ICST M2085 Vcso fec pll with autoswitch for sonet/otn Datasheet

M2080/81/82
M2085/86/87
Preliminary Information
Integrated
Circuit
Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
PIN ASSIGNMENT (9 x 9 mm SMT)
FIN_SEL1
GND
P_SEL2
DIF_REF0
nDIF_REF0
REF_SEL
DIF_REF1
nDIF_REF1
VCC
GENERAL DESCRIPTION
27
26
25
24
23
22
21
20
19
The M2080/81/82 and M2085/86/87 are VCSO (Voltage
Controlled SAW Oscillator) based
clock PLLs designed for FEC clock
ratio translation in 10Gb optical
systems such as OC-192 or 10GbE.
They support FEC (Forward Error
Correction) clock multiplication
ratios, both forward (mapping) and
inverse (de-mapping). Multiplication ratios are
pin-selected from pre-programming look-up tables.
FIN_SEL0
FEC_SEL0
FEC_SEL1
LOL
NBW
VCC
DNC
DNC
DNC
FEATURES
◆ LVPECL clock output (CML and LVDS options available)
◆ Pin-selectable PLL divider ratios support FEC ratios
• M2080/85: OTU1 (255/238) and OTU2 (255/237) Mapping
• M2081/86: OTU1 (238/255) or OTU2 (237/255) De-mapping
• M2082/87: OTU1 (238/255) and OTU2 (237/255) De-mapping
◆ Loss of Lock (LOL) output pin; Narrow Bandwidth
control input (NBW pin)
◆ AutoSwitch (AUTO pin) - automatic (non-revertive)
reference clock reselection upon clock failure
◆ Acknowledge pin (REF_ACK pin) indicates the actively
selected reference input
◆ Options for Hitless Switching (HS) with or without
Phase Build-out (PBO) to enable SONET (GR-253) /SDH
(G.813) MTIE and TDEV compliance during reselection
◆ Single 3.3V power supply
M2080
Series
(Top View)
GND
GND
GND
OP_IN
nOP_OUT
nVC
VC
OP_OUT
nOP_IN
◆ Low phase jitter < 0.5 ps rms typical
(12kHz to 20MHz or 50kHz to 80MHz)
◆ Reference clock inputs support differential LVDS,
LVPECL, as well as single-ended LVCMOS, LVTTL
P_SEL0
P_SEL1
nFOUT
FOUT
GND
REF_ACK
AUTO
VCC
GND
18
17
16
15
14
13
12
11
10
1
2
3
4
5
6
7
8
9
◆ Integrated SAW delay line; Output of 15 to 700 MHz *
28
29
30
31
32
33
34
35
36
Figure 1: Pin Assignment
Example I/O Clock Frequency Combinations
Using M2081-11-622.0800 FEC De-Map Ratios
FEC De-Map
PLL Ratio
Mfec / Rfec
Base Input Rate 1
(MHz)
1/1
622.0800
237/255
666.5143
238/255
Output Clock
(either output)
MHz
622.08
or
155.52
669.3266
Table 1: Example I/O Clock Frequency Combinations
Note 1: Input reference clock can be the base frequency shown
divided by “Mfin” (as shown in Tables 3 and 4 on pg. 3).
* Specify VCSO center frequency at time of order.
◆ Small 9 x 9 mm SMT (surface mount) package
SIMPLIFIED BLOCK DIAGRAM
Loop Filter
M2080 Series
NBW
PLL
Phase
Detector
MUX
DIF_REF0
nDIF_REF0
0
DIF_REF1
nDIF_REF1
1
Rfec
Div
VCSO
REF_ACK
REF_SEL
Mfec Div
0
LOL Phase
Detector
1
Mfin Divider
(1, 4, 8, 32 or
1, 4, 8, 16)
LOL
AUTO
Auto
Ref Sel
P Divider
(1, 4, 8, 32 or TriState)
FEC_SEL1:0
FIN_SEL1:0
2
FOUT
nFOUT
Tri-state
Mfec / Rfec Divider
LUT
2
Mfin Divider
LUT
3
P_SEL2:0
P Divider
LUT
Figure 2: Simplified Block Diagram
M2080/81/82 M2085/86/87 Datasheet Rev 0.4
Revised 30Jul2004
M2080/81/82 VCSO FEC PLL with AutoSwitch for SONET/OTN
Integrated Circuit Systems, Inc.
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M2080/81/82, M2085/86/87
Integrated
Circuit
Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
PIN DESCRIPTIONS
Number
1, 2, 3, 10, 14, 26
4
9
5
8
6
7
11, 19, 33
Name
GND
OP_IN
nOP_IN
nOP_OUT
OP_OUT
nVC
VC
VCC
I/O
Configuration
Input
Power
Input
13
REF_ACK
Output
15
16
17
18
25
FOUT
nFOUT
P_SEL1
P_SEL0
P_SEL2
Output
20
nDIF_REF1
22
REF_SEL
23
nDIF_REF0
24
DIF_REF0
27
28
29
30
FIN_SEL1
FIN_SEL0
FEC_SEL0
FEC_SEL1
External loop filter connections.
See Figure 5, External Loop Filter, on pg. 9.
Output
AUTO
DIF_REF1
Power supply ground connections.
Input
12
21
Description
Ground
Input
Input
Input
Input
Power supply connection, connect to +3.3V.
1
Internal pull-down resistor
No internal terminator
Clock output pair. Differential LVPECL.
, P divider selection. LVCMOS/LVTTL. See Table 8,
Internal pull-down resistor1 Post-PLL
P Divider Look-Up Table (LUT), on pg. 4.
Biased to Vcc/2 2
1
Internal pull-down resistor
Internal pull-down resistor1
Biased to Vcc/2 2
Internal pull-down resistor
Input
Input
31
LOL
Output
32
NBW
Input
34, 35, 36
DNC
Automatic/manual reselection mode for clock input:
Logic 1 automatic reselection upon clock failure
(non-revertive)
Logic 0 manual selection only (using REF_SEL)
Reference Acknowledgement pin for input mux state; outputs
the currently selected reference input pair:
Logic 1 indicates nDIF_REF1, DIF_REF1
Logic 0 indicates nDIF_REF0, DIF_REF0
1
Reference clock input pair 1. Differential LVPECL or LVDS.
Resistor bias on inverting terminal supports TTL or LVCMOS.
Reference clock input selection. LVCMOS/LVTTL:
Logic 1 selects DIF_REF1, nDIF_REF1.
Logic 0 selects DIF_REF0, nDIF_REF0.
Reference clock input pair 0. Differential LVPECL or LVDS.
Resistor bias on inverting terminal supports TTL or LVCMOS.
Internal pull-down resistor1 Input clock frequency selection. LVCMOS/LVTTL. See
Tables 3 and 4 Mfin Divider Look-Up Tables (LUT) on pg. 3.
and Rfec divider value selection. LVCMOS/ LVTTL.
Internal pull-down resistor1 Mfec
See Tables 5, 6, and 7 on pg. 3.
Internal pull-UP resistor1
Loss of Lock indicator output. Asserted when internal PLL is
not tracking the input reference for frequency and phase. 3
Logic 1 indicates loss of lock.
Logic 0 indicates locked condition.
Narrow Bandwidth enable. LVCMOS/LVTTL:
Logic 1 - Narrow loop bandwidth, RIN = 2100kΩ.
Logic 0 - Wide bandwidth, RIN = 100kΩ.
Do Not Connect.
Table 2: Pin Descriptions
Note 1: For typical values of internal pull-down and pull-UP resistors, see DC Characteristics on pg. 11.
Note 2: Biased toVcc/2, with 50kΩ to Vcc and 50kΩ to ground. See Differential Inputs Biased to VCC/2 on pg. 11.
Note 3: See LVCMOS Outputs in DC Characteristics on pg. 11.
M2080/81/82 M2085/86/87 Datasheet Rev 0.4
Integrated Circuit Systems, Inc.
●
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M2080/81/82, M2085/86/87
Integrated
Circuit
Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
DETAILED BLOCK DIAGRAM
RLOOP
CLOOP
RPOST
External
Loop Filter
Components
CPOST
CPOST
RLOOP
RPOST
CLOOP
M2080 Series
OP_IN
nOP_IN
OP_OUT
nOP_OUT
nVC
VC
NBW
PLL
Phase
Detector
MUX
DIF_REF0
nDIF_REF0
0
DIF_REF1
nDIF_REF1
1
RIN
RIN
Loop Filter
Amplifier
REF_ACK
REF_SEL
Phase
Locked
Loop
(PLL)
Rfec
Div
1
Phase
Shifter
VCSO
Mfin Divider
Mfec Div
0
SAW Delay Line
(1, 4, 8, 32) or
(1, 4, 8, 16)
LOL
Phase
Detector
AUTO
Auto
Ref Sel
FEC_SEL1:0
FIN_SEL1:0
P_SEL2:0
LOL
2
Mfec / Rfec
Divider LUT
2
FOUT
nFOUT
P Divider
(1, 4, 8, 32,
or TriState)
Mfin Divider
LUT
3
CML or PECL
Options
P Divider
LUT
Figure 3: Detailed Block Diagram
DIVIDER SELECTION TABLES
Mfec and Rfec Divider Look-Up Tables (LUTs)
Mfin Divider Look-Up Tables (LUT)
The FEC_SEL pins select the Mfec/Rfec divider ratio. The
look-up tables vary by device variant. The Mfec and
Rfec values also establish phase detector frequency.
A lower phase detector frequency improves jitter
tolerance and lowers loop bandwidth.
The FIN_SEL1:0 pins select the feedback divider value
(“Mfin”), which sets the overall PLL ratio range. Since
the VCSO frequency is fixed, this allows input reference
selection. The look-up tables vary by device variant.
M2080/81/82: Mfin Value LUT (Includes Divide by 32)
FIN_SEL1:0
0
0
1
1
0
1
0
1
Mfin Sample Input Reference Freq. (MHz) Options
For M20801, M2081 & M20822
Value
32
8
4
1
M2080/85: FEC Map LUT, OTU1 (255/238) and OTU2 (255/237)
FEC_SEL1:0
Mfec Rfec
1 0
For M2080 or M2085 with Fvcso = 666.5143 (OTU1 FEC rate):
0
0
19.44
77.76
155.52
622.08
1
1
Note 1: For M2080 with Fvcso = 666.5143 or 669.3266
Note 2: For M2081 and M2082 with Fvcso = 622.0800.
255/238 OC-48 to OTU1 encode
OTU1 repeater or jitter attenuator
622.08 666.5143
666.5143 666.5143
0
1
85 79
85 85
255/237 OC-192 to OTU2 encode
OTU2 repeater or jitter attenuator
622.08 669.3266
669.3266 669.3266
M2081/86: FEC De-map LUT, OTU1 (238/255) or OTU2 (237/255)
Use this option for either OTU1 or OTU2 de-mapping
applications, but not both.
Mfin Sample Input Reference Freq. (MHz) Options
FIN_SEL1:0
For M20851, M2086 & M20872
Value
16
8
4
1
15 14
15 15
Table 5: M2080/85: FEC Map LUT, OTU1 (255/238) and OTU2 (255/237)
M2085/86/87: Mfin Value LUT (Includes Divide by 16)
0
1
0
1
0
1
For M2080 or M2085 with Fvcso = 669.3266 (OTU2 FEC rate):
Table 3: M2080/81/82: Mfin Value LUT (Includes Divide by 32)
0
0
1
1
Fvcso =
Base Input Base
Output
Rate (MHz) Rate (MHz)
Description
38.88
77.76
155.52
622.08
FEC_SEL1:0
Mfec Rfec
1 0
Fvcso =
Base Input Base
Output
Rate (MHz) Rate (MHz)
Description
For M2081 or M2086 with Fvcso = 622.08 (OTU1 or OTU2 FEC rate):
Table 4: M2085/86/87: Mfin Value LUT (Includes Divide by 16)
Note 1: For M2085 with Fvcso = 666.5143 or 669.3266
Note 2: For M2086 and M2087 with Fvcso = 622.0800.
0
0
79 85
237/255 OTU2 to OC-192 decode
669.3266
622.08
0
1
79 79
1
0
14 15
OC-192 repeater or jitter attenuator
622.08
622.08
238/255 OTU1 to OC-48 decode
666.5143
622.08
1
1
14 14
OC-48 repeater or jitter attenuator
622.08
622.08
Table 6: M2081/86: FEC De-map LUT, OTU1 (238/255) or OTU2 (237/255)
M2080/81/82 Datasheet Rev 0.4
Integrated Circuit Systems, Inc.
3 of 14
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Revised 30Jul2004
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M2080/81/82, M2085/86/87
Integrated
Circuit
Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
M2082/87: FEC De-map LUT, Both OTU1 and OTU2
FUNCTIONAL DESCRIPTION
Use this option for both OTU1 or OTU2 de-mapping
applications. The Mfec divider value is kept nearly
constant to maintain similar loop bandwidth using one
set of external filter component values.
The M208x Series is a PLL (Phase Locked Loop) based
clock generator that generates output clocks synchronized to one of two selectable input reference clocks.
FEC_SEL1:0
Mfec Rfec
1 0
Description
Fvcso =
Base Input
Base Output
Rate (MHz)
Rate (MHz)
For M2082 or M2087 with Fvcso = 622.08 (OTU1 or OTU2 FEC rate):
0
0
79 85
237/255 OTU2 to OC-192 decode
669.3266
622.08
0
1
79 79
OC-192 repeater or jitter attenuator
622.08
622.08
1
0
84 90
238/255 OTU1 to OC-48 decode
666.5143
622.08
1
1
84 84
OC-48 repeater or jitter attenuator
622.08
622.08
Table 7: M2082/87: FEC De-map LUT, Both OTU1 and OTU2
P Divider Look-Up Table (LUT)
The P_SEL2:0 pins select the P divider values, which set
the output clock frequency. A P divider of value of 1 will
provide a 622.08MHz output when using a 622.08MHz
VCSO, for example. P divider values of 4, 8, or 32 are
also available, plus a TriState mode. The output can be
placed into the valid states as listed in Table 8.
P_SEL2:0
P Value
M2080-622.0800 or M2085-622.0800
0
0
0
0
1
1
1
1
32
32
1
4
8
4
8
TriState
19.44
19.44
622.08
155.52
77.76
155.52
77.76
N/A
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Output Frequency (MHz)
frequency:
• The FEC de-mapper PLL ratios (in Tables 6 and 7)
General Guidelines for Phase Detector Frequency
The phase detector frequency (Fpd) is equal to the
input reference frequency (Fref) divided by the Rfec
divider value, or:
Fpd = Fref / Rfec
• A lower phase detector frequency should be used for
•
loop timing applications to assure PLL tracking,
especially during GR-253 jitter tolerance testing. The
recommended maximum phase detector frequency
for loop timing mode is 19.44MHz.
When LOL is to be used for system health monitoring,
the phase detector frequency should be 5MHz or
greater. Low phase detector frequencies make LOL
overly sensitive, and higher phase detector
frequencies make LOL less sensitive. The LOL pin
should not be used during loop timing mode.
The preceding guideline also applies when using the
AutoSwitch Mode, since AutoSwitch uses the LOL
output for clock fault detection.
M2080/81/82 M2085/86/87 Datasheet Rev 0.4
Integrated Circuit Systems, Inc.
●
Pin selectable dividers are used within the PLL and
for the output clock. This enables tailoring of device
functionality and performance. The FEC feedback and
reference dividers (the “Mfec Divider” and “Rfec
Divider”) provide the multiplication ratios necessary to
accomodate clock translation for both forward and
inverse Forward Error Correction. The Mfec and Rfec
dividers also control the phase detector frequency. The
feedback divider (labeled “Mfin Divider”) provides the
broader division options needed to accomodate various
reference clock frequencies.
For example, the M2082-11-622.0800 (see “Ordering
Information” on pg. 14) has a 622.08MHz VCSO
Table 8: P Divider Look-Up Table (LUT)
•
An internal high "Q" SAW delay line provides low jitter
signal performance and establishes the output
frequency of the VCSO (Voltage Controlled SAW
Oscillator). In a given M208x Series device, the VCSO
center frequency is fixed. A common center frequency
is 622.08MHz, for SONET or SDH optical network
applications. The VCSO center frequency is specified at
time of order (see “Ordering Information” on pg. 14).
The VCSO has a guaranteed tuning range of ±120 ppm
(commercial temperature grade).
enable the M2082-11-622.0800 to accept “base” input
reference frequencies of: 666.5143 (OTU1), 669.3266
(OTU2), and 622.08MHz (OC-192).
• The Mfin feedback divider enables the actual input
reference clock to be the base input frequency
divided by 1, 4, 8, or 32 or 16. Therefore, for the base
input frequency of 622.08MHz, the actual input
reference clock frequencies can be: 622.08, 155.52,
77.76, and 19.44 or 38.88MHz. (See Tables 3 and 4 on
pg. 3.)
Key to Device Variants and Look-up Table Options
Device
Variant
M2080
M2081
M2082
M2085
M2086
M2087
Look-up Table Option
Mfin Lookup Table is:
Mfec Look-up Table is:
Table
5 (FEC mapper LUT)
Table 3
Table 6 (FEC de-mapper LUT)
(includes divider value 32)
Table 7 (FEC de-mapper LUT)
Table 5 (FEC mapper LUT)
Table 4
Table 6 (FEC de-mapper LUT)
(includes divider value 16)
Table 7 (FEC de-mapper LUT)
Table 9: Key to Device Variants and Look-up Table Options
The P divider scales the VCSO output enabling lower
output frequency selections (Table 8).
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M2080/81/82, M2085/86/87
Integrated
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Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
The M208x Series includes a Loss of Lock (LOL)
indicator, which provides status information to system
management software. A Narrow Bandwidth (NBW)
control pin is provided as an additional mechanism for
adjusting PLL loop bandwidth without affecting the
phase detector frequency.
Options are available for Hitless Switching (HS) with or
without Phase Build-out (PBO). They provide SONET/
SDH MTIE and TDEV compliance during a reference
clock reselection.
Input Reference Clocks
Two clock reference inputs and a selection mux are
provided. Either reference clock input can accept a
differential clock signal (such as LVPECL or LVDS) or
a single-ended clock input (LVCMOS or LVTTL on the
non-inverting input).
DIF_REF0
50k Ω
nDIF_REF0
VCC
DIF_REF1
VCC
MUX
50kΩ
0
X
50kΩ
1
127Ω
82Ω
LVPECL
nDIF_REF1
VCC
50k Ω
VCC
127 Ω
50kΩ
82 Ω
50kΩ
REF_SEL
Figure 4: Input Reference Clocks
M2080/81/82 Datasheet Rev 0.4
Integrated Circuit Systems, Inc.
Single-ended Inputs
Single-ended inputs (LVCMOS or LVTTL) are
connected to the non-inverting reference input pin
(DIF_REF0 or DIF_REF1). The inverting reference input pin
(nDIF_REF0 or nDIF_REF1) must be left unconnected.
PLL Operation
The M2080/81/82 and M2085/86/87 are complete clock
PLLs. They use a phase detector and configurable
dividers to synchronize the output of the VCSO with the
selected reference clock.
Configuration of a single-ended input has been
facilitated by biasing nDIF_REF0 and nDEF_REF1 to Vcc/2,
with 50kΩ to Vcc and 50kΩ to ground. The input clock
structure, and how it is used with either
LVCMOS/LVTTL inputs or a DC- coupled LVPECL
clock, is shown in Figure 4.
LVCMOS/
LVTTL
Differential LVPECL inputs are connected to both
reference input pins in the usual manner. The external
load termination resistors shown in Figure 4 (the 127Ω
and 82Ω resistors) is ideally suited for both AC and DC
coupled LVPECL reference clock lines. These provide
the 50Ω load termination and the VTT bias voltage.
In single-ended operation, when the unused inverting
input pin (nDIF_REF0 or nDEF_REF1) is left floating (not
connected), the input will self-bias at VCC/2.
A single-ended reference clock on the unselected
reference input can cause an increase in output
clock jitter. For this reason, differential reference
inputs are preferred; interference from a differential
input on the non-selected input is minimal.
.
Differential Inputs
The M208x Series components are similar to the
M2060 Series components except that the M208x
Series includes the selectable AutoSwitch feature. The
M208x Series also has only one clock output, as the
AutoSwitch control pins replace of the second output.
The PLL will work correctly, meaning it will phase-lock
the VCSO output to the input reference clock, when the
internal phase detector inputs are able to run at the
same frequency. This means the PLL dividers must be
set appropriately and a suitable reference frequency
must be chosen for the intended output frequency.
When the PLL is not set up appropriately, the VCSO is
forced to its upper or lower operating limit which is typically about 200 ppm above or below the VCSO center
frequency. See “APR, VCSO Absolute Pull-Range” row,
in the AC Characteristics table on pg. 12.
In normal phase-locked condition, the instantaneous
phase error is measured by the phase detector and is
converted to charge pump current pulses. These
current pulses are then integrated by the external loop
filter to create a VCSO control voltage. The loop filter
acts as a low pass filter to remove unwanted reference
clock jitter above a determined frequency or PLL
bandwidth. For reference phase jitter frequencies within
the loop bandwidth, phase jitter amplitude is passed on
to the output clock according to the PLL loop frequency
response curve.
5 of 14
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M2080/81/82, M2085/86/87
Integrated
Circuit
Systems, Inc.
VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
The relationship between the nominal VCSO center
frequency (Fvcso), the Mfin divider, the Mfec divider,
the Rfec divider, and the input reference frequency (Fin)
is:
Mfec
Fvcso = Fin × Mfin × -------------Rfec
The Mfec, Rfec, and Mfin dividers can be set by pin
configuration using the input pins FEC_SEL1, FEC_SEL0,
FIN_SEL1, and FIN_SEL0.
Post-PLL Divider
The M2080/81/82 and M2085/86/87 also feature a
post-PLL (P) divider.
Under normal device operation, when the PLL is locked,
the LOL Phase Detector drives LOL to logic 0. Under
circumstances when the VCSO cannot fully phase lock
to the input (as measured by a greater than 4 ns
discrepancy between the feedback and reference clock
rising edges at the LOL Phase Detector) the LOL output
goes to logic 1. The LOL pin will return back to logic 0
when the phase detector error is less than 2 ns. The
loss of lock indicator is a low current LVCMOS output.
Guidelines for Using LOL
Through use of the P divider, the device’s output
frequency (Fout) can be that of the VCSO (such as
622.08MHz) or the VCSO frequency divided by 4, 8 or 32
(common optical reference clocks in SONET and SDH
systems).
The P_SEL2:0 pins select the value for the P divider. (See
Table 8 on pg. 4.)
Accounting for the P divider, the complete relationship
between the input clock reference frequency (Fin) and
output clock frequency (Fout) is defined as:
Mfin × Mfec
Fvcso = Fin × --------------------------------Fout = ------------------P
Loss of Lock Indicator (LOL) Output Pin
Rfec × P
In a given application, the magnitude of peak-to-peak
jitter at the phase detector will usually increase as the
Rfec divider is increased. If the LOL pin will be used to
detect an unusual clock condition, or a clock fault, the
FEC_SEL1:0 pins should be set to provide a phase
detector frequency of 5MHz or greater (the phase
detector frequency is equal to Fin divided by the Rfec
divider). Otherwise, false LOL indications may result. A
phase detector frequency of 10MHz or greater is
desirable when reference jitter is over 500ps, or when
the device is used within a noisy system environment.
LOL should not be used when the device is used in a
loop timing application.
Due to the narrow tuning range of the VCSO (+120ppm
guaranteed), appropriate selection of all of the following
are required for the PLL be able to lock: VCSO center
frequency, input frequency, and divider selections.
TriState
The TriState feature puts the LVPECL output driver into
a high impedance state, effectively disconnecting the
driver from the FOUT and nFOUT pins of the device. In
TriState, the M208x Series is not driving the output
clock net with a defined logic level. The impedance of
the clock net is then set to 50Ω by the external circuit
resistors. The 50Ω impedance level of the LVPECL
TriState allows manufacturing In-circuit Test to drive the
clock net with an external LVPECL source to validate
the integrity of clock net and the clock load.
Any unused output (single-ended or differential) should
be left unconnected (floating) in system application.
This minimizes output switching current and therefore
minimizes noise modulation of the VCSO.
M2080/81/82 M2085/86/87 Datasheet Rev 0.4
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
AutoSwitch (AUTO) Reference Clock Reselection
This device offers an automatic reference clock
reselection feature for switching input reference clocks
upon a reference clock failure. With the AUTO input pin
set to high and the LOL output low, the device is placed
into automatic reselection (AutoSwitch) mode. Once in
AutoSwitch mode, when LOL then goes high (due to a
reference clock fault), the input clock reference is
automatically reselected internally, as indicated by the
state change of the REF_ACK output. Automatic clock
reselection is made only once (it is non-revertive).
Re-arming of automatic mode requires placing the
device into manual selection (Manual Select) mode
(AUTO pin low) before returning to AutoSwitch mode
(AUTO pin high).
Using the AutoSwitch Feature
See also Table 10, Example AutoSwitch Sequence.
In application, the system is powered up with the device
in Manual Select mode (AUTO pin is set low), allowing
sufficient time for the reference clock and device PLL to
settle. The REF_SEL input selects the reference clock to
be used in Manual Select mode and the initial reference
clock used in AutoSwitch mode. The REF_SEL input state
must be maintained when switching to AutoSwitch
mode (AUTO pin high) and must still be maintained until a
reference fault occurs.
Once a reference fault occurs, the LOL output goes high
and the input reference is automatically reselected. The
REF_ACK output always indicates the reference selection
status and the LOL output always indicates the PLL lock
status.
A successful automatic reselection is indicated by a
change of state of the REF_ACK output and a momentary
level high of the LOL output (minimum high time is 10
ns).
If an automatic reselection is made to a non-valid
reference clock (one to which the PLL cannot lock),
the REF_ACK output will change state but the LOL
output will remain high.
No further automatic reselection is made; only one
reselection is made each time the AutoSwitch mode is
armed. AutoSwitch mode is re-armed by placing the
device into Manual Select mode (AUTO pin low) and then
into AutoSwitch mode again (AUTO pin high).
Following an automatic reselection and prior to
selecting Manual Select mode (AUTO pin low), the
REF_SEL pin has no control of reference selection.
To prevent an unintential reference reselection,
AutoSwitch mode must not be re-enabled until the
desired state of the REF_SEL pin is set and the LOL output
is low. It is recommended to delay the re-arming of
AutoSwitch mode, following an automatic reselection, to
ensure the PLL is fully locked on the new reference. In
most system configurations, where loop bandwidth is in
the range of 100-1000 Hz and damping factor below 10,
a delay of 500 ms should be sufficient. Until the PLL is
fully locked intermittent LOL pulses may occur.
Example AutoSwitch Sequence
0 = Low; 1 = High. Example with REF_SEL initially set to 0 (i.e., DIF_REF0 selected)
REF_SEL Selected REF_ACK AUTO LOL Conditions
Input
Clock Input
Output
Input
Output
0
DIF_REF0
0
0
1
0
DIF_REF0
0
0
-0-
0
DIF_REF0
0
-1-
0
Initialization
Device power-up. Manual Select mode. DIF_REF0 input selected reference, not yet locked to.
LOL to 0: Device locked to reference (may get intermittent LOL pulses until fully locked).
AUTO set to 1: Device placed in AutoSwitch mode (with DIF_REF0 as initial reference clock).
Operation & Activation
Normal operation with AutoSwitch mode armed, with DIF_REF0 as initial reference clock.
0
DIF_REF0
0
1
0
0
0
DIF_REF0
-DIF_REF1-
0
-1-
1
1
-11
LOL to 1: Clock fault on DIF_REF0, loss of lock indicated by LOL pin, ...
... and immediate automatic reselection to DIF_REF1 (indicated by REF_ACK pin).
0
DIF_REF1
1
1
-0-
LOL to 0: Device locks to DIF_REF1 (assuming valid clock on DIF_REF1).
-1-
DIF_REF1
1
1
0
REF_SEL set to 1: Prepares for Manual Selection of DIF_REF1 before then re-arming AutoSwitch.
1
DIF_REF1
1
-0-
0
AUTO set to 0: Manual Select mode entered briefly, manually selecting DIF_REF1 as reference.
1
DIF_REF1
1
-1-
0
AUTO set to 1: Device is placed in AutoSwitch mode (delay recommended to ensure device fully
locked), re-initializing AutoSwitch with DIF_REF1 now specified as the initial reference clock.
Re-initialization
Table 10: Example AutoSwitch Sequence
M2080/81/82 Datasheet Rev 0.4
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
Optional Hitless Switching and Phase Build-out
HS/PBO Operation
The M208x Series is available with a Hitless Switching
feature that is enabled during device manufacturing.
In addition, a Phase Build-out feature is also offered.
These features are offered as device options and are
specified by device order code. Refer to “Ordering
Information” on pg. 14.
Once triggered, the following HS/PBO sequence
occurs:
The Hitless Switching feature (with or without Phase
Build-out) is designed for applications where switching
occurs between two stable system reference clocks. It
should not be used in loop timing applications, or when
reference clock jitter is greater than 1 ns pk-pk. The
Hitless Switching sequence is triggered by the LOL
circuit, which is activated by a 4 ns phase transient. This
magnitude of phase transient can generated by the
CDR (Clock & Data Recovery unit) in loop timing mode,
especially during a system jitter tolerance test. It can
also be generated by some types of Stratum clock
DPLLs (digital PLL), especially those that do not include
a post de-jitter APLL (analog PLL).
When the M208x Series is operating in wide bandwidth
mode (NBW=0), the optional Hitless Switching function
puts the device into narrow bandwidth mode when
during the Hitless Switching sequence. This allows the
PLL to lock the new input clock phase gradually. With
proper configuration of the external loop filter, the output
clock phase change complies with MTIE and TDEV
specifications for GR-253 (SONET) and ITU G.813
(SDH) during input reference clock changes.
The optional proprietary Phase Build-out (PBO)
function enables the PLL to absorb most of the phase
change of the input clock during reference switching.
The PBO function selects a new VCSO clock edge for
the PLL Phase Detector feedback clock, selecting the
edge closest in phase to the new input clock phase.
This reduces re-lock time, the generation of wander,
and extra output clock cycles.
1. The HS function disables the PLL Phase Detector
and puts the device into NBW (narrow bandwidth)
mode. The internal resistor Rin is changed to
2100kΩ . See the Narrow Bandwidth (NBW) Control
Pin on pg. 8.
2. If included, the PBO function adds to (builds out) the
phase in the clock feedback path (in VCSO clock
cycle increments) to align the feedback clock with
the (new) reference clock input phase.
3. The PLL Phase Detector is enabled, allowing the
PLL to re-lock.
4. Once the PLL Phase Detector feedback and input
clocks are locked to within 2 nsec for 8 consecutive
cycles, a timer (WBW timer) for resuming wide
bandwidth (in 175 nsec) is started.
5. When the WBW timer times out, the device reverts
to wide loop bandwidth mode (i.e., Rin is returned to
100kΩ) and the HS/PBO function is re-armed.
The LOL pin will indicate lock status on a cycle-to-cycle
basis and may be intermittent until PLL phase lock has
fully stabilized.
Narrow Bandwidth (NBW) Control Pin
A Narrow Loop Bandwidth control pin (NBW pin) is
included to enable adjustment of the PLL loop
bandwidth. In wide bandwidth mode (NBW=0), the
internal resistor Rin is 100kΩ . With the NBW pin
asserted (NBW=1), the internal resistor Rin is changed to
2100kΩ . This lowers the loop bandwidth by a factor of
about 21 (2100 / 100) and lowers the damping factor by
about 4.6 (the square root of 21), assuming the same
external loop filter component values.
The Hitless Switching and Phase Build-out functions
are triggered by the LOL circuit. For proper operation,
a low phase detector frequency must be avoided. See
“Guidelines for Using LOL” on pg. 6 for information
regarding the phase detector frequency.
HS/PBO Sequence Trigger Mechanism
The HS function (or the combined HS/PBO function)
is armed after the device locks to the input clock reference. Once armed, HS is triggered by the occurance of
a Loss of Lock condition. This would typically occur as a
consequence of a clock reference failure, a clock failure
upstream to the M208x Series, or a M208x Series clock
reference mux reselection.
M2080/81/82 M2085/86/87 Datasheet Rev 0.4
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
External Loop Filter
PLL Simulator Tool Available
To provide stable PLL operation, the M2080/81/82
requires the use of an external loop filter. This is
provided via the provided filter pins (see Figure 5).
The loop filter is implemented as a differential circuit
to minimize system noise interference.
A free PC software utility is available on the ICS website
(www.icst.com). The M2000 Timing Modules PLL
Simulator is a downloadable application that simulates
PLL jitter and wander transfer characteristics. This
enables the user to set appropriate external loop
component values in a given application.
RLOOP
CLOOP
RPOST
CPOST
CPOST
RLOOP
OP_IN
nOP_IN
4
CLOOP
RPOST
OP_OUT
9
nOP_OUT
8
nVC
5
VC
6
7
Figure 5: External Loop Filter
PLL bandwidth is affected by loop filter component
values, “Mfec” and “Mfin” values, and the “PLL Loop
Constants” listed in AC Characteristics on pg. 12.
The FEC_SEL setting can be used to actively change PLL
loop bandwidth in a given application. See “Mfec and
Rfec Divider Look-Up Tables (LUTs)” on pg. 3.
See Table 11, Example Values for Loop Filter External
Components, below.
Example Values for Loop Filter External Components 1
for Particular M208x Series Devices
VCSO Parameters: KVCO = 800kHz/V, RIN = 100kΩ (pin NBW = 0), VCSO Bandwidth = 700kHz.
Device
Device Configuration
FVCSO FIN_SEL MRSEL
1:0
1:0
(MHz)
(MHz)
FRef
Example External Component Values
R loop
5.6kΩ
C post
Nominal Performance With These Values
C loop
R post
PLL Loop Damping Passband
Bandwidth Factor Peaking (dB)
10µF
68kΩ
470pF
530Hz
6.5
0.05
0.1µF
34kΩ
470pF
1kHz
5.9
0.06
0.05
0.05
M2080, M2080 622.08
622.08
1 1
0 1
M2080, M2085 155.52
669.3266
1 0
1 0 0243.0kΩ
M2081, M2086
77.76
622.08
0 1
0 1
8.2kΩ
10µF
100kΩ
470pF
360Hz
6.5
M2081
19.44
622.08
0 0
1 1
8.2kΩ
10µF
100kΩ
470pF
360Hz
6.5
Table 11: Example Values for Loop Filter External Components
Note 1: KVCO , VCSO Bandwidth, M Divider Value, and External Loop Filter Component Values determine Loop Bandwidth, Damping Factor, and
Passband Peaking. For PLL Simulator software, go to www.icst.com.
Refer to the M208x Series product web page at
www.icst.com/products/summary/m2080-2087.htm
for additional product information.
M2080/81/82 Datasheet Rev 0.4
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
ABSOLUTE MAXIMUM RATINGS1
Symbol Parameter
Rating
Unit
VI
Inputs
-0.5 to VCC +0.5
V
VO
Outputs
-0.5 to VCC +0.5
V
VCC
Power Supply Voltage
4.6
V
TS
Storage Temperature
-45 to +100
oC
Table 12: Absolute Maximum Ratings
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the
device. These ratings are stress specifications only. Functional operation of product at these conditions
or any conditions beyond those listed in Recommended Conditions of Operation, DC Characteristics, or
AC Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods
may affect product reliability.
RECOMMENDED CONDITIONS OF OPERATION
Symbol Parameter
VCC
Positive Supply Voltage
TA
Ambient Operating Temperature
Commercial
Industrial
Min
Typ
Max
Unit
3.135
3.3
3.465
V
oC
+70
+85
0
-40
oC
Table 13: Recommended Conditions of Operation
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
ELECTRICAL SPECIFICATIONS
DC Characteristics
Unless stated otherwise, VCC = 3.3V +5%,TA = 0 oC to +70 oC (commercial), TA = -40 oC to +85 oC (industrial), FVCSO = FOUT = 622-675MHz,
LVPECL outputs terminated with 50Ω to VCC - 2V
Symbol Parameter
Power Supply VCC
Positive Supply Voltage
ICC
Power Supply Current
All
Differential
Inputs
VP-P
Peak to Peak Input Voltage
VCMR
Common Mode Input
CIN
Input Capacitance
Differential
Inputs with
Pull-down
IIH
Input High Current (Pull-down)
IIL
Input Low Current (Pull-down)
Differential
Inputs
Biased to
VCC/2 1
All LVCMOS
/ LVTTL
Inputs
IIH
LVCMOS /
LVTTL
Inputs with
Pull-down
LVCMOS /
LVTTL
Inputs with
Pull-UP
Differential
Output
LVCMOS
Outputs
DIF_REF0, nDIF_REF0,
DIF_REF1, nDIF_REF1
Min
Typ
Max
Unit Conditions
3.135
3.3
3.465
V
175
225
0.15
V
0.5
Vcc - .85 V
DIF_REF0, DIF_REF1
Input Low Current (Biased)
Rbias
Biased to Vcc/2 1
VIH
Input High Voltage
VIL
Input Low Voltage
CIN
Input Capacitance
IIH
Input High Current (Pull-down)
pF
150
µA
µA
50
Input High Current (Biased) 1
IIL
4
-5
Rpulldown Internal Pull-down Resistance
IIH
Input High Current (Pull-UP)
IIL
Input Low Current (Pull-UP)
Rpullup
Internal Pull-UP Resistance
VOH
Output High Voltage
VOL
Output Low Voltage
-0.3
Peak to Peak Output Voltage
VOH
Output High Voltage
VOL
Output Low Voltage
0.8
V
4
pF
150
µA
µA
-5
NBW
Integrated Circuit Systems, Inc.
Vcc - 1.4
Vcc - 1.0 V
Vcc - 2.0
Vcc - 1.7 V
0.4
0.85
V
2.4
VCC
V
IOH= 1mA
GND
0.4
V
IOL= 1mA
LOL, REF_ACK
Table 14: DC Characteristics
11 of 14
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VCC = 3.456V
VIN = 0 V
kΩ
50
Note 1: Biased to Vcc/2, with 50kΩ to Vcc and 50kΩ to ground. See Figure 4, Input Reference Clocks, on pg. 5
Note 2: Single-ended measurement. See Figure 6, Output Rise and Fall Time, on pg. 12.
M2080/81/82 Datasheet Rev 0.4
µA
µA
-150
2
VCC = VIN =
3.456V
kΩ
50
5
FOUT, nFOUT
VP-P
Vcc + 0.3 V
2
AUTO, REF_SEL, FIN_SEL1,
FIN_SEL0, FEC_SEL1,
IIL
Input Low Current (Pull-down) FEC_SEL0, P_SEL2, P_SEL1,
Rpulldown Internal Pull-down Resistance P_SEL0
VIN =
0 to 3.456V
kΩ
(Note 1)
AUTO, REF_SEL, FIN_SEL1,
FIN_SEL0, FEC_SEL1,
FEC_SEL0, P_SEL2, P_SEL1,
P_SEL0, NBW
µA
µA
-150
nDIF_REF0, nDIF_REF1
VCC = VIN =
3.456V
kΩ
150
1
mA
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
ELECTRICAL SPECIFICATIONS (CONTINUED)
AC Characteristics
Unless stated otherwise, VCC = 3.3V +5%,TA = 0 oC to +70 oC (commercial), TA = -40 oC to +85 oC (industrial), FVCSO = FOUT = 622-675MHz,
LVPECL outputs terminated with 50Ω to VCC - 2V
Symbol Parameter
PLL Loop
Constants 1
Min
Typ
Max
Unit Conditions
FIN
Input Frequency
DIF_REF0, nDIF_REF0,
DIF_REF1, nDIF_REF1
10
700
MHz
FOUT
Output Frequency
FOUT, nFOUT
15
700
MHz
APR
VCSO Absolute
Pull-Range
Commercial
KVCO
VCO Gain
RIN
Internal Loop Resistor
±120
±50
800
100
kΩ
2100
kΩ
700
kHz
1kHz Offset
-73
dBc/Hz Fin=19.44 or
10kHz Offset
-103
100kHz Offset
-126
dBc/Hz Mfin=32 or 16,
dBc/Hz Mfec=Rfec
Wide Bandwidth
Narrow Bandwidth
BWVCSO VCSO Bandwidth
Φn
Phase Noise
and Jitter
Single Side Band
Phase Noise
@622.08MHz
0.5
0.25
0.5
50
55
ps
ps
%
40
50
60
%
200
450
500
ps
20% to 80%
200
450
500
ps
20% to 80%
Jitter (rms)
@622.08MHz
12kHz to 20MHz
odc
Output Duty Cycle 2
P = 4, 8, or 32
45
FOUT, nFOUT
P=1
50kHz to 80MHz
2
Output Rise Time
tF
Output Fall Time 2
38.88 MHz
0.25
J(t)
tR
±200
±150
ppm
ppm
kHz/V
Industrial
FOUT, nFOUT
Table 15: AC Characteristics
Note 1: Parameters needed for PLL Simulator software; see Table 11, Example Values for Loop Filter External Components, on pg. 9.
Note 2: See Parameter Measurement Information on pg. 12.
PARAMETER MEASUREMENT INFORMATION
Output Rise and Fall Time
Output Duty Cycle
nFOUT
80%
FOUT
80%
V P -P
Clock Output
tPW
(Output Pulse Width)
20%
tF
20%
tR
tPERIOD
odc =
tPW
tPERIOD
Figure 7: Output Duty Cycle
Figure 6: Output Rise and Fall Time
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Preliminary Information
DEVICE PACKAGE - 9 x 9mm CERAMIC LEADLESS CHIP CARRIER
Mechanical Dimensions:
Refer to the M208x Series product web page at
www.icst.com/products/summary/m2080-2087.htm
for recommended PCB footprint, solder mask,
furnace profile, and related information.
Figure 8: Device Package - 9 x 9mm Ceramic Leadless Chip Carrier
M2080/81/82 Datasheet Rev 0.4
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VCSO FEC PLL WITH AUTOSWITCH FOR SONET/OTN
Standard VCSO Output Frequencies (MHz)*
ORDERING INFORMATION
Part Numbering Scheme
Part Number:
M2080/81/82, M2085/86/87
Preliminary Information
M208x- yz - xxx.xxxx
Divider Look-up Table Option
See Table 9, page 4.
Output type
1 = LVPECL
(For CML or LVDS clock output, consult factory)
Hitless Switching / Phase Build-out Options
1 = none
2 = Hitless Switching
3 = Hitless Switching with Phase Build-out
Temperature
“ - ” = 0 to +70 oC (commercial)
I = - 40 to +85 oC (industrial)
VCSO Frequency (MHz)
See Table 16, right. Consult ICS for other frequencies.
Figure 9: Part Numbering Scheme
622.0800
669.3120
625.0000
669.3266
627.3296
669.6429
644.5313
670.8386
666.5143
672.1600
669.1281
690.5692
Table 16: Standard VCSO Output Frequencies
Note *: Fout can equal Fvcso divided by: 1, 4, 8, or 32.
Consult ICS for the availability of other VCSO frequencies.
Example Part Numbers
VCSO Frequency (MHz) Temperature
622.0800
669.3266
commercial
industrial
commercial
industrial
Order Part Number (Examples)
M2081 - 11 - 622.0800 or M2082- 11 - 622.0800
M2081 - 11I 622.0800 or M2082- 11I 622.0800
M2080 - 11 - 669.3266 or M2085 - 11 - 669.3266
M2080 - 11I 669.3266 or M2085- 11I 669.3266
Table 17: Example Part Numbers
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS)
assumes no responsibility for either its use or for the infringement of any patents or other rights of third parties, which would
result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial
applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary
environmental requirements are not recommended without additional processing by ICS. ICS reserves the right to change any
circuitry or specifications without notice. ICS does not authorize or warrant any ICS product for use in life support devices or
critical medical instruments.
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