AD ADCMP572BCP Ultrafast 3.3 v single-supply comparator Datasheet

FEATURES
3.3 V/5.2 V single-supply operation
150 ps propagation delay
15 ps overdrive and slew rate dispersion
8 GHz equivalent input risetime bandwidth
80 ps minimum pulse width
35 ps typical output rise/fall
10 ps deterministic jitter (DJ)
200 fs random jitter (RJ)
On-chip terminations at both input pins
Robust inputs with no output phase reversal
Resistor programmable hysteresis
Differential latch control
Power supply rejection > 70 dB
FUNCTIONAL BLOCK DIAGRAM
VCCI
VCCO
VTP TERMINATION
VP NONINVERTING
INPUT
VN INVERTING
INPUT
Q OUTPUT
ADCMP572
ADCMP573
CML/
RSPECL
Q OUTPUT
VTN TERMINATION
LE INPUT
HYS
LE INPUT
04409-0-025
Preliminary Technical Data
Ultrafast 3.3 V
Single-Supply Comparators
ADCMP572/ADCMP573
Figure 1.
APPLICATIONS
Automatic test equipment (ATE)
High speed instrumentation
Pulse spectroscopy
Medical imaging and diagnostics
High speed line receivers
Threshold detection
Peak and zero-crossing detectors
High speed trigger circuitry
Clock and data signal restoration
GENERAL DESCRIPTION
The ADCMP572/ADCMP573 are ultrafast comparators
fabricated on Analog Devices, Inc.’s proprietary XFCB3 Silicon
Germanium (SiGe) bipolar process. The ADCMP572 features
CML output drivers, and the ADCMP573 features reduced
swing PECL (RSPECL) output drivers.
Both devices offer 150 ps propagation delay and 100 ps
minimum pulse width for 10 Gbps operation with 200 fs RMS
random jitter (RJ). Overdrive and slew rate dispersion is
typically less than 15 ps.
A flexible power supply scheme allows either device to operate
with a single +3.3 V positive supply and a −0.2 V to +1.2 V
input signal range, or with split input/output supplies to
support a wider −0.2 V to +3.2 V input signal range and an
independent range of output levels. 50 Ω on-chip termination
resistors are provided at both inputs with the optional capability
to leave open (on an individual pin basis) for applications
requiring high impedance inputs.
The CML output stage is designed to directly drive 400 mV into
50 Ω transmission lines terminated to between 3.3 V to 5.2 V.
The RSPECL output stage is designed to drive 400 mV into
50 Ω terminated to VCCO − 2 V and is compatible with several
commonly used PECL logic families. The comparator input
stage offers robust protection against large input overdrive, and
the outputs do not phase reverse when the valid input signal
range is exceeded. High speed latch and programmable
hysteresis features are also provided.
The ADCMP572/ADCMP573 are available in a 16-lead LFCSP
package.
Rev. PrB
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However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
ADCMP572/ADCMP573
Preliminary Technical Data
TABLE OF CONTENTS
Electrical Characteristics ................................................................. 3
Optimizing High Speed Performance ..................................... 10
Absolute Maximum Ratings............................................................ 5
Comparator Propagation Delay Dispersion ........................... 10
ESD Caution.................................................................................. 5
Comparator Hysteresis .............................................................. 11
Pin Configuration and Function Descriptions............................. 6
Minimum Input Slew Rate Requirement ................................ 11
Typical Performance Characteristics ............................................. 7
Typical Application Circuits.......................................................... 12
Application Information.................................................................. 9
Timing Information ....................................................................... 13
Power/Ground Layout and Bypassing ....................................... 9
Outline Dimensions ....................................................................... 14
CML/RSPECL Output Stage ....................................................... 9
Ordering Guide .......................................................................... 14
Using/Disabling the Latch Feature............................................. 9
REVISION HISTORY
6/04—Revision PrB: Preliminary Version
2/04—Revision PrA: Preliminary Version
Rev. PrB | Page 2 of 16
Preliminary Technical Data
ADCMP572/ADCMP573
ELECTRICAL CHARACTERISTICS
VCCI = VCCO = 3.3 V, TA = 25°C, unless otherwise noted.
Table 1.
Parameter
DC INPUT CHARACTERISTICS
Input Voltage Range
Input Differential Voltage
Input Offset Voltage
Offset Voltage Tempco
Input Bias Current
Input Bias Current Tempco
Input Offset Current
Input Capacitance
Input Impedance
Input Resistance, Differential Mode
Input Resistance, Common Mode
Active Gain
Common-Mode Rejection
Symbol
Conditions
Min
VP, VN
VCCI = 3.3 V, VCCO = 3.3 V
VCCI = 5.2 V, VCCO = 3.3 V
−0.2
−0.2
−1.2
−5.0
VOS
∆VOS/dT
IP, IN
Latch Minimum Pulse Width
DC OUTPUT CHARACTERISTICS
ADCMP572 (CML)
Output Impedance
Output Voltage High Level
Output Voltage Low Level
Output Voltage Differential
Temperature Coefficient, VOH
Temperature Coefficient, VOL
ADCMP573 (RSPECL)
Output Voltage High Level
Output Voltage Low Level
Output Voltage Differential
−50.0
−5.0
CP, CN
47.5
Open termination
Open termination
AV
CMRR
VCCI = 3.3 V, VCCO = 3.3 V,
VCM = 0.0 V to 1.0 V
VCCI = 5.2 V, VCCO = 3.3 V,
VCM = 0.0 V to 3.0 V
RHYS = ∞
Hysteresis
LATCH ENABLE CHARACTERISTICS
ADCMP572
Latch Enable Input Range
Latch Enable Input Differential
Latch Setup Time
Latch Hold Time
ADCMP573
Latch Enable Input Range
Latch Enable Input Differential
Latch Setup Time
Latch Hold Time
Latch Enable Input Impedance
Latch to Output Delay
Open termination
2.8
0.2
tS
tH
VOD = 100 mV
VOD = 100 mV
1.8
0.2
Typ
±2.0
10.0
−25.0
50.0
±2.0
TBD
50
50
500
54
50
Max
Unit
+1.2
+3.2
+1.2
+5.0
V
V
V
mV
µV/°C
µA
nA/°C
µA
pF
Ω
kΩ
kΩ
dB
dB
0.0
+5.0
52.5
40
dB
±1
mV
0.4
15
0
VCCO+0.2
0.5
V
V
ps
ps
VCCO−0.6
0.5
V
V
ps
ps
Ω
ps
tPLOH,
tPLOL
tPL
VOD = 100 mV
0.4
0
50
50.0
150
VOD = 100 mV
100
ZOUT
VOH
VOL
−8 mA < I OUT < 8 mA
50 Ω terminate to VCCO
50 Ω terminate to VCCO
50 Ω terminate to VCCO
50 Ω terminate to VCCO
50 Ω terminate to VCCO
47.5
VCCO−0.10
VOH−0.45
350
50.0
VCCO−0.05
VOH−0.40
400
TBD
TBD
52.5
VCCO
VOH−0.35
450
Ω
V
V
mV
mV/°C
mV/°C
50 Ω terminate to VCCO−2.0
50 Ω terminate to VCCO−2.0
50 Ω terminate to VCCO−2.0
VCCO−0.90
VOH−0.45
350
VCCO−0.80
VOH−0.40
400
VCCO−0.70
VOH−0.35
450
V
V
mV
tS
tH
VOD = 100 mV
VOD = 100 mV
47.5
∆VOH/dT
∆VOL/dT
VOH
VOL
Rev. PrB | Page 3 of 16
52.5
ps
ADCMP572/ADCMP573
Parameter
AC PERFORMANCE
Propagation Delay
Propagation Delay Tempco
Prop Delay Skew—Rising Transition
to Falling Transition
Overdrive Dispersion
Preliminary Technical Data
Symbol
Conditions
tPD
VCCI = 3.3 V, VOD = 200 mV
VCCI = 3.3 V, VOD = 20 mV
VCCI = 5.2 V, VOD = 200 mV
∆tPD/dT
VOD = 200 mV, 5 V/ns
Slew Rate Dispersion
Pulse Width Dispersion
Duty Cycle Dispersion
Common-Mode Dispersion
Equivalent Input Bandwidth1
BWEQ
Toggle Rate
Deterministic Jitter
DJ
Deterministic Jitter
DJ
RMS Random Jitter
Minimum Pulse Width
Minimum Pulse Width
Rise Time
Fall Time
POWER SUPPLY
Input Supply Voltage Range
Output Supply Voltage Range
Positive Supply Differential
ADCMP572 (CML)
Positive Supply Current
Power Dissipation
ADCMP573 (RSPECL)
Positive Supply Current
Power Dissipation
Power Supply Rejection—VCCI
1
Min
RJ
PWMIN
PWMIN
tR
tF
50 mV < VOD < 1.0 V, 5 V/ns
10 mV < VOD < 1.0 V, 5 V/ns
2 V/ns to 10 V/ns
100 ps to 5 ns
VCCI = 3.3 V, 1 V/ns, VCM = 0 V
VCCI = 5.2 V, 1 V/ns, VCM = 0 V
VOD=0.4V, 0.0 V < VCM < 1.0 V
0.0 V to 400 mV input
tR = tF = 25 ps, 20/80
> 50% Output Swing
VOD = 200 mV, 5 V/ns,
PRBS31−1 NRZ, 4 Gbps
VOD = 200 mV, 5 V/ns,
PRBS31−1 NRZ, 10 Gbps
VOD = 200 mV, 5 V/ns, 1.25 GHz
∆tPD/∆PW < 5 ps
∆tPD/∆PW < 10 ps
20/80
20/80
VCCI
VCCO
VCCI
−VCCO
IVCCI +
IVCCO
PD
IVCCI +
IVCCO
PD
PSRVCCI
Typ
Max
Unit
150
165
145
0.5
10
ps
ps
ps
ps/°C
ps
10
15
15
5
5
10
5
8.0
ps
ps
ps
ps
ps
ps/V
GHz
12.5
10
Gbps
ps
TBD
ps
0.2
100
80
35
35
ps
ps
ps
ps
ps
3.1
3.1
−0.2
5.4
5.4
+2.3
V
V
V
mA
VCCI = 3.3 V, VCCO = 3.3 V,
terminate 50 Ω to VCCO
VCCI = 5.2 V, VCCO = 5.2 V,
terminate 50 Ω to VCCO
VCCI = 3.3 V, VCCO = 3.3 V,
terminate 50 Ω to VCCO
VCCI = 5.2 V, VCCO = 5.2 V,
terminate 50 Ω to VCCO
44
52
44
52
145
160
240
265
VCCI = 3.3 V, VCCO = 3.3 V,
50 Ω to VCCO − 2 V
VCCI = 5.2 V, VCCO = 5.2 V,
50 Ω to VCCO − 2V
VCCI = 3.3 V, VCCO = 3.3 V,
50 Ω to VCCO − 2 V
VCCI = 5.2 V, VCCO = 5.2 V,
50 Ω to VCCO − 2 V
VCCI = 3.3 V ±5%,
VCCO = 3.3 V
66
74
68
76
145
160
175
195
74
mW
mA
mW
dB
Equivalent Input Bandwidth assumes a simple first-order response and is calculated with the following formula: BWEQ = 0.22/•(trCOMP2-trIN2), where trIN is the 20/80
transition time of a quasi-Gaussian signal applied to the comparator input and trCOMP is the effective transition time digitized by the comparator.
Rev. PrB | Page 4 of 16
Preliminary Technical Data
ADCMP572/ADCMP573
ABSOLUTE MAXIMUM RATINGS
Thermal Considerations
Table 2.
Parameter
SUPPLY VOLTAGES
Input Supply Voltage (VCCI to GND)
Output Supply Voltage
(VCCO to GND)
Positive Supply Differential
(VCCI − VCCO)
INPUT VOLTAGES
Input Voltage
Differential Input Voltage
Input Voltage, Latch Enable
HYSTERESIS CONTROL PIN
Applied Voltage (HYS to GND)
Maximum Input/Output Current
OUTPUT CURRENT
ADCMP572 (CML)
ADCMP573 (RSPECL)
TEMPERATURE
Operating Temperature, Ambient
Operating Temperature, Junction
Storage Temperature Range
Rating
The ADCMP572/ADCMP573 LFCSP 16-lead package has a θJA
(junction to ambient thermal resistance) of 70°C/W in still air.
−0.5 V to +6.0 V
−0.5 V to +6.0 V
−0.5 V to +3.5 V
−0.5 V to VCCI + 0.5 V
±(VCCI + 0.5 V)
−0.5 V to VCCO + 0.5 V
Stress above those listed under Absolute Maximum Ratings may
cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other
conditions above those indicated in the operational sections of
this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device
reliability.
−0.5 V to +1.5 V
±1 mA
±20 mA
−35 mA
−40°C to +85°C
125°C
−65°C to +150°C
ESD 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 this product 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.
Rev. PrB | Page 5 of 16
ADCMP572/ADCMP573
Preliminary Technical Data
GND
15
14
13
PIN1
VTP 1
ADCMP572
ADCMP573
VP 2
VN 3
TOP VIEW
(Not to Scale)
5
6
7
8
VCCI
LE
LE
VCCO/VTT
VTN 4
12
VCCO
11
Q
10
Q
9
VCCO
04409-0-026
HYS
16
GND
VCCI
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 2. ADCMP572/ADCMP573 Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1
2
3
4
5, 16
6
Mnemonic
VTP
VP
VN
VTN
VCCI
LE
7
LE
8
VCCO/VTT
13, 15
9, 12
10
GND
VCCO
Q
11
Q
14
HYS
Heatsink
N/C
Description
Termination Resistor Return Pin for VP Input.
Noninverting Analog Input.
Inverting Analog Input.
Termination Resistor Return Pin for VN Input.
Positive Supply Voltage for Input Stage.
Latch Enable Input Pin, Inverting Side.
In compare mode (LE = low), the output tracks changes at the input of the comparator.
In latch mode (LE = high), the output reflects the input state just prior to the comparator’s being
placed in latch mode. LE must be driven in compliment with LE.
Latch Enable Input Pin, Noninverting Side.
In compare mode (LE = high), the output tracks changes at the input of the comparator.
In latch mode (LE = low), the output reflects the input state just prior to the comparator’s being
placed in latch mode. LE must be driven in compliment with LE.
Termination Return Pin for the LE/LE Input Pins.
For the ADCMP572 (CML output stage), this pin should be connected to the positive VCCO supply.
For the ADCMP573 (RSPECL output stage), this pin should be connected to the VCCO – 2 V
termination potential.
Ground.
Positive Supply Voltage for the CML/RSPECL Output Stage.
Inverting Output. Q is at logic low if the analog voltage at the noninverting input, VP, is greater than
the analog voltage at the inverting input, VN, provided the comparator is in compare mode. See the
LE/LE description (Pins 6 and 7) for more information.
Noninverting Output. Q is at logic high if the analog voltage at the noninverting input VP is greater
than the analog voltage at the inverting input, VN, provided the comparator is in compare mode. See
the LE/LE description (Pins 6 and 7) for more information.
Hysteresis Control Pin. Leave this pin disconnected for zero hysteresis. Connect to GND with a
suitably sized resistor to add the desired amount of hysteresis. Refer to Figure 7 for proper sizing of
RHYS hysteresis control resistor.
The metallic back surface of the package is not electrically connected to any part of the circuit, and it
can be left floating for best electrical isolation between the package handle and the substrate of the
die. But it can also be soldered to the application board if improved thermal and/or mechanical
stability is desired.
Rev. PrB | Page 6 of 16
Preliminary Technical Data
ADCMP572/ADCMP573
TYPICAL PERFORMANCE CHARACTERISTICS
VCCI = VCCO = 3.3 V, TA = 25°C, unless otherwise noted.
39.0
38.5
RISE/FALL TIME (ps)
15
10
38.0
37.5
37.0
5
0
0
50
100
150
200
250
INPUT OVERDRIVE VOLTAGE (mV)
36.0
–60
–40
20
40
60
80
100
Figure 6. Rise/Fall Time vs. Temperature
158.5
60
158.0
50
157.5
HYSTERESIS (mV)
157.0
156.5
40
30
20
156.0
0
0.2
0.4
0.6
0.8
1.0
1.2
INPUT COMMON-MODE VOLTAGE (V)
0
04409-0-040
155.5
0
2
3
4
5
6
RHYS (kΩ)
Figure 4. Propagation Delay vs. Input Common Mode
Figure 7. Hysteresis vs. RHYS Control Resistor
160
–15.0
158
INPUT BIAS CURRENT (µA)
–15.5
156
154
152
150
148
–16.0
–16.5
–17.0
–17.5
–18.0
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
100
04409-0-041
146
–60
1
04409-0-043
10
–18.5
–0.5
Figure 5. Propagation Delay vs. Temperature
–0.3
–0.1
0.1
0.3
0.5
0.7
0.9
1.1
1.3
VP INPUT VOLTAGE (VN = –0.2V)
Figure 8. Input Bias Current vs. Input Differential
Rev. PrB | Page 7 of 16
1.5
04409-0-044
PROPAGATION DELAY (ps)
0
TEMPERATURE (°C)
Figure 3. Propagation Delay vs. Input Overdrive
PROPAGATION DELAY (ps)
–20
04409-0-042
36.5
04409-0-039
PROPAGATION DELAY ERROR (ps)
20
Preliminary Technical Data
380
–16.3
379
–16.4
378
OUTPUT LEVELS (mV)
–16.2
–16.5
–16.6
–16.7
–16.9
–60
377
376
375
374
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
100
Figure 9. Input Bias Current vs. Temperature
373
–60
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
Figure 11. Output Levels vs. Temperature
Figure 10. Input Offset Voltage vs. Temperature
Rev. PrB | Page 8 of 16
100
04409-0-046
–16.8
04409-0-045
INPUT BIAS CURRENT (µA)
ADCMP572/ADCMP573
Preliminary Technical Data
ADCMP572/ADCMP573
APPLICATION INFORMATION
POWER/GROUND LAYOUT AND BYPASSING
The ADCMP572/ADCMP573 comparators are very high speed
SiGe devices. Consequently, it is essential to use proper high
speed design techniques to achieve the specified performance.
Of critical importance is the use of low impedance supply
planes, particularly the output supply plane (VCCO) and the
ground plane (GND). Individual supply planes are recommended as part of a multilayer board. Providing the lowest
inductance return path for switching currents ensures the best
possible performance in the target application.
stripline techniques are essential to ensure proper transition
times and to prevent output ringing and pulse-width dependant
propagation delay dispersion. For the most timing critical
applications where transmission line reflections pose the
greatest risk to performance, the ADCMP572 provides the best
match to 50 Ω output transmission paths.
VCCO
50Ω
Q
It is also important to adequately bypass the input and output
supplies. A 1 µF electrolytic bypass capacitor should be placed
within several inches of each power supply pin to ground. In
addition, multiple high quality 0.1 µF bypass capacitors should
be placed as close as possible to each of the VCCI and VCCO
supply pins and should be connected to the GND plane with
redundant vias. High frequency bypass capacitors should be
carefully selected for minimum inductance and ESR. Parasitic
layout inductance should also be strictly avoided to maximize
the effectiveness of the bypass at high frequencies.
Q
GND
04409-0-037
16mA
Figure 12. Simplified Schematic Diagram of
the ADCMP572 CML Output Stage
If the input and output supplies are connected separately such
that VCCI ≠ VCCO, then care should be taken to bypass each of
these supplies separately to the GND plane. A bypass capacitor
should not be connected between them. It is recommended that
the GND plane separate the VCCI and VCCO planes when the
circuit board layout is designed to minimize coupling between
the two supplies and to take advantage of the additional bypass
capacitance from each respective supply to the ground plane.
This enhances the performance when split input/output supplies
are used. If the input and output supplies are connected
together for single-supply operation such that VCCI = VCCO, then
coupling between the two supplies is unavoidable; however,
every effort should be made to keep the supply plane adjacent
to the GND plane to maximize the additional bypass capacitance
this arrangement provides.
VCCO
Q
GND
04409-0-038
Q
Figure 13. Simplified Schematic Diagram of
the ADCMP573 RSPECL Output Stage
CML/RSPECL OUTPUT STAGE
USING/DISABLING THE LATCH FEATURE
Specified propagation delay dispersion performance can be
achieved only by using proper transmission line terminations.
The outputs of the ADCMP572 are designed to directly drive
400 mV into 50 Ω cable or microstrip and/or stripline transmission lines properly terminated to the VCCO supply plane. The
CML output stage is shown in the simplified schematic diagram
of Figure 12. The outputs are each back-terminated with 50 Ω
for best transmission line matching. The RSPECL outputs of the
ADCMP573 are illustrated in Figure 13 and should be terminated
to VCCO − 2 V. As an alternative, Thevenin equivalent termination networks may also be used in either case if the direct
termination voltage is not readily available. If high speed output
signals must be routed more than a centimeter, microstrip or
The latch inputs (LE/LE) are active low for latch mode, and are
internally terminated with 50 Ω resistors to Pin 8. This
corresponds to the VCCO supply for the ADCMP572 and the VTT
pin for the ADCMP573. All VCCO pins should be connected to
the supply plane for maximum performance, and the VTT pin
should be connected externally to VCCO – 2 V, preferably to its
own low inductance plane. When using the ADCMP572, the
latch function can be disabled by connecting the LE pin to
GND with an external pull-down resistor and leaving the LE
pin unconnected. To prevent excessive power dissipation, the
resistor should be 750 Ω when VCCO = 3.3 V, and 1.2 kΩ when
VCCO = 5.2 V. When using the ADCMP573 comparator, the latch
can be disabled by connecting the LE pin to VCCO with an
Rev. PrB | Page 9 of 16
ADCMP572/ADCMP573
Preliminary Technical Data
As with any high speed comparator, proper design and layout
techniques are essential to obtaining the specified performance.
Stray capacitance, inductance, inductive power and ground
impedances, or other layout issues can severely limit performance
and can often cause oscillation. Discontinuities along input and
output transmission lines can also severely limit the specified
pulse-width dispersion performance.
For applications working in a 50 Ω environment, input and
output matching has a significant impact on data dependant (or
deterministic) jitter (DJ) and pulse-width dispersion performance. The ADCMP572/ADCMP573 comparators provide
internal 50 Ω termination resistors for both VP and VN inputs,
and the ADCMP572 provides 50 Ω back terminated outputs.
The return side for each input termination is pinned out
separately with the VTP and VTN pins, respectively. If a 50 Ω
termination is desired at one or both of the VP/VN inputs, then
the VTP and VTN pins can be connected (or disconnected) to
(from) the desired termination potential as required. The
termination potential should be carefully bypassed using high
quality bypass capacitors as discussed above to prevent undesired
aberrations on the input signal due to parasitic inductance in
the circuit board layout. If a 50 Ω input termination is not
desired, either one or both of the VTP/VTN termination pins can
be left disconnected. In this case, the pins should be left floating
with no external pull-downs or bypassing capacitors.
The ADCMP572/ADCMP573 comparators are designed to
reduce propagation delay dispersion over a wide input overdrive
range of 5 mV to 500 mV. Propagation delay dispersion is a
variation in propagation delay that results from a change in the
degree of overdrive or slew rate (how far or how fast the input
signal exceeds the switching threshold).
Propagation delay dispersion is a specification that becomes
important in high speed time critical applications such as data
communication, automatic test and measurement, instrumentation, and event-driven applications such as pulse spectroscopy,
nuclear instrumentation, and medical imaging. Dispersion is
defined as the variation in propagation delay as the input overdrive conditions are changed (Figure 14 and Figure 15). For the
ADCMP572/ADCMP573, dispersion is typically <15 ps because
the overdrive is varied from 10 mV to 500 mV, and the input
slew rate is varied from 2 V/ns to 10 V/ns. This specification
applies for both positive and negative signals since the
ADCMP572/ADCMP573 has substantially equal delays for
either positive-going or negative-going inputs.
500mV OVERDRIVE
INPUT VOLTAGE
10mV OVERDRIVE
VN ± VOS
DISPERSION
Q/Q OUTPUT
It should be understood that when leaving an input termination
disconnected, the internal resistor acts as a small stub on the
input transmission path and can cause problems for very high
speed inputs. Reflections should then be expected from the
comparator inputs because they no longer provide a matched
impedance to the input path leading to the device. It then
becomes important to back-match the drive source impedance
to the input transmission path to minimize multiple reflections.
For applications in which the comparator is very close to the
driving signal source, the source impedance should be minimized. High source impedance in combination with parasitic
input capacitance of the comparator could cause an undesirable
degradation in bandwidth at the input, thus degrading the overall
response. Although the ADCMP572/ ADCMP573 comparators
have been designed to minimize input capacitance, some parasitic
capacitance is inevitable. It is therefore recommended that the
drive source impedance be no more than 50 Ω for best high
speed performance.
Rev. PrB | Page 10 of 16
04409-0-027
OPTIMIZING HIGH SPEED PERFORMANCE
COMPARATOR PROPAGATION
DELAY DISPERSION
Figure 14. Propagation Delay—Overdrive Dispersion
INPUT VOLTAGE
1V/ns
VN ± VOS
10V/ns
DISPERSION
Q/Q OUTPUT
04409-0-028
external 500 Ω resistor, and leaving the LE pin disconnected. In
this case, the resistor value does not depend on the chosen VCCO
supply voltage, assuming the VTT pin is properly connected to
VCCO – 2 V.
Figure 15. Propagation Delay—Slew Rate Dispersion
Preliminary Technical Data
ADCMP572/ADCMP573
COMPARATOR HYSTERESIS
The addition of hysteresis to a comparator is often desirable in a
noisy environment or when the differential input amplitudes are
relatively small or slow moving. The transfer function for a
comparator with hysteresis is shown in Figure 16. If the input
voltage approaches the threshold (0.0 V in this example) from
the negative direction, the comparator switches from a low to a
high when the input crosses +VH/2. The new switching threshold
becomes −VH/2. The comparator remains in the high state until
the threshold −VH/2 is crossed from the positive direction. In
this manner, noise centered on 0.0 V input does not cause the
comparator to switch states unless it exceeds the region
bounded by ±VH/2.
60
50
HYSTERESIS (mV)
OUTPUT
connecting an external pull-down resistor from the HYS pin to
GND, a variable amount of hysteresis can be applied. Leaving
the HYS pin disconnected disables the feature, and hysteresis is
then less than 1 mV as specified. The maximum hysteresis that
can be applied using this method is approximately ±25 mV.
Figure 17 illustrates the amount of hysteresis applied as a
function of external resistor value. The advantages of applying
hysteresis in this manner are improved accuracy, stability, and
reduced component count. An external bypass capacitor is not
recommended on the HYS pin because it would likely degrade
the jitter performance of the device.
VOH
VOL
40
30
20
0
–VH
2
+VH
2
INPUT
04409-0-005
0
0
1
2
3
4
5
6
RHYS (kΩ)
04409-0-043
10
Figure 17. Hysteresis vs. RHYS Control Resistor
Figure 16. Comparator Hysteresis Transfer Function
MINIMUM INPUT SLEW RATE REQUIREMENT
The customary technique for introducing hysteresis into a
comparator uses positive feedback from the output back to the
input. A limitation of this approach is that the amount of
hysteresis varies with the output logic levels, resulting in
hysteresis that is not symmetric about the threshold. The
external feedback network can also introduce significant
parasitics that reduce high speed performance, and can even
induce oscillation in some cases.
As with all high speed comparators, a minimum slew rate
requirement must be met to ensure that the device does not
oscillate as the input signal crosses the threshold. This
oscillation is due in part to the high input bandwidth of the
comparator and the feedback parasitics inherent in the package.
Analog Devices recommends a minimum slew rate of 50 V/µs
to ensure a clean output transition from the ADCMP572/
ADCMP573 comparators unless hysteresis is programmed as
discussed previously.
The ADCMP572/ADCMP573 comparators offer a
programmable hysteresis feature that can significantly improve
the accuracy and stability of the desired hysteresis. By
Rev. PrB | Page 11 of 16
ADCMP572/ADCMP573
Preliminary Technical Data
TYPICAL APPLICATION CIRCUITS
VCCI = 5.2V
VCCI
VCCO
3.3V
50Ω
VTP
VIN
3.3V/5.2V
50Ω
VP
VN
VCCO = 3.3V/5.2V
50Ω
Q
Q
VIN
ADCMP572
ADCMP572
VTH
Q
50Ω
Q
VTN
Figure 21. Comparator with 0 V to 3 V Input Range and
3.3 V or 5.2 V Positive CML Outputs
Figure 18. Zero-Crossing Detector with 3.3 V CML Outputs
VCCI = 5.2V
VCCI
VCCO = 3.3V
VCCO
VTP
50Ω
VN
VN
5V
50Ω
VP
VP
04409-0-032
LATCH
INPUTS
04409-0-029
LATCH
INPUTS
75Ω
Q
ADCMP572
100Ω
ADCMP572
Q
VTN
100Ω
LATCH
INPUTS
Figure 22. Interfacing 3.3 V CML to a 50 Ω
Ground Terminated Instrument
Figure 19. LVDS to50 Ω Back-Terminated (RS)PECL Receiver
VCCI = 3.3V
VCCO = 2.5V/3.3V
VCCI
2.5V/3.3V
50Ω
VIN
+
VTH
–
04409-0-034
04409-0-030
50Ω
50Ω
LATCH
INPUTS
VCCO = 3.3V
50Ω
VCCO
50Ω
50Ω
Q
VP
ADCMP572
VN
Q
ADCMP572
VCCO
04409-0-035
Figure 23. Disabling the Latch Feature
Figure 20. Comparator with ±1 V Input Range and
2.5 V or 3.3 V CML Outputs
VCCI
VCCO
VCCO
50Ω
50Ω
ADCMP572
HYS
0Ω TO 5kΩ
04409-0-036
GND = –1V
750Ω
04409-0-031
LATCH
INPUTS
Figure 24. Adding Hysteresis Using the HYS Control Pin
Rev. PrB | Page 12 of 16
Preliminary Technical Data
ADCMP572/ADCMP573
TIMING INFORMATION
Figure 25 illustrates the ADCMP572/ADCMP573 compare and
latch timing relationships. Table 4 provides definitions of the
terms shown in the figure.
LATCH ENABLE
50%
LATCH ENABLE
tS
tPL
tH
DIFFERENTIAL
INPUT VOLTAGE
VIN
VN ± VOS
VOD
tPDL
tPLOH
Q OUTPUT
50%
tF
tPDH
tPLOL
tR
04409-0-003
50%
Q OUTPUT
Figure 25. System Timing Diagram
Table 4. Timing Descriptions
Symbol
tPDH
Timing
Input to output high delay
tPDL
Input to output low delay
tPLOH
Latch enable to output high delay
tPLOL
Latch enable to output low delay
tH
Minimum hold time
tPL
tS
Minimum latch enable pulse width
Minimum setup time
tR
Output rise time
tF
Output fall time
VOD
Voltage overdrive
Description
Propagation delay measured from the time the input signal crosses the reference (± the
input offset voltage) to the 50% point of an output low-to-high transition.
Propagation delay measured from the time the input signal crosses the reference (± the
input offset voltage) to the 50% point of an output high-to-low transition.
Propagation delay measured from the 50% point of the latch enable signal low-to-high
transition to the 50% point of an output low-to-high transition.
Propagation delay measured from the 50% point of the latch enable signal low-to-high
transition to the 50% point of an output high-to-low transition.
Minimum time after the negative transition of the latch enable signal that the input signal
must remain unchanged to be acquired and held at the outputs.
Minimum time that the latch enable signal must be high to acquire an input signal change.
Minimum time before the negative transition of the latch enable signal that an input
signal change must be present to be acquired and held at the outputs.
Amount of time required to transition from a low to a high output as measured at the
20% and 80% points.
Amount of time required to transition from a high to a low output as measured at the
20% and 80% points.
Difference between the input voltages VA and VB.
Rev. PrB | Page 13 of 16
ADCMP572/ADCMP573
Preliminary Technical Data
OUTLINE DIMENSIONS
3.00
BSC SQ
0.60 MAX
2.75
BSC SQ
TOP VIEW
0.80 MAX
0.65 TYP
12° MAX
SEATING
PLANE
16
1
1.65
1.50 SQ*
1.35
BOTTOM
VIEW
0.50
BSC
1.00
0.85
0.80
PIN 1 INDICATOR
13
12
0.45
PIN 1
INDICATOR
0.50
0.40
0.30
9
8
5
4
0.25 MIN
1.50 REF
0.05 MAX
0.02 NOM
0.30
0.23
0.18
0.20 REF
* COMPLIANT TO JEDEC STANDARDS MO-220-VEED-2
EXCEPT FOR EXPOSED PAD DIMENSION
Figure 26. 16-Lead Lead Frame Chip Scale Package [LFCSP]
(CP-16)
Dimensions shown in millimeters
ORDERING GUIDE
Model
ADCMP572BCP
ADCMP573BCP
Temperature Range
−40°C to 85°C
−40°C to 85°C
Package Description
LFCSP-16
LFCSP-16
Rev. PrB | Page 14 of 16
Package Option
CP-16
CP-16
Preliminary Technical Data
ADCMP572/ADCMP573
NOTES
Rev. PrB | Page 15 of 16
ADCMP572/ADCMP573
Preliminary Technical Data
NOTES
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
PR04409–0–6/04(PrB)
Rev. PrB | Page 16 of 16
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