C
Parameter
INPUT CHARACTERISTICS
Input Offset Voltage4
Input Offset Voltage Drift
Input Bias Current
Input Offset Current
Input Capacitance
Input Voltage Range
± 5.0 V
+5.0 V
Common Mode Rejection Ratio
± 5.0 V
+5.0 V
SWITCHING PERFORMANCE
Propagation Delay (tPD)5
Input to Output HIGH
Input to Output LOW
Latch Enable to Output HIGH
Latch Enable to Output LOW
Delta Delay Between Outputs
Propagation Delay Dispersion
20 mV to 100 mV Overdrive
100 mV to 1.0 V Overdrive
Rise Time10
Fall Time10
Latch Enable
Pulse Width [tPW(E)]
Setup Time (tS)
Hold Time (tH)
1.0
10
16
0.4
–558C to +1258C
AD9696/AD9698
TQ
Min
Typ
Max
2.0
3.0
1.0
10
16
55
110
1.0
1.3
0.4
3
2.0
3.0
55
110
1.0
1.3
3
+3.7
+3.7
85
63
–2.2
+1.4
80
57
+3 7
+3.7
85
63
V
V
0.8
10
1
V
V
µA
µA
3.5
0.4
0.5
3.5
0.4
0.5
V
V
IV
IV
IV
IV
IV
4.5
4.5
6.5
6.5
0.5
7.0
7.0
8.5
8.5
1.5
4.5
4.5
6.5
6.5
0.5
7.0
7.0
8.5
8.5
1.5
ns
ns
ns
ns
ns
+25°C
+25°C
+25°C
+25°C
V
IV
V
V
100
100
1.85
1.35
+25°C
+25°C
+25°C
IV
IV
IV
3.5
3
3
–2–
2.5
1.7
1.9
2.7
mV
mV
µV/°C
µA
µA
µA
µA
pF
dB
dB
2.0
0.8
10
1
Units
100
100
1.85
1.35
200
3.5
3
3
2.5
1.7
1.9
200
ps
ps
ns
ns
ns
ns
ns
REV. B
AD9696/AD9698
Parameter
08C to +708C
AD9696/AD9698
KN/KQ/KR
Min
Typ
Max
–558C to +1258C
AD9696/AD9698
TQ
Min
Typ
Max
Temp
Test
Level
Full
Full
VI
VI
26
52
32
64
26
52
32
64
Full
Full
VI
VI
2.5
5.0
4.0
8.0
2.5
5.0
4.0
8.0
Full
Full
Full
Full
+25°C
Full
V
V
V
V
VI
VI
130
146
260
292
Units
6
POWER SUPPLY
Positive Supply Current7
AD9696
AD9698
Negative Supply Current8
AD9696
AD9698
Power Dissipation
AD9696 +5.0 V
AD9696 ± 5.0 V
AD9698 +5.0 V
AD9698 ± 5.0 V
Power Supply Rejection Ratio 9
70
65
NOTES
1
Absolute maximum ratings are limiting values, to be applied individually,
and beyond which the serviceability of the circuit may be impaired. Functional
operability is not necessarily implied. Exposure to absolute maximum rating
conditions for an extended period of time may affect device reliability.
2
Typical thermal impedances:
AD9696 Metal Can
θJA = 170°C/W
θJC = 50°C/W
AD9696 Ceramic DIP
θJA = 110°C/W
θJC = 20°C/W
AD9696 Plastic DIP
θJA = 160°C/W
θJC = 30°C/W
AD9696 Plastic SOIC
θJA = 180°C/W
θJC = 30°C/W
AD9698 Ceramic DIP
θJA = 90°C/W
θJC = 25°C/W
AD9698 Plastic DIP
θJA = 100°C/W
θJC = 20°C/W
AD9698 Plastic SOIC
θJA = 120°C/W
θJC = 20°C/W
130
146
260
292
(+5.0 V)
mA
mA
(–5.2 V)
mA
mA
mW
mW
mW
mW
dB
dB
70
65
Load circuit has 420 Ω from +VS to output; 460 Ω from output to ground.
RS ≤100 Ω.
5
Propagation delays measured with 100 mV pulse; 10 mV overdrive.
6
Supply voltages should remain stable within ± 5% for normal operation.
7
Specification applies to both +5 V and ± 5 V supply operation.
8
Specification applies to only ± 5 V supply operation.
9
Measured with nominal values ± 5% of +VS and –VS.
10
Although fall time is faster than rise time, the complementary outputs cross at
midpoint of logic swing because of delay on start of falling edge.
Specifications subject to change without notice.
3
4
ORDERING GUIDE
EXPLANATION OF TEST LEVELS
Test Level
I
II
III
IV
V
VI
– 100% production tested.
– 100% production tested at +25°C, and sample tested at
specified temperatures.
– Sample tested only.
– Parameter is guaranteed by design and characterization
testing.
– Parameter is a typical value only.
– All devices are 100% production tested at +25°C.
100% production tested at temperature extremes for
extended temperature devices; sample tested at temperature extremes for commercial/industrial devices.
Model
Package
Temperature
Package
Option1
AD9696KN
AD9696KR
AD9696KQ
AD9696TQ
AD9696TZ/883B2
AD9698KN
AD9698KR
AD9698KQ
AD9698TQ
AD9698TZ/883B3
Plastic DIP
SOIC
Cerdip
Cerdip
Gullwing
Plastic DIP
SOIC
Cerdip
Cerdip
Gullwing
0°C to +70°C
0°C to +70°C
0°C to +70°C
–55°C to +125°C
–55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
–55°C to +125°C
–55°C to +125°C
N-8
R-8
Q-8
Q-8
Z-8A
N-16
R-16A
Q-16
Q-16
Z-16
NOTES
1
N = Plastic DIP, Q = Cerdip, R = Small Outline (SOIC), Z = Ceramic Leaded
Chip Carrier.
2
Refer to AD9696TZ/883B military data sheet.
3
Refer to AD9698TZ/883B military data sheet.
REV. B
–3–
AD9696/AD9698
PIN CONFIGURATIONS
1
16 Q2OUT (LATCH ENABLE 1)
Q1OUT (–VS)
2
15 Q2OUT (GROUND)
GROUND (–IN1)
3
14 GROUND (Q1OUT)
4
13
Q1OUT (N/C)
LATCH ENABLE 1 (+IN1)
N/C (+IN2)
–VS (–IN2)
–IN1 (+VS)
+IN1 (N/C)
5
6
7
8
TOP VIEW
(Not to Scale)
LATCH ENABLE 2 (Q1OUT)
12 N/C (Q2OUT)
11 +VS (Q2OUT)
10 –IN2 (GROUND)
9
+IN2 (LATCH ENABLE 2)
AD9698KN/KQ/TQ
[AD9698KR/TZ PINOUTS SHOWN IN ( )]
+VS
1
8
QOUT
+IN
2
7
QOUT
–IN
3
6
GROUND
5
LATCH
ENABLE
–VS
TOP VIEW
(Not to Scale)
4
AD9696KN/KR/KQ/TQ/TZ
Name
Function
Q1OUT
One of two complementary outputs. Q1OUT will be at logic HIGH if voltage at +IN1 is greater than voltage at
–IN1 and LATCH ENABLE 1 is at logic LOW.
One of two complementary outputs. Q1OUT will be at logic HIGH if voltage at –IN1 is greater than voltage at
+IN1 and LATCH ENABLE 1 is at logic LOW.
Analog and digital ground return. All GROUND pins should be connected together and to a low impedance
ground plane near the comparator.
Output at Q1OUT will track differential changes at the inputs when LATCH ENABLE 1 is at logic LOW.
When LATCH ENABLE 1 is at logic HIGH, the output at Q1OUT will reflect the input state at the application of
the latch command, delayed by the Latch Enable Setup Time (tS). Since the architecture of the input stage (see
block diagram) is faster than the logic of the latch stage, data will typically be latched if applied to the comparator(s)
within 1.7 ns after the latch. This is the Setup Time (tS); for guaranteed performance, tS must be 3 ns.
No internal connection to comparator.
Negative power supply connection; nominally –5.2 V.
Inverting input of differential input stage for Comparator #1.
Noninverting input of differential input stage for Comparator #1.
Noninverting input of differential input stage for Comparator #2.
Inverting input of differential input stage for Comparator #2.
Positive power supply connection; nominally +5 V.
Output at Q2OUT will track differential changes at the inputs when LATCH ENABLE 2 is at logic LOW.
When LATCH ENABLE 2 is at logic HIGH, the output at Q2OUT will reflect the input state at the application of
the latch command, delayed by the Latch Enable Setup Time (tS). Since the architecture of the input stage (see
block diagram) is faster than the logic of the latch stage, data will typically be latched if applied to the comparator(s)
within 1.7 ns after the latch. This is the Setup Time (tS); for guaranteed performance, tS must be 3 ns.
One of two complementary outputs. Q2OUT will be at logic HIGH if voltage at –IN2 is greater than voltage at
+IN2 and LATCH ENABLE 2 is at logic LOW.
One of two complementary outputs. Q2OUT will be at logic HIGH if voltage at +IN2 is greater than voltage at
–IN2 and LATCH ENABLE 2 is at logic LOW.
Q1OUT
GROUND
LATCH
ENABLE 1
N/C
–VS
–IN1
+IN1
+IN2
–IN2
+VS
LATCH
ENABLE 2
Q2OUT
Q2OUT
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD9696/AD9698 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.
–4–
WARNING!
ESD SENSITIVE DEVICE
REV. B
AD9696/AD9698
LATCH
ENABLE
TWO DIODES
ABOVE GROUND
LATCH
COMPARE
VOS
tPW (E)
tH
DIFFERENTIAL
INPUT VOLTAGE
tS
VIN
VOD
Q
50%
tPD
Q
tPD (E)
50%
tPW (E) – MINIMUM LATCH ENABLE PULSE WIDTH (Typically 2.5ns)
t S – MINIMUM SETUP TIME (Typically 1.7ns)
t H – MINIMUM HOLD TIME (Typically 1.9ns)
VOS – INPUT OFFSET VOLTAGE
VOD – OVERDRIVE VOLTAGE
t PD – INPUT TO OUTPUT DELAY
t PD (E) – LATCH ENABLE TO OUTPUT DELAY
AD9696/AD9698 Timing Diagram
DIE LAYOUT AND MECHANICAL INFORMATION
Die Dimensions AD9696 . . . . . . . . . . . . . 59×71×15 (± 2) mils
AD9698 . . . . . . . . . . . . 79×109×15 (± 2) mils
Pad Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4×4 mils
Metalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aluminum
Backing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . None
Substrate Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –VS
Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitride
THEORY OF OPERATION
Refer to the block diagram of the AD9696/AD9698 comparators. The AD9696 and AD9698 TTL voltage comparator architecture consists of five basic stages: input, latch, gain, level shift
and output. Each stage is designed to provide optimal performance and make it easy to use the comparators.
The input stage operates with either a single +5-volt supply, or
with a +5-volt supply and a –5.2-volt supply. For optimum
power efficiency, the remaining stages operate with only a single
+5-volt supply. The input stage is an input differential pair
without the customary emitter follower buffers. This configuration increases input bias currents but maximizes the input voltage range.
A latch stage allows the most recent output state to be retained
as long as the latch input is held high. In this way, the input to
the comparator can be changed without any change in the output state. As soon as the latch enable input is switched to LOW,
the output changes to the new value dictated by the signal applied to the input stage.
The gain stage assures that even with small values of input voltage, there will be sufficient levels applied to the following stages
to cause the output to switch TTL states as required. A level
shift stage between the gain stage and the TTL output stage
guarantees that appropriate voltage levels are applied from the
gain stage to the TTL output stage.
Only the output stage uses TTL logic levels; this minimum use
of TTL circuits maximizes speed and minimizes power consumption. The outputs are clamped with Schottky diodes to assure that the rising and falling edges of the output signal are
closely matched.
The AD9696 and AD9698 represent the state of the art in high
speed TTL voltage comparators. Great care has been taken to
optimize the propagation delay dispersion performance. This assures that the output delays will remain constant despite varying
levels of input overdrive. This characteristic, along with closely
matched rising and falling outputs, provides extremely consistent results at previously unattainable speeds.
REV. B
–5–
AD9696/AD9698
APPLICATIONS
General
R
R
Two characteristics of the AD9696 and AD9698 should be considered for any application. First is the fact that all TTL comparators are prone to oscillate if the inputs are close to equal for
any appreciable period of time. One instance of this happening
would be slow changes in the unknown signal; the probability of
oscillation is reduced when the unknown signal passes through
the threshold at a high slew rate. Another instance is if the unknown signal does not overdrive the comparator logic. Unless
they are overdriven, TTL comparators have undershoot when
switching logic states. The smaller the overdrive, the greater the
undershoot; when small enough, the comparator will oscillate,
not being able to determine a valid logic state. For the AD9696
and AD9698, 20 mV is the smallest overdrive which will assure
crisp switching of logic states without significant undershoot.
R1
R2
VIN
+IN1
AD9698
(±5V)
Q1 OUT
(+5V)
–IN1
Q1 OUT
VSIGNAL
+IN2
–VREF
Q1 OUT
+Q2 OUT
Q2 OUT
–IN2
Q2 OUT
Figure 1. AD9698 Used as Window Detector
When configured as shown, the op amps generate reference levels for the comparators that are equally spaced above and below
the applied VIN. The width of the window is established by the
ratio of R1 and R2. For a given ratio of R1 and R2, +VREF and
–VREF will be fixed percentages above and below VIN. As an example, using 2.2 kΩ for R1 and 10 kΩ for R2 creates a ± 10%
window. When VIN equals +3 V, +VREF will be +3.3 V and
–VREF will be +2.7 V. Likewise, for a –2 V input, the thresholds
will be –1.8 V and –2.2 V. Windows of differing percentage
width can be calculated with the equation:
During the time both transistors in the differential pair are conducting, the ac input impedance drops by orders of magnitude.
Additionally, the input bias current switches from one input to
the other, depending upon whether or not the threshold is exceeded. As a result, the input currents follow approximately the
characteristic curves shown below.
LINEAR
REGION
R = 10kΩ
R1 + R2 >5kΩ
A1 ,A2 = AD708 or OP– 290
+VREF
The second characteristic to keep in mind when designing
threshold circuits for these comparators is twofold: (1) bias currents change when the threshold is exceeded; and (2) ac input
impedance decreases when the comparator is in its linear region.
SIGNAL
VOLTAGE
AT +INPUT
A2
A1
{
(1–X)/2X = R2/R1
where:
X = % window
+INPUT
CURRENT
Additionally, the low impedance of the op amp outputs assures
that the threshold voltages will remain constant when the input
currents change as the signal passes through the threshold voltage levels.
– INPUT
CURRENT
The output of the AND gate will be high while the signal is inside the window. Q1OUT will be high when the signal is above
+VREF, and Q2OUT will be high when the signal is below –VREF.
Threshold Input Currents
This characteristic will not cause problems unless a high impedance threshold circuit or drive circuit is employed. A circuit
similar to that shown in the window comparator application can
eliminate this possible problem.
Crystal Oscillator
Oscillators are used in a wide variety of applications from audio
circuits to waveform generators, from ATE triggers and telecommunications transceivers to radar. Figure 2 shows a versatile
and inexpensive oscillator. The circuit uses the AD9696, in a
positive feedback mode, and is capable of generating accurate
and stable oscillations with frequencies ranging from 1 MHz to
more than 40 MHz.
Window Comparator
Many applications require determining when a signal’s voltage
falls within, above, or below a particular voltage range. A simple
tracking window comparator can provide this data. Figure 1
shows such a window comparator featuring high speed, TTL
compatibility, and ease of implementation.
To generate oscillations from 1 to 25 MHz, a fundamental
mode crystal is used without the dc blocking capacitor and
choke. The parallel capacitor on the inverting input is selected
for stability (0.1 µF for 1–10 MHz; 220 pF for frequencies
above 10 MHz).
Two comparators are required to establish a “window” with upper and lower threshold voltages. The circuit shown uses the
AD9698 dual ultrafast TTL comparator. In addition to the cost
and space savings over a design using two single comparators,
the dual comparator on a single die produces better matching of
both dc and dynamic characteristics.
–6–
REV. B
AD9696/AD9698
+V S
LAYOUT CONSIDERATIONS
When working with high speed circuits, proper layout is critical.
Analog signal paths should be kept as short as possible and be
properly terminated to avoid reflections. In addition, digital signal paths should be kept short, and run lengths should be matched to avoid propagation delay mismatch. All analog signals
should be kept as far away from digital signal paths as possible;
this reduces the amount of digital switching noise that might be
capacitively coupled into the analog section of the circuit.
2kΩ
0.1µF
1– 40MHz
AD9696
(VALUE
DEPENDS
ON FREQ.)
FOR USE WITH
OVERTONE
CRYSTAL
+VS
LATCH
ENABLE
1
5
+IN
2kΩ
2
+
7
3
–
8
QOUT
QOUT
–IN
–VS
4
OSCILLATOR
OUTPUT
6
GROUND
2kΩ
0.1µF
(220pF for Freq. > 10MHz)
In high speed circuits, layout of the ground circuit is the most
important factor. A single, low impedance ground plane, on the
component side of the board, will reduce noise in the circuit
ground. It is especially important to maintain continuity of the
ground plane under and around the AD9696 or AD9698.
Sockets limit the dynamic performance of the device and should
be used only for prototypes or evaluation.
– VS
+VS
Figure 2. AD9696 Oscillator Circuit (Based on DIP Pinouts)
0.1µF
0.1µF
When generating frequencies using a nonfundamental mode
crystal, a choke and dc blocking capacitor are added. As an example, a 36 MHz oscillator can be achieved by using a 12 MHz
crystal operating on its third overtone. To suppress oscillation at
the 12 MHz fundamental, the value of the choke is chosen to
provide a low reactive impedance at the fundamental frequency
while maintaining a high reactive impedance at the desired output frequency (for 36 MHz operation, L = 1.8 µH). The shunt
capacitor at the inverting input has a value of 220 pF for a stable
36 MHz frequency.
1
4
AD1
2
AD2
3
7
AD9696
(8-PIN DIP)
5
6
GND
RESISTORS ARE 1kΩ ±5%
–0.9V
AD1
–1.7V
5µs
–0.9 V
AD2
–1.7V
Burn-In Circuit
REV. B
8
–7–
AD9696/AD9698
OUTLINE DIMENSIONS
PRINTED IN U.S.A.
C1320a–10–2/91
Dimensions shown in inches and (mm).
–8–
REV. B