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Ultrafast SiGe Voltage Comparators ADCMP580/ADCMP581/ADCMP582
FEATURES
180 ps propagation delay 25 ps overdrive and slew rate dispersion 8 GHz equivalent input rise time bandwidth 100 ps minimum pulse width 37 ps typical output rise/fall 10 ps deterministic jitter (DJ) 200 fs random jitter (RJ) -2 V to +3 V input range with +5 V/-5 V supplies On-chip terminations at both input pins Resistor-programmable hysteresis Differential latch control Power supply rejection > 70 dB
FUNCTIONAL BLOCK DIAGRAM
VCCI
VTP TERMINATION VP NONINVERTING INPUT
VCCO
VN INVERTING INPUT VTN TERMINATION
ADCMP580/ ADCMP581/ ADCMP582
Q OUTPUT CML/ECL/ PECL Q OUTPUT
VEE LE INPUT
04672-001
HYS VEE
LE INPUT
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
Figure 1.
GENERAL DESCRIPTION
The ADCMP580/ADCMP581/ADCMP582 are ultrafast voltage comparators fabricated on the Analog Devices, Inc. proprietary XFCB3 Silicon Germanium (SiGe) bipolar process. The ADCMP580 features CML output drivers, the ADCMP581 features reduced swing ECL (negative ECL) output drivers, and the ADCMP582 features reduced swing PECL (positive ECL) output drivers. All three comparators offer 180 ps propagation delay and 100 ps minimum pulse width for 10 Gbps operation with 200 fs random jitter (RJ). Overdrive and slew rate dispersion are typically less than 15 ps. The 5 V power supplies enable a wide -2 V to +3 V input range with logic levels referenced to the CML/NECL/PECL outputs. The inputs have 50 on-chip termination resistors with the optional capability to be left open (on an individual pin basis) for applications requiring high impedance input. The CML output stage is designed to directly drive 400 mV into 50 transmission lines terminated to ground. The NECL output stages are designed to directly drive 400 mV into 50 terminated to -2 V. The PECL output stages are designed to directly drive 400 mV into 50 terminated to VCCO - 2 V. High speed latch and programmable hysteresis are also provided. The differential latch input controls are also 50 terminated to an independent VTT pin to interface to either CML or ECL or to PECL logic. The ADCMP580/ADCMP581/ADCMP582 are available in a 16-lead LFCSP_VQ.
Rev. A
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 that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2005-2007 Analog Devices, Inc. All rights reserved.
ADCMP580/ADCMP581/ADCMP582 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Information ......................................................................... 5 Absolute Maximum Ratings............................................................ 6 Thermal Considerations.............................................................. 6 ESD Caution.................................................................................. 6 Pin Configurations and Function Descriptions ........................... 7 Typical Performance Characteristics ............................................. 8 Typical Application Circuits ......................................................... 10 Application Information................................................................ 11 Power/Ground Layout and Bypassing..................................... 11 ADCMP58x Family of Output Stages ..................................... 11 Using/Disabling the Latch Feature........................................... 11 Optimizing High Speed Performance ..................................... 12 Comparator Propagation Delay Dispersion............................... 12 Comparator Hysteresis .............................................................. 13 Minimum Input Slew Rate Requirement ................................ 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 14
REVISION HISTORY
8/07--Rev. 0 to Rev. A Changes to Figure 1.......................................................................... 1 Changes to Table 4............................................................................ 7 Changes to Figure 9.......................................................................... 8 Changes to Figure 21, Figure 22, and Figure 23 ......................... 10 Changes to Using/Disabling the Latch Feature .......................... 11 Changes to Comparator Hysteresis Section and Figure 29....... 13 Changes to Ordering Guide .......................................................... 14 7/05--Revision 0: Initial Version
Rev. A | Page 2 of 16
ADCMP580/ADCMP581/ADCMP582 SPECIFICATIONS
VCCI = 5.0 V; VEE = -5.0 V; VCCO = 3.3 V; TA = 25C, unless otherwise noted. Table 1.
Parameter DC INPUT CHARACTERISTICS Input Voltage Range Input Differential Range Input Offset Voltage Offset Voltage Temperature Coefficient Input Bias Current Input Bias Current Temperature Coefficient Input Offset Current Input Resistance Input Resistance, Differential Mode Input Resistance, Common Mode Active Gain Common-Mode Rejection Ratio Hysteresis LATCH ENABLE CHARACTERISTICS Latch Enable Input Impedance Latch-to-Output Delay Latch Minimum Pulse Width ADCMP580 (CML) Latch Enable Input Range Latch Enable Input Differential Latch Setup Time Latch Hold Time ADCMP581 (NECL) Latch Enable Input Range Latch Enable Input Differential Latch Setup Time Latch Hold Time ADCMP582 (PECL) Latch Enable Input Range Latch Enable Input Differential Latch Setup Time Latch Hold Time DC OUTPUT CHARACTERISTICS ADCMP580 (CML) Output Impedance Output Voltage High Level Output Voltage Low Level Output Voltage Differential ADCMP581 (NECL) Output Voltage High Level Output Voltage High Level Output Voltage High Level Output Voltage Low Level Output Voltage Low Level Output Voltage Low Level Output Voltage Differential Symbol VP, VN VOS VOS/dT IP, IN IB/dT Condition Min -2.0 -2.0 -10.0 Open termination Typ Max +3.0 +2.0 +10.0 30.0 5.0 Unit V V mV V/C A nA/C A k k dB dB mV ps ps 0 0.5 V V ps ps V V ps ps V V ps ps
Open termination Open termination AV CMRR VCM = -2.0 V to +3.0 V RHYS = Each pin, VTT at ac ground VOD = 200 mV VOD = 200 mV -0.8 0.2 tS tH VOD = 200 mV VOD = 200 mV -1.8 0.2 tS tH VOD = 200 mV VOD = 200 mV VCCO - 1.8 0.2 tS tH VOD = 200 mV VOD = 200 mV
4 10 15 50 +2 47 to 53 50 500 48 60 1 47 to 53 175 100
ZIN tPLOH, tPLOL tPL
0.4 95 -90
0.4 70 -65
+0.8 0.5
0.4 30 -25
VCCO - 0.8 0.5
ZOUT VOH VOL
50 to GND 50 to GND 50 to GND 50 to -2 V, TA = 125C 50 to -2 V, TA = 25C 50 to -2 V, TA = -55C 50 to -2 V, TA = 125C 50 to -2 V, TA = 25C 50 to -2 V, TA = -55C 50 to -2.0 V
-0.10 -0.50 340 -0.99 -1.06 -1.11 -1.43 -1.50 -1.55 340
50 0 -0.40 395 -0.87 -0.94 -0.99 -1.26 -1.33 -1.38 395
+0.03 -0.35 450 -0.75 -0.82 -0.87 -1.13 -1.20 -1.25 450
V V mV V V V V V V mV
VOH VOH VOH VOL VOL VOL
Rev. A | Page 3 of 16
ADCMP580/ADCMP581/ADCMP582
Parameter ADCMP582 (PECL) Output Voltage High Level Output Voltage High Level Output Voltage High Level Output Voltage Low Level Output Voltage Low Level Output Voltage Low Level Output Voltage Differential AC PERFORMANCE Propagation Delay Propagation Delay Temperature Coefficient Propagation Delay Skew--Rising Transition to Falling Transition Overdrive Dispersion Slew Rate Dispersion Pulse Width Dispersion Duty Cycle Dispersion 5% to 95% Common-Mode Dispersion Equivalent Input Bandwidth 1 Toggle Rate Deterministic Jitter Deterministic Jitter RMS Random Jitter Minimum Pulse Width Minimum Pulse Width Rise/Fall Time POWER SUPPLY Positive Supply Voltage Negative Supply Voltage ADCMP580 (CML) Positive Supply Current Negative Supply Current Power Dissipation ADCMP581 (NECL) Positive Supply Current Negative Supply Current Power Dissipation ADCMP582 (PECL) Logic Supply Voltage Input Supply Current Output Supply Current Negative Supply Current Power Dissipation Power Supply Rejection (VCCI) Power Supply Rejection (VEE) Power Supply Rejection (VCCO)
1
Symbol VOH VOH VOH VOL VOL VOL
Condition VCCO = 3.3 V 50 to VCCO - 2 V, TA = 125C 50 to VCCO - 2 V, TA = 25C 50 to VCCO - 2 V, TA = -55C 50 to VCCO - 2 V, TA = 125C 50 to VCCO - 2 V, TA = 25C 50 to VCCO - 2 V, TA = -55C 50 to VCCO - 2.0 V VOD = 500 mV VOD = 500 mV, 5 V/ns 50 mV < VOD < 1.0 V 10 mV < VOD < 200 mV 2 V/ns to 10 V/ns 100 ps to 5 ns 1.0 V/ns, 15 MHz, VCM = 0.0 V VOD = 0.2 V, -2 V < VCM < 3 V 0.0 V to 400 mV input, tR = tF = 25 ps, 20/80 >50% output swing VOD = 500 mV, 5 V/ns, PRBS31 - 1 NRZ, 5 Gbps VOD = 200 mV, 5 V/ns, PRBS31 - 1 NRZ, 10 Gbps VOD = 200 mV, 5 V/ns, 1.25 GHz tPD < 5 ps tPD < 10 ps 20/80
Min VCCO - 0.99 VCCO - 1.06 VCCO - 1.11 VCCO - 1.43 VCCO - 1.50 VCCO - 1.55 340
Typ VCCO - 0.87 VCCO - 0.94 VCCO - 0.99 VCCO - 1.26 VCCO - 1.33 VCCO - 1.35 395 180 0.25 10 10 15 15 15 10 5 8 12.5 15 25 0.2 100 80 37
Max VCCO - 0.75 VCCO - 0.82 VCCO - 0.87 VCCO - 1.13 VCCO - 1.20 VCCO - 1.25 450
Unit V V V V V V mV ps ps/C ps ps ps ps ps ps ps/V GHz Gbps ps ps ps ps ps ps
tPD tPD/dT
BWEQ
DJ DJ RJ PWMIN PWMIN tR, tF VCCI VEE IVCCI IVEE PD IVCCI IVEE PD VCCO IVCCI IVCCO IVEE PD PSRVCCI PSRVEE PSRVCCO
+4.5 -5.5 VCCI = 5.0 V, 50 to GND VEE = -5.0 V, 50 to GND 50 to GND VCCI = 5.0 V, 50 to -2 V VEE = -5.0 V, 50 to -2 V 50 to -2 V
+5.0 -5.0 6 -40 230 6 -25 155 +3.3 6 44 -25 310 -75 -60 -75
+5.5 -4.5 8 -34 260 8 -19 200 +5.0 8 55 -19 350
V V mA mA mW mA mA mW V mA mA mA mW dB dB dB
-50
-35
+2.5 VCCI = 5.0 V, 50 to VCCO - 2 V VCCO = 5.0 V, 50 to VCCO - 2 V VEE = -5.0 V, 50 to VCCO - 2 V 50 to VCCO - 2 V VCCI = 5.0 V + 5% VEE = -5.0 V + 5% VCCO = 3.3 V + 5% (ADCMP582)
-35
Equivalent input bandwidth assumes a simple first-order input 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 input edge applied to the comparator input and trCOMP is the effective transition time digitized by the comparator.
Rev. A | Page 4 of 16
ADCMP580/ADCMP581/ADCMP582 TIMING INFORMATION
Figure 2 shows the ADCMP580/ADCMP581/ADCMP582 compare and latch timing relationships. Table 2 provides the definitions of the terms shown in Figure 2.
LATCH ENABLE 50% LATCH ENABLE
tS tH
tPL
DIFFERENTIAL INPUT VOLTAGE
VN VOD
VN VOS
tPDL
Q OUTPUT
tPLOH
50%
tPDH
tF
50%
Q OUTPUT
tR
Figure 2. Comparator Timing Diagram
Table 2. Timing Descriptions
Symbol tPDH tPDL tPLOH tPLOL tH tPL tS tR tF VN VOD Timing Input-to-Output High Delay Input-to-Output Low Delay Latch Enable-to-Output High Delay Latch Enable-to-Output Low Delay Minimum Hold Time Minimum Latch Enable Pulse Width Minimum Setup Time Output Rise Time Output Fall Time Normal Input Voltage 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 VP and VN for output true. Difference between the input voltages VP and VN for output false.
Rev. A | Page 5 of 16
04672-028
tPLOL
ADCMP580/ADCMP581/ADCMP582 ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter SUPPLY VOLTAGES Positive Supply Voltage (VCCI to GND) Negative Supply Voltage (VEE to GND) Logic Supply Voltage (VCCO to GND) INPUT VOLTAGES Input Voltage Differential Input Voltage Input Voltage, Latch Enable HYSTERESIS CONTROL PIN Applied Voltage (HYS to VEE) Maximum Input/Output Current OUTPUT CURRENT ADCMP580 (CML) ADCMP581 (NECL) ADCMP582 (PECL) TEMPERATURE Operating Temperature Range, Ambient Operating Temperature, Junction Storage Temperature Range Rating -0.5 V to +6.0 V -6.0 V to +0.5 V -0.5 V to +6.0 V -3.0 V to +4.0 V -2 V to +2 V -2.5 V to +5.5 V -5.5 V to +0.5 V 1 mA -25 mA -40 mA -40 mA -40C to +125C 125C -65C to +150C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
THERMAL CONSIDERATIONS
The ADCMP580/ADCMP581/ADCMP582 16-lead LFCSP option has a JA (junction-to-ambient thermal resistance) of 70C/W in still air.
ESD CAUTION
Rev. A | Page 6 of 16
ADCMP580/ADCMP581/ADCMP582 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
15 GND 16 VCCI
16 VCCI
15 GND
14 HYS
13 VEE
14 HYS
16 VCCI
15 GND
14 HYS
13 VEE
VTP 1 VP 2 VN 3 VTN 4
PIN 1 INDICATOR
12 GND 11 Q 10 Q 9 GND
VTP 1 VP 2 VN 3 VTN 4
PIN 1 INDICATOR
12 GND 11 Q 10 Q 9 GND
VTP 1 VP 2 VN 3 VTN 4
PIN 1 INDICATOR
13 VEE
12 VCCO 11 Q 10 Q 9 VCCO
ADCMP580
TOP VIEW (Not to Scale)
VCCI 5 VTT 8
LE 6
ADCMP581
TOP VIEW (Not to Scale)
VTT 8 VCCI 5 LE 7
LE 6
ADCMP582
TOP VIEW (Not to Scale)
VCCI 5
04672-004
VTT 8
LE 6
LE 7
04672-003
Figure 3. ADCMP580 Pin Configuration
Figure 4. ADCMP581 Pin Configuration
Figure 5. ADCMP582 Pin Configuration
Table 4. Pin Function Descriptions
Pin No. 1 2 3 4 5, 16 6 Mnemonic VTP VP VN VTN VCCI LE Description Termination Resistor Return Pin for VP Input. Noninverting Analog Input. Inverting Analog Input. Termination Resistor Return Pin for VN Input. Positive Supply Voltage. 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 being placed into latch mode. LE must be driven in complement 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 being placed into latch mode. LE must be driven in complement with LE. Termination Return Pin for the LE/LE Input Pins. For the ADCMP580 (CML output stage), this pin should be connected to the GND ground. For the ADCMP581 (ECL output stage), this pin should be connected to the -2 V termination potential. For the ADCMP582 (PECL output stage), this pin should be connected to the VCCO - 2 V termination potential. Digital Ground Pin/Positive Logic Power Supply Terminal. For the ADCMP580/ADCMP581, this pin should be connected to the GND pin. For the ADCMP582, this pin should be connected to the positive logic power VCCO supply. Inverting Output. Q is logic low if the analog voltage at the noninverting input, VP, is greater than the analog voltage at the inverting input, VN, provided that the comparator is in compare mode. See the LE/LE descriptions (Pin 6 to Pin 7) for more information. Noninverting Output. Q is logic high if the analog voltage at the noninverting input, VP, is greater than the analog voltage at the inverting input, VN, provided that the comparator is in compare mode. See the LE/LE descriptions (Pin 6 to Pin 7) for more information. Negative Power Supply. Hysteresis Control. Leave this pin disconnected for zero hysteresis. Connect this pin to the VEE supply with a suitably sized resistor to add the desired amount of hysteresis. Refer to Figure 9 for proper sizing of the HYS hysteresis control resistor. Analog Ground. The metallic back surface of the package is not electrically connected to any part of the circuit. It can be left floating for optimal electrical isolation between the package handle and the substrate of the die. It can also 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.
7
LE
8
VTT
9, 12
GND/VCCO
10
Q
11
Q
13 14
VEE HYS
15 Heat Sink Paddle
GND N/C
Rev. A | Page 7 of 16
04672-005
LE 7
ADCMP580/ADCMP581/ADCMP582 TYPICAL PERFORMANCE CHARACTERISTICS
VCCI = 5.0 V, VEE = -5.0 V, VCCO = 3.3 V, TA = 25C, unless otherwise noted.
12
80 70
10 VIN COMMON-MODE BIAS SWEEP
60
BIAS CURRENT (A)
HYSTERESIS (mV)
8
50 40 30 20
6
4
2
10 0
-2
0 COMMON-MODE (V)
2
04672-006
4
1
10
100
1k
10k
RHYS CONTROL RESISTOR ()
Figure 6. Bias Current vs. Common-Mode Voltage
Figure 9. Hysteresis vs. RHYS Control Resistor
2.5
-0.8 -0.9 -1.0 VOH vs. TEMPERATURE OUTPUT (NECL)
2.4 VOH vs. TEMPERATURE OUTPUT (PECL)
2.3
OUTPUT (V)
-1.1 -1.2 -1.3 -1.4 -1.5 -55 VOL vs. TEMPERATURE OUTPUT (NECL)
OUTPUT (V)
2.2
2.1
2.0 VOL vs. TEMPERATURE OUTPUT (PECL)
04672-007
-5
45 TEMPERATURE (C)
95
145
-5
45 TEMPERATURE (C)
95
145
Figure 7. ADCMP581 Output Voltage vs. Temperature
80 70 60
8
Figure 10. ADCMP582 Output Voltage vs. Temperature
+125C COMMON-MODE OFFSET SWEEP 7 6
HYSTERESIS (mV)
40 30 20 10 0
OFFSET (mV)
50
5 4 3 +25C COMMON-MODE OFFSET SWEEP 2 1 0 -2 -55C COMMON-MODE OFFSET SWEEP
04672-008
0
100
200
300 -IHYST (A)
400
500
600
0
2
4
COMMON-MODE (V)
Figure 8. Hysteresis vs. -IHYST
Figure 11. A Typical VOS vs. Common-Mode Voltage
Rev. A | Page 8 of 16
04672-011
04672-010
1.9 -55
04672-009
0 -4
ADCMP580/ADCMP581/ADCMP582
5 4
45 43 41 39
PROPAGATION DELAY ERROR (ps)
3 2
tR/tF (ps)
LOT2 CHAR1 RISE LOT2 CHAR1 FALL LOT3 CHAR1 RISE LOT3 CHAR1 FALL
04672-012
1 0 -1 -2 -3 -4 -5 -2
37 35 33 31 29 27 QRISE QRISE QFALL QFALL -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
04672-015
-1
0 VCM (V)
1
2
3
25 -55
Figure 12. ADCMP580 Propagation Delay Error vs. Common-Mode Voltage
Figure 15. ADCMP581 tR/tF vs. Temperature
500mV
M1
M1
M1
M1
04672-013
500mV
20ps/DIV
Figure 13. ADCMP580 Eye Diagram at 7.5 Gbps
18 16 14
DISPERSION (ps)
Figure 16. ADCMP582 Eye Diagram at 2.5 Gbps
12 10 8 6 4 2 0 OD DISPERSION FALL
OD DISPERSION RISE 0 50 100 150 200 250
04672-014
OVERDRIVE (mV)
Figure 14. Dispersion vs. Overdrive
Rev. A | Page 9 of 16
04672-016
ADCMP580/ADCMP581/ADCMP582 TYPICAL APPLICATION CIRCUITS
GND VTP VIN VP VN VTN 50 50 Q
VP VN
ADCMP580
CML
ADCMP580
Q
1k
50
50
04672-021
LATCH INPUTS
04672-017
VEE
Figure 17. Zero-Crossing Detector with CML Outputs
VTP VP VN VP VN VTN Q
Figure 21. Disabling the Latch Feature on the ADCMP580
ADCMP581
Q 50 VTT LATCH INPUTS 50
VP VN
ADCMP581
750 50 VTT
RSECL
50
04672-022
04672-018
VTT = -2V
VEE
Figure 18. LVDS to a 50 Back-Terminated (RS) ECL Receiver
Figure 22. Disabling the Latch Feature on the ADCMP581
ADCMP580
HYS
VP VN
ADCMP582
RSPECL
0 TO 5k
50
50
04672-019
750 VCCO
50
50
04672-023
VEE
VTT = VCCO - 2V
Figure 19. Adding Hysteresis Using the HYS Control
GND 50 VIN VTH
+
Figure 23. Disabling the Latch Feature on the ADCMP582
50 Q Q
ADCMP580
-
Figure 20. Comparator with -2 to +3 V Input Range
04672-020
LATCH INPUTS
Rev. A | Page 10 of 16
ADCMP580/ADCMP581/ADCMP582 APPLICATION INFORMATION
POWER/GROUND LAYOUT AND BYPASSING
The ADCMP58x family of comparators is designed for very high speed applications. Consequently, high speed design techniques must be used to achieve the specified performance. It is critically important to use low impedance supply planes, particularly for the negative supply (VEE), 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 the switching currents ensures the best possible performance in the target application. It is also important to adequately bypass the input and output supplies. A 1 F electrolytic bypass capacitor should be placed within several inches of each power supply pin to ground. In addition, multiple high quality 0.1 F bypass capacitors should be placed as close as possible to each of the VEE, 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 strictly avoided to maximize the effectiveness of the bypass at high frequencies.
GND 50 50
Q Q
16mA
04672-024
VEE
Figure 24. Simplified Schematic Diagram of the ADCMP580 CML Output Stage
GND/VCCO
Q Q
ADCMP58x FAMILY OF OUTPUT STAGES
Specified propagation delay dispersion performance is achieved by using proper transmission line terminations. The outputs of the ADCMP580 family comparators are designed to directly drive 400 mV into 50 cable or microstrip/stripline transmission lines terminated with 50 referenced to the proper return. The CML output stage for the ADCMP580 is shown in the simplified schematic diagram in Figure 24. Each output is back-terminated with 50 for best transmission line matching. The outputs of the ADCMP581/ADCMP582 are illustrated in Figure 25; they should be terminated to -2 V for ECL outputs of ADCMP581 and VCCO - 2 V for PECL outputs of ADCMP582. As an alternative, Thevenin equivalent termination networks can also be used. If these high speed signals must be routed more than a centimeter, either microstrip or stripline techniques are required to ensure proper transition times and to prevent excessive output ringing and pulse width-dependent propagation delay dispersion.
VEE
Figure 25. Simplified Schematic Diagram of the ADCMP581/ADCMP582 ECL/PECL Output Stage
USING/DISABLING THE LATCH FEATURE
The latch inputs (LE/LE) are active low for latch mode and are internally terminated with 50 resistors to the VTT pin. When using the ADCMP580, VTT should be connected to ground. When using the ADCMP581, VTT should be connected to -2 V. When using the ADCMP582, VTT should be connected externally to VCCO - 2 V, preferably with its own low inductance plane. When using the ADCMP580, the latch function can be disabled by connecting the LE pin to VEE with an external pull-down resistor and by leaving the LE pin to ground. To prevent excessive power dissipation, the resistor should be 1 k for the ADCMP580. When using the ADCMP581 comparators, the latch can be disabled by connecting the LE pin to VEE with an external 750 resistor and leaving the LE pin connected to -2 V. The idea is to create an approximate 0.5 V offset using the internal resistor as half of the voltage divider. The VTT pin should be connected as recommended.
Rev. A | Page 11 of 16
04672-025
ADCMP580/ADCMP581/ADCMP582
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 can cause oscillation. Discontinuities along input and output transmission lines can also severely limit the specified pulse width dispersion performance. For applications in a 50 environment, input and output matching have a significant impact on data-dependent (or deterministic) jitter (DJ) and pulse width dispersion performance. The ADCMP58x family of comparators provides internal 50 termination resistors for both VP and VN inputs. The return side for each termination is pinned out separately with the VTP and VTN pins, respectively. If a 50 termination is desired at one or both of the VP/VN inputs, the VTP and VTN pins can be connected (or disconnected) to (from) the desired termination potential as appropriate. The termination potential should be carefully bypassed using ceramic capacitors as discussed previously to prevent undesired aberrations on the input signal due to parasitic inductance in the termination return path. If a 50 termination is not desired, either one or both of the VTP/VTN termination pins can be left disconnected. In this case, the open pins should be left floating with no external pull downs or bypassing capacitors. For applications that require high speed operation but do not have on-chip 50 termination resistors, some reflections should be expected, because the comparator inputs can no longer provide matched impedance to the input trace leading up to the device. It then becomes important to back-match the drive source impedance to the input transmission path leading to the input to minimize multiple reflections. For applications in which the comparator is less than 1 cm from the driving signal source, the source impedance should be minimized. High source impedance in combination with parasitic input capacitance of the comparator could cause undesirable degradation in bandwidth at the input, thus degrading the overall response. It is therefore recommended that the drive source impedance should be no more than 50 for best high speed performance.
COMPARATOR PROPAGATION DELAY DISPERSION
The ADCMP58x family of comparators has been specifically designed to reduce propagation delay dispersion over a wide input overdrive range of 5 mV to 500 mV. Propagation delay dispersion is a change in propagation delays that results from a change in the degree of overdrive or slew rate (how far or fast the input signal exceeds the switching threshold). The overall result is a higher degree of timing accuracy. Propagation delay dispersion is a specification that becomes important in critical timing applications, such as data communications, 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 the overall propagation delay as the input overdrive conditions are changed (see Figure 26 and Figure 27). For the ADCMP58x family of comparators, dispersion is typically <25 ps, because the overdrive varies from 5 mV to 500 mV, and the input slew rate varies from 1 V/ns to 10 V/ns. This specification applies for both positive and negative signals because the ADCMP58x family of comparators has almost equal delays for positive- and negative-going inputs.
500mV OVERDRIVE
INPUT VOLTAGE 5mV OVERDRIVE VN VOS
Q/Q OUTPUT
Figure 26. Propagation Delay--Overdrive Dispersion
INPUT VOLTAGE 1V/ns VN VOS 10V/ns
Q/Q OUTPUT
Figure 27. Propagation Delay--Slew Rate Dispersion
Rev. A | Page 12 of 16
04672-027
DISPERSION
04672-026
DISPERSION
ADCMP580/ADCMP581/ADCMP582
COMPARATOR HYSTERESIS
Adding hysteresis to a comparator is often desirable in a noisy environment or when the differential inputs are very small or slow moving. The transfer function for a comparator with hysteresis is shown in Figure 28. If the input voltage approaches the threshold 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 V input does not cause the comparator to switch states unless it exceeds the region bounded by VH/2. 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 reduce overall stability in some cases.
-VH 2 0V +VH 2 INPUT
The hysteresis pin can also be driven by a current source. It is biased approximately 400 mV above VEE and has an internal series resistance of approximately 600 .
80 70
COMPARATOR HYSTERESIS (mV)
60 50 40 30 20 10 0
1
10
100
1k
10k
RHYS CONTROL RESISTOR ()
Figure 29. Comparator Hysteresis vs. RHYS Control Resistor
MINIMUM INPUT SLEW RATE REQUIREMENT
As with many 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/s should ensure clean output transitions from the ADCMP58x family of 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 is 120 V of thermal noise generated over the bandwidth of the comparator by the two 50 terminations at room temperature. With a slew rate of only 50 V/s, the inputs are inside this noise band for over 2 ps, rendering the comparator's jitter performance of 200 fs irrelevant. Raising the slew rate of the input signal and/or reducing the bandwidth over which that resistance is seen at the input can greatly reduce jitter. Devices are not characterized this way but simply bypassing a reference input close to the package can reduce jitter 30% in low slew rate applications.
1
0
04672-028
OUTPUT
Figure 28. Comparator Hysteresis Transfer Function
The ADCMP58x family of comparators offers a programmable 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 VEE, 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 range of hysteresis that can be applied by using this method is approximately 70 mV. Figure 29 illustrates the amount of applied hysteresis as a function of the external resistor value. The advantage of applying hysteresis in this manner is improved accuracy, stability, and reduced component count. An external bypass capacitor is not required on the HYS pin, and it would likely degrade the jitter performance of the device.
Rev. A | Page 13 of 16
04672-029
ADCMP580/ADCMP581/ADCMP582 OUTLINE DIMENSIONS
3.00 BSC SQ 0.45 PIN 1 INDICATOR TOP VIEW 2.75 BSC SQ 0.50 BSC 12 MAX 0.90 0.85 0.80 SEATING PLANE 0.30 0.23 0.18 0.80 MAX 0.65 TYP 0.05 MAX 0.02 NOM 0.20 REF 1.50 REF 0.60 MAX 0.50 0.40 0.30
13 12
16
EXPOSED PAD
1
PIN 1 INDICATOR *1.65 1.50 SQ 1.35
9 (BOTTOM VIEW) 4 8 5
0.25 MIN
*COMPLIANT TO JEDEC STANDARDS MO-220-VEED-2 EXCEPT FOR EXPOSED PAD DIMENSION.
Figure 30. 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 3 mm x 3 mm Body, Very Thin Quad (CP-16-3) Dimensions shown in millimeters
ORDERING GUIDE
Model ADCMP580BCP-WP ADCMP580BCP-R2 ADCMP580BCP-RL7 ADCMP580BCPZ-WP 1 ADCMP580BCPZ-R21 ADCMP580BCPZ-RL71 ADCMP581BCP-WP ADCMP581BCP-R2 ADCMP581BCP-RL7 ADCMP581BCPZ-WP1 ADCMP581BCPZ-R21 ADCMP581BCPZ-RL71 ADCMP582BCP-WP ADCMP582BCP-R2 ADCMP582BCP-RL7 ADCMP582BCPZ-WP1 ADCMP582BCPZ-R21 ADCMP582BCPZ-RL71 EVAL-ADCMP580BCPZ1 EVAL-ADCMP581BCPZ1 EVAL-ADCMP582BCPZ1
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ Evaluation Board Evaluation Board Evaluation Board
Package Option CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3 CP-16-3
Branding G07 G07 G07 G12 G12 G12 G09 G09 G09 G11 G11 G11 G0B G0B G0B G10 G10 G10
Z = RoHS Compliant Part.
Rev. A | Page 14 of 16
ADCMP580/ADCMP581/ADCMP582 NOTES
Rev. A | Page 15 of 16
ADCMP580/ADCMP581/ADCMP582 NOTES
(c)2005-2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04672-0-8/07(A)
T T
Rev. A | Page 16 of 16

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