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83940BYLF

P1-P3P4-P6P7-P9P10-P12P13-P13
83940BY www.idt.com REV. B JANUARY 31, 2014
7
Low Skew, 1-to-18 LVPECL-to-
LVCMOS/LVTTL Fanout Buffer
ICS83940
PRODUCT DISCONTINUATION NOTICE - LAST TIME BUY EXPIRES JANUARY 27, 2015
APPLICATION INFORMATION
Figure 1
shows how the differential input can be wired to accept
single ended levels. The reference voltage V_REF = V
DD
/2 is
generated by the bias resistors R1, R2 and C1. This bias circuit
should be located as close as possible to the input pin. The ratio
FIGURE 1. SINGLE ENDED SIGNAL DRIVING DIFFERENTIAL INPUT
of R1 and R2 might need to be adjusted to position the V_REF in
the center of the input voltage swing. For example, if the input
clock swing is only 2.5V and V
DD
= 3.3V, V_REF should be 1.25V
and R2/R1 = 0.609.
WIRING THE DIFFERENTIAL INPUT TO ACCEPT SINGLE ENDED LEVELS
VDD
R2
1K
V_REF
C1
0.1u
R1
1K
Single Ended Clock Input
PCLK
nPCLK
83940BY www.idt.com REV. B JANUARY 31, 2014
8
Low Skew, 1-to-18 LVPECL-to-
LVCMOS/LVTTL Fanout Buffer
ICS83940
PRODUCT DISCONTINUATION NOTICE - LAST TIME BUY EXPIRES JANUARY 27, 2015
LVPECL CLOCK INPUT INTERFACE
The PCLK /nPCLK accepts LVPECL, CML, SSTL and other
differential signals. Both V
SWING
and V
OH
must meet the V
PP
and V
CMR
input requirements.
Figures 2A to 2E
show interface
examples for the PCLK/nPCLK input driven by the most
common driver types. The input interfaces suggested here
are examples only. If the driver is from another vendor, use
their termination recommendation. Please consult with the
vendor of the driver component to confirm the driver
termination requirements.
FIGURE 2A. PCLK/NPCLK INPUT DRIVEN
BY A CML DRIVER
FIGURE 2B. PCLK/NPCLK INPUT DRIVEN
BY AN SSTL DRIVER
FIGURE 2C. PCLK/NPCLK INPUT DRIVEN
BY A 3.3V LVPECL DRIVER
FIGURE 2D. PCLK/NPCLK INPUT DRIVEN
BY
A 3.3V LVDS DRIVER
PCLK/nPCLK
2.5V
Zo = 60 Ohm
SSTL
HiPerClockS
PCLK
nPCLK
R2
120
3.3V
R3
120
Zo = 60 Ohm
R1
120
R4
120
2.5V
FIGURE 2E. PCLK/NPCLK INPUT DRIVEN
BY
A 3.3V LVPECL DRIVER WITH AC COUPLE
HiPerClockS
PCLK
nPCLK
PCLK/nPCLK
3.3V
R2
50
R1
50
3.3V
Zo = 50 Ohm
CML
3.3V
Zo = 50 Ohm
3.3V
HiPerClockS
PCLK
nPCLK
R2
84
R3
125
Input
Zo = 50 Ohm
R4
125
R1
84
LVPECL
3.3V
3.3V
Zo = 50 Ohm
C2
R2
1K
R5
100
Zo = 50 Ohm
3.3V
3.3V
C1
R3
1K
LVDS
R4
1K
HiPerClockS
PCLK
nPCLK
R1
1K
Zo = 50 Ohm
3.3V
PCLK/nPCLK
3.3V
R5
100 - 200
3.3V
3.3V
HiPerClockS
PCLK
nPCLK
R1
125
PCLK/nPCLK
R2
125
R3
84
C1
C2
Zo = 50 Ohm
R4
84
Zo = 50 Ohm
R6
100 - 200
3.3V LVPECL
83940BY www.idt.com REV. B JANUARY 31, 2014
9
Low Skew, 1-to-18 LVPECL-to-
LVCMOS/LVTTL Fanout Buffer
ICS83940
PRODUCT DISCONTINUATION NOTICE - LAST TIME BUY EXPIRES JANUARY 27, 2015
RELIABILITY INFORMATION
TRANSISTOR COUNT
The transistor count for ICS83940 is: 820
TABLE 6. θ
JA
VS
. AIR FLOW TABLE FOR 32 LEAD LQFP
θθ
θθ
θ
JA
by Velocity (Linear Feet per Minute)
0 200 500
Single-Layer PCB, JEDEC Standard Test Boards 67.8°C/W 55.9°C/W 50.1°C/W
Multi-Layer PCB, JEDEC Standard Test Boards 47.9°C/W 42.1°C/W 39.4°C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
P1-P3P4-P6P7-P9P10-P12P13-P13

83940BYLF

Mfr. #:
Buy 83940BYLF
Manufacturer:
Description:
IC CLK BUFFER 2:18 250MHZ 32TQFP
Lifecycle:
New from this manufacturer.
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