SY89851U
Low Power, 3GHz, 1:2 LVPECL Fanout
Buffer/Translator with Internal Termination
General Description
The SY89851U is a low jitter, low skew, high-speed
1:2 differential fanout buffer optimized for precision
telecom
and
enterprise
server
distribution
applications. The SY89851U distributes clock
frequencies from DC to >3GHz, and data rates to
2.5Gbps guaranteed over temperature and voltage.
The SY89851U 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 (200mVpp) without
any level shifting or termination resistor networks in
the signal path. The outputs are 800mV, 100K-
compatible LVPECL with extremely fast rise/fall time
guaranteed to be less than 180ps.
The SY89851U 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
SY89851U is part of Micrel's high-speed, Precision
®
Edge product line.
All support documentation can be found on Micrel's
web site at www.micrel.com.
Precision Edge
®
Features
•
Precision 1:2, 800mV LVPECL fanout buffer
•
Low power consumption: 80mW typ. (2.5V)
•
Guaranteed AC performance over temperature
and voltage:
– DC to >3GHz clock throughput
– <340ps propagation delay
– <180ps rise/fall time
– <20ps output-to-output skew
•
Ultra-low jitter design:
– <1ps
RMS
random jitter
– <10ps
PP
deterministic jitter
– <10ps
PP
total jitter (clock)
•
Unique, patented input termination and VT pin
accepts DC- and AC-coupled inputs (CML,
LVPECL, LVDS)
•
100K LVPECL-compatible outputs
•
Power supply 2.5V ±5% or 3.3V ±10%
•
–40°C to +85°C industrial temperature range
•
Available in 16-pin (3mm x 3mm) QFN package
Functional Block Diagram
Applications
•
•
•
•
All SONET and GigE clock distribution
Fibre Channel applications
Backplane distribution
High-end, low skew, multiprocessor synchronous
clock distribution
Precision Edge is a registered trademark of Micrel, Inc.
July 2005
M9999-071205
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89851U
Ordering Information
(1)
Part Number
SY89851UMG
SY89851UMGTR
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-16
QFN-16
Operating Range
Industrial
Industrial
Package Marking
851U with
Pb-Free bar-line indicator
851U with
Pb-Free bar-line indicator
Lead Finish
Pb-Free
NiPdAU
Pb-Free
NiPdAu
Pin Configuration
16-Pin QFN
July 2005
2
M9999-071205
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89851U
Pin Description
Pin Number
1,4
Pin Name
IN, /IN
Pin Function
Differential Inputs: This input pair is the differential signal input to the device.
Inputs accept AC- or DC-coupled signals as small as 100mV (200mV
pp
). Each
pin terminates to a V
T
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 V
T
pin. The V
T
pins provide a center-tap to a termination network for
maximum interface flexibility. See “Input Interface Applications” section for more
details.
Reference Voltage: This output biases to V
CC
–1.2V. It is used when AC-
coupling the inputs (IN, /IN). For AC-coupled applications, connect V
REF-AC
to the
V
T
pin and bypass with a 0.01µF low ESR capacitor to V
CC
. Maximum
sink/source current is ±1.5mA. See “Input Interface Applications” section for
more details.
Positive Power Supply: Bypass with 0.1µF//0.01µF low ESR capacitors and
place as close to each V
CC
pin as possible.
Differential Outputs: These 100K LVPECL-compatible output pairs are the
precision, low skew copies of the inputs. Unused output pairs may be left open.
Terminate with 50Ω
to V
CC
–2V. See “LVPECL Output Interface Application”
section for more details.
Ground. GND and exposed pad must both be connected to the same ground
plane.
2
VT
3
VREF-AC
5,8,13,16
12,11
9,10
VCC
Q0, /Q0,
Q1, /Q1
6,7,14,15
GND,
Exposed Pad
July 2005
3
M9999-071205
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89851U
Absolute Maximum Ratings
(1)
Supply Voltage (V
CC
) .......................... –0.5V to +4.0V
Input Voltage (IN, /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
Current
Source or sink current ............................... ±2mA
Input Current
Source or sink current on IN, /IN .............. ±50mA
Lead Temperature (soldering, 20sec.) ........... +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 ..................................................... 60°C/W
QFN (ψ
JB
)
Junction-to-Board .................................... 33°C/W
DC Electrical Characteristics
(4)
TA = –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 the 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 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
IH
(min) not lower than 1.2V
Parameter
Power Supply
Power Supply Current
Single-Ended 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
V
CC
–1.3
V
CC
–1.2
See Figure 1a.
See Figure 1b.
Note 5
No load, max. V
CC
45
90
V
CC
–1.6
0
0.1
0.2
1.28
V
CC
–1.1
Condition
Min
2.375
3.0
Typ
2.5
3.3
32
50
100
Max
2.625
3.6
45
55
110
V
CC
V
IH
-0.1
1.7
Units
V
V
mA
Ω
Ω
V
V
V
V
V
V
July 2005
4
M9999-071205
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SY89851U
100K LVPECL Output 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
Note:
6. The circuit is designed to meet the DC specifications shown in the above table after thermal equilibrium has been
established.
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
July 2005
5
M9999-071205
hbwhelp@micrel.com
or (408) 955-1690
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