SY89473U
Precision LVPECL 2:1 Multiplexer with 1:2
Fanout and Internal Termination
General Description
The SY89473U is a 2.5V/3.3V precision, high-speed 2:1
differential MUX capable of processing clocks up to
2.5GHz and data up to 2.5Gbps.
The differential input includes Micrel’s unique, 3-pin
input termination architecture that directly interfaces to
any differential signal (AC- or DC-coupled) as small as
100mV (200mV
PP
) without any level shifting or
termination resistor networks in the signal path. The
output is 800mV, 100K-compatible, LVPECL with fast
rise/fall times guaranteed to be less than 190ps.
The SY89473U operates from a 2.5V ±5% or 3.3V
±10% supply and is guaranteed over the full industrial
temperature range of –40°C to +85°C. The SY89473U is
part of Micrel’s high-speed, Precision Edge
®
product
line. For multiple-clock switchover solutions, please refer
to the SY89840–SY89843U family.
All support documentation can be found on Micrel’s web
site at:
www.micrel.com.
Precision Edge
®
Features
•
Selects between two input channels and provides two
copies of the selected output
•
Guaranteed AC performance over temperature and
supply voltage:
- DC to 2.5Gbps data throughput
- DC to 2.5GHz f
MAX
(clock)
- <500ps In-to-Out t
pd
- <190ps t
r
/t
f
- <20ps Output-to-output skew
•
Unique patented input isolation design minimizes
crosstalk
•
Ultra-low Jitter Design:
- <1ps
RMS
random jitter
- <1ps
RMS
cycle-to-cycle jitter
- <10ps
PP
total jitter (clock)
- <0.7ps
RMS
crosstalk induced jitter
•
Unique patent-pending input termination and VT pin
accepts DC- and AC-coupled inputs (CML, PECL,
LVDS)
•
800mV (100K) LVPECL output swing
•
2.5V ±5% or 3.3V ±10% supply voltage
•
-40°C to +85°C industrial temperature range
•
Available in 24-pin (4mm x 4mm) QFN package
Functional Block Diagram
Applications
•
Clock switchover
•
Data distribution
Markets
•
•
•
•
United States Patent No. RE44,134
Precision Edge is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
LAN/WAN
Enterprise servers
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Test and measurement
May 2007
M9999-052207-B
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89473U
Ordering Information
(1)
Part Number
SY89473UMG
SY89473UMGTR
(2)
Notes:
1. Contact factory for die availability. Dice are guaranteed at T
A
= 25°C, DC Electricals Only.
2. Tape and Reel.
Package Type
QFN-24
QFN-24
Operating
Range
Industrial
Industrial
Package Marking
473U with Pb-Free bar-line indicator
473U with Pb-Free bar-line indicator
Lead
Finish
NiPdAu
Pb-Free
NiPdAu
Pb-Free
Pin Configuration
24-Pin QFN
May 2007
2
M9999-052207-B
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89473U
Pin Description
Pin Number
5, 2,
23, 20
Pin Name
IN0, /IN0
IN1, /IN1
Pin Function
Differential Inputs: These input pairs are the differential signal inputs to the device.
They accept AC or DC-coupled signals as small as 100mV (200mV
PP
). Note that
these inputs will default to an indeterminate state if left open. Each pin of a pair
internally terminates to a VT pin through 50Ω. Please refer to the “Input Interface
Applications” section for more details.
Reference Voltage: These outputs bias to V
CC
-1.2V. They are used for AC-
coupling inputs IN and /IN. Connect VREF-AC directly to the corresponding VT pin.
Bypass with 0.01µF low ESR capacitor to VCC. Maximum sink/source current is
±1.5mA. Due to the limited drive capability, the VREF-AC pin is only intended to
drive its respective VT pin. Please refer to the “Input Interface Applications” section
for more details.
Input Termination Center-Tap: Each side of the differential input pair terminates to
a VT pin. The VT0 and VT1 pins provide a center-tap to a termination network for
maximum interface flexibility. Please refer to the “Input Interface Applications”
section for more details.
Positive Power Supply: Connect to +2.5V or +3.3V power supply. Bypass with
0.1µF//0.01µF low ESR capacitors as close to VCC pins as possible.
Differential Outputs: These differential LVPECL output pairs are a logic function of
the IN0, IN1, and SEL inputs. Please refer to the truth table below for details.
Unused output pairs can be left floating with no impact on jitter.
This single-ended TTL/CMOS-compatible input selects the inputs to the
multiplexer. Note that this input is internally connected to a 25kΩ pull-up resistor
and will default to a logic HIGH state if left open. V
TH
= V
CC
/2. Please refer to the
“Timing Diagram” section for more details.
Ground: Ground pins and exposed pad must be connected to the same ground
plane.
3, 21
VREF-AC0
,
VREF-AC1
4, 22
1, 6, 9, 10, 13,
19, 24
7, 8
11, 12
VT0
,
VT1
VCC
Q0, /Q0
Q1, /Q1
15
SEL
GND, Exposed
Pad
14, 17, 18
Truth Table
INPUTS
IN0
0
1
X
X
/IN0
1
0
X
X
IN1
X
X
0
1
/IN1
X
X
1
0
SEL
0
0
1
1
OUTPUTS
Q
0
1
0
1
/Q
1
0
1
0
May 2007
3
M9999-052207-B
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89473U
Absolute Maximum Ratings
(1)
Supply Voltage (V
CC
) .................................... -0.5V to +4.0V
Input Voltage (V
IN
) ........................................... -0.5V to V
CC
LVPECL Output Current (I
OUT
)
Continuous ...........................................................±50mA
Surge ..................................................................±100mA
Input Current
Source/sink Current on IN, /IN..............................±50mA
Source/sink Current on V
T
..................................±100mA
V
REF-AC
Current
Source/sink Current on V
REF-AC
...............................±2mA
Lead Temperature (soldering, 20 sec.) ...................+260°C
Storage Temperature (T
S
) ...........................-65°C to 150
°
C
Operating Ratings
(2)
Supply Voltage (V
CC
) .................................. +2.375V to +2.625V
.................................................................... +3.0V to +3.6V
Ambient Temperature (T
A
).................................–40°C to +85°C
(3)
Package Thermal Resistance
QFN (θ
JA
)
Still-Air .................................................................... 50°C/W
QFN (Ψ
JB
)
Junction-to-Board ................................................... 30°C/W
DC Electrical Characteristics
(4)
T
A
= –40°C to +85°C; unless otherwise stated.
Symbol
V
CC
I
CC
R
IN
R
DIFF_IN
V
IH
V
IL
V
IN
V
DIFF_IN
V
T_IN
V
REF-AC
Notes:
1. Permanent device damage may occur if absolute maximum ratings are exceeded. This is a stress rating only and functional operation is not
implied at conditions other than those detailed in the operational sections of this data sheet. Exposure to absolute maximum ratings conditions
for extended periods may affect device reliability.
2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
3. Package thermal resistance assumes exposed pad is soldered (or equivalent) to the devices most negative potential on the PCB.
θ
JA
and
Ψ
JB
values are determined for a 4-layer board in still air unless otherwise stated.
4. The circuit is designed to meet the DC specifications shown in the above table after thermal equilibrium has been established.
5. V
IN
(max) is specified when V
T
is floating.
Parameter
Power Supply
Power Supply Current
Input Resistance
(IN-to-V
T
)
Differential Input Resistance
(IN-to-/IN)
Input High Voltage
(IN, /IN)
Input Low Voltage
(IN, /IN)
Input Voltage Swing
(IN, /IN)
Differential Input Voltage Swing
|IN-/IN|
IN-to-V
T
(IN, /IN)
Output Reference Voltage
Condition
Min
2.375
3.0
Typ
2.5
3.3
45
50
100
Max
2.625
3.6
65
55
110
V
CC
V
IH
-0.1
V
CC
Units
V
V
mA
Ω
Ω
V
V
V
V
No load, max V
CC
.
45
90
1.2
0
See Figure 1a. Note 5
See Figure 1b.
0.1
0.2
1. 28
V
CC
-1.3
V
CC
-1.2
V
CC
-1.1
V
V
May 2007
4
M9999-052207-B
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89473U
LVPECL Outputs DC Electrical Characteristics
(6)
V
CC
= 2.5V ±5% or 3.3V ±10%; T
A
= -40°C to + 85°C; R
L
= 50Ω to V
CC
-2V, unless otherwise stated.
Symbol
V
OH
V
OL
V
OUT
V
DIFF-OUT
Parameter
Output HIGH Voltage
Q, /Q
Output LOW Voltage
Q, /Q
Output Voltage Swing
Q, /Q
Differential Output Voltage Swing
Q, /Q
See Figure 1a.
See Figure 1b.
Condition
Min
V
CC
–1.145
V
CC
–1.945
550
1100
800
1600
Typ
Max
V
CC
-0.895
V
CC
-1.695
Units
V
V
mV
mV
LVTTL/CMOS DC Electrical Characteristics
(6)
V
CC
= 2.5V ±5% or 3.3V ±10%; T
A
= -40°C to + 85°C, unless otherwise stated.
Symbol
V
IH
V
IL
I
IH
I
IL
Note:
6.
The circuit is designed to meet the DC specifications shown in the above table after thermal equilibrium has been established.
Parameter
Input HIGH Voltage
Input LOW Voltage
Input HIGH Current
Input LOW Current
Condition
Min
2.0
Typ
Max
0.8
Units
V
V
µA
µA
-125
-300
30
May 2007
5
M9999-052207-B
hbwhelp@micrel.com
or (408) 955-1690
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