Maxim MAX3785ITT 6.25gbps, 1.8v pc board equalizer Datasheet

19-2630; Rev 4; 10/08
6.25Gbps, 1.8V PC Board Equalizer
The MAX3785 6.25Gbps equalizer operates from a single 1.8V supply and compensates for transmissionmedium losses encountered with FR-4 transmission
lines. Optimized for low-voltage, high-density, DC-coupled interconnections between the line card and switch
card, the MAX3785 enables a system upgrade path
while maintaining a legacy rate of 2.5Gbps to
3.125Gbps. Roughly the size of two 0603 passive components, the MAX3785 easily provides placement and
routing flexibility.
The MAX3785 is composed of an equalizer, limiting
amplifier, and output driver. For data rates of 3.2Gbps
and lower, the MAX3785 equalizes signals for spans up
to 40in of FR-4 board material. For data rates up to
6.25Gbps, the MAX3785 compensates for 30in of FR-4
board material. The MAX3785 is coding independent,
functioning equally well for 8b/10b or scrambled signals.
The MAX3785 features DC-coupled current-mode logic
(CML) data inputs and outputs. It is packaged in a tiny
1.5mm × 1.5mm chip-scale package (USCP™) and a
6-pin TDFN package.
Features
♦ Single 1.8V Supply
♦ Very Low Power, 60mW
♦ Spans 30in with FR-4 at 6.25Gbps
♦
♦
♦
♦
Operates from 1.0Gbps to 6.4Gbps
Coding Independent, 8b/10b or Scrambled
DC-Coupled CML Inputs and Outputs
Small 1.5mm × 1.5mm Footprint
Ordering Information
PART
TEMP RANGE
0°C to +85°C
6 UCSP (3 3)
MAX3785UWL+
0°C to +85°C
6 WLP
MAX3785UTT
0°C to +85°C
6 TDFN-EP*
MAX3785UTT+
0°C to +85°C
6 TDFN-EP*
MAX3785ITT
-20°C to +85°C
6 TDFN-EP*
MAX3785ITT+
-20°C to +85°C
6 TDFN-EP*
+Denotes a lead-free/RoHS-compliant package.
*EP = Exposed pad.
Applications
HSBI for ≤ 6.4Gbps
PIN-PACKAGE
MAX3785UBL
Pin Configurations
TOP VIEW (BUMPS ON BOTTOM OF DIE)
Double IEEE 802.3ae XAUI
Δ
Double STM-16/OC-48
A1
A2
A3
IN-
GND
OUT-
IN- 1
MAX3785UTT
GND 2
6
IN+
5
VCC
4
OUT+
MAX3785UBL
UCSP is a trademark of Maxim Integrated Products, Inc.
C1
C2
C3
IN+
VCC
OUT+
OUT- 3
3 x 3 UCSP
TDFN
Typical Application Circuit
LINE CARD
SWITCH CARD
BACKPLANE
MAC
SWITCH
ASIC WITH
SERDES
1.8V
VCC
Rx
Tx
IN
1.8V
MAX3785
OUT
Rx
6.25Gbps
VCC
Tx
Rx
OUT
MAX3785
Tx
IN
30in (0.75m)
________________________________________________________________ Maxim Integrated Products
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.
1
MAX3785
General Description
MAX3785
6.25Gbps, 1.8V PC Board Equalizer
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC to GND.................................-0.5V to +6.0V
Continuous Output Current (OUT+, OUT-) .......-25mA to +25mA
Input Voltage (IN+, IN-) ..............................-0.5V to (VCC + 0.5V)
Operating Ambient Temperature Range
(UBL, UTB)......................................................... 0°C to +85°C
Operating Ambient Temperature Range (ITT).....-20°C to +85°C
Storage Ambient Temperature Range...............-55°C to +150°C
Continuous Power Dissipation (TA = +70°C)
6-Pin TDFN (derate 24.4mW above +70°C)..................1.95W
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
(Typical values measured at V CC = 1.8V and T A= +25°C. Specifications guaranteed over specified operating conditions.)
(See Operating Conditions table.)
PARAMETER
CONDITIONS
MIN
Supply Current
Input Swing (IN)
Measured differentially at data source before
encountering loss (Point A in Figure 1) (Note 1)
Input Common-Mode Voltage Range (Note 1)
Input Return Loss
100MHz to 3.2GHz, power off
Differential Input Resistance
IN+ and IN-
Output Swing
Measured differentially at OUT+ and OUT- with 50
±1% load at each side
Output Resistance
OUT+ or OUT-
Output Return Loss
100MHz to 3.2GHz, IN+ = high
Output Transition Time (tr, t f)
20% to 80% (Note 2)
Residual Deterministic Jitter
(Notes 1, 3, 4)
Output Random Jitter
TYP
MAX
UNITS
35
55
mA
1600
mVP-P
400
VCC (INMIN/4)
VCC (INMAX/4)
15
85
100
450
42
50
dB
115
800
mVP-P
58
14
30
55
2.5Gbps, 3.2Gbps, 5.0Gbps; 0in to 30in FR-4
400mVP-P IN 1600mV P-P
0.10
0.15
2.5Gbps, 3.2Gbps; 40in FR-4
400mVP-P IN 1600mV P-P
0.15
0.20
6.25Gbps; 0in to 30in FR-4
600mVP-P IN 1600mV P-P
0.15
0.25
6.25Gbps; 0in to 30in FR-4
IN = 400mVP-P
0.20
0.30
(Notes 1, 2)
0.75
1.0
50
Latency
Minimum Bit Rate
(Note 1)
ps
UI
Low-Frequency Cutoff Frequency
(Note 1)
dB
40
Maximum Bit Rate
V
6.25
psRMS
kHz
200
ps
6.4
Gbps
1.0
2.5
Gbps
Note 1: Guaranteed by design and characterization.
Note 2: Using input pattern 0000011111 at 6.25Gbps.
Note 3: Difference in deterministic jitter between data source and equalizer output, evaluated at 2.5Gbps, 3.2Gbps, 5Gbps, and
6.25Gbps. Pattern used: PRBS (27), ninety-six 0s, 1, 0, 1, 0, PRBS (27), ninety-six 1s, 0, 1, 0, 1.
Note 4: Signal is applied differentially at input to a 6-mil wide, loosely coupled stripline. Deterministic jitter at the output of the
transmission line is from media-induced loss, not from clock source modulation (see Figure 1).
2
_______________________________________________________________________________________
6.25Gbps, 1.8V PC Board Equalizer
PARAMETER
CONDITIONS
Supply Voltage (VCC)
MIN
TYP
MAX
UNITS
1.71
1.8
1.89
V
25
85
°C
Operating Ambient Temperature (UBL, UTT)
0
10Hz ≤ f < 100Hz
100
Supply Noise Tolerance
100Hz ≤ f < 1MHz
40
Bit Rate
NRZ data
1MHz ≤ f ≤ 1GHz
mVP-P
10
2.50
Operating Ambient Temperature (ITT)
-20
25
6.25
Gbps
85
°C
PC BOARD
SIGNAL SOURCE
3in ≤ L ≤ 30in
A
B
C
IN
<1.0pF SMA
CONNECTOR
<1.0pF SMA
CONNECTOR
MAX3785
OUT
FR-4
4.0 < εr < 4.4
tanδ = 0.022
Figure 1. Conditions of Testing
Typical Operating Characteristics
(VCC = +1.8V, TA = +25°C, unless otherwise noted. Measurements done at 6.25Gbps, 500mVP-P at the source with a test pattern:
PRBS (27), ninety-six 0s, 1, 0, 1, 0, PRBS (27), ninety-six 1s, 0, 1, 0, 1. Deterministic jitter of the MAX3785 and the board was measured using Tektronix’s FrameScan™. Deterministic jitter of the system was subtracted from the measured value. Eye diagrams were
acquired by FrameScan, which includes system jitter but eliminates random jitter.)
EYE DIAGRAM OF UNEQUALIZED
SIGNAL AFTER 30in OF FR-4
MAX3785 toc01
70mV/div
30ps/div
MAX3785 toc03
MAX3785 toc02
70mV/div
70mV/div
TEST PATTERN, 6.25Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
EYE DIAGRAM OF EQUALIZED
SIGNAL AFTER 30in OF FR-4
EYE DIAGRAM OF EQUALIZED
SIGNAL AFTER 30in OF FR-4
30ps/div
TEST PATTERN, 6.25Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
30ps/div
210 - 1 PRBS, 6.25Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
FrameScan is a trademark of Tektronix.
_______________________________________________________________________________________
3
MAX3785
Operating Conditions
Typical Operating Characteristics (continued)
(VCC = +1.8V, TA = +25°C, unless otherwise noted. Measurements done at 6.25Gbps, 500mVP-P at the source with a test pattern:
PRBS (27), ninety-six 0s, 1, 0, 1, 0, PRBS (27), ninety-six 1s, 0, 1, 0, 1. Deterministic jitter of the MAX3785 and the board was measured
using Tektronix’s FrameScan. Deterministic jitter of the system was subtracted from the measured value. Eye diagrams were acquired
by FrameScan, which includes system jitter but eliminates random jitter.)
EYE DIAGRAM OF UNEQUALIZED
SIGNAL AFTER 30in OF FR-4
70mV/div
MAX3785 toc06
MAX3785 toc05
70mV/div
70mV/div
50ps/div
50ps/div
CRPAT, 3.125Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
TEST PATTERN, 3.125Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
DETERMINISTIC JITTER
vs. BOARD LENGTH (FR-4)
(INPUT LEVEL OF 500mVP-P, TEST PATTERN)
EQUALIZER OPERATING CURRENT
vs. TEMPERATURE
90
80
20
MAX3785 toc08
65
60
55
MAX3785 toc07
100
DETERMINISTIC JITTER vs. SIGNAL LEVEL
(TEST PATTERN, 30in OF FR-4 BOARD)
50
60
50
40
30
20
10
0
0
10
20
30
40
50
60
TEMPERATURE (°C)
70
80
15
45
40
35
30
25
20
15
10
5
3.125Gbps
2.5Gbps
JITTER (ps)
JITTER (ps)
70
MAX3785 toc09
50ps/div
TEST PATTERN, 3.125Gbps,
WITHOUT RANDOM JITTER,
INCLUDING 13ps SYSTEM JITTER
4
EYE DIAGRAM OF EQUALIZED
SIGNAL AFTER 30in OF FR-4
EYE DIAGRAM OF EQUALIZED
SIGNAL AFTER 30in OF FR-4
MAX3785 toc04
CURRENT (mA)
MAX3785
6.25Gbps, 1.8V PC Board Equalizer
3.125Gbps
6Gbps
10
6.4Gbps
5
5Gbps
5Gbps
2.5Gbps
0
10
15
20
25
30
BOARD LENGTH (in)
35
40
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
DIFFERENTIAL SIGNAL LEVEL (VP-P)
_______________________________________________________________________________________
2.0
6.25Gbps, 1.8V PC Board Equalizer
25
210 - 1
25
10
15
K28.5
0
15
5
5.5
6.5
0
2.5
DATA RATE (Gbps)
3.5
4.5
5.5
2.5
6.5
EQUALIZER INPUT RETURN GAIN (SDD11)
(INPUT SIGNAL LEVEL = -40dBm, POWER OFF)
30
20
3.5
4.5
5.5
6.5
DATA RATE (Gbps)
DATA RATE (Gbps)
EQUALIZER INPUT RETURN GAIN (SDD22)
(INPUT SIGNAL LEVEL = -40dBm, IN+ HIGH)
30
MAX3785 toc14
4.5
MAX3785 toc13
20
10
10
GAIN (dB)
3.5
K28.5
27 - 1
0
2.5
210 - 1
10
K28.5
5
TEST
PATTERN
27 - 1
TEST
PATTERN
10
27 - 1
JITTER (ps)
JITTER (ps)
15
GAIN (dB)
JITTER (ps)
CRPAT
TEST PATTERN
20
20
5
CRPAT
25
CRPAT
210 - 1
20
30
MAX3785 toc11
30
MAX3785 toc10
30
DETERMINISTIC JITTER vs. DATA RATE
FOR 30in OF FR-4 BOARD
(INPUT LEVEL OF 500mVP-P)
DETERMINISTIC JITTER vs. DATA RATE
FOR 20in OF FR-4 BOARD
(INPUT LEVEL OF 500mVP-P)
MAX3785 toc12
DETERMINISTIC JITTER vs. DATA RATE
FOR 10in OF FR-4 BOARD
(INPUT LEVEL OF 500mVP-P)
0
-10
0
-10
-20
-20
-30
-30
-40
-40
100
1000
FREQUENCY (MHz)
10,000
100
1000
10,000
FREQUENCY (MHz)
_______________________________________________________________________________________
5
MAX3785
Typical Operating Characteristics (continued)
(VCC = +1.8V, TA = +25°C, unless otherwise noted. Measurements done at 6.25Gbps, 500mVP-P at the source with a test pattern:
PRBS (27), ninety-six 0s, 1, 0, 1, 0, PRBS (27), ninety-six 1s, 0, 1, 0, 1. Deterministic jitter of the MAX3785 and the board was measured
using Tektronix’s FrameScan. Deterministic jitter of the system was subtracted from the measured value. Eye diagrams were acquired
by FrameScan, which includes system jitter but eliminates random jitter.)
6.25Gbps, 1.8V PC Board Equalizer
MAX3785
MAX3785UBL Pin Description
PIN
NAME
A1
IN-
FUNCTION (MAX3785UBL)
Negative Data Input, CML
A2
GND
A3
OUT-
Supply Ground
C1
IN+
Positive Data Input, CML
C2
VCC
Supply Voltage
C3
OUT+
Negative Data Output, CML
Positive Data Input, CML
Functional Description
The MAX3785 6.25Gbps PC board equalizer consists
of an equalizer, limiting amplifier, offset driver, and offset cancellation circuit (see Figure 2). The equalizer
block compensates for the attenuation caused by the
PC board. The limiting amplifier squares up the signal
at the output of the equalizer block. The offset cancellation circuit corrects for internal offset in the limiting
amplifier to minimize pulse-width distortion. This introduces a low-frequency cutoff. The data must achieve a
50% mark/space ratio in less than 100µs. The specified
minimum differential input must be maintained to avoid
oscillation.
Input and Output Structures
An equivalent DC input circuit is shown in Figure 3. It
has an equivalent DC differential input resistance of
100Ω. The output buffer is implemented using currentmode logic (CML), as shown in Figure 4.
Package Description
The chip-scale package (UCSP) has a bump pitch of
0.5mm (19.7 mils) and a bump diameter of 0.3mm (12
mils). Lay out the solder pad spacing on 0.5mm (19.7
mils), a pad size of 0.25mm (10 mils) and a solder
LIMITER
OUTPUT
BUFFER
OUT+
IN+
EQUALIZER
OUT-
IN-
MAX3785
OFFSET
ADJUST
Figure 2. Functional Diagram of the MAX3785
mask opening of 0.33mm (13 mils). Round or square
pads are permissible. For detailed information on UCSP
layout and handling, go to Maxim’s website,
www.maxim-ic.com. The enclosed package description
was accurate at the time of publication. For the
MAX3785, all the balls shown in row B of the drawing
are unpopulated. See the Package Information section
for the latest package information.
MAX3785UTT Pin Description
PIN
6
NAME
FUNCTION (MAX3785UTT)
1
IN-
2
GND
Negative Data Input (CML)
Supply Ground
3
OUT-
Negative Data Output (CML)
4
OUT+
5
VCC
6
IN+
Positive Data Input (CML)
—
EP
Exposed Pad
Positive Data Output (CML)
Supply Voltage
_______________________________________________________________________________________
6.25Gbps, 1.8V PC Board Equalizer
MAX3785
VCC
50Ω
37Ω
37Ω
28Ω
37Ω
37Ω
50Ω
IN+
INESD
STRUCTURES
OFFSET
CORRECTION
Figure 3. Equalizer Input DC Equivalent Circuit
Package Information
VCC
50Ω
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
50Ω
OUT+
OUT-
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
6 UCSP
B9-3
21-0093
6 WLP
W91B1+2
21-0067
6 TDFN
T633-2
21-0137
ESD
STRUCTURES
Figure 4. CML Output Equivalent Circuit
_______________________________________________________________________________________
7
MAX3785
6.25Gbps, 1.8V PC Board Equalizer
Revision History
REVISION
NUMBER
REVISION
DATE
0
10/02
1
8/03
Added the MAX3785UTT (6-pin TDFN) package.
2
5/04
Added the MAX3785ITT (“I” temperature grade range for -20°C to +85°C).
3
12/05
Updated the Ordering Information table to include lead-free packages.
1
4
10/08
Updated the Ordering Information table to include the WLP package.
1
DESCRIPTION
Initial release.
PAGES
CHANGED
—
1, 2, 6, 9
1, 2, 3
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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