Microchip SY89825U Handleiding


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1
GENERAL DESCRIPTION
SY89825U 1:22 LVPECL fanout buer
Single +2.5V or +3.3V power supply
AC-coupled conguration for ease-of-use
I/O interface includes onboard termination
Fully assembled and tested
Can be recongured for DC-coupled operation
FEATURES
2.5/3.3V 1:22 HIGH-PERFORMANCE,
LOW VOLTAGE PECL BUS CLOCK DRIVER
AND TRANSLATOR W/INTERNAL TERMINATION
Precision Edge™
SY89825U
Evaluation Board
Rev.: A Amendment: /0
Issue Date: July 2004
The SY89825U evaluation board is designed for
convenient setup and quick evaluation of the SY89825U. It
allows the user to evaluate the part over its full voltage-
range without requiring any modications to the board.
The evaluation board standard configuration is AC-
coupled for direct interface to a 50 compatible oscilloscope
without split supplies. For applications that require a DC-
coupled configuration, step-by-step instructions for modifying
the board are included.
The board is fully assembled and tested.
All data sheets and support documentation can be found
on Micrel’s web site at www.micrel.com.
EVALUATION BOARD
Precision Edge is a trademark of Micrel, Inc.
AC-Coupled Evaluation Board
Part Number Function Data Sheet Link
SY89825U 2.5/3.3V, 1:22 High-Performance, Low-Voltage PECL Bus www.micrel.com/product-info/products/sy89825u.shtml
Clock Driver and Translator w/Internal Termination Data Sheet
RELATED PRODUCT AND SUPPORT DOCUMENTATION
2
SY89825U Evaluation BoardMicrel
M9999-070104
hbwhelp@micrel.com or (408) 955-1690
EVALUATION BOARD DESCRIPTION
Direct 50 Scope Interface: AC-Coupled Evaluation
Board
The SY89825U is packaged in a 64-pin EPAD-TQFP
with the EPAD attached to a metal pad on the component
side of the board for improved heat dissipation. The two
high-speed clock inputs, LVDS_CLK and LVPECL_CLK are
brought out to SMA connectors through matched length
dierential traces. The LVPECL_CLK input is AC-coupled
on the board and biased with Thevenin Equivalent resistor
networks to supply the correct bias for the LVDS and
LVPECL levels. Three of the outputs, Q0, Q11, and Q17,
are brought out through SMA connectors from three sides
of the chip. These LVPECL outputs are AC-coupled for
direct connection to an oscilloscope with a standard 50
termination to Ground. The LVTTL/CMOS control inputs
OE and CLK_SEL are connected to a dip switch on the
board to allow the different modes to be conveniently
selected.
DC-Coupled Evaluation Board
For DC-coupled operation, the board can be modied to
use a direct connection to the dierential inputs from a
signal source such as an Agilent 8133A signal generator.
The common mode voltage levels for the inputs would need
to be set differently for the LVDS and LVPECL inputs. These
levels are specied in the “DC-Coupled Evaluation Board
Set-Up.” The outputs will still be congured for AC-coupled
operation.
Step-by-step instructions for modifying an AC-coupled
evaluation board for DC-coupled operation is described in
“Modifying your AC-coupled board for DC-coupled Operation
section of this document.
64
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
VCCO
NC
NC
VCCI
LVDS_CLK
/LVDS_CLK
CLK_SEL
LVPECL_CLK
/LVPECL_CLK
GND
OE
NC
NC
Q21
/Q21
VCCO
VCCO
Q7
/Q7
Q8
/Q8
Q9
/Q9
Q10
/Q10
Q11
/Q11
Q12
/Q12
Q13
/Q13
VCCO
S39
S38
VCCO
Q0
/Q0
Q1
/Q1
Q2
/Q2
Q3
/Q3
Q4
/Q4
Q5
/Q5
Q6
/Q6
VCCO
VCCO
Q20
/Q20
Q19
/Q19
Q18
/Q18
Q17
/Q17
Q16
/Q16
Q15
/Q15
Q14
/Q14
VCCO
S62S63
S5
S6
S8
S5
S25S24
U1 SY89825U
V
CC
V
CC
R16
82.5
R18
130
R15
82.5
R17
130
C5
C6
S1
S2
S3
S4
S5
S6
V
CC
R2
10k
R3
10k
V
CCI
V
CCI
C29
0.01µF
C38
6.8µF
V
CCO
V
CCO
C28
0.01µF
C39
6.8µF
SW Dip-6
C16
0.1µF
C15
0.1µF
C9
0.1µF
C10
0.1µF
R30
180
R29
180
R37
180
R38
180
R32
180
R31
180
C12
0.1µF
C11
0.1µF
C3
C4
V
CCO
or V
CCI
C17, C18, C19, C20, C21,
C22, C25, C26, C27 are 0.1µF
at power pins 1, 4, 16, 17, 32,
33, 48, 49, 64, respectively.
Figure 1. AC-Coupled Evaluation Board Schematic
I/O VCCI VCCO GND
AC-Coupled Input/AC-Coupled Output +3.3V +3.3V 0V
Table 1. Evaluation Board Power Supply Connections
3
SY89825U Evaluation BoardMicrel
M9999-070104
hbwhelp@micrel.com or (408) 955-1690
EVALUATION BOARD SET-UP
AC-coupled I/O allows the evaluation board to operate
from a single power supply and interface directly to a 50
scope. The following steps describe the procedure for setting
up the evaluation board.
1. Set up a voltage source for 3.3V and turn o the
supply.
2. Connect the GND terminal to the negative side of
the power supply. This is the 0V ground potential.
3. Short the VCCI and VCCO terminals together on the
board and connect to the positive side of the 3.3V
supply. Turn on the power supply and verify that
the power supply current is <150mA.
4. Turn off the power supply.
5. Using a dierential signal source set the amplitude
of each side of the dierential pair to be 400mV
(800mV measured dierentially). Set the oset to
+1.2V. Turn o or disable the outputs of the signal
source.
6. Using equal length 50 impedance coaxial cables,
connect the signal source to the LVDS_CLK inputs
on the evaluation board (S5 and S6).
7. Using a second dierential signal source set the
amplitude of each side of the dierential pair to be
800mV (1600mV measured dierentially). Set the
oset to a positive value, the value of this oset is
not critical, as the AC-coupled inputs will be
automatically biased to the correct oset. Turn o
or disable the outputs of the signal source.
Switch Position Signal Name SY89825U Pin
SW1-1 — —
SW1-2 CLK_SEL 7
SW1-3 OE 11
SW1-4 — —
SW1-5 — —
SW1-6 — —
Table 1. SW1 (DIP-6) Switch Settings
Note: Switch in ON position sets signal LOW.
8. Using equal length 50 impedance coaxial cables,
connect the signal source to the LVPECL_CLK
inputs on the evaluation board (S8 and S9).
9. Using equal length 50 impedance coaxial cables,
connect the outputs of the evaluation board (S24,
S25, S38, S39, S62 and S63) to the oscilloscope or
other measurement device that has an internal 50
termination. If not all outputs are to be monitored,
the unused outputs must be terminated with 50 to
ground.
10. Turn on the power.
11. Enable the signal source and monitor the outputs.
EVALUATION BOARD LAYOUT
PC Board Layout
The evaluation boards are constructed with FRA material
and are coplanar in design and fabricated to minimize noise,
achieve high bandwidth and minimize crosstalk.
L1 Signal/GND
L2 Impedance GND
L3 VCCO Power
L4 VCCI Power
L5 GND
L6 Signal/GND
Table 2. Layer Stack


Product specificaties

Merk: Microchip
Categorie: Niet gecategoriseerd
Model: SY89825U

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