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FEATURES 4.5 ns Propagation Delay 200 ps Maximum Propagation Delay Dispersion Single +5 V or 5 V Supply Operation Complementary Matched TTL Outputs APPLICATIONS High Speed Line Receivers Peak Detectors Window Comparators High Speed Triggers Ultrafast Pulse Width Discriminators
Ultrafast TTL Comparators AD9696/AD9698
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 A. A latch enable input is provided to allow operation in either sample-and-hold or track-and-hold applications. The AD9696 and AD9698 are both available as commercial temperature range devices operating from ambient temperatures of 0C to +70C, and as extended temperature range devices for ambient temperatures from -55C to +125C. Both versions are available qualified to MIL-STD-883 class B. 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.
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.
FUNCTIONAL BLOCK DIAGRAM
AD9696 AD9696/AD9698 Architecture
NONINVERTING INPUT INVERTING INPUT Q OUTPUT Q OUTPUT
INPUT
LATCH
GAIN
LEVEL SHIFT
OUTPUT
LATCH ENABLE
AD9698
NONINVERTING INPUT INVERTING INPUT Q OUTPUT #1 Q OUTPUT Q OUTPUT Q OUTPUT #2 NONINVERTING INPUT INVERTING INPUT
LATCH ENABLE
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 (c) Analog Devices, Inc., 1997
AD9696/AD9698-SPECIFICATIONS
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
Operating Temperature Range2 AD9696/AD9698KN/KQ/KR . . . . . . . . . . . . 0C to +70C AD9696/AD9698TQ . . . . . . . . . . . . . . . . -55C to +125C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Junction Temperature KQ/TQ Suffixes . . . . . . . . . . . . . . . . . . . . . . . . . . . +175C KN/KR Suffixes . . . . . . . . . . . . . . . . . . . . . . . . . . . +150C Lead Soldering Temperature (10 sec) . . . . . . . . . . . . +300C
ELECTRICAL CHARACTERISTICS
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 LATCH ENABLE INPUT Logic "1" Voltage Threshold Logic "0" Voltage Threshold Logic "1" Current Logic "0" Current DIGITAL OUTPUTS Logic "1" Voltage (Source 4 mA) Logic "0" Voltage (Sink 10 mA) 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)
(Supply Voltages = -5.2 V and +5.0 V; load as specified in Note 4, unless otherwise noted)
0 C to +70 C AD9696/AD9698 KN/KQ/KR Min Typ Max 1.0 10 16 0.4 3 -2.2 +1.4 80 57 2.0 0.8 10 1 2.7 3.5 0.4 2.7 0.5 3.5 0.4 85 63 +3.7 +3.7 -2.2 +1.4 80 57 2.0 0.8 10 1 85 63 2.0 3.0 55 110 1.0 1.3 -55 C to +125 C AD9696/AD9698 TQ Min Typ Max 1.0 10 16 0.4 3 +3 7 +3.7 2.0 3.0 55 110 1.0 1.3
Temp +25C Full Full +25C Full +25C Full +25C Full Full Full Full Full Full Full Full Full Full
Test Level I VI V I VI I VI V VI VI VI VI VI VI VI VI VI VI
Units mV mV V/C A A A A pF V V dB dB V V A A V V
0.5
Full Full +25C +25C +25C +25C +25C +25C +25C +25C +25C +25C
IV IV IV IV IV V IV V V IV IV IV 3.5 3 3
4.5 4.5 6.5 6.5 0.5 100 100 1.85 1.35 2.5 1.7 1.9
7.0 7.0 8.5 8.5 1.5
4.5 4.5 6.5 6.5 0.5 100 100 1.85 1.35 3.5 3 3 2.5 1.7 1.9
7.0 7.0 8.5 8.5 1.5
ns ns ns ns ns ps ps ns ns ns ns ns
200
200
-2-
REV. B
AD9696/AD9698
Test Level 0 C to +70 C AD9696/AD9698 KN/KQ/KR Min Typ Max -55 C to +125 C AD9696/AD9698 TQ Min Typ Max
Parameter 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
6
Temp
Units (+5.0 V) mA mA (-5.2 V) mA mA mW mW mW mW dB dB
Full Full Full Full Full Full Full Full +25C Full
VI VI VI VI V V V V VI VI
26 52 2.5 5.0 130 146 260 292 70 65
3 4
32 64 4.0 8.0
26 52 2.5 5.0 130 146 260 292 70 65
32 64 4.0 8.0
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 JA = 170C/W JC = 50C/W AD9696 Ceramic DIP JA = 110C/W JC = 20C/W AD9696 Plastic DIP JA = 160C/W JC = 30C/W AD9696 Plastic SOIC JA = 180C/W JC = 30C/W AD9698 Ceramic DIP JA = 90C/W JC = 25C/W AD9698 Plastic DIP JA = 100C/W JC = 20C/W AD9698 Plastic SOIC JA = 120C/W JC = 20C/W
Load circuit has 420 from +VS to output; 460 from output to ground. RS 100 . 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.
ORDERING GUIDE EXPLANATION OF TEST LEVELS Test Level
Model AD9696KN AD9696KR AD9696KQ AD9696TQ AD9696TZ/883B2 AD9698KN AD9698KR AD9698KQ AD9698TQ AD9698TZ/883B3
Package Plastic DIP SOIC Cerdip Cerdip Gullwing Plastic DIP SOIC Cerdip Cerdip Gullwing
Temperature 0C to +70C 0C to +70C 0C to +70C -55C to +125C -55C to +125C 0C to +70C 0C to +70C 0C to +70C -55C to +125C -55C to +125C
Package Option1 N-8 R-8 Q-8 Q-8 Z-8A N-16 R-16A Q-16 Q-16 Z-16
I II III IV V VI
- 100% production tested. - 100% production tested at +25C, 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 +25C. 100% production tested at temperature extremes for extended temperature devices; sample tested at temperature extremes for commercial/industrial devices.
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
Q1OUT (N/C) Q1OUT (-VS) GROUND (-IN1) LATCH ENABLE 1 (+IN1) N/C (+IN2) -VS (-IN2) -IN1 (+VS) +IN1 (N/C) 1 2 3 4 5 6 7 8 TOP VIEW (Not to Scale) 16 Q2OUT (LATCH ENABLE 1) 15 Q2OUT (GROUND) 14 GROUND (Q1OUT) 13 LATCH ENABLE 2 (Q1OUT) +VS +IN -IN -VS 1 2 3 4 TOP VIEW (Not to Scale) 8 7 6 5 QOUT QOUT GROUND LATCH ENABLE
12 N/C (Q2OUT) 11 +VS (Q2OUT) 10 -IN2 (GROUND) 9 +IN2 (LATCH ENABLE 2)
AD9698KN/KQ/TQ [AD9698KR/TZ PINOUTS SHOWN IN ( )]
AD9696KN/KR/KQ/TQ/TZ
Name Q1OUT Q1OUT GROUND LATCH ENABLE 1
Function 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.
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.
WARNING!
ESD SENSITIVE DEVICE
-4-
REV. B
AD9696/AD9698
LATCH ENABLE LATCH COMPARE VOS TWO DIODES ABOVE GROUND
tH
DIFFERENTIAL INPUT VOLTAGE VIN
tPW (E)
tS
VOD
Q
50%
tPD
tPD (E)
Q
50%
t S - MINIMUM SETUP TIME (Typically 1.7ns) t H - MINIMUM HOLD TIME (Typically 1.9ns) t PD - INPUT TO OUTPUT DELAY t PD (E) - LATCH ENABLE TO OUTPUT DELAY
tPW (E) - MINIMUM LATCH ENABLE PULSE WIDTH (Typically 2.5ns)
VOS - INPUT OFFSET VOLTAGE VOD - OVERDRIVE VOLTAGE
AD9696/AD9698 Timing Diagram
DIE LAYOUT AND MECHANICAL INFORMATION THEORY OF OPERATION
Die Dimensions AD9696 . . . . . . . . . . . . . 59x71x15 ( 2) mils AD9698 . . . . . . . . . . . . 79x109x15 ( 2) mils Pad Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4x4 mils Metalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aluminum Backing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . None Substrate Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -VS Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitride
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 R1 A1 R2 +VREF VIN +IN1 -IN1 VSIGNAL +IN2 -VREF -IN2 Q2 OUT Q1 OUT Q2 OUT Q1 OUT +Q2 OUT A2 R = 10k R1 + R2 >5k A1 ,A2 = AD708 or OP- 290 (5V) Q1 OUT (+5V)
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. 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. 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
AD9698
Figure 1. AD9698 Used as Window Detector
SIGNAL VOLTAGE AT +INPUT
{
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 k for R1 and 10 k 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:
(1-X)/2X = R2/R1
where: X = % window
+INPUT CURRENT
- 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. 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.
Crystal Oscillator
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.
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. 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.
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. 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 F for 1-10 MHz; 220 pF for frequencies above 10 MHz).
-6-
REV. B
AD9696/AD9698
+VS
LAYOUT CONSIDERATIONS
2k 0.1F 1- 40MHz
(VALUE DEPENDS ON FREQ.) FOR USE WITH OVERTONE CRYSTAL
AD9696
+VS +IN 2 2k 3 -IN + - 7 8 1 5
LATCH ENABLE
QOUT OSCILLATOR OUTPUT
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. 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
QOUT
-VS 2k 0.1F (220pF for Freq. > 10MHz)
4
6 GROUND
Figure 2. AD9696 Oscillator Circuit (Based on DIP Pinouts)
0.1F 0.1F 4 AD1 AD2 2 3 5 1 7
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 H). The shunt capacitor at the inverting input has a value of 220 pF for a stable 36 MHz frequency.
AD9696 (8-PIN DIP)
8 6
GND RESISTORS ARE 1k 5% -0.9V AD1 -1.7V -0.9 V AD2 -1.7V 5s
Burn-In Circuit
REV. B
-7-
AD9696/AD9698
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
-8-
REV. B
PRINTED IN U.S.A.
C1320a-10-2/91

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