ICS873990
L
OW
V
OLTAGE
, LVCMOS/
C
RYSTAL
-
TO
-LVPECL/ECL C
LOCK
G
ENERATOR
G
ENERAL
D
ESCRIPTION
The ICS873990 is a low voltage, low skew, 3.3V LVPECL/
ECL Clock Generator. The ICS873990 has two selectable
clock inputs. The XTAL1 and XTAL2 are used to interface to
a crystal and the TEST_CLK pin can accept a LVCMOS or
LVTTL input. This device has a fully integrated PLL along
with frequency configurable outputs. An external feedback
input and output regenerates clocks with “zero delay”.
The four independent banks of outputs each have their own
output dividers, which allow the device to generate a
multitude of different bank frequency ratios and output-to-
input frequency ratios. The output frequency range is 25MHz
to 400MHz and the input frequency range is 6.25MHz to
125MHz. The PLL_SEL input can be used to bypass the
PLL for test and system debug purposes. In bypass mode,
the input clock is routed around the PLL and into the
internal output dividers.
The ICS873990 also has a SYNC output which can be used
for system synchronization purposes. It monitors Bank A
and Bank C outputs for coincident rising edges and signals
a pulse per the timing diagrams in this data sheet. This
feature is used primarily in applications where Bank A and
Bank C are
running at different frequencies, and is particularly useful
when they are running at non-integer multiples of each
other.
Example Applications:
1. Line Card Multiplier: Multiply 19.44MHz from a back-plane
to 77.76MHz on the line card ASIC and Serdes.
2. Zero Delay Buffer: Fan out up to thirteen 100MHz copies
from a reference clock to multiple processing units on an
embedded system.
nQB3
QB3
V
CCO
nQA0
QA0
nQA1
QA1
nQA2
QA2
nQA3
QA3
SYNC_SEL
VCO_SEL
F
EATURES
•
14 differential LVPECL outputs
•
Selectable crystal oscillator interface or TEST_CLK inputs
•
TEST_CLK accepts the following input levels:
LVCMOS, LVTTL
•
Output frequency: 400MHz (maximum)
•
Crystal input frequency range: 10MHz to 25MHz
•
VCO range: 200MHz to 800MHz
•
Output skew: 250ps (maximum)
•
Cycle-to-cyle jitter: ±50ps (typical)
•
LVPECL mode operating voltage supply range:
V
CC
= 3.135V to 3.465V, V
EE
= 0V
•
ECL mode operating voltage supply range:
V
CC
= 0V, V
EE
= -3.465V to -3.135V
•
0°C to 70°C ambient operating temperature
•
Industrial temperature available upon request
•
Lead-Free package fully RoHS compliant
P
IN
A
SSIGNMENT
FSEL0
FSEL1
FSEL2
39 38 37 36 35 34 33 32 31 30 29 28 27
40
26
41
42
43
44
45
46
47
48
49
50
51
52
1
V
EE
FSEL3
nQC2
nQB2
nQB1
nQB0
V
CCO
QC2
QB2
QB1
QB0
QC1
nQC1
QC0
nQC0
V
CCO
QD1
nQD1
QD0
nQD0
V
CCO
QFB
nQFB
V
CCA
25
24
23
22
21
ICS873990
20
19
18
17
16
15
14
2 3
MR
PLL_EN
4
REF_SEL
5
FSEL_FB2
6
FSEL_FB1
7 8 9 10 11 12 13
FSEL_FB0
XTAL_OUT
TEST_CLK
V
CC
EXT_FB
nEXT_FB
XTAL_IN
52-Lead LQFP
10mm x 10mm x 1.4mm package body
Y package
Top View
873990AY
www.idt.com
1
REV. B JULY 25, 2010
ICS873990
L
OW
V
OLTAGE
, LVCMOS/
C
RYSTAL
-
TO
-LVPECL/ECL C
LOCK
G
ENERATOR
T
ABLE
1. P
IN
D
ESCRIPTIONS
Number
1
2
Name
V
EE
MR
Type
Power
Input
Description
Negative supply pin.
Active High Master Reset. When logic HIGH, the internal dividers are
reset causing the true outputs (Qx) to go low and the inver ted outputs
Pulldown
(nQx) to go high. When logic LOW, the internal dividers and the
outputs are enabled. LVCMOS/LVTTL interface levels.
PLL enable pin. When logic LOW, PLL is enabled. When logic HIGH,
Pulldown
PLL is in bypass mode. LVCMOS/LVTTL interface levels.
Selects between the different reference inputs as the PLL reference
Pulldown source. When logic LOW, selects cr ystal inputs. When logic HIGH,
selects TEST_CLK. LVCMOS/LVTTL interface levels.
Pulldown Feedback frequency select pins. LVCMOS/LVTTL interface levels.
Pulldown LVCMOS/LVTTL test clock input.
Cr ystal oscillator interface. XTAL_IN is the input, XTAL_OUT is the
output.
Core supply pin.
Pulldown External feedback input.
Pullup/ External feedback input. V /2 default when left floating.
CC
Pulldown
Analog supply pin.
Differential feedback output pair. LVPECL interface levels.
Output supply pins.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Pulldown Frequency select pins. LVCMOS/LVTTL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Sync output select pin. When LOW, the SYNC output follows the
Pulldown
timing diagram (page 5). When HIGH, QD output follows QC output.
Pulldown Selects VCO range. LVCMOS/LVTTL interface levels.
3
4
5
6
7
8
9, 10
11
12
13
14
15,
16
17, 22, 30, 42
18, 1 9
20, 21
23, 24
25, 26
27
33
36
39
28, 29
31, 32
34, 35
37, 38
40, 41
43, 44
45, 46
47, 48
49, 50
51
52
PLL_EN
REF_SEL
FSEL_FB2
FSEL_FB1
FSEL_FB0
TEST_CLK
XTAL_IN,
XTAL_OUT
V
CC
EXT_FB
nEXT_FB
V
CCA
nQFB,
QFB
V
CCO
nQD0, QD0
nQD1, QD1
nQC0, QC0
nQC1, QC1
FSEL3
FSEL2
FSEL1
FSEL0
nQC2, QC2
nQB0, QB0
nQB1, QB1
nQB2, QB2
nQB3, QB3
nQA0, QA0
nQA1, QA1
nQA2, QA2
nQA3, QA3
SYNC_SEL
VCO_SEL
Input
Input
Input
Input
Input
Power
Input
Input
Power
Output
Power
Output
Output
Output
Output
Input
Output
Output
Output
Output
Output
Output
Output
Output
Output
Input
Input
NOTE:
Pullup and Pulldown
refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
873990AY
www.idt.com
3
REV. B JULY 25, 2010
微控制器 MCU
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