Cirrus CDK-2000-CLK Fractional-n clock synthesizer & clock multiplier Datasheet

CS2000-OTP
Fractional-N Clock Synthesizer & Clock Multiplier
Features
General Description
 Delta-Sigma Fractional-N Frequency Synthesis
The CS2000-OTP is an extremely versatile system
clocking device that utilizes a programmable phase lock
loop. The CS2000-OTP is based on a hybrid analogdigital PLL architecture comprised of a unique combination of a Delta-Sigma Fractional-N Frequency
Synthesizer and a Digital PLL. This architecture allows
for both frequency synthesis/clock generation from a
stable reference clock as well as generation of a low-jitter clock relative to an external noisy synchronization
clock with frequencies as low as 50 Hz. The CS2000OTP has many configuration options which are set once
prior to runtime. At runtime there are three hardware
configuration pins available for mode and feature
selection.
–
Generates a Low Jitter 6 - 75 MHz Clock
from an 8 - 75 MHz Reference Clock
 Clock Multiplier / Jitter Reduction
–
Generates a Low Jitter 6 - 75 MHz Clock
from a Jittery or Intermittent 50 Hz to
30 MHz Clock Source
 Highly Accurate PLL Multiplication Factor
–
Maximum Error Less Than 1 PPM in HighResolution Mode
 One-Time Programmability
–
–
Configurable Hardware Control Pins
Configurable Auxiliary Output
 Flexible Sourcing of Reference Clock
–
–
External Oscillator or Clock Source
Supports Inexpensive Local Crystal
 Minimal Board Space Required
–
No External Analog Loop-filter
Components
The CS2000-OTP is available in a 10-pin MSOP package in Commercial (-10°C to +70°C) grade. Customer
development kits are also available for custom device
prototyping, small production programming, and device
evaluation. Please see “Ordering Information” on
page 30 for complete details.
3.3 V
Hardware Control
Timing Reference
Frequency Reference
PLL Output
Lock Indicator
Hardware Configuration
Fractional-N
Frequency Synthesizer
8 MHz to 75 MHz
Low-Jitter Timing Reference
Output to Input
Clock Ratio
50 Hz to 30 MHz
Frequency Reference
Auxiliary
Output
6 to 75 MHz
PLL Output
N
Digital PLL & Fractional
N Logic
Output to Input
Clock Ratio
Preliminary Product Information
http://www.cirrus.com
This document contains information for a new product.
Cirrus Logic reserves the right to modify this product without notice.
Copyright © Cirrus Logic, Inc. 2008
(All Rights Reserved)
JUN '08
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TABLE OF CONTENTS
1. PIN DESCRIPTION ................................................................................................................................. 4
2. TYPICAL CONNECTION DIAGRAM ..................................................................................................... 5
3. CHARACTERISTICS AND SPECIFICATIONS ...................................................................................... 6
RECOMMENDED OPERATING CONDITIONS .................................................................................... 6
ABSOLUTE MAXIMUM RATINGS ........................................................................................................ 6
DC ELECTRICAL CHARACTERISTICS ................................................................................................ 6
AC ELECTRICAL CHARACTERISTICS ................................................................................................ 7
4. ARCHITECTURE OVERVIEW ............................................................................................................... 8
4.1 Delta-Sigma Fractional-N Frequency Synthesizer ........................................................................... 8
4.2 Hybrid Analog-Digital Phase Locked Loop ...................................................................................... 8
4.2.1 Fractional-N Source Selection for the Frequency Synthesizer ................................................ 9
5. APPLICATIONS ................................................................................................................................... 10
5.1 One Time Programmability ............................................................................................................ 10
5.2 Timing Reference Clock Input ........................................................................................................ 10
5.2.1 Internal Timing Reference Clock Divider ............................................................................... 10
5.2.2 Crystal Connections (XTI and XTO) ...................................................................................... 11
5.2.3 External Reference Clock (REF_CLK) .................................................................................. 11
5.3 Frequency Reference Clock Input, CLK_IN ................................................................................... 11
5.3.1 CLK_IN Skipping Mode ......................................................................................................... 11
5.3.2 Adjusting the Minimum Loop Bandwidth for CLK_IN ............................................................ 13
5.4 Output to Input Frequency Ratio Configuration ............................................................................. 14
5.4.1 User Defined Ratio (RUD), Frequency Synthesizer Mode .................................................... 14
5.4.2 User Defined Ratio (RUD), Hybrid PLL Mode ....................................................................... 14
5.4.3 Manual Ratio Modifier (R-Mod) ............................................................................................. 15
5.4.4 Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only ......................................... 15
5.4.5 Effective Ratio (REFF) .......................................................................................................... 16
5.4.6 Fractional-N Source Selection ............................................................................................... 16
5.4.6.1 Manual Fractional-N Source Selection for the Frequency Synthesizer ..................... 17
5.4.6.2 Automatic Fractional-N Source Selection for the Frequency Synthesizer ................. 17
5.4.7 Ratio Configuration Summary ............................................................................................... 18
5.5 PLL Clock Output ........................................................................................................................... 19
5.6 Auxiliary Output .............................................................................................................................. 19
5.7 Mode Pin Functionality ................................................................................................................... 20
5.7.1 M1 and M0 Mode Pin Functionality ....................................................................................... 20
5.7.2 M2 Mode Pin Functionality .................................................................................................... 20
5.7.2.1 M2 Configured as Output Disable .............................................................................. 20
5.7.2.2 M2 Configured as R-Mod Enable .............................................................................. 20
5.7.2.3 M2 Configured as Auto Fractional-N Source Selection Disable ................................ 21
5.7.2.4 M2 Configured as Auto R-Mod Enable ...................................................................... 21
5.7.2.5 M2 Configured as Fractional-N Source Select .......................................................... 21
5.7.2.6 M2 Configured as AuxOutSrc Override ..................................................................... 21
5.8 Clock Output Stability Considerations ............................................................................................ 21
5.8.1 Output Switching ................................................................................................................... 21
5.8.2 PLL Unlock Conditions .......................................................................................................... 22
6. PARAMETER DESCRIPTIONS ........................................................................................................... 23
6.1 Modal Configuration Sets ............................................................................................................... 23
6.1.1 R-Mod Selection (RModSel[1:0]) ........................................................................................... 23
6.1.2 Auxiliary Output Source Selection (AuxOutSrc[1:0]) ............................................................. 24
6.1.3 Auto R-Modifier Enable (AutoRMod) ..................................................................................... 24
6.1.4 Lock Clock Ratio (LockClk[1:0]) ............................................................................................ 24
6.1.5 Fractional-N Source for Frequency Synthesizer (FracNSrc) ................................................. 24
6.2 Ratio 0 - 3 ...................................................................................................................................... 24
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6.3 Global Configuration Parameters ................................................................................................... 25
6.3.1 Clock Skip Enable (ClkSkipEn) ............................................................................................. 25
6.3.2 AUX PLL Lock Output Configuration (AuxLockCfg) .............................................................. 25
6.3.3 Reference Clock Input Divider (RefClkDiv[1:0]) .................................................................... 25
6.3.4 Enable PLL Clock Output on Unlock (ClkOutUnl) ................................................................. 25
6.3.5 Low-Frequency Ratio Configuration (LFRatioCfg) ................................................................ 26
6.3.6 M2 Pin Configuration (M2Config[2:0]) ................................................................................... 26
6.3.7 Clock Input Bandwidth (ClkIn_BW[2:0]) ................................................................................ 26
7. CALCULATING THE USER DEFINED RATIO .................................................................................... 27
7.1 High Resolution 12.20 Format ....................................................................................................... 27
7.2 High Multiplication 20.12 Format ................................................................................................... 27
8. PROGRAMMING INFORMATION ........................................................................................................ 28
9. PACKAGE DIMENSIONS .................................................................................................................... 29
THERMAL CHARACTERISTICS ......................................................................................................... 29
10. ORDERING INFORMATION .............................................................................................................. 30
11. REVISION HISTORY .......................................................................................................................... 30
LIST OF FIGURES
Figure 1. Typical Connection Diagram ........................................................................................................ 5
Figure 2. Delta-Sigma Fractional-N Frequency Synthesizer ....................................................................... 8
Figure 3. Hybrid Analog-Digital PLL ............................................................................................................ 9
Figure 4. Fractional-N Source Selection Overview ..................................................................................... 9
Figure 5. Internal Timing Reference Clock Divider ................................................................................... 10
Figure 6. External Component Requirements for Crystal Circuit .............................................................. 11
Figure 7. CLK_IN removed for > 223 SysClk cycles ................................................................................. 12
Figure 8. CLK_IN removed for < 223 SysClk cycles but > tCS ................................................................. 12
Figure 9. CLK_IN removed for < tCS ........................................................................................................ 13
Figure 10. Low bandwidth and new clock domain .................................................................................... 13
Figure 11. High bandwidth with CLK_IN domain re-use ........................................................................... 14
Figure 12. Ratio Feature Summary ........................................................................................................... 18
Figure 13. PLL Clock Output Options ....................................................................................................... 19
Figure 14. Auxiliary Output Selection ........................................................................................................ 19
Figure 15. M2 Mapping Options ................................................................................................................ 20
Figure 16. Parameter Configuration Sets .................................................................................................. 23
LIST OF TABLES
Table 1. Modal and Global Configuration .................................................................................................. 10
Table 2. Ratio Modifier .............................................................................................................................. 15
Table 3. Automatic Ratio Modifier ............................................................................................................. 15
Table 4. Example Audio Oversampling Clock Generation from CLK_IN .................................................. 16
Table 5. Example 12.20 R-Values ............................................................................................................ 27
Table 6. Example 20.12 R-Values ............................................................................................................ 27
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1. PIN DESCRIPTION
VD
1
10
M0
GND
2
9
M1
CLK_OUT
3
8
M2
AUX_OUT
4
7
XTI/REF_CLK
CLK_IN
5
6
XTO
Pin Name
#
Pin Description
VD
1
Digital Power (Input) - Positive power supply for the digital and analog sections.
GND
2
Ground (Input) - Ground reference.
CLK_OUT
3
PLL Clock Output (Output) - PLL clock output.
AUX_OUT
4
Auxiliary Output (Output) - This pin outputs a buffered version of one of the input or output clocks,
or a status signal, depending on configuration.
CLK_IN
5
Frequency Reference Clock Input (Input) - Clock input for the Digital PLL frequency reference.
XTO
XTI/REF_CLK
6
7
Crystal Connections (XTI/XTO) / Timing Reference Clock Input (REF_CLK) (Input/Output) XTI/XTO are I/O pins for an external crystal which may be used to generate the low-jitter PLL input
clock. REF_CLK is an input for an externally generated low-jitter reference clock.
M2
8
Mode Select (Input) - M2 is a configurable mode selection pin.
M1
9
Mode Select (Input) - M1 is a configurable mode selection pin.
M0
10 Mode Select (Input) - M0 is a configurable mode selection pin.
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2. TYPICAL CONNECTION DIAGRAM
0.1 µF
1 µF
+3.3 V
VD
M2
System Microcontroller
M1
M0
Frequency Reference
CS2000-OTP
CLK_IN
1
or
2
XTI/REF_CLK
CLK_OUT
To circuitry which requires
a low-jitter clock
AUX_OUT
To other circuitry or
Microcontroller
XTO
GND
Low-Jitter
Timing Reference
1
N.C. x
REF_CLK
XTO
or
Crystal
2
40 pF
XTI
XTO
40 pF
Figure 1. Typical Connection Diagram
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3. CHARACTERISTICS AND SPECIFICATIONS
RECOMMENDED OPERATING CONDITIONS
GND = 0 V; all voltages with respect to ground. (Note 1)
Parameters
DC Power Supply
Symbol
Min
Typ
Max
Units
VD
3.1
3.3
3.5
V
TAC
-10
-
+70
°C
Ambient Operating Temperature (Power Applied)
Commercial Grade
Notes: 1. Device functional operation is guaranteed within these limits. Functionality is not guaranteed or implied
outside of these limits. Operation outside of these limits may adversely affect device reliability.
ABSOLUTE MAXIMUM RATINGS
GND = 0 V; all voltages with respect to ground.
Parameters
Symbol
Min
Max
Units
DC Power Supply
VD
-0.3
6.0
V
Input Current
IIN
-
±10
mA
Digital Input Voltage (Note 1)
VIN
-0.3
VD + 0.4
V
Ambient Operating Temperature (Power Applied)
TA
-55
125
°C
Storage Temperature
Tstg
-65
150
°C
WARNING: Operation at or beyond these limits may result in permanent damage to the device.
Notes: 1. The maximum over/under voltage is limited by the input current except on the power supply pin.
DC ELECTRICAL CHARACTERISTICS
Test Conditions (unless otherwise specified): VD = 3.1 V to 3.5 V; TA = -10°C to +70°C (Commercial Grade).
Parameters
Symbol
Min
Typ
Max
Units
Power Supply Current - Unloaded
(Note 2)
ID
-
12
18
mA
Power Dissipation - Unloaded
(Note 2)
PD
-
40
60
mW
Input Leakage Current
IIN
-
-
±10
µA
Input Capacitance
IC
-
8
-
pF
High-Level Input Voltage
VIH
70%
-
-
VD
Low-Level Input Voltage
VIL
-
-
30%
VD
High-Level Output Voltage (IOH = -1.2 mA)
VOH
80%
-
-
VD
Low-Level Output Voltage (IOH = 1.2 mA)
VOL
-
-
20%
VD
Notes: 2. To calculate the additional current consumption due to loading (per output pin), multiply clock output
frequency by load capacitance and power supply voltage.
For example, fCLK_OUT (49.152 MHz) * CL (15 pF) * VD (3.3 V) = 2.4 mA of additional current due to
these loading conditions on CLK_OUT.
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AC ELECTRICAL CHARACTERISTICS
Test Conditions (unless otherwise specified): VD = 3.1 V to 3.5 V; TA = -10°C to +70°C (Commercial Grade);
CL = 15 pF.
Parameters
Crystal Frequency
Symbol
Conditions
Min
Typ
Max
Units
fXTAL
Fundamental Mode
8
-
50
MHz
Reference Clock Input Frequency
fREF_CLK
8
-
75
MHz
Reference Clock Input Duty Cycle
DREF_CLK
45
-
55
%
Internal System Clock Frequency
fSYS_CLK
8
18.75
MHz
Clock Input Frequency (Auto R-Mod Disabled)
fCLK_IN
50 Hz
-
30
MHz
Clock Input Frequency (Auto R-mod Enabled)
fCLK_IN
Auto R Modifier = 1
Auto R Modifier = 0.5
Auto R Modifier = 0.25
4
72
168
-
59
138
256
kHz
kHz
kHz
pwCLK_IN
fCLK_IN < fSYS_CLK/96
fCLK_IN > fSYS_CLK/96
2
10
-
-
UI
ns
tCS
(Notes 4, 5)
20
-
-
ms
Clock Skipping Input Frequency
fCLK_SKIP
(Note 5)
50 Hz
-
80
kHz
PLL Clock Output Frequency
fCLK_OUT
6
-
75
MHz
Clock Input Pulse Width (Note 3)
Clock Skipping Timeout
PLL Clock Output Duty Cycle
tOD
Measured at VD/2
48
50
52
%
Clock Output Rise Time
tOR
20% to 80% of VD
-
1.7
3.0
ns
Clock Output Fall Time
tOF
80% to 20% of VD
-
1.7
3.0
ns
Period Jitter
tJIT
(Note 6)
-
70
150
ps rms
Base Band Jitter (100 Hz to 40 kHz)
(Notes 6, 7)
-
50
-
ps rms
Wide Band JItter (100 Hz Corner)
(Notes 6, 8)
-
175
-
ps rms
-
100
1
200
3
UI
ms
PLL Lock Time - CLK_IN (Note 9)
tLC
fCLK_IN < 200 kHz
fCLK_IN > 200 kHz
PLL Lock Time - REF_CLK
tLR
fREF_CLK = 8 to 75 MHz
-
1
2
ms
Output Frequency Synthesis Resolution (Note 10)
ferr
High Resolution
High Multiplication
0
0
-
±0.5
±112
ppm
ppm
Notes: 3. 1 UI (unit interval) corresponds to tSYS_CLK or 1/fSYS_CLK.
4. tCS represents the time from the removal of CLK_IN by which CLK_IN must be re-applied to ensure that
PLL_OUT continues while the PLL re-acquires lock. This timeout is based on the internal VCO frequency, with the minimum timeout occurring at the maximum VCO frequency. Lower VCO frequencies will
result in larger values of tCS.
5. Only valid in clock skipping mode; See “CLK_IN Skipping Mode” on page 11 for more information.
6. fCLK_OUT = 24.576 MHz; Sample size = 10,000 points; AuxOutSrc[1:0] = 11.
7. In accordance with AES-12id-2006 section 3.4.2. Measurements are Time Interval Error taken with 3rd
order 100 Hz to 40 kHz bandpass filter.
8. In accordance with AES-12id-2006 section 3.4.1. Measurements are Time Interval Error taken with 3rd
order 100 Hz Highpass filter.
9. 1 UI (unit interval) corresponds to tCLK_IN or 1/fCLK_IN.
10. The frequency accuracy of the PLL clock output is directly proportional to the frequency accuracy of the
reference clock.
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4. ARCHITECTURE OVERVIEW
4.1
Delta-Sigma Fractional-N Frequency Synthesizer
The core of the CS2000 is a Delta-Sigma Fractional-N Frequency Synthesizer which has very high-resolution for Input/Output clock ratios, low phase noise, very wide range of output frequencies and the ability to
quickly tune to a new frequency. In very simplistic terms, the Fractional-N Frequency Synthesizer multiplies
the Timing Reference Clock by the value of N to generate the PLL output clock. The desired output to input
clock ratio is the value of N that is applied to the delta-sigma modulator (see Figure 2).
The analog PLL based frequency synthesizer uses a low-jitter timing reference clock as a time and phase
reference for the internal voltage controlled oscillator (VCO). The phase comparator compares the fractional-N divided clock with the original timing reference and generates a control signal. The control signal is filtered by the internal loop filter to generate the VCO’s control voltage which sets its output frequency. The
delta-sigma modulator modulates the loop integer divide ratio to get the desired fractional ratio between the
reference clock and the VCO output (thus the duty cycle of the modulator sets the fractional value). This
allows the design to be optimized for very fast lock times for a wide range of output frequencies without the
need for external filter components. As with any Fractional-N Frequency Synthesizer the timing reference
clock should be stable and jitter-free.
Timing Reference
Clock
Phase
Comparator
Internal
Loop Filter
Voltage Controlled
Oscillator
PLL Output
Fractional-N
Divider
Delta-Sigma
Modulator
N
Figure 2. Delta-Sigma Fractional-N Frequency Synthesizer
4.2
Hybrid Analog-Digital Phase Locked Loop
The addition of the Digital PLL and Fractional-N Logic (shown in Figure 3) to the Fractional-N Frequency
Synthesizer creates the Hybrid Analog-Digital Phase Locked Loop with many advantages over classical analog PLL techniques. These advantages include the ability to operate over extremely wide frequency ranges
without the need to change external loop filter components while maintaining impressive jitter reduction performance. In the Hybrid architecture, the Digital PLL calculates the ratio of the PLL output clock to the frequency reference and compares that to the desired ratio. The digital logic generates a value of N which is
then applied to the Fractional-N frequency synthesizer to generate the desired PLL output frequency. Notice
that the frequency and phase of the timing reference signal do not affect the output of the PLL since the
digital control loop will correct for the PLL output. A major advantage of the Digital PLL is the ease with which
the loop filter bandwidth can be altered. The PLL bandwidth is set to a wide-bandwidth mode to quickly
achieve lock and then reduced for optimal jitter rejection.
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Delta-Sigma Fractional-N Frequency Synthesizer
Timing Reference
Clock
Phase
Comparator
Internal
Loop Filter
Voltage Controlled
Oscillator
PLL Output
Fractional-N
Divider
Delta-Sigma
Modulator
Digital PLL and Fractional-N Logic
N
Digital Filter
Frequency
Comparator for
Frac-N Generation
Frequency Reference
Clock
Output to Input Ratio for Hybrid mode
Figure 3. Hybrid Analog-Digital PLL
4.2.1
Fractional-N Source Selection for the Frequency Synthesizer
The fractional-N value for the frequency synthesizer can be sourced from either a static ratio or a dynamic
ratio generated from the digital PLL (see Figure 4). This allows for the selection between operating in the
static ratio based Frequency Synthesizer Mode as a simple frequency synthesizer (for frequency generation from the Timing Reference Clock) and in the dynamic ratio based Hybrid PLL Mode (for jitter reduction and clock multiplication). Selection between these two modes can either be made automatically
based on the presence of the Frequency Reference Clock or manually through the mode select pins.
Fractional-N
Frequency Synthesizer
Timing Reference Clock
PLL Output
N
Output to Input Ratio for Synthesizer Mode
Frequency Reference Clock
Digital PLL & Fractional-N Logic
Output to Input ratio for Hybrid Mode
Figure 4. Fractional-N Source Selection Overview
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5. APPLICATIONS
5.1
One Time Programmability
The one time programmable (OTP) circuitry in the CS2000-OTP allows for pre-configuration of the device
prior to use in a system. There are two types of parameters that are used for device pre-configuration: modal
and global. The modal parameters are features which, when grouped together, create a modal configuration
set (see Figure 16 on page 23). Up to four modal configuration sets can be permanently stored and then
dynamically selected using the M[1:0] mode select pins (see Table 1). The global parameters are the remaining configuration settings which do not change with the mode select pins. The modal and global parameters can be pre-set at the factory or user programmed using the customer development kit, CDK2000;
Please see “Programming Information” on page 28 for more details.
Parameter Type
M[1:0] pins = 00
M[1:0] pins = 01
M[1:0] pins = 10
M[1:0] pins = 11
Modal
Configuration Set 0
Ratio 0
Configuration Set 1
Ratio 1
Configuration Set 2
Ratio 2
Configuration Set 3
Ratio 3
Global
Configuration settings set once for all modes.
Table 1. Modal and Global Configuration
5.2
Timing Reference Clock Input
The low jitter timing reference clock (RefClk) can be provided by either an external reference clock or an
external crystal in conjunction with the internal oscillator. In order to maintain a stable and low-jitter PLL output the timing reference clock must also be stable and low-jitter; the quality of the timing reference clock
directly affects the performance of the PLL and hence the quality of the PLL output.
5.2.1
Internal Timing Reference Clock Divider
The Internal Timing Reference Clock (SysClk) is limited to a lower maximum frequency than that allowed
on the XTI/REF_CLK pin. The CS2000-OTP supports the wider external frequency range by offering an
internal divider for RefClk. The RefClkDiv[1:0] global parameter should be configured such that SysClk,
the divided RefClk, then falls within the valid range as indicated in Figure 5.
XTI/REF_CLK
Timing Reference Clock
8 MHz < RefClk <
50 MHz (XTI)
75 MHz (REF_CLK)
Timing Reference
Clock Divider
÷1
÷2
÷4
Internal Timing
Reference Clock
8 MHz < SysClk < 18.75 MHz
RefClkDiv[1:0]
Fractional-N
Frequency
Synthesizer
PLL Output
N
Figure 5. Internal Timing Reference Clock Divider
It should be noted that the maximum allowable input frequency of the XTI/REF_CLK pin is dependent
upon its configuration as either a crystal connection or external clock input. See the “AC Electrical Characteristics” on page 7 for more details.
Referenced Control
Parameter Definition
RefClkDiv[1:0] .......................“Reference Clock Input Divider (RefClkDiv[1:0])” on page 25
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5.2.2
Crystal Connections (XTI and XTO)
An external crystal may be used to generate RefClk. To accomplish this, a 20 pF fundamental mode parallel resonant crystal must be connected between the XTI and XTO pins as shown in Figure 6. As shown,
nothing other than the crystal and its load capacitors should be connected to XTI and XTO. Please refer
to the “AC Electrical Characteristics” on page 7 for the allowed crystal frequency range.
XTI
40 pF
XTO
40 pF
Figure 6. External Component Requirements for Crystal Circuit
5.2.3
External Reference Clock (REF_CLK)
For operation with an externally generated REF_CLK signal, XTI/REF_CLK should be connected to the
reference clock source and XTO should be left unconnected or terminated through a 47 kΩ resistor to
GND.
5.3
Frequency Reference Clock Input, CLK_IN
The frequency reference clock input (CLK_IN) is used in Hybrid PLL Mode by the Digital PLL and FractionalN Logic block to dynamically generate a fractional-N value for the Frequency Synthesizer (see “Hybrid Analog-Digital PLL” on page 9). The Digital PLL first compares the CLK_IN frequency to the PLL output. The
Fractional-N logic block then translates the desired ratio based off of CLK_IN to one based off of the internal
timing reference clock (SysClk). This allows the low-jitter timing reference clock to be used as the clock
which the Frequency Synthesizer multiplies while maintaining synchronicity with the frequency reference
clock through the Digital PLL. The allowable frequency range for CLK_IN is found in the “AC Electrical Characteristics” on page 7.
5.3.1
CLK_IN Skipping Mode
CLK_IN skipping mode allows the PLL to maintain lock even when the CLK_IN signal has missing pulses
for up to 20 ms (tCS) at a time (see “AC Electrical Characteristics” on page 7 for specifications). CLK_IN
skipping mode can only be used when the CLK_IN frequency is below 80 kHz. The ClkSkipEn global parameter enables this function.
Regardless of the setting of the ClkSkipEn parameter the PLL output will continue for 223 SysClk cycles
(466 ms to 1048 ms) after CLK_IN is removed (see Figure 7). This is true as long as CLK_IN does not
glitch or have an effective change in period as the clock source is removed, otherwise the PLL will interpret this as a change in frequency causing clock skipping and the 223 SysClk cycle time-out to be bypassed and the PLL to immediately unlock. If the prior conditions are met while CLK_IN is removed and
223 SysClk cycles pass, the PLL will unlock and the PLL_OUT state will be determined by the ClkOutUnl
parameter; See “PLL Clock Output” on page 19. If CLK_IN is re-applied after such time, the PLL will re-
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main unlocked for the specified time listed in the “AC Electrical Characteristics” on page 7 after which lock
will be acquired and the PLL output will resume.
223 SysClk cycles
223 SysClk cycles
Lock Time
Lock Time
CLK_IN
ClkSkipEn=0 or 1
ClkOutUnl=0
CLK_IN
ClkSkipEn=0 or 1
ClkOutUnl=1
PLL_OUT
UNLOCK
PLL_OUT
UNLOCK
= invalid clocks
Figure 7. CLK_IN removed for > 223 SysClk cycles
f CLK_IN is removed and then reapplied within 223 SysClk cycles but later than tCS, the ClkSkipEn parameter will have no effect and the PLL output will continue until CLK_IN is re-applied (see Figure 8).
Once CLK_IN is re-applied, the PLL will go unlocked only for the time it takes to acquire lock; the
PLL_OUT state will be determined by the ClkOutUnl parameter during this time.
223 SysClk cycles
223 SysClk cycles
tCS
tCS
Lock Time
Lock Time
CLK_IN
ClkSkipEn=0 or 1
ClkOutUnl=0
PLL_OUT
UNLOCK
CLK_IN
ClkSkipEn=0 or 1
ClkOutUnl=1
PLL_OUT
UNLOCK
= invalid clocks
Figure 8. CLK_IN removed for < 223 SysClk cycles but > tCS
If CLK_IN is removed and then re-applied within tCS, the ClkSkipEn parameter determines whether
PLL_OUT continues while the PLL re-acquires lock (see Figure 9). When ClkSkipEn is disabled and
CLK_IN is removed the PLL output will continue until CLK_IN is re-applied at which point the PLL will go
unlocked only for the time it takes to acquire lock; the PLL_OUT state will be determined by the ClkOutUnl
parameter during this time. When ClkSkipEn is enabled and CLK_IN is removed the PLL output clock will
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remain continuous throughout the missing CLK_IN period including the time while the PLL re-acquires
lock.
tCS
tCS
Lock Time
CLK_IN
ClkSkipEn=1
ClkOutUnl=0 or 1
CLK_IN
ClkSkipEn=0
ClkOutUnl=1
PLL_OUT
UNLOCK
PLL_OUT
UNLOCK
= invalid clocks
Lock Time
tCS
CLK_IN
ClkSkipEn=0
ClkOutUnl=0
PLL_OUT
UNLOCK
Figure 9. CLK_IN removed for < tCS
Referenced Control
Parameter Definition
ClkSkipEn..............................“Clock Skip Enable (ClkSkipEn)” on page 25
ClkOutUnl..............................“Enable PLL Clock Output on Unlock (ClkOutUnl)” on page 25
5.3.2
Adjusting the Minimum Loop Bandwidth for CLK_IN
The CS2000 allows the minimum loop bandwidth of the Digital PLL to be adjusted between 1 Hz and
128 Hz using the ClkIn_BW[2:0] global parameter. The minimum loop bandwidth of the Digital PLL directly affects the jitter transfer function; specifically, jitter frequencies below the loop bandwidth corner are
passed from the PLL input directly to the PLL output without attenuation. In some applications it is desirable to have a very low minimum loop bandwidth to reject very low jitter frequencies, commonly referred
to as wander. In others it may be preferable to remove only higher frequency jitter, allowing the input wander to pass through the PLL without attenuation.
Typically, applications in which the PLL_OUT signal creates a new clock domain from which all other system clocks and associated data are derived will benefit from the maximum jitter and wander rejection of
the lowest PLL bandwidth setting. See Figure 10.
PLL
BW = 1 Hz
CLK_IN
Wander > 1 Hz
PLL_OUT
MCLK
Jitter
MCLK
or
Wander and Jitter > 1 Hz Rejected
Subclocks generated
from new clock domain.
LRCK
LRCK
SCLK
SCLK
SDATA
D0
D1
SDATA
D0
D1
Figure 10. Low bandwidth and new clock domain
Systems in which some clocks and data are derived from the PLL_OUT signal while other clocks and data
are derived from the CLK_IN signal will often require phase alignment of all the clocks and data in the
system. See Figure 11. If there is substantial wander on the CLK_IN signal in these applications, it may
be necessary to increase the minimum loop bandwidth allowing this wander to pass through to the
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CS2000-OTP
CLK_OUT signal in order to maintain phase alignment. For these applications, it is advised to experiment
with the loop bandwidth settings and choose the lowest bandwidth setting that does not produce system
timing errors due to wandering between the clocks and data synchronous to the CLK_IN domain and
those synchronous to the PLL_OUT domain.
PLL
BW = 128 Hz
CLK_IN
Wander < 128 Hz
PLL_OUT
Jitter
MCLK
or
Jitter > 128 Hz Rejected
Wander < 128 Hz Passed to Output
MCLK
Subclocks and data re-used
from previous clock domain.
LRCK
LRCK
SCLK
SCLK
SDATA
D0
D1
SDATA
D0
D1
Figure 11. High bandwidth with CLK_IN domain re-use
While acquiring lock, the digital loop bandwidth is automatically set to a large value. Once lock is
achieved, the digital loop bandwidth will settle to the minimum value selected by the ClkIn_BW[2:0] parameter.
Referenced Control
Parameter Definition
ClkIn_BW[2:0] .......................“Clock Input Bandwidth (ClkIn_BW[2:0])” on page 26
5.4
5.4.1
Output to Input Frequency Ratio Configuration
User Defined Ratio (RUD), Frequency Synthesizer Mode
The User Defined Ratio, RUD, is a 32-bit un-signed fixed-point number which determines the basis for the
desired input to output clock ratio. Up to four different ratios, Ratio0-3, can be stored in the CS2000’s one
time programmable memory. Selection between the four ratios is achieved by the M[1:0] mode select
pins. The 32-bit RUD is represented in a high-resolution 12.20 format where the 12 MSBs represent the
integer binary portion while the remaining 20 LSBs represent the fractional binary portion. The maximum
multiplication factor is approximately 4096 with a resolution of 0.954 PPM in this configuration. See “Calculating the User Defined Ratio” on page 27 for more information.
The status of internal dividers, such as the internal timing reference clock divider, are automatically taken
into account. Therefore RUD is simply the desired ratio of the output to input clock frequencies.
Referenced Control
Parameter Definition
Ratio 0-3................................“Ratio 0 - 3” on page 24
M[1:0] ....................................“M1 and M0 Mode Pin Functionality” on page 20
5.4.2
User Defined Ratio (RUD), Hybrid PLL Mode
The same four ratio locations, Ratio0-3, are used to store the User Defined Ratios for Hybrid PLL Mode.
Selection of the User Defined Ratio for the dynamic ratio based Hybrid PLL Mode is made with the M[1:0]
pins (unless auto fractional N source selection is enabled; see section 5.4.6 on page 16).
In addition to the High-Resolution ratio format, a High-Multiplication format is also available. In the HighMultiplication format mode, the 32-bit fixed-point number for RUD is represented in a 20.12 format where
the 20 MSBs represent the integer binary portion while the remaining 12 LSBs represent the fractional
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CS2000-OTP
binary portion. In this configuration, the maximum multiplication factor is approximately 1,048,575 with a
resolution of 244 PPM.
The 20.12 format is enabled by the LFRatioCfg global parameter. The 20.12 ratio format is only available
when the device is running in Hybrid PLL Mode. In Auto Fractional-N Source Selection Mode (see section
5.4.6.2 on page 17) when CLK_IN is not present the LFRatioCfg parameter is ignored and the ratio format
is 12.20.
It is recommended that the 12.20 High-Resolution format be utilized whenever the desired ratio is less
than 4096 since the output frequency accuracy of the PLL is directly proportional to the accuracy of the
timing reference clock and the resolution of the RUD.
Referenced Control
Parameter Definition
LockClk[1:0] ..........................“Lock Clock Ratio (LockClk[1:0])” section on page 24
LFRatioCfg ............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 26
FracNSrc ...............................“Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 24
5.4.3
Manual Ratio Modifier (R-Mod)
The manual Ratio Modifier is used to internally multiply/divide the currently addressed RUD (Ratio0-3
stored in the register space remain unchanged). The available options for R-Mod are summarized in
Table 2 on page 15. R-Mod is enabled via the M2 pin in conjunction with the appropriate setting of the
M2Config[2:0] global parameter (see Section 5.7.2 on page 20).
RModSel[1:0]
R Modifier
00
0.5
01
0.25
10
0.125
11
0.0625
Table 2. Ratio Modifier
Referenced Control
Parameter Definition
Ratio 0-3................................“Ratio 0 - 3” on page 24
RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 23
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 26
5.4.4
Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only
The Automatic R-Modifier uses the CLK_IN Frequency Range Detector to implement a frequency dependent multiply of the currently addressed RUD as shown in Table 3. The CLK_IN Frequency Range Detector determines the ratio between the frequency of the internal SysClk and the CLK_IN input signal. The
result of the ratio measurement is the internal status signal called FsDetect[1:0].
Like with R-Mod, the Ratio0-3 parameters stored in the one time programmable memory remain unchanged. The Automatic Ratio Modifier is enabled either by the AutoRMod modal parameter or via the
M2 pin in conjunction with the appropriate setting of the M2Config[2:0] global parameter (see Section
5.7.2 on page 20).
FsDetect[1:0]
fSysClk / fCLK_IN
Auto R Modifier
00
> 224
1
01
96 - 224
0.5
10
< 96
0.25
Table 3. Automatic Ratio Modifier
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CS2000-OTP
It is important to note that Auto R-Mod (if enabled) is applied in addition to any R-Mod already selected
by the RModSel[1:0] modal parameter and is used to calculate the Effective Ratio (see Section 5.4.5 on
page 16).
Auto R-Mod can be used to generate the appropriate oversampling clock (MCLK) for audio A/D and D/A
converters. For example, if the clock applied to CLK_IN is the audio sample rate, Fs (also known as the
word, frame or Left/Right clock), and SysClk is 12.288 MHz (REF_CLK = 12.288 MHz with RefClkDiv[1:0]
set to ‘10’), FsDetect[1:0] would then reflect the frequency range of the audio sample rate. An RUD of 512
generates the audio oversampling clocks as shown in Table 4.
FsDetect[1:0]
Inferred Audio Sample Rate
when SysClk = 12.288 MHz
Speed Mode (used for
audio converters)
Audio Oversampling
Clock
00
< 54.8 kHz
Single Speed
512 x
01
54.8 kHz to 128 kHz
Double Speed
256 x
10
> 128 kHz
Quad Speed
128 x
Table 4. Example Audio Oversampling Clock Generation from CLK_IN
Referenced Control
Parameter Definition
Ratio 0-3................................“Ratio 0 - 3” on page 24
RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 23
AutoRMod .............................“Auto R-Modifier Enable (AutoRMod)” on page 24
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 26
5.4.5
Effective Ratio (REFF)
The Effective Ratio (REFF) is an internal calculation comprised of RUD and the appropriate modifiers, as
previously described. REFF is calculated as follows:
Frequency Synthesizer (Static Ratio) Mode: REFF = RUD • R-Mod
Hybrid PLL (Dynamic Ratio) Mode: REFF = RUD • R-Mod • Auto R-Mod
To simplify operation the device handles some of the ratio calculation functions automatically (such as
when the internal timing reference clock divider is set). For this reason, the Effective Ratio does not need
to be altered to account for internal dividers.
Ratio modifiers which would produce an overflow or truncation of REFF should not be used. In all cases,
the maximum and minimum allowable values for REFF are dictated by the frequency limits for both the
input and output clocks as shown in the “AC Electrical Characteristics” on page 7.
Selection of the user defined ratio from the four stored ratios is made by using the M[1:0] pins unless auto
clock switching is enabled in which case the LockClk[1:0] modal parameter also selects the ratio (see
“Fractional-N Source Selection” on page 16).
Referenced Control
Parameter Definition
M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 20
LockClk[1:0] ..........................“Lock Clock Ratio (LockClk[1:0])” section on page 24
5.4.6
Fractional-N Source Selection
To select between the static ratio based Frequency Synthesizer Mode and the dynamic ratio based Hybrid
PLL Mode, the source for the fractional-N value for the Frequency Synthesizer must be changed. The
Fractional-N value can either be sourced directly from the Effective Ratio (static ratio) or from the output
of the Digital PLL (dynamic ratio) (see Figure 12 on page 18). The setting of this function can be made
manual or automatically depending on the presence of CLK_IN.
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CS2000-OTP
5.4.6.1
Manual Fractional-N Source Selection for the Frequency Synthesizer
Manual selection of the fractional-N source for the frequency synthesizer can be done in one of two
ways. The FracNSrc modal parameter can be set to the desired setting for each available configuration mode and then the Fractional N source is selected by the M1 and M0 pins. In order for this
manual selection to work, the LockClk[1:0] modal parameter (even if unused) must be set to the
same value as the modal ratio (Ratio 0 for Mode 0, Ratio 1 for Mode 1, etc.), see Section 5.4.6.2
on page 17. Alternatively, the M2 pin in conjunction with the M2Config[2:0] global parameter can
be set to control the fractional N source directly and thus override the FracNSrc modal parameter
(see Section 5.7.2.5 on page 21 for details).
Referenced Control
Parameter Definition
M[1:0] pins ............................ “M1 and M0 Mode Pin Functionality” on page 20
LockClk[1:0] .......................... “Lock Clock Ratio (LockClk[1:0])” section on page 24
FracNSrc............................... “Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 24
M2Config[2:0] ....................... “M2 Pin Configuration (M2Config[2:0])” on page 26
5.4.6.2
Automatic Fractional-N Source Selection for the Frequency Synthesizer
Automatic source selection allows for the selection of the frequency synthesizer’s fractional-N value
to be made dependent on the presence of the CLK_IN signal. When CLK_IN is present the device
will use the dynamic ratio generated from the Digital PLL and CLK_IN for Hybrid PLL Mode. When
CLK_IN is not present, the device will use RefClk and the static ratio for Frequency Synthesizer
Mode. After losing CLK_IN, the CS2000-OTP will wait for 223 SysClk cycles before switching to SysClk and re-acquiring lock, during which time the PLL is unlocked
The modal ratio location (see Table 1 on page 10) should contain the desired CLK_OUT to RefClk
ratio to be used when CLK_IN is not present. The User Defined Ratio pointed to by LockClk[1:0]
should contain the desired CLK_OUT to CLK_IN ratio to be used when CLK_IN is present. Automatic source selection is enabled when the LockClk[1:0] modal parameter is set to a different User
Defined Ratio from the modal ratio location.
When automatic source selection is enabled, the FracNSrc modal parameter (used for manual
clock selection) will be ignored.
The automatic source selection feature can be disabled by setting the LockClk[1:0] modal parameter to the modal ratio location. The FracNSrc modal parameter must then be used to select the
desired clock used for the PLL’s frequency reference. The automatic source selection feature can
also be disabled by using the M2 pin in conjunction with the M2Config[2:0] global parameter.
Referenced Control
Parameter Definition
M[1:0] pins ............................ “M1 and M0 Mode Pin Functionality” on page 20
LockClk[1:0] .......................... “Lock Clock Ratio (LockClk[1:0])” section on page 24
FracNSrc............................... “Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 24
M2Config[2:0] ....................... “M2 Pin Configuration (M2Config[2:0])” on page 26
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CS2000-OTP
5.4.7
Ratio Configuration Summary
The RUD is the user defined ratio for which up to four different values (Ratio0-3) can be stored in the one
time programmable memory. The M[1:0] pins or LockClk[1:0] modal parameter then select the user defined ratio to be used (depending on if static or dynamic ratio mode is to be used). The resolution for the
RUD is selectable for the dynamic ratio mode. R-Mods can be applied to both modes whereas Auto R-Mod
is only available in dynamic mode. The user defined ratio, ratio modifier, and automatic ratio modifier
make up the effective ratio REFF, the final calculation used to determine the output to input clock ratio. The
effective ratio is then corrected for the internal dividers. The frequency synthesizer’s fractional-N source
selection is made between the static ratio (in frequency synthesizer mode) or the dynamic ratio generated
from the digital PLL (in Hybrid PLL mode) by either the FracNSrc modal parameter for manual mode or
the presence of CLK_IN in automatic mode. The conceptual diagram in Figure 12 summarizes the features involved in the calculation of the ratio values used to generate the fractional-N value which controls
the Frequency Synthesizer. The subscript ‘4’ indicates the modal parameters.
M2 pin force Manual
or
M[1:0] pins =? LockClk[1:0]
Auto Selection
(CLK_IN sense)
≠
Manual Selection
(FracNSrc4 or M2 pin)
=
Effective Ratio REFF
M2 pin
M[1:0] pins
User Defined Ratio RUD
Ratio 0
RModSel[1:0]4
Ratio Format
Ratio 1
12.20
only
Ratio 2
Ratio
Modifier
Timing Reference Clock
(XTI/REF_CLK)
Divide
RefClkDiv[1:0]
R Correction
SysClk
RefClkDiv[1:0]
Frequency
Synthesizer
PLL Output
Static Ratio
N
Dynamic Ratio
Ratio 3
12.20
20.12
Ratio
Modifier
Auto
R-Mod
R Correction
LFRatioCfg
LockClk[1:0]4
AutoRMod4
or M2 pin
FsDet[1:0]
Digital PLL &
Fractional N Logic
Frequency Reference Clock
(CLK_IN)
Figure 12. Ratio Feature Summary
Referenced Control
Parameter Definition
Ratio 0-3................................“Ratio 0 - 3” on page 24
M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 20
LockClk[1:0] ..........................“Lock Clock Ratio (LockClk[1:0])” section on page 24
LFRatioCfg ............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 26
RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 23
AutoRMod .............................“Auto R-Modifier Enable (AutoRMod)” on page 24
RefClkDiv[1:0] .......................“Reference Clock Input Divider (RefClkDiv[1:0])” on page 25
FracNSrc ...............................“Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 24
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CS2000-OTP
5.5
PLL Clock Output
The PLL clock output pin (CLK_OUT) provides a buffered version of the output of the frequency synthesizer.
The driver can be set to high-impedance with the M2 pin when the M2Config[1:0] global parameter is set to
either 000 or 010. The output from the PLL automatically drives a static low condition while the PLL is unlocked (when the clock may be unreliable). This feature can be disabled by setting the ClkOutUnl global
parameter, however the state CLK_OUT may then be unreliable during an unlock condition.
ClkOutUnl
PLL Locked/Unlocked
0
0
2:1 Mux
M2 pin with
M2Config[1:0] = 000, 010
0
1
2:1 Mux
PLL Clock Output
PLLClkOut
PLL Clock Output Pin
(CLK_OUT)
1
PLL Output
Figure 13. PLL Clock Output Options
Referenced Control
Parameter Definition
ClkOutUnl..............................“Enable PLL Clock Output on Unlock (ClkOutUnl)” on page 25
ClkOutDis ..............................“M2 Configured as Output Disable” on page 20
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 26
5.6
Auxiliary Output
The auxiliary output pin (AUX_OUT) can be mapped, as shown in Figure 14, to one of four signals: reference clock (RefClk), input clock (CLK_IN), additional PLL clock output (CLK_OUT), or a PLL lock indicator
(Lock). The mux is controlled via the AuxOutSrc[1:0] modal parameter. If AUX_OUT is set to Lock, the AuxLockCfg global parameter is then used to control the output driver type and polarity of the LOCK signal (see
section 6.3.2 on page 25). If AUX_OUT is set to CLK_OUT, the phase of the PLL Clock Output signal on
AUX_OUT may differ from the CLK_OUT pin. The driver for the pin can be set to high-impedance using the
M2 pin when the M2Config[1:0] global parameter is set to either 001 or 010.
AuxOutSrc[1:0]
Timing Reference Clock
(RefClk)
M2 pin with
M2Config[1:0] = 001, 010
Frequency Reference Clock
(CLK_IN)
Auxiliary Output Pin
(AUX_OUT)
4:1 Mux
PLL Clock Output
(PLLClkOut)
AuxLockCfg
PLL Lock/Unlock Indication
(Lock)
Figure 14. Auxiliary Output Selection
Referenced Control
Parameter Definition
AuxOutSrc[1:0]......................“Auxiliary Output Source Selection (AuxOutSrc[1:0])” on page 24
AuxOutDis .............................“M2 Configured as Output Disable” on page 20
AuxLockCfg...........................“AUX PLL Lock Output Configuration (AuxLockCfg)” section on page 25
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 26
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CS2000-OTP
5.7
Mode Pin Functionality
5.7.1
M1 and M0 Mode Pin Functionality
M[1:0] determine the functional mode of the device and select both the default User Defined Ratio and
the set of modal parameters. The modal parameters are RModSel[1:0], AuxOutSrc[1:0], AutoRMod, LockClk[1:0], and FracNSrc. By modifying one or more of the modal parameters between the 4 sets, different
functional configurations can be achieved. However, global parameters are fixed and the same value will
be applied to each functional configuration. Figure 16 on page 23 provides a summary of all parameters
used by the device.
5.7.2
M2 Mode Pin Functionality
M2 usage is mapped to one of the optional special functions via the M2Config[2:0] global parameter. Depending on what M2 is mapped to, it will either act as an output enable/disable pin or override certain modal parameters. Figure 15 summarizes the available options and the following sections will describe each
option in more detail.
M2Config[2:0] global parameter
M2 pin
000
Disable CLK_OUT pin
001
Disable AUX_OUT pin
010
Disable CLK_OUT and AUX_OUT pins
011
RModSel[1:0] Modal Parameter Enable
100
Force Manual Fractional N Source Selection
101
AutoRMod Modal Parameter Override
110
FracNSrc Modal Parameter Override
111
Force AuxOutSel[1:0] = 10 (PLL Clock Out)
Figure 15. M2 Mapping Options
5.7.2.1
M2 Configured as Output Disable
If M2Config[2:0] is set to either ‘000’, ‘001’, or ‘010’, M2 becomes an output disable pin for one or
both output pins. If M2 is driven ‘low’, the corresponding output(s) will be enabled, if M2 is driven
‘high’, the corresponding output(s) will be disabled.
5.7.2.2
M2 Configured as R-Mod Enable
If M2Config[2:0] is set to ‘011’, M2 becomes the R-Mod enable pin. It should be noted that M2 is
the only way to enable R-Mod. Even though the RModSel[1:0] modal parameter can be set arbitrarily for each configuration set, it will not take effect unless enabled via M2. If M2 is driven ‘low’,
R-Mod will be disabled, if M2 is driven ‘high’ R-Mod will be enabled.
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CS2000-OTP
5.7.2.3
M2 Configured as Auto Fractional-N Source Selection Disable
If M2Config[2:0] is set to ‘100’, M2 becomes a disable pin for the auto fractional-N source selection
functionality. If auto fractional-N source selection is enabled (see section 5.4.6 on page 16), driving
M2 ‘high’ will disable the auto fractional-N source selection and revert control over the fractional-N
source to the FracNSrc modal parameter, regardless of the LockClk[1:0] modal parameter and the
presence of a clock on CLK_IN. If auto fractional-N source selection is not enabled, toggling M2 will
have no effect in this case.
5.7.2.4
M2 Configured as Auto R-Mod Enable
If M2Config[2:0] is set to ‘101’, M2 becomes the Auto R-Mod enable pin and will override the AutoRMod modal parameter. If M2 is driven ‘low’, Auto R-Mod will be disabled, if M2 is driven ‘high’
Auto R-Mod will be enabled.
5.7.2.5
M2 Configured as Fractional-N Source Select
If M2Config[2:0] is set to ‘110’, M2 becomes the Fractional-N Source Select pin and will override
the FracNSrc modal parameter. It should be noted that overriding FracNSrc has no effect when
auto clock switching is enabled (see section 5.4.6 on page 16). If M2 is driven ‘low’, the fractionalN value will be the Static Ratio sourced directly from REFF for Frequency Synthesizer Mode. If M2
is driven ‘high’ the fractional-N value will be the Dynamic Ratio sourced from the Digital PLL for Hybrid PLL Mode.
5.7.2.6
M2 Configured as AuxOutSrc Override
If M2Config[2:0] is set to ‘111’, M2 when driven ‘high’ will override the AuxOutSrc[1:0] modal parameter and force the AUX_OUT source to PLL Clock Output. When M2 is driven ‘low’, AUX_OUT
will function according to AuxOutSrc[1:0].
5.8
5.8.1
Clock Output Stability Considerations
Output Switching
The CS2000-OTP is designed such that re-configuration of the clock routing functions do not result in a
partial clock period on any of the active outputs (CLK_OUT and/or AUX_OUT). In particular, enabling or
disabling an output, changing the auxiliary output source between REF_CLK and CLK_OUT, changing
between Frequency Synthesizer and Hybrid PLL Mode, and the automatic disabling of the output(s) during unlock will not cause a runt or partial clock period.
The following exceptions/limitations exist:
•
Enabling/disabling AUX_OUT when AuxOutSrc = 11 (unlock indicator).
•
Switching AuxOutSrc[1:0] to or from 01 (CLK_IN) and to or from 11 (unlock indicator)
(Transitions between AuxOutSrc[1:0] = [00,10] will not produce a glitch).
When any of these exceptions occur, a partial clock period on the output may result.
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CS2000-OTP
5.8.2
PLL Unlock Conditions
Certain changes to the clock inputs and mode pins can cause the PLL to lose lock which will affect the
presence of a clock signal on CLK_OUT. The following outlines which conditions cause the PLL to go unlocked:
22
•
Any change in the state of the M1 and M0 pins will cause the PLL to temporarily lose lock as the new
setting takes affect.
•
Changes made to the state of the M2 when the M2Config[2:0] global parameter is set to 011, 100, 101,
or 110 can cause the PLL to temporarily lose lock as the new setting takes affect.
•
Any discontinuities on the Timing Reference Clock, REF_CLK.
•
Discontinuities on the Frequency Reference Clock, CLK_IN, except when the Clock Skipping feature
is enabled and the requirements of Clock Skipping are satisfied (see “CLK_IN Skipping Mode” on
page 11).
•
Gradual changes in CLK_IN frequency greater than ±30% from the starting frequency.
•
Step changes in CLK_IN frequency.
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6. PARAMETER DESCRIPTIONS
As mentioned in Section 5.1 on page 10, there are two different kinds of parameter configuration sets, Modal and
Global. These configuration sets, shown in Figure 16, can be programmed in the field using the CDK2000 or preprogrammed at the factory. Please see “Programming Information” on page 28 for more details.
M[1:0] pins
Modal Configuration Set #0
RModSel[1:0]
Ratio 0
AuxOutSrc[1:0]
AutoRmod
LockClk[1:0]
FracNSrc
00
AuxOutSrc[1:0]
AutoRmod
LockClk[1:0]
FracNSrc
01
AuxOutSrc[1:0]
AutoRmod
LockClk[1:0]
FracNSrc
10
AuxOutSrc[1:0]
AutoRmod
LockClk[1:0]
FracNSrc
11
Ratio 1
RModSel[1:0]
Modal Configuration Set #2
Ratio 2
RModSel[1:0]
Modal Configuration Set #3
Ratio 3
RModSel[1:0]
Digital/PLL Core
Modal Configuration Set #1
Global Configuration Set
ClkSkipEn
AuxLockCfg
RefClkDiv[1:0]
ClkOutUnl
LFRatioCfg
M2Config[2:0]
ClkIn_BW[2:0]
Figure 16. Parameter Configuration Sets
6.1
Modal Configuration Sets
There are four instances of each of these configuration parameters. Selection between the four stored sets
is made using the M[1:0] pins.
6.1.1
R-Mod Selection (RModSel[1:0])
Selects the R-Mod value, which is used as a factor in determining the PLL’s Fractional N.
RModSel[1:0]
R-Mod Selection
00
Right-shift R-value by 1 (÷ 2).
01
Right-shift R-value by 2 (÷ 4).
10
Right-shift R-value by 3 (÷ 8).
11
Right-shift R-value by 4 (÷ 16).
Application:
“Manual Ratio Modifier (R-Mod)” on page 15
Note: This parameter does not take affect unless M2 pin is high and the M2Config[2:0] global parameter is set to ‘011’.
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CS2000-OTP
6.1.2
Auxiliary Output Source Selection (AuxOutSrc[1:0])
Selects the source of the AUX_OUT signal.
AuxOutSrc[1:0]
Auxiliary Output Source
00
RefClk.
01
CLK_IN.
10
CLK_OUT.
11
PLL Lock Status Indicator.
Application:
“Auxiliary Output” on page 19
Note: When set to 11, the AuxLockCfg global parameter sets the polarity and driver type (“AUX PLL
Lock Output Configuration (AuxLockCfg)” on page 25).
6.1.3
Auto R-Modifier Enable (AutoRMod)
Controls the automatic ratio modifier function.
6.1.4
AutoRMod
Automatic R-Mod State
0
Disabled.
1
Enabled.
Application:
“Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only” on page 15
Lock Clock Ratio (LockClk[1:0])
Selects one of the four stored User Defined Ratios for use in the dynamic ratio based Hybrid PLL Mode.
LockClk[1:0]
CLK_IN Ratio Selection
00
Ratio 0.
01
Ratio 1.
10
Ratio 2.
11
Ratio 3.
Application:
Section 5.4.2 on page 14
Note: The User Defined Ratio for the static ratio based Frequency Synthesizer mode is the ratio that
corresponds with the currently chosen configuration set as shown in Figure 16 on page 23.
6.1.5
Fractional-N Source for Frequency Synthesizer (FracNSrc)
Selects static or dynamic ratio mode when auto clock switching is disabled.
6.2
FracNSrc
Fractional-N Source Selection
0
Static Ratio directly from REFF for Frequency Synthesizer Mode
1
Dynamic Ratio from Digital PLL for Hybrid PLL Mode
Application:
“Fractional-N Source Selection” on page 16
Ratio 0 - 3
The four 32-bit User Defined Ratios are stored in the CS2000’s one time programmable memory. See “Output to Input Frequency Ratio Configuration” on page 14 and “Calculating the User Defined Ratio” on
page 27 for more details.
24
DS758PP1
CS2000-OTP
6.3
6.3.1
Global Configuration Parameters
Clock Skip Enable (ClkSkipEn)
This parameter enables clock skipping mode for the PLL and allows the PLL to maintain lock even when
the CLK_IN has missing pulses.
ClkSkipEn
PLL Clock Skipping Mode
0
Disabled.
1
Enabled.
Application:
“CLK_IN Skipping Mode” on page 11
Note:
6.3.2
fCLK_IN must be < 80 kHz to use this feature.
AUX PLL Lock Output Configuration (AuxLockCfg)
When the AUX_OUT pin is configured as a lock indicator (AuxOutSrc[1:0] modal parameter = ‘11’), this
global parameter configures the AUX_OUT driver to either push-pull or open drain. It also determines the
polarity of the lock signal. If AUX_OUT is configured as a clock output, the state of this parameter is disregarded.
AuxLockCfg
AUX_OUT Driver Configuration
0
Push-Pull, Active High (output ‘high’ for unlocked condition, ‘low’ for locked condition).
1
Open Drain, Active Low (output ‘low’ for unlocked condition, high-Z for locked condition).
Application:
“Auxiliary Output” on page 19
Note: AUX_OUT is an unlock indicator, signalling an error condition when the PLL is unlocked. Therefore, the pin polarity is defined relative to the unlock condition.
6.3.3
Reference Clock Input Divider (RefClkDiv[1:0])
Selects the input divider for the timing reference clock.
6.3.4
RefClkDiv[1:0]
Reference Clock Input Divider
REF_CLK Frequency Range
00
÷ 4.
32 MHz to 75 MHz (50 MHz with XTI)
01
÷ 2.
16 MHz to 37.5 MHz
10
÷ 1.
8 MHz to 18.75 MHz
11
Reserved.
Application:
“Internal Timing Reference Clock Divider” on page 10
Enable PLL Clock Output on Unlock (ClkOutUnl)
Defines the state of the PLL output during the PLL unlock condition.
ClkOutUnl
Clock Output Enable Status
0
Clock outputs are driven ‘low’ when PLL is unlocked.
1
Clock outputs are always enabled (results in unpredictable output when PLL is unlocked).
Application:
“PLL Clock Output” on page 19
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25
CS2000-OTP
6.3.5
Low-Frequency Ratio Configuration (LFRatioCfg)
Determines how to interpret the currently indexed 32-bit User Defined Ratio when the dynamic ratio based
Hybrid PLL Mode is selected (either manually or automatically, see section 5.4.6 on page 16).
LFRatioCfg
Ratio Bit Encoding Interpretation when Input Clock Source is CLK_IN
0
20.12 - High Multiplier.
1
12.20 - High Accuracy.
Application:
“User Defined Ratio (RUD), Frequency Synthesizer Mode” on page 14
Note: When the static ratio based Frequency Synthesizer Mode is selected (either manually or automatically), the currently indexed User Defined Ratio will always be interpreted as a 12.20 fixed point value,
regardless of how this parameter is set.
6.3.6
M2 Pin Configuration (M2Config[2:0])
Controls which special function is mapped to the M2 pin.
6.3.7
M2Config[2:0]
M2 pin function
000
Disable CLK_OUT pin.
001
Disable AUX_OUT pin.
010
Disable CLK_OUT and AUX_OUT.
011
RModSel[1:0] Modal Parameter Enable.
100
Force Manual Fractional N Source Selection.
101
AutoRMod Modal Parameter Override.
110
FracNSrc Modal Parameter Override
111
Force AuxOutSrc[1:0] = 10 (PLL Clock Out).
Application:
“M2 Mode Pin Functionality” on page 20
Clock Input Bandwidth (ClkIn_BW[2:0])
Sets the minimum loop bandwidth when locked to CLK_IN.
26
ClkIn_BW[2:0]
Minimum Loop Bandwidth
000
1 Hz
001
2 Hz
010
4 Hz
011
8 Hz
100
16 Hz
101
32 Hz
110
64 Hz
111
128 Hz
Application:
“Adjusting the Minimum Loop Bandwidth for CLK_IN” on page 13
DS758PP1
CS2000-OTP
7. CALCULATING THE USER DEFINED RATIO
Note:
The software for use with the evaluation kit has built in tools to aid in calculating and converting the User
Defined Ratio. This section is for those who would like to know more about how the User Defined Ratio is
calculated and stored.
Most calculators do not interpret the fixed point binary representation which the CS2000-OTP uses to define the
output to input clock ratio (see Section 5.4.1 on page 14); However, with a simple conversion we can use these tools
to generate a binary or hex value for Ratio0-3 to be stored in one time programmable memory. Please see “Programming Information” on page 28 for more details on programming.
7.1
High Resolution 12.20 Format
To calculate the User Defined Ratio (RUD) to store in the register(s), divide the desired output clock frequency by the given input clock (CLK_IN or RefClk). Then multiply the desired ratio by the scaling factor of 220
to get the scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and write to the register. A few examples have been provided in Table 5.
Scaled Decimal
Representation =
(output clock/input clock) • 220
Hex Representation of
Binary RUD
12.288 MHz/10 MHz=1.2288
1288490
00 13 A9 2A
11.2896 MHz/44.1 kHz=256
268435456
10 00 00 00
Desired Output to Input Clock Ratio
(output clock/input clock)
Table 5. Example 12.20 R-Values
7.2
High Multiplication 20.12 Format
To calculate the User Defined Ratio (RUD) to store in the register(s), divide the desired output clock frequency by the given input clock (CLK_IN). Then multiply the desired ratio by the scaling factor of 212 to get the
scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and
write to the register. A few examples have been provided in Table 6.
Desired Output to Input Clock Ratio
(output clock/input clock)
Scaled Decimal
Representation =
(output clock/input clock) • 212
Hex Representation of
Binary RUD
12.288 MHz/60 Hz=204,800
838860800
32 00 00 00
11.2896 MHz/59.97 Hz =188254.127...
771088904
2D F5 E2 08
Table 6. Example 20.12 R-Values
DS758PP1
27
CS2000-OTP
8. PROGRAMMING INFORMATION
Field programming of the CS2000-OTP is achieved using the hardware and software tools included with the
CDK2000. The software tools can be downloaded from www.cirrus.com for evaluation prior to ordering a CDK. The
CDK2000 is designed with built-in features to ease the process of programming small quantities of devices for prototype and small production builds. In addition to its field programming capabilities, the CDK2000 can also be used
for the complete evaluation of programmed CS2000-OTP devices.
The CS2000-OTP can also be factory programmed for large quantity orders. When ordering factory programmed
devices, the CDK should first be used to program and evaluate the desired configuration. When evaluation is complete, the CS2000 Configuration Wizard is used to generate a file containing all device configuration information;
this file is conveyed to Cirrus Logic as a complete specification for the factory programming configuration. Please
contact your local Cirrus Logic sales representative for more information regarding factory programmed parts.
See the CDK2000 datasheet, available at www.cirrus.com, for detailed information on the use of the CDK2000 programming and evaluation tools.
Below is a form which represents the information required for programming a device (noted in gray). The “Parameter
Descriptions” section beginning on page 23 describes the functions of each parameter. This form may be used either for personal notation for device configuration or it can be filled out and given to a Cirrus representative in conjunction with the programming file from the CDK2000 as an additional check. The User Defined Ratio may be filled
out in decimal or it may be entered as hex as outlined in “Calculating the User Defined Ratio” on page 27. For all
other parameters mark a ‘0’ or ‘1’ below the parameter name.
OTP Modal and Global Configuration Parameters Form
Modal Configuration Set #0
Ratio 0 (dec)
Ratio 0 (hex) __ __ : __ __ : __ __ : __ __
RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0
AutoRMod
LockClk1
LockClk0
FracNSrc
Modal Configuration Set #1
Ratio 0 (dec)
Ratio 0 (hex) __ __ : __ __ : __ __ : __ __
RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0
AutoRMod
LockClk1
LockClk0
FracNSrc
Modal Configuration Set #2
Ratio 0 (dec)
Ratio 0 (hex) __ __ : __ __ : __ __ : __ __
RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0
AutoRMod
LockClk1
LockClk0
FracNSrc
Modal Configuration Set #3
Ratio 0 (dec)
Ratio 0 (hex) __ __ : __ __ : __ __ : __ __
RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0
AutoRMod
LockClk1
LockClk0
FracNSrc
Global Configuration Set
ClkSkipEn AuxLockCfg RefClkDiv1
LFRatioCfg
M2Cfg2
M2Cfg1
M2Cfg0
ClkIn_BW2
28
ClkIn_BW1
RefClkDiv0
ClkOutUnl
ClkIn_BW0
DS758PP1
CS2000-OTP
9. PACKAGE DIMENSIONS
10L MSOP (3 mm BODY) PACKAGE DRAWING (Note 1)
N
D
E11
c
E
A2
e
b
∝
A1
SIDE VIEW
1 2 3
A
END VIEW
L
SEATING
PLANE
L1
TOP VIEW
DIM
MIN
INCHES
NOM
A
A1
A2
b
c
D
E
E1
e
L
L1
-0
0.0295
0.0059
0.0031
----0.0157
--
-----0.1181 BSC
0.1929 BSC
0.1181 BSC
0.0197 BSC
0.0236
0.0374 REF
MAX
0.0433
0.0059
0.0374
0.0118
0.0091
----0.0315
--
MIN
MILLIMETERS
NOM
NOTE
MAX
-0
0.75
0.15
0.08
----0.40
--
-----3.00 BSC
4.90 BSC
3.00 BSC
0.50 BSC
0.60
0.95 REF
1.10
0.15
0.95
0.30
0.23
----0.80
--
4, 5
2
3
Notes: 1. Reference document: JEDEC MO-187
2. D does not include mold flash or protrusions which is 0.15 mm max. per side.
3. E1 does not include inter-lead flash or protrusions which is 0.15 mm max per side.
4. Dimension b does not include a total allowable dambar protrusion of 0.08 mm max.
5. Exceptions to JEDEC dimension.
THERMAL CHARACTERISTICS
Parameter
Junction to Ambient Thermal Impedance
DS758PP1
JEDEC 2-Layer
JEDEC 4-Layer
Symbol
Min
Typ
Max
Units
θJA
θJA
-
170
100
-
°C/W
°C/W
29
CS2000-OTP
10.ORDERING INFORMATION
The CS2000-OTP is ordered as an un-programmed device. The CS2000-OTP can also be factory programmed for
large quantity orders. Please see “Programming Information” on page 28 for more details.
Product
Description
Package
Pb-Free
CS2000-OTP
Clocking Device
10L-MSOP
Yes
CS2000-OTP
Clocking Device
10L-MSOP
Yes
CDK2000
Evaluation Platform
-
Yes
Grade
Commercial
-
Temp Range Container
Order#
-10° to +70°C
Rail
CS2000P-CZZ
-10° to +70°C
Tape and
Reel
CS2000P-CZZR
-
-
CDK-2000-CLK
11.REVISION HISTORY
Release
A1
PP1
Changes
Initial Release
Updated “AC Electrical Characteristics” on page 7
Contacting Cirrus Logic Support
For all product questions and inquiries, contact a Cirrus Logic Sales Representative.
To find one nearest you, go to www.cirrus.com.
IMPORTANT NOTICE
“Preliminary” product information describes products that are in production, but for which full characterization data is not yet available.
Cirrus Logic, Inc. and its subsidiaries (“Cirrus”) believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided “AS IS” without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus
for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third
parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights,
copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This consent
does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED FOR USE
IN PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER’S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR CUSTOMER’S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY
INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, INCLUDING ATTORNEYS’ FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES.
Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks
or service marks of their respective owners.
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DS758PP1