8745B-21 Datasheet, PDF (1/19 Pages) Integrated Device Technology – Differential CLK

1:1 Differential-to-LVDS Zero Delay
Clock Generator
8745B-21
DATA SHEET
General Description
The 8745B-21 is a highly versatile 1:1 LVDS Clock Generator. The
8745B-21 has a fully integrated PLL and can be configured as zero
delay buffer, multiplier or divider, and has an output frequency range
of 31.25MHz to 700MHz. The Reference Divider, Feedback Divider
and Output Divider are each programmable, thereby allowing for the
following output-to-input frequency ratios: 8:1, 4:1, 2:1, 1:1, 1:2, 1:4,
1:8. The external feedback allows the device to achieve “zero delay”
between the input clock and the output clock. The PLL_SEL pin can
be used to bypass the PLL for system test and debug purposes. In
bypass mode, the reference clock is routed around the PLL and into
the internal output dividers.
Features
• One differential LVDS output designed to meet
or exceed the requirements of ANSI TIA/EIA-644
One differential feedback output pair
• Differential CLK, nCLK input pair
• CLKx, nCLKx pair can accept the following differential
input levels: LVPECL, LVDS, LVHSTL, HCSL, SSTL
• Output frequency range: 31.25MHz to 700MHz
• Input frequency range: 31.25MHz to 700MHz
• VCO range: 250MHz to 700MHz
• External feedback for “zero delay” clock regeneration
with configurable frequencies
• Programmable dividers allow for the following output-to-input
frequency ratios: 8:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:8
• Cycle-to-cycle jitter: 30ps (maximum)
• Output skew: 35ps (maximum)
• Static phase offset: 25ps ± 125ps
• Full 3.3V supply voltage
• 0°C to 70°C ambient operating temperature
• Available in lead-free (RoHS 6) package
Block Diagram
PLL_SEL ^Pullup
CLK ^Pulldown
nCLK ^Pullup
÷1, ÷2, ÷4, ÷8,
÷16, ÷32, ÷64
0
1
PLL
FB_IN ^Pulldown
nFB_IN ^Pullup
8:1, 4:1, 2:1, 1:1,
1:2, 1:4, 1:8
SEL0 ^Pulldown
SEL1 ^Pulldown
SEL2 ^Pulldown
SEL3 ^Pulldown
MR ^Pulldown
8745B-21 Rev D 2/17/15
Q
nQ
QFB
nQFB
Pin Assignment
CLK 1
nCLK 2
MR 3
nFB_IN 4
FB_IN 5
SEL2 6
VDDO 7
nQFB 8
QFB 9
GND 10
20 SEL1
19 SEL0
18 VDD
17 PLL_SEL
16 VDDA
15 SEL3
14 GND
13 Q
12 nQ
11 VDDO
8745B-21
20-Lead SOIC
7.5mm x 12.8mm x 2.3mm package body
M Package
Top View
1
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