Ultrafast 3.3 V/5 V
Single-Supply SiGe Comparators
Data Sheet ADCMP572/ADCMP573
Rev. B Document Feedback
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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 rise time 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
Extended industrial −40°C to +125°C temperature range
APPLICATIONS
Clock and data signal restoration and level shifting
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
FUNCTIONAL BLOCK DIAGRAM
V
P
NONINVERTING
INPUT
V
TP
TERMINATION
V
TN
TERMINATION
V
N
INVERTING
INPUT
LE INPUTHYS
Q OUTPUT
Q OUTPUT
LE INPUT
04409-025
ADCMP572
ADCMP573
CML/
RSPECL
V
CCO
V
CCI
Figure 1.
GENERAL DESCRIPTION
The ADCMP572 and ADCMP573 are ultrafast comparators
fabricated on Analog Devices, Inc., proprietary XFCB3 Silicon
Germanium (SiGe) bipolar process. The ADCMP572 features
CML output drivers and latch inputs, and the ADCMP573
features reduced swing PECL (RSPECL) output drivers and
latch inputs.
Both devices offer 150 ps propagation delay and 80 ps
minimum pulse width for 10 Gbps operation with 200 fs rms
random jitter (RJ). Overdrive and slew rate dispersion are
typically less than 15 ps.
A flexible power supply scheme allows both devices 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 be left
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 and ADCMP573 are available in a 16-lead
LFCSP package and have been characterized over an extended
industrial temperature range of −40°C to +125°C.
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 2 of 14
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Electrical Characteristics ................................................................. 3
Absolute Maximum Ratings ............................................................ 5
Thermal Considerations .............................................................. 5
ESD Caution .................................................................................. 5
Pin Configuration and Function Descriptions ............................. 6
Typical Performance Characteristics ............................................. 7
Applications Information ................................................................ 9
Power/Ground Layout and Bypassing ........................................9
CML/RSPECL Output Stage ........................................................9
Using/Disabling the Latch Feature ..............................................9
Optimizing High Speed Performance ..................................... 10
Comparator Propagation Delay Dispersion ........................... 10
Comparator Hysteresis .............................................................. 11
Minimum Input Slew Rate Requirements .............................. 11
Typical Application Circuits ......................................................... 12
Timing Information ....................................................................... 13
Outline Dimensions ....................................................................... 14
Ordering Guide .......................................................................... 14
REVISION HISTORY
3/15—Rev. A to Rev. B
Changes to Figure 2 and Table 3 ..................................................... 6
Changes to Figure 23 ...................................................................... 12
Updated Outline Dimensions ....................................................... 14
Changes to Ordering Guide .......................................................... 14
4/09—Rev. 0 to Rev. A
Changes to Figure 26 ...................................................................... 12
Updated Outline Dimensions ....................................................... 14
Changes to Ordering Guide .......................................................... 14
4/05—Revision 0: Initial Version
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 3 of 14
ELECTRICAL CHARACTERISTICS
VCCI = VCCO = 3.3 V, TA = −40°C to +125°C, typical at TA = +25°C, unless otherwise noted.
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
DC INPUT CHARACTERISTICS
Input Voltage Range VP, VN V
CCI = 3.3 V, VCCO = 3.3 V −0.2 +1.2 V
V
CCI = 5.2 V, VCCO = 3.3 V −0.2 +3.1 V
Input Differential Voltage −1.2 +1.2 V
Input Offset Voltage VOS −5.0 ±2.0 +5.0 mV
Offset Voltage Tempco ∆VOS/dT 10.0 μV/°C
Input Bias Current IP, IN Open termination −50.0 −25.0 0.0 μA
Input Bias Current Tempco 50.0 nA/°C
Input Offset Current ±2.0 μA
Input Impedance 50 Ω
Input Resistance, Differential Open termination 50 kΩ
Input Resistance, Common-Mode Open termination 500 kΩ
Active Gain AV 54 dB
Common-Mode Rejection CMRR VCCI = 3.3 V, VCCO = 3.3 V,
VCM = 0.0 V to 1.0 V
65 dB
VCCI = 5.2 V, VCCO = 3.3 V,
VCM = 0.0 V to 3.0 V
65 dB
Power Supply Rejection—VCCI PSRVCCI V
CCI = 3.3 V ± 5%, VCCO = 3.3 V 74 dB
Hysteresis RHYS = ∞ ±1 mV
LATCH ENABLE CHARACTERISTICS
ADCMP572
Latch Enable Input Range 2.8 VCCO + 0.2 V
Latch Enable Input Differential 0.2 0.4 0.5 V
Latch Setup Time tS V
OD = 100 mV 15 ps
Latch Hold Time tH V
OD = 100 mV 5 ps
ADCMP573
Latch Enable Input Range 1.8 VCCO − 0.6 V
Latch Enable Input Differential 0.2 0.4 0.5 V
Latch Setup Time tS V
OD = 100 mV 90 ps
Latch Hold Time tH V
OD = 100 mV 100 ps
Latch Enable Input Impedance 50.0 Ω
Latch to Output Delay tPLOH, tPLOL V
OD = 100 mV 150 ps
Latch Minimum Pulse Width tPL V
OD = 100 mV 100 ps
DC OUTPUT CHARACTERISTICS
ADCMP572 (CML)
Output Impedance ZOUT −8 mA < IOUT < 8 mA 50.0 Ω
Output Voltage High Level VOH 50 Ω terminate to VCCO VCCO − 0.10 VCCO − 0.05 VCCO V
Output Voltage Low Level VOL 50 Ω terminate to VCCO V
CCO − 0.60 VCCO − 0.45 VCCO − 0.30 V
Output Voltage Differential 50 Ω terminate to VCCO 300 375 450 mV
ADCMP573 (RSPECL)
Output Voltage High −40°C VOH 50 Ω terminate to VCCO − 2.0 VCCO − 1.14 VCCO − 1.02 VCCO − 0.90 V
Output Voltage High +25°C VOH 50 Ω terminate to VCCO − 2.0 VCCO − 1.10 VCCO − 0.98 VCCO − 0.86 V
Output Voltage High +125°C VOH 50 Ω terminate to VCCO − 2.0 VCCO − 1.04 VCCO − 0.92 VCCO − 0.80 V
Output Voltage Low −40°C VOL 50 Ω terminate to VCCO − 2.0 VCCO − 1.54 VCCO − 1.39 VCCO − 1.24 V
Output Voltage Low +25°C VOL 50 Ω terminate to VCCO − 2.0 VCCO − 1.50 VCCO − 1.35 VCCO − 1.20 V
Output Voltage Low +125°C VOL 50 Ω terminate to VCCO − 2.0 VCCO − 1.44 VCCO − 1.29 VCCO − 1.14 V
Output Voltage Differential 50 Ω terminate to VCCO − 2.0 300 375 450 mV
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 4 of 14
Parameter Symbol Conditions Min Typ Max Unit
AC PERFORMANCE
Propagation Delay tPD V
CCI = 3.3 V, VOD = 200 mV 150 Ps
V
CCI = 3.3 V, VOD = 20 mV 165 Ps
V
CCI = 5.2 V, VOD = 200 mV 145 Ps
Propagation Delay Tempco ∆tPD/dT 0.5 ps/°C
Prop Delay Skew—Rising Transition
to Falling Transition
V
OD = 200 mV, 5 V/ns 10 Ps
Overdrive Dispersion 50 mV < VOD < 0.2 V, 5 V/ns 15 Ps
10 mV < VOD < 0.2 V, 5 V/ns 15 Ps
Slew Rate Dispersion 2 V/ns to 10 V/ns, 250 mV OD 15 Ps
Pulse Width Dispersion 100 ps to 5 ns, 250 mV OD 5 Ps
10% – 90% Duty Cycle Dispersion VCCI = 3.3 V, 1 V/ns, 250 mV OD 5 Ps
VCCI = 5.2 V, 1 V/ns, 250 mV OD 10
Common-Mode Dispersion VOD = 0.2 V, 0.0 V < VCM < 2.9 V 5 ps/V
Equivalent Input Bandwidth1 BWEQ 0.0 V to 250 mV input
tR = tF = 17 ps, 20/80
8.0 GHz
Toggle Rate >50% Output Swing 12.5 Gbps
Deterministic Jitter DJ VOD = 200 mV, 5 V/ns,
PRBS31 − 1 NRZ, 4 Gbps
10 Ps
VOD = 200 mV, 5 V/ns,
PRBS31 − 1 NRZ, 10 Gbps
20 Ps
RMS Random Jitter RJ VOD = 200 mV, 5 V/ns, 1.25 GHz 0.2 Ps
Minimum Pulse Width PWMIN ∆tPD/∆PW < 5 ps, 200 mV OD 100 Ps
PWMIN ∆tPD/∆PW < 10 ps, 200 mV OD 80 Ps
Rise Time tR 20/80 35 Ps
Fall Time tF 20/80 35 Ps
POWER SUPPLY
Input Supply Voltage Range VCCI 3.1 5.4 V
Output Supply Voltage Range VCCO 3.1 5.4 V
Positive Supply Differential VCCI − VCCO −0.2 +2.3 V
ADCMP572 (CML)
Positive Supply Current IVCCI + IVCCO VCCI = 3.3 V, VCCO = 3.3 V,
terminate 50 Ω to VCCO
44 52 mA
VCCI = 5.2 V, VCCO = 5.2 V,
terminate 50 Ω to VCCO
44 52
Device Power Dissipation PD VCCI = 3.3 V, VCCO = 3.3 V,
terminate 50 Ω to VCCO
140 165 mW
VCCI = 5.2 V, VCCO = 5.2 V,
terminate 50 Ω to VCCO
230 265
ADCMP573 (RSPECL)
Positive Supply Current IVCCI + IVCCO VCCI = 3.3 V, VCCO = 3.3 V,
50 Ω to VCCO − 2 V
62 80 mA
VCCI = 5.2 V, VCCO = 5.2 V,
50 Ω to VCCO – 2 V
64 80
Device Power Dissipation PD VCCI = 3.3 V, VCCO = 3.3 V,
50 Ω to VCCO − 2 V
110 160 mW
VCCI = 5.2 V, VCCO = 5.2 V,
50 Ω to VCCO − 2 V
146 230
1 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.
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 5 of 14
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
SUPPLY VOLTAGE
Input Supply Voltage
(VCCI to GND)
−0.5 V to +6.0 V
Output Supply Voltage
(VCCO to GND)
−0.5 V to +6.0 V
Positive Supply Differential
(VCCI − VCCO)
−0.5 V to +3.5 V
INPUT VOLTAGE
Input Voltage −0.5 V to VCCI + 0.5 V
Differential Input Voltage ±(VCCI + 0.5 V)
Input Voltage, Latch Enable −0.5 V to VCCO + 0.5 V
HYSTERESIS CONTROL PIN
Applied Voltage (HYS to GND) −0.5 V to +1.5 V
Maximum Input/Output Current ±1 mA
OUTPUT CURRENT
ADCMP572 (CML) ±20 mA
ADCMP573 (RSPECL) −35 mA
TEMPERATURE
Operating Temperature, Ambient −40°C to +125°C
Operating Temperature, Junction +150°C
Storage Temperature Range −65°C to +150°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
THERMAL CONSIDERATIONS
The ADCMP572/ADCMP573 LFCSP 16-lead package has a θJA
(junction-to-ambient thermal resistance) of 70°C/W in still air.
ESD CAUTION
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 6 of 14
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
04409-026
LE
Q
12
11
10
1
3
49
2
6
5
7
8
16
15
14
13
NOTES
1. LEAVE EPAD FLOATING UNLESS IMPROVED THERMAL OR MECHANICAL
STABILITY IS DESIRED, IN WHICH CASE SOLDER IT TO THE APPLICATION BOARD.
V
TP
V
P
V
N
V
TN
V
CCO
GND
HYS
GND
V
CCI
Q
V
CCO
V
CCI
LE
V
CCO
/V
TT
ADCMP572
ADCMP573
TOP VIEW
Figure 2. ADCMP572/ADCMP573 Pin Configuration
Table 3. Pin Function Descriptions
Pin
No. Mnemonic Description
1 VTP Termination Resistor Return Pin for VP Input.
2 VP Noninverting Analog Input.
3 VN Inverting Analog Input.
4 VTN Termination Resistor Return Pin for VN Input.
5, 16 VCCI Positive Supply Voltage for Input Stage.
6 LE 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 into latch
mode. LE must be driven in complement with LE.
7 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 into latch
mode. LE must be driven in complement with LE.
8 VCCO/VTT Termination Return Pin for the LE/LE Input Pins.
For the ADCMP572 (CML output stage), this pin is internally connected to and also should be externally connected
to the positive VCCO supply.
For the ADCMP573 (RSPECL output stage), this pin should normally be connected to the VCCO – 2 V termination
potential.
9, 12 VCCO Positive Supply Voltage for the CML/RSPECL Output Stage.
13, 15 GND Ground.
10 Q 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 descriptions (Pins 6
and 7) for more information.
11 Q 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 descriptions (Pins 6 and 7) for more information.
14 HYS 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.
Isolated
Heat Sink
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. However, it can be
soldered to the application board if improved thermal and/or mechanical stability is desired. Exposed metal at
package corners is connected to the heat sink paddle.
EPAD Exposed Pad. Leave EPAD floating unless improved thermal or mechanical stability is desired, in which case solder
it to the application board.
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 7 of 14
TYPICAL PERFORMANCE CHARACTERISTICS
VCCI = VCCO = 3.3 V, TA = 25°C, unless otherwise noted.
PROPAGATION DELAY ERROR (ps)
0
5
10
15
20
0 50 100 150 200 250
INPUT OVERDRIVE VOLTAGE (mV)
04409-039
Figure 3. Propagation Delay vs. Input Overdrive
155.5
156.0
156.5
157.0
157.5
158.0
158.5
PROPAGATION DELAY (ps)
0.4 0.60 0.2 0.8 1.0 1.2
INPUT COMMON-MODE VOLTAGE (V)
04409-040
Figure 4. Propagation Delay vs. Input Common-Mode
146
148
150
152
154
156
158
160
PROPAGATION DELAY (ps)
200–40 –20–60 40 60 80 100
TEMPERATURE (°C)
04409-041
Figure 5. Propagation Delay vs. Temperature
36.0
36.5
37.0
37.5
38.0
38.5
39.0
RISE/FALL TIME (ps)
200–40 –20–60 40 60 80 100
TEMPERATURE (°C)
04409-042
Figure 6. Rise/Fall Time vs. Temperature
0
10
20
30
40
50
60
HYSTERESIS (mV)
2301 456
R
HYS
(k)
04409-043
Figure 7. Hysteresis vs. RHYS Control Resistor
R
HYS
SINK CURRENT (A)
HYSTERESIS (mV)
80
70
40
30
50
60
20
10
0
–600 –500 –400 –300 –200 –100 0
04409-047
Figure 8. Hysteresis vs. RHYS Sink Current
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 8 of 14
–18.5
–18.0
–17.5
–17.0
–16.5
–16.0
–15.5
–15.0
INPUT BIAS CURRENT (A)
–0.5 –0.3 –0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
V
P
INPUT VOLTAGE (V
N
= –0.2V)
04409-044
Figure 9. Input Bias Current vs. Input Differential
–16.9
–16.8
–16.7
–16.6
–16.5
–16.4
–16.3
–16.2
INPUT BIAS CURRENT (A)
200–40 –20–60 40 60 80 100
TEMPERATURE (°C)
04409-045
Figure 10. Input Bias Current vs. Temperature
TEMPERATURE (C)
OFFSET (mV)
0.5
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
–50 0 50 1007525–25 125
04409-024
Figure 11. Input Offset Voltage vs. Temperature
373
374
375
376
377
378
379
380
OUTPUT LEVELS (mV)
200–40 –20–60 40 60 80 100
TEMPERATURE (°C)
04409-046
Figure 12. Output Levels vs. Temperature
04409-049
496.0mV
504.0mV 60.00ps/DIV
M1
Figure 13. ADCMP572 Eye Diagram at 2.5 Gbps
04409-050
500.0mV
500.0mV 25.00ps/DIV
Figure 14. ADCMP572 Eye Diagram at 6.5 Gbps
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 9 of 14
APPLICATIONS 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.
It is 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 0.01 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
be avoided to maximize the effectiveness of the bypass at high
frequencies.
If the input and output supplies are connected separately such
that VCCI ≠ VCCO, 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 capaci-
tance 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, 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.
CML/RSPECL OUTPUT STAGE
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, microstrip, or strip line transmission
lines properly terminated to the VCCO supply plane. The CML
output stage is shown in the simplified schematic diagram of
Figure 15. The outputs are each back terminated with 50 Ω for
best transmission line matching. The RSPECL outputs of the
ADCMP573 are illustrated in Figure 16 and should be terminated
to VCCO − 2 V. As an alternative, evenin equivalent termination
networks can 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 strip line
techniques are essential to ensure proper transition times and to
prevent output ringing and pulse width dependent 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.
Q
16mA
50
Q
04409-037
VCCO
GND
Figure 15. Simplified Schematic Diagram of
the ADCMP572 CML Output Stage
04409-038
VCCO
GND
Q
Q
Figure 16. Simplified Schematic Diagram of
the ADCMP573 RSPECL Output Stage
USING/DISABLING THE LATCH FEATURE
The latch inputs (LE/LE) are active low for latch mode and are
internally terminated with 50 Ω resistors to Pin 8. This pin
corresponds to and is internally connected to the VCCO supply
for the CML-compatible ADCMP572. With the aid of these
resistors, the ADCMP572 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 avoid excessive
power dissipation, the resistor should be 750 Ω when VCCO =
3.3 V, and 1.2 kΩ when VCCO = 5.2 V. In the PECL-compatible
ADCMP573, the VTT pin should be connected externally to the
PECL termination supply at VCCO – 2 V. The latch can then be
disabled by connecting the LE pin to VCCO with an external
500 Ω resistor and leaving the LE pin disconnected. In this case,
the resistor value does not depend on the VCCO supply voltage.
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 10 of 14
VCCO is the signal return for the output stage and VCCO pins
should of course be connected to a supply plane for maximum
performance.
OPTIMIZING HIGH SPEED PERFORMANCE
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 often cause oscillation. Discontinuities along input and
output transmission lines can 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 dependent (or
deterministic) jitter (DJ) and on pulse width dispersion
performance. The ADCMP572/ADCMP573 comparators
provide internal 50 Ω termination resistors for both the 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 earlier 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.
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 matched impedance to the input path
leading to the device. In this case, it is 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
might cause an undesirable degradation in bandwidth at the
input, therefore 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.
COMPARATOR PROPAGATION
DELAY DISPERSION
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 variation
in the 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, instrumenta-
tion, 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 over-
drive conditions vary (Figure 17 and Figure 18). For the
ADCMP572/ADCMP573, dispersion is typically <15 ps
because the overdrive varies from 10 mV to 500 mV, and the
input slew rate varies 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.
Q/Q OUTPUT
INPUT VOLTAGE
500mV OVERDRIVE
10mV OVERDRIVE
DISPERSION
V
N
± V
OS
04409-0-027
Figure 17. Propagation Delay—Overdrive Dispersion
Q/Q OUTPUT
INPUT VOLTAGE
10V/ns
1V/ns
DISPERSION
V
N
± V
OS
04409-0-028
Figure 18. Propagation Delay—Slew Rate Dispersion
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 11 of 14
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, but excessive hysteresis has a
cost in degraded accuracy and slew-induced timing shifts. The
transfer function for a comparator with hysteresis is shown in
Figure 19. If the input voltage approaches the threshold (0.0 V
in this example) from the negative direction, the comparator
switches from low to 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.
OUTPUT
INPUT
0
V
OL
V
OH
+V
H
2
–V
H
2
04409-005
Figure 19. Comparator Hysteresis Transfer Function
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 can be load dependent and is not symmetrical
about the threshold. The external feedback network can also
introduce significant parasitics, which reduce high speed
performance and can even induce oscillation in some cases.
The ADCMP572/ADCMP573 comparators offer a program-
mable hysteresis feature that can significantly improve the
accuracy and stability of the desired hysteresis. By 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 with the
pin grounded. Figure 20 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. The hysteresis pin could also
be driven by a CMOS DAC. It is biased to approximately 250 mV
and has an internal series resistance of 600 Ω.
0
10
20
30
40
50
60
HYSTERESIS (mV)
2301 456
R
HYS
(k)
04409-043
Figure 20. Hysteresis vs. RHYS Control Resistor
MINIMUM INPUT SLEW RATE REQUIREMENTS
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. A minimum
slew rate of 50 V/μs should ensure clean output transitions from
the ADCMP572/ADCMP573 comparators.
The slew rate may be too slow for other reasons. The extremely
high bandwidth of these devices means that broadband noise
can be a significant factor when input slew rates are low. There
will be at least 120 μV of thermal noise generated over the full
comparator bandwidth by two 50 Ω terminations at room
temperature. With a slew rate of only 50 V/μs the input will be
inside this noise band for over 2 ps, rendering the comparator’s
jitter performance of 200 fs moot. Raising the slew rate of the
input signal and/or reducing the bandwidth over which this
resistance is seen at the input can greatly reduce jitter.
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 12 of 14
TYPICAL APPLICATION CIRCUITS
Q
3.3V
5050
ADCMP572
Q
VIN
VP
VTP
VTN
VN
LATCH
INPUTS
04409-029
VCCI
VCCO
Figure 21. Zero-Crossing Detector with 3.3 V CML Outputs
Q
5050
Q
V
P
V
N
V
P
V
TP
V
TN
V
N
LATCH
INPUTS
04409-030
V
CCI
= 5.2V
ADCMP572
V
CCO
Figure 22. LVDS to 50 Ω Back Terminated RSPECL Receiver
50Ω50Ω
+
–
Q
Q
V
IN
V
TH
LATCH
INPUTS
GND = –1V
04409-031
V
CCI
= 3.3V
V
CCO
= 3.3V 3.3V
ADCMP572
Figure 23. Comparator with ±1 V Input Range and 3.3 V CML Outputs
5050
Q
Q
V
IN
V
TH
LATCH
INPUTS
04409-032
V
CCI
= 5.2V
V
CCO
= 3.3V/5.2V 3.3V/5.2V
ADCMP572
Figure 24. Comparator with 0 V to 3 V Input Range and
3.3 V or 5.2 V Positive CML Outputs
LATCH
INPUTS
04409-034
VCCI
VCCO = 3.3V 5V
75
50
50
100
100
ADCMP572
Figure 25. Interfacing 3.3 V CML to a 50 Ω
Ground Terminated Instrument
VP
VN
VCCO = 3.3V VCCO
VCCO
0
4409-035
V
CCI
ADCMP572
50Ω
1.35kΩ
50Ω
Figure 26. Disabling the ADCMP572 Latch Feature
V
P
V
N
500
04409-048
V
CCI
= 5.2V = V
CCO
V
TT
= 3.2V
V
CCO
ADCMP573
5050
Figure 27. Disabling the ADCMP573 Latch Feature
HYS
V
CCO
V
CCO
04409-036
V
CCI
ADCMP572
5050
0 TO 5k
Figure 28. Adding Hysteresis Using the HYS Control Pin
Data Sheet ADCMP572/ADCMP573
Rev. B | Page 13 of 14
TIMING INFORMATION
Figure 29 illustrates the ADCMP572/ADCMP573 compare and latch timing relationships. Table 4 provides definitions of the terms
shown in the figure.
50%
50%
V
N
± V
OS
50%
DIFFERENTIAL
INPUT VOLTAGE
LATCH ENABLE
Q OUTPUT
Q OUTPUT
LATCH ENABLE
tH
tPDL
tPDH
tPLOH
tPLOL
tR
tF
V
IN
V
OD
tStPL
04409-003
Figure 29. System Timing Diagram
Table 4. Timing Descriptions
Symbol Timing Description
tPDH Input to output high delay 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.
tPDL Input to output low delay 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.
tPLOH Latch enable to output high delay 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.
tPLOL Latch enable to output low delay 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.
tH Minimum hold time 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.
tPL Minimum latch enable pulse width Minimum time that the latch enable signal must be high to acquire an input signal
change.
tS Minimum setup time 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.
tR Output rise time Amount of time required to transition from a low to a high output as measured at the
20% and 80% points.
tF Output fall time Amount of time required to transition from a high to a low output as measured at the
20% and 80% points.
VOD Voltage overdrive Difference between the input voltages VA and VB.
ADCMP572/ADCMP573 Data Sheet
Rev. B | Page 14 of 14
OUTLINE DIMENSIONS
1.45
1.30 SQ
1.15
111808-A
1
0.50
BSC
BOTTOM VIEWTOP VIEW
16
5
8
9
12
13
4
EXPOSED
PAD
PIN 1
INDICATOR
3.10
3.00 SQ
2.90
0.50
0.40
0.30
SEATING
PLANE
0.05 MAX
0.02 NOM
0.20 REF
0.25 MIN
COPLANARITY
0.08
PIN 1
INDICATOR
0.30
0.23
0.18
COMPLIANT
TO
JEDEC STANDARDS MO-220-WEED.
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
0.80
0.75
0.70
Figure 30. 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
3 mm × 3 mm Body, Very Very Thin Quad
(CP-16-21)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option Branding
ADCMP572BCPZ-WP −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Y
ADCMP572BCPZ-R2 −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Y
ADCMP572BCPZ-RL7 −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Y
EVAL-ADCMP572BCPZ Evaluation Board
ADCMP573BCPZ-WP −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Z
ADCMP573BCPZ-R2 −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Z
ADCMP573BCPZ-RL7 −40°C to +125°C 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] CP-16-21 G0Z
EVAL-ADCMP573BCPZ Evaluation Board
1 Z = RoHS Compliant Part
©2005–2015 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04409-0-3/15(B)
