Low Voltage, Low Skew,
PCI / PCI-X Clock Generator
8761I
Data Sheet
©2016 Integrated Device Technology, Inc Revision C January 25, 20161
GENERAL DESCRIPTION
The 8761I is a low voltage, low skew PCI / PCI-X clock
generator . The 8761I has a selectable REF_CLK or
crystal input. The REF_CLK input accepts LVCMOS or
LVTTL input levels. The 8761I has a fully integrated PLL
along with frequency confi gurable clock and feedback out-
puts for multiplying and regenerating clocks with “zero de-
lay”. Using a 20MHz or 25MHz crystal or a 33.333MHz or
66.666MHz reference frequency, the 8761I will generate output
frequencies of 33.333MHz, 66.666MHz, 100MHz and
133.333MHz simultaneously.
The low impedance LVCMOS/LVTTL outputs of the 8761I
are designed to drive 50Ω series or parallel terminated
transmission lines.
FEATURES
Fully integrated PLL
Seventeen LVCMOS/LVTTL outputs,
15Ω typical output impedance
Selectable crystal oscillator interface
or LVCMOS/LVTTL REF_CLK
Maximum output frequency: 166.67MHz
Maximum crystal input frequency: 40MHz
Maximum REF_CLK input frequency: 83.33MHz
Individual banks with selectable output dividers
for generating 33.333MHz, 66.66MHz, 100MHz
and 133.333MHz simultaneously
Separate feedback control for generating PCI / PCI-X
frequencies from a 20MHz or 25MHz crystal or 33.333MHz
or 66.666MHz reference frequency
Cycle-to-cycle jitter: 70ps (maximum)
Period jitter, RMS: 17ps (maximum)
Output skew: 250ps (maximum)
Bank skew: 50ps (maximum)
Static phase offset: 0 ± 150ps (maximum)
Full 3.3V or 3.3V core, 2.5V multiple output supply modes
-40°C to 85°C ambient operating temperature
Available in both standard and lead-free RoHS-compliant
packages
BLOCK DIAGRAM
P
IN ASSIGNMENT
64-Lead LQFP
10mm x 10mm x 1.4mm package body
Y package
Top View
8761I Data Sheet
©2016 Integrated Device Technology, Inc Revision C January 25, 20162
TABLE 1. PIN DESCRIPTIONS
Number Name Type Description
1 REF_CLK Input Pulldown Reference clock input. LVCMOS / LVTTL interface levels.
2, 16, 17, 21,
25, 29, 33, 48,
52, 56, 60, 64
GND Power Power supply ground.
3, 4 XTAL1, XTAL2 Input Crystal oscillator interface. XTAL1 is the input. XTAL2 is the output.
5, 9, 40, 44 V
DD
Power Core supply pins.
6 XTAL_SEL Input Pullup
Selects between crystal oscillator or reference clock as the PLL refer-
ence source. Selects XTAL inputs when HIGH. Selects REF_CLK when
LOW. LVCMOS / LVTTL interface levels.
7 PLL_SEL Input Pullup
Selects between PLL and bypass mode. When HIGH, selects PLL.
When LOW, selects reference clock. LVCMOS / LVTTL interface levels.
8V
DDA
Power Analog supply pin. See Applications Note for fi ltering.
10, 11
D_SELC0,
D_SELC1
Input Pulldown
Selects divide value for Bank C outputs as described in Table 3.
LVCMOS / LVTTL interface levels.
12 OEC Input Pullup
Determines state of Bank C outputs. When HIGH, outputs are enabled.
When LOW, outputs are disabled. LVCMOS / LVTTL interface levels.
13 OEA Input Pullup
Determines state of Bank A outputs. When HIGH, outputs are enabled.
When LOW, outputs are disabled. LVCMOS / LVTTL interface levels.
14, 15
D_SELA0,
D_SELA1
Input Pulldown
Selects divider value for Bank A outputs as described in Table 3.
LVCMOS / LVTTL interface levels.
18, 20,
22, 24
QA0, QA1,
QA2, QA3
Output
Bank A clock outputs. 15
Ω typical output impedance.
LVCMOS / LVTTL interface levels.
19, 23 V
DDOA
Power Output supply pins for Bank A outputs.
26, 28,
30, 32
QB0, QB1,
QB2, QB3
Output
Bank B clock outputs. 15
Ω typical output impedance.
LVCMOS / LVTTL interface levels.
27, 31 V
DDOB
Power Output supply pins for Bank B outputs.
34, 35
D_SELB1,
D_SELB0
Input Pulldown
Selects divider value for Bank B outputs as described in Table 3.
LVCMOS / LVTTL interface levels.
36 OEB Input Pullup
Determines state of Bank B outputs. When HIGH, outputs are enabled.
When LOW, outputs are disabled. LVCMOS / LVTTL interface levels.
37 OED Input Pullup
Determines state of Bank D outputs. When HIGH, outputs are enabled.
When LOW, outputs are disabled. LVCMOS / LVTTL interface levels.
38, 39
D_SELD1,
D_SELD0
Input Pulldown
Selects divider value for Bank D outputs as described in Table 3.
LVCMOS / LVTTL interface levels.
41 MR Input Pulldown
Active HIGH Master reset. When logic HIGH, the internal dividers
are reset causing the outputs to go low. When logic LOW, the
internal dividers and the outputs are enabled.
LVCMOS / LVTTL interface levels.
42 FBDIV_SEL1 Input Pulldown
Selects divider value for bank feedback output as described in Table 3.
LVCMOS / LVTTL interface levels.
43 FBDIV_SEL0 Input Pullup
Selects divider value for bank feedback output as described in Table 3.
LVCMOS / LVTTL interface levels.
45 FB_IN Input Pulldown
Feedback input to phase detector for generating clocks with
“zero delay”. LVCMOS / LVTTL interface levels.
8761I Data Sheet
©2016 Integrated Device Technology, Inc Revision C January 25, 20163
TABLE 2. PIN CHARACTERISTICS
TABLE 3A. OUTPUT CONTROL PIN FUNCTION TABLE
Inputs Outputs
MR OEA OEB OEC OED QA0:QA3 QB0:QB3 QC0:QC3 QD0:QD3
1 1 1 1 1 LOW LOW LOW LOW
0 1 1 1 1 Active Active Active Active
X 0 0 0 0 HiZ HiZ HiZ HiZ
TABLE 3B. OPERATING MODE FUNCTION TABLE
Inputs
Operating Mode
PLL_SEL
0 Bypass
1 PLL
TABLE 3C. PLL INPUT FUNCTION TABLE
Inputs
XTAL_SEL PLL Input
0 REF_CLK
1 XTAL Oscillator
Number Name Type Description
46 V
DDOFB
Power Output supply pin for FB_Out output.
47 FB_OUT Output
Feedback output. Connect to FB_IN. 15Ω typical output impedance.
LVCMOS / LVTTL interface levels.
49, 51,
53, 55
QD3, QD2,
QD1, QD0
Output
Bank D clock outputs. 15Ω typical output impedance.
LVCMOS / LVTTL interface levels.
50, 54 V
DDOD
Power Output supply pins for Bank D outputs.
57, 59,
61, 63
QC3, QC2,
QC1, QC0
Output
Bank C clock outputs. 15
Ω typical output impedance.
LVCMOS / LVTTL interface levels.
58, 62 V
DDOC
Power Output supply pins for Bank C outputs.
NOTE:
Pullup and Pulldown refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
Symbol Parameter Test Conditions Minimum Typical Maximum Units
C
IN
Input Capacitance 4 pF
R
PULLUP
Input Pullup Resistor 51
kΩ
R
PULLDOWN
Input Pulldown Resistor 51
kΩ
C
PD
Power Dissipation Capacitance
(per output); NOTE 1
V
DD
, V
DDA
= 3.465V; V
DDOx
= 3.465V 9 pF
V
DD
, V
DDA
= 3.465V; V
DDOx
= 2.625V 11 pF
R
OUT
Output Impedance 15
Ω
NOTE 1: V
DDOx
denotes V
DDOA
, V
DDOB
, V
DDOC
, V
DDOD
, V
DDOFB
.

8761CYILF

Mfr. #:
Manufacturer:
IDT
Description:
Clock Generators & Support Products 17 LVCMOS OUT CLOCK GEN
Lifecycle:
New from this manufacturer.
Delivery:
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