19-2565; Rev 4; 10/07
5Gbps PCB Equalizer
General Description
The MAX3784/MAX3784A 5Gbps equalizers provide
compensation for transmission-medium losses in up to
40in of FR-4. They are optimized for short-run length
and balanced codes such as 8b10b, as found in multi-
plexed 1.25Gbps Ethernet systems and 4.25Gbps
Fibre Channel.
The equalizers use differential CML data inputs and
outputs. A standby mode reduces power consumption
when the parts are not in use. The MAX3784/
MAX3784A are available in a 4mm
×
4mm, 16-pin QFN
package that consumes only 185mW at +3.3V.
♦
Spans 40in (1m) of FR-4 PCB
♦
0.18UI Deterministic Jitter Up to 40in
♦
Low Power Consumption: 185mW (MAX3784)
♦
Equalization Reduces Intersymbol Interference
♦
Single +3.3V Supply
♦
Standby Mode
♦
Small 4mm
×
4mm, 16-Pin QFN Package
Features
MAX3784/MAX3784A
Pin Configurations
OUT+
GND
V
CC
Applications
Chassis Life Extension
4.25Gbps Fibre Channel
4x Multiplexed 1.25Gbps Ethernet (5Gbps)
TOP VIEW
OUT-
12
11
10
9
8
EN
13
N.C.
N.C.
14
N.C.
15
*EP
7
V
CC
GND
Ordering Information
PART
MAX3784UGE
MAX3784UTE+
MAX3784AUGE
MAX3784AUTE+
TEMP
RANGE
PIN-
PACKAGE
PKG
CODE
G1644-1
T1644-3
G1644-1
T1644-3
MAX3784/
MAX3784A
6
N.C.
16
5
2
IN+
3
IN-
4
GND
N.C.
0°C to +85°C 16 QFN-EP*
0°C to +85°C 16 TQFN-EP*
0°C to +85°C 16 QFN-EP*
0°C to +85°C 16 TQFN-EP*
1
V
CC
QFN
* THE EXPOSED PAD MUST BE SOLDERED TO SUPPLY GROUND
FOR CORRECT THERMAL AND ELECTRICAL PERFORMANCE.
Pin Configurations continued at end of data sheet.
+Denotes
a lead-free package.
*Exposed pad.
Typical Application Circuit
LINE CARD
PCB
BACKPLANE
SWITCH CARD
1.25Gbps
Rx
Tx
Rx
Tx
Rx
Tx
Rx
Tx
T/R 1
+3.3V
SWITCH
1.25Gbps
T/R 2
T/R 1
T/R 2
Tx
+3.3V
5Gbps
IN
MAX3784/
MAX3784A
EQUALIZER
OUT
Rx
1.25Gbps
T/R 3
T/R 3
Rx
T/R 4
OUT
MAX3784/
MAX3784A
EQUALIZER
IN
Tx
1.25Gbps
T/R 4
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
5Gbps PCB Equalizer
MAX3784/MAX3784A
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
.................................................-0.5V to +6V
Input Voltage............................................(-0.5V) to (V
CC
+ 0.5V)
Continuous Output Current ...............................-25mA to +25mA
Continuous Power Dissipation (T
A
= +85°C)
16-Pin QFN (derate 25mW/°C above +85°C) ............1600mW
Operating Ambient Temperature Range ................0°C to +85°C
Storage Temperature Range .............................-55°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +3V to +3.6V, T
A
= 0°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless otherwise noted.)
PARAMETER
Supply Power
SYMBOL
EN = low
EN = high
10Hz < f < 100Hz
Supply-Noise Tolerance
Latency
CML RECEIVER INPUT
Input Voltage Swing
Return Loss
Input Resistance
EQUALIZATION
Residual Deterministic Jitter,
5Gbps
Residual Deterministic Jitter,
2.5Gbps
Residual Deterministic Jitter,
1.25Gbps
Random Jitter
Table 1 (Notes 2–5)
Table 1 (Notes 2–5)
Table 1 (Notes 2–5)
(Notes 5, 6)
Differential swing, measured
differentially at point C in Figure 1
20% to 80% (Notes 5, 8)
Single ended
MAX3784
MAX3784A
400
550
30
40
45
50
20in
40in
20in
40in
20in
40in
0.13
0.18
0.08
0.13
0.04
0.07
1.3
0.21
0.23
0.14
0.28
0.07
0.15
1.9
600
750
60
60
UI
P-P
UI
P-P
UI
P-P
ps
RMS
V
IN
Measured differentially at point A in Figure 1
100MHz to 2.5GHz
Differential
80
400
15
100
120
1000
mV
P-P
dB
Ω
(Note 1)
From input to output
100Hz < f < 1MHz
1MHz < f < 2.5GHz
185
100
40
10
200
ps
mV
P-P
CONDITIONS
MIN
TYP
MAX
30
250
UNITS
mW
CML TRANSMITTER OUTPUT (into 100Ω
±1Ω)
Output Voltage Swing
Transition Time
Output Resistance
V
O
t
f,
t
r
mV
P-P
ps
Ω
2
_______________________________________________________________________________________
5Gbps PCB Equalizer
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3V to +3.6V, T
A
= 0°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless otherwise noted.)
PARAMETER
ENABLE CONTROL PIN
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
(Note 7)
(Note 7)
-150
-150
1.5
0.5
+10
+10
V
V
µA
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX3784/MAX3784A
Note 1:
Allowed supply noise during jitter tests.
Note 2:
Test pattern. This is a combination of K28.5± characters running at the full bit rate and at one-quarter the bit rate. This simu-
lates the multiplexing of four each 1.25Gbps Ethernet data streams.
Pattern (hex) 100 bits
00 FFFF F0F0 FF 0000 0F0F
(quarter rate K28.5+, quarter rate K28.5-)
3EB05
(K28.5± 00 1111 1010 11 0000 0101)
Note 3:
Difference in deterministic jitter between reference points A and C in Figure 1.
Note 4:
Signal source amplitude range is 400mV
P-P
to 1000mV
P-P
differential. Signal is applied differentially at point A as shown in
Figure 1. The deterministic jitter at point B must be from media-induced loss and not from clock-source modulation.
Deterministic jitter is measured at the 50% vertical level of the signal at point C.
Note 5:
Guaranteed by design and characterization.
Note 6:
Test pattern is K28.5 with 40in trace.
Note 7:
On-chip pullup resistor of 40kΩ (typ). Negative current indicates equalizer sources current.
Note 8:
Using 00 0001 1111 or equivalent pattern. Measured over entire input voltage range, max and min media loss and within 2in
of output pins.
SIGNAL
SOURCE
A
SMA CONNECTOR
BACKPLANE PCB
SMA CONNECTOR
B
MAX3784/MAX3784A
EQUALIZER
C
IN
OUT
6mil LINE
L
≤
40in
Figure 1. Test Conditions
Table 1. PCB Assumptions
(PCB material is FR-4)
PARAMETER
Transmission Line
Relative Permittivity
Loss Tangent
Metal Thickness
Impedance
FR-4 or similar
FR-4 or similar
0.7 mils (0.5oz copper)
Differential
90
CONDITIONS
Edge-coupled stripline
4.4
0.02
0.7
100
110
MIN
TYP
6
4.5
0.022
MAX
UNITS
mils
—
—
mils
_______________________________________________________________________________________
3
5Gbps PCB Equalizer
MAX3784/MAX3784A
Typical Operating Characteristics
(V
CC
= +3.3V, measurements done at 5Gbps, 800mV
P-P
board input with 100-bit pattern from Note 2 of the
EC Table,
T
A
= +25°C,
unless otherwise noted.)
EQUALIZER INPUT EYE DIAGRAM
BEFORE EQUALIZATION AT 5Gbps
(40in, FR-4, 6-mil STRIPLINE)
MAX3784/4A toc01
EQUALIZER OUTPUT EYE DIAGRAM
AFTER EQUALIZATION AT 5Gbps
(40in, FR-4, 6-mil STRIPLINE, MAX3784)
MAX3784/4A toc02
EQUALIZER OUTPUT EYE DIAGRAM
AFTER EQUALIZATION AT 5Gbps
(40in, FR-4, 6-mil STRIPLINE, MAX3784A)
MAX3784/4A toc03
55mV/
div
80mV/
div
80mV/
div
32ps/div
35ps/div
35ps/div
DIFFERENTIAL RETURN LOSS
MAX3784/4A toc04
DETERMINISTIC JITTER
vs. LINE LENGTH
MAX3784/4A toc05
DETERMINISTIC JITTER vs. AMPLITUDE
(20in FR-4 STRIPLINE)
90
DETERMINISTIC JITTER (ps)
80
70
60
50
40
30
20
10
0
1.25GHz
5GHz
2.5GHz
MAX3784/4A toc06
30
25
RETURN LOSS (dB)
20
15
10
5
0
0
1
2
3
4
5
FREQUENCY (GHz)
100
90
DETERMINISTIC JITTER (ps)
80
70
60
50
40
30
20
10
0
0
10
20
30
40
50
1.25GHz
2.5GHz
100
5GHz
60
200
400
600
800
1000
1200
LINE LENGTH (in)
(FR-4 6-mil STRIPLINE)
INPUT AMPLITUDE (mV
P-P
)
(FIGURE 1, POINT A)
DETERMINISTIC JITTER vs. AMPLITUDE
(40in FR-4 STRIPLINE)
90
DETERMINISTIC JITTER (ps)
80
70
LATENCY (ps)
60
50
40
30
20
10
0
200
400
600
800
1000
1200
INPUT AMPLITUDE (mV
P-P
)
(FIGURE 1, POINT A)
0
0
5GHz
100
2.5GHz
1.25GHz
300
MAX3784/4A toc07
LATENCY vs. TEMPERATURE
MAX3784/4A toc08
SUPPLY CURRENT vs. TEMPERATURE
70
SUPPLY CURRENT (mA)
60
50
40
30
20
10
0
I
SHUTDOWN
0
25
50
75
I
CC
MAX3784A
I
CC
MAX3784
MAX3784/4A toc09
100
500
80
400
200
25
50
TEMPERATURE (°C)
75
100
TEMPERATURE (°C)
4
_______________________________________________________________________________________
5Gbps PCB Equalizer
Pin Description
PIN
1, 7, 12
2
3
4, 6, 9
5, 8, 14, 15,
16
10
11
13
EP
NAME
V
CC
IN+
IN-
GND
N.C.
OUT-
OUT+
EN
Exposed
Pad
+3.3V Supply Voltage
Positive Input, CML
Negative Input, CML
Supply Ground
No Connection. Leave unconnected.
Negative Output, CML
Positive Output, CML
Enable Equalizer. A logic high or open selects normal operation. A logic low selects low-power
standby mode.
Connect to Ground. The exposed pad must be soldered to the circuit board ground plane for proper
thermal and electrical performance.
FUNCTION
MAX3784/MAX3784A
5Gbps EQUALIZER
V
CC
OFFSET
CANCELLATION
LOWPASS FILTER
100Ω
IN-
V
CC
40kΩ
EN
MAX3784/
MAX3784A
50Ω
50Ω
OUT+
IN+
EQUALIZER
LIMITER
OUT-
Figure 2. Functional Diagram
Detailed Description
General Theory of Operation
The MAX3784/MAX3784A adaptive equalizers extend
the reach of transmission lines in high-frequency back-
plane interconnect applications. They can be used for
4.25Gbps Fibre Channel, 4x 1.25Gbps Ethernet (5Gbps)
and other NRZ, 8b10b or short (≤ 20 bits) CID data
types. Internally, the MAX3784/MAX3784A are com-
prised of an equalizer control loop and limiting output
driver. The equalizer block reduces intersymbol interfer-
ence (ISI), compensating for frequency-dependent
media-induced loss. The equalization control detects the
spectral contents of the input signal and provides a con-
trol voltage to the equalizer core, adapting it to different
media. The equalizer operation is optimized for short-run,
DC-balanced transmission codes.
Standby Mode
Standby saves power when the equalizer is not in use.
The EN logic input must be set high or open for normal
operation. Logic low at EN forces the equalizer into the
standby state.
CML Input and Output Buffers
The input and output buffers are implemented using cur-
rent-mode logic (CML). Equivalent circuits are shown in
Figures 3 and 4. For details on interfacing with CML,
refer to Maxim Application Note HFAN-01.0:
Introduction
to LVDS, PECL, and CML.
The common-mode voltage
of the input and output is above +2.5V. AC-coupling
capacitors are required when interfacing this part with
devices terminated in voltages such as +1.8V. Values of
0.10µF or greater are recommended.
_______________________________________________________________________________________________________
5
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