SY89856U
2GHz, Low-Power, 1:6 LVPECL Fanout Buffer
with 2:1 Input MUX and Internal Termination
General Description
The SY89856U is a 2.5V/3.3V precision, high-speed, 1:6
fanout capable of handling clocks up to 2.0GHz. A
differential 2:1 MUX input is included for redundant clock
switchover applications.
The differential input includes Micrel’s unique, 3-pin input
termination architecture that allows the device to interface
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 outputs are
LVPECL (100k, temperature compensated), with
extremely fast rise/fall times guaranteed to be less than
200ps.
The SY89856U operates from a 2.5V ±5% supply or a
3.3V ±10% supply and is guaranteed over the full industrial
temperature range of –40°C to +85°C. The SY89856U is
®
part of Micrel’s high-speed, Precision Edge product line.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Features
6 ultra-low skew copies of the selected input
2:1 MUX input included for clock switchover applications
Low power: 225mW typical (2.5V)
2.5V to 3.3V supply voltage
Unique input isolation design minimizes crosstalk
Guaranteed AC performance over temperature and
voltage:
Clock frequency range: DC to >2.0GHz
<400ps IN-to-OUT t
pd
<200ps t
r
/t
f
times
<30ps skew (output-to-output)
Ultra-low jitter design:
40fs RMS phase jitter
0.7ps
RMS
crosstalk-induced jitter
Unique input termination and VT pin accepts DC- and
AC-coupled inputs (CML, PECL, LVDS)
100k LVPECL compatible output swing
–40°C to +85°C industrial temperature range
Available in 32-pin (5mm x 5mm) QFN package
Applications
Redundant clock distribution
All SONET/SDH clock/data distribution
All Fibre Channel distribution
All Gigabit Ethernet clock distribution
Markets
LAN/WAN
Enterprise servers
ATE
Test and measurement
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
Oct. 1, 2013
Revision 3.1
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89856U
Ordering Information
(1)
Part Number
SY89856UMG
SY89856UMGTR
Notes:
1. Contact factory for die availability. Dice are guaranteed at T
A
= 25°C, DC Electricals only.
2. Tape and Reel.
(2)
Package Type
QFN-32
QFN-32
Operating Range
Industrial
Industrial
Package Marking
SY89856U with Pb-Free bar-line indicator
SY89856U with Pb-Free bar-line indicator
Lead Finish
NiPdAu Pb-Free
NiPdAu Pb-Free
Pin Configuration
32-Pin QFN
Oct. 1, 2013
2
Revision 3.1
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89856U
Pin Description
Pin Number
1, 4
5, 8
Pin Name
IN0, /IN0
IN1, /IN1
Pin Function
Differential Input: These input pairs are the differential signal inputs to the device. These inputs
accept AC- or DC-coupled signals as small as 100mV (200mV
p-p
). Each pin of a pair internally
terminates to a VT pin through 50Ω. Note that these inputs will default to an indeterminate state if
left open. 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 VTI pins provide a center-tap to a termination network for maximum interface flexibility.
See the “Input
Interface Applications”
section for more details.
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 logic HIGH state if left
open. The MUX select switchover function is asynchronous.
No connect.
Positive Power Supply: Bypass with 0.1µF//0.01µF low ESR capacitors as close to VCC pins as
possible.
Differential Outputs: These 100k (temperature compensated) LVPECL output pairs are low skew
copies of the selected input. Unused output pins may be left floating. Please refer to the “LVPECL
Output Interface Applications”
section for details.
2, 6
VT0, VT1
31
SEL
10
11, 16, 18,
23, 25, 30
29, 28
27, 26
22, 21
20, 19
15, 14
13, 12
9, 17, 24, 32
3, 7
NC
VCC
Q0, /Q0,
Q1, /Q1,
Q2, /Q2,
Q3, /Q3,
Q4, /Q4,
Q5, /Q5
GND,
Exposed Pad
VREF-AC0
VREF-AC1
Ground: Ground pins and exposed pad must be connected to the same ground plane.
Reference Voltage: This output biases to V
CC
– 1.2V. It is used for AC-coupling inputs (IN, /IN).
Connect VREF_AC directly to the VT pin. Bypass with 0.01µF low ESR capacitor to V
CC
. See the
“Input
Interface Applications”
section. Maximum sink/source current is ±1.5mA. Due to the limited
drive capability use for input at the same package only.
LVPECL Output Interface Applications
SEL
0
1
Output
IN0 Input Selected
IN1 Input Selected
Oct. 1, 2013
3
Revision 3.1
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89856U
Functional Block Diagram
Oct. 1, 2013
4
Revision 3.1
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89856U
Absolute Maximum Ratings
(3)
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
Termination Current
Source or sink current on V
T
............................. ±100mA
V
REF-AC
Source or sink current………… .................... ±2.0mA
Lead Temperature (soldering, 20s) .......................... +260°C
Storage Temperature (T
s
) ........................... –65°C to 150°C
Operating Ratings
(4)
Supply Voltage (V
CC
) ............................ +2.375V to +2.625V
............................................................... +3.0V to +3.6V
Ambient Temperature (T
A
) .......................... –40°C to +85°C
(5)
Package Thermal Resistance
QFN (
JA
)
Still-Air ............................................................... 35°C/W
QFN (
JB
)
Junction-to-Board .............................................. 16°C/W
DC Electrical Characteristics
(6)
T
A
= –40°C to +85°C, unless otherwise noted.
Symbol
V
CC
Parameter
Power Supply Voltage
Condition
Min.
2.375
3.0
I
CC
R
IN
R
DIFF_IN
V
IH
V
IL
V
IN
V
DIFF_IN
V
T_IN
V
REF-AC
Notes:
3. 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 for extended periods
may affect device reliability.
4. The datasheet limits are not guaranteed if the device is operated beyond the operating ratings.
5. Package thermal resistance assumes exposed pad is soldered (or equivalent) to the device’s most negative potential on the PCB.
JA
and
JB
values
are determined for a 4-layer board in still air, unless otherwise stated.
6. The circuit is designed to meet the DC specifications shown in the above table after thermal equilibrium has been established.
7. V
IH
(min) not lower than 1.2V.
Typ.
2.5
3.3
90
Max.
2.625
3.6
140
55
110
V
CC
V
IH
–0.1
1.7
Units
V
V
mA
Ω
Ω
V
V
V
V
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
No load, max V
CC
.
45
90
Note 7
V
IH
– 1.6
0
See Figure 1.
See Figure 2.
0.1
0.2
50
100
1.28
V
CC
– 1.3
V
CC
– 1.2
V
CC
– 1.1
V
V
Oct. 1, 2013
5
Revision 3.1
hbwhelp@micrel.com
or (408) 955-1690
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