Product
Folder
Sample &
Buy
Support &
Community
Tools &
Software
Technical
Documents
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
LMX2531 High-Performance Frequency Synthesizer System With Integrated VCO
1 Features
3 Description
•
The LMX2531 is a low-power, high-performance
frequency synthesizer system which includes a fully
integrated delta-sigma PLL and VCO with fully
integrated tank circuit. The third and fourth poles are
also integrated and adjustable. Ultra-low noise and
high-precision LDOs are integrated for the PLL and
VCO, which yield higher supply-noise immunity and
more consistent performance. When combined with a
high-quality reference oscillator, the LMX2531 device
generates very stable, low-noise local-oscillator
signals for up and down conversion in wireless
communication devices. The LMX2531 device is a
monolithic integrated circuit, fabricated in an
advanced BiCMOS process. Several different
versions of this product accommodate different
frequency bands.
1
•
•
•
Multiple Frequency Options Available
– See Device Information Table
– Frequencies From: 553 MHz to 3132 MHz
PLL Features
– Fractional-N Delta-Sigma Modulator Order
Programmable up to Fourth Order
– FastLock/Cycle Slip Reduction with Timeout
Counter
– Partially Integrated, Adjustable Loop Filter
– Very Low Phase Noise and Spurs
VCO Features
– Integrated Tank Inductor
– Low Phase Noise
Other Features
– 2.8-V to 3.2-V Operation
– Low Operating Current
– Low Power-Down Current
– 1.8-V MICROWIRE Support
– 36-Pin 6-mm × 6-mm × 0.8-mm WQFN
Package
Device Information(1)
PART
LOW BAND
HIGH BAND
LMX2531LQ1146E
553 — 592 MHz
1106 — 1184 MHz
LMX2531LQ1226E
592 — 634 MHz
1184 — 1268 MHz
LMX2531LQ1312E
634 — 680 MHz
1268 — 1360 MHz
LMX2531LQ1415E
680 — 735 MHz
1360 — 1470 MHz
LMX2531LQ1500E
749.5 — 755 MHz
1499 — 1510 MHz
LMX2531LQ1515E
725 — 790 MHz
1450 — 1580 MHz
2 Applications
LMX2531LQ1570E
765 — 818 MHz
1530 — 1636 MHz
•
•
•
•
•
•
•
•
•
•
LMX2531LQ1650E
795 — 850 MHz
1590 — 1700 MHz
LMX2531LQ1700E
831 — 885 MHz
1662 — 1770 MHz
LMX2531LQ1742
880 — 933 MHz
1760 — 1866 MHz
LMX2531LQ1778E
863 — 920 MHz
1726 — 1840 MHz
LMX2531LQ1910E
917 — 1014 MHz
1834 — 2028 MHz
LMX2531LQ2080E
952 — 1137 MHz
1904 — 2274 MHz
LMX2531LQ2265E
1089 — 1200 MHz
2178 — 2400 MHz
LMX2531LQ2570E
1168 — 1395 MHz
2336 — 2790 MHz
LMX2531LQ2820E
1355 — 1462 MHz
2710 — 2925 MHz
LMX2531LQ3010E
1455 — 1566 MHz
2910 — 3132 MHz
Cellular Base Stations
Wireless LANs
Broadband Wireless Access
Satellite Communications
Wireless Radios
Automotive
CATV Equipment
Instrumentation and Test Equipment
RFID Readers
Data Converter Clocking
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Simplified Schematic
Vtune
Charge
Pump
CPout
Fast
Lock
FLout
VregVCO
VrefVCO
VCO
VREG
Prescaler
N
Divider
I
Fout
1/2
Comp
MUX
Ftest/ LD
OSCin
R
Divider
OSCin*
DATA
CLK
LE
CE
Serial Interface
Control
DIG
VREG
PLL
VREG1
PLL
VREG2
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Simplified Schematic.............................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
7.1
7.2
7.3
7.4
7.5
7.6
7.7
8
1
1
1
1
2
3
5
Absolute Maximum Ratings ...................................... 5
ESD Ratings.............................................................. 5
Recommended Operating Conditions....................... 5
Thermal Information .................................................. 5
Electrical Characteristics........................................... 6
MICROWIRE Timing Requirements........................ 13
Typical Performance Characteristics ...................... 14
Detailed Description ............................................ 15
8.1 Overview ................................................................. 15
8.2 Functional Block Diagram ....................................... 15
8.3 Feature Description................................................. 15
8.4 Device Functional Modes........................................ 20
8.5 Programming........................................................... 20
8.6 Register Maps ......................................................... 21
9
Application and Implementation ........................ 33
9.1 Application Information............................................ 33
9.2 Typical Application ................................................. 33
9.3 Do's and Don'ts ....................................................... 35
10 Power Supply Recommendations ..................... 35
11 Layout................................................................... 35
11.1 Layout Guidelines ................................................. 35
11.2 Layout Example .................................................... 36
12 Device and Documentation Support ................. 37
12.1
12.2
12.3
12.4
Device Support......................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
37
37
37
37
13 Mechanical, Packaging, and Orderable
Information ........................................................... 37
5 Revision History
Changes from Revision R (April 2013) to Revision S
•
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section .................................................................................................. 1
Changes from Revision Q (February 2013) to Revision R
•
2
Page
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 32
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
6 Pin Configuration and Functions
VregDIG
NC
GND
Test
OSCin*
OSCin
Ftest/LD
NC
VregPLL2
NJH0036D Package
36-Pin WQFN, D Version, (LMX2531LQ1146E/1226E/1312E/1415E/1515E/2820E/3010E)
Top View
36
35
34
33
32
31
30
29
28
VCCDIG
1
27
VCCPLL
NC
2
26
VregPLL1
GND
3
25
FLout
NC
4
24
CPout
GND
NC
5
23
Vtune
VregBUF
6
22
VCCBUF
NC
7
21
Fout
DATA
8
20
GND
CLK
9
19
GND
NC
18
VrefVCO
17
VregVCO
16
VCCVCO
15
NC
14
NC
13
NC
12
NC
11
CE
LE
10
VCCDIG
1
NC
VregDIG
NC
GND
Test
OSCin*
OSCin
Ftest/LD
NC
VregPLL2
NJG0036A Package
36-Pin WQFN, A Version, (All Other Versions)
Top View
36
35
34
33
32
31
30
29
28
27
VCCPLL
2
26
VregPLL1
GND
3
25
FLout
NC
4
24
CPout
NC
5
23
Vtune
VregBUF
6
22
VCCBUF
NC
7
21
Fout
DATA
8
20
GND
CLK
9
19
GND
GND
GND
10
11
12
13
14
15
16
17
18
LE
CE
NC
NC
NC
NC
VCCVCO
VregVCO
VrefVCO
NC
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
3
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Pin Functions
PIN
4
TYPE
DESCRIPTION
11
Input
Chip Enable Input. High impedance CMOS input. This pin must not exceed 2.75 V. When
CE is brought high the LMX2531 is powered up corresponding to the internal power control
bits. Although the part can be programmed when powered down, it is still necessary to
reprogram the R0 register to get the part to re-lock.
CLK
9
Input
MICROWIRE clock input. High impedance CMOS input. This pin must not exceed 2.75 V.
Data is clocked into the shift register on the rising edge.
CPout
24
Output
Charge pump output for PLL. For connection to Vtune through an external passive loop
filter.
DATA
8
Input
MICROWIRE serial data input. High impedance CMOS input. This pin must not exceed
2.75 V. Data is clocked in MSB first. The last bits clocked in form the control or register
select bits.
FLout
25
Output
An open drain NMOS output which is used for FastLock or a general purpose output.
Fout
21
Output
Buffered RF Output for the VCO.
Ftest/LD
30
Output
Multiplexed CMOS output. Typically used to monitor PLL lock condition.
GND
3
—
Ground
GND
19
—
Ground for the VCO circuitry.
GND
20
—
Ground for the VCO Output Buffer circuitry.
GND
34
—
Ground
LE
10
Input
NC
2, 4, 5, 7, 12,
13, 29, 35
—
No Connect.
NC
14, 15
—
No Connect. Do NOT ground. This also includes the pad above these pins.
OSCin
31
Input
Oscillator input.
OSCin*
32
Input
Oscillator complimentary input. When a single ended source is used, then a bypass
capacitor should be placed as close as possible to this pin and be connected to ground.
Test
33
Output
VccBUF
22
—
Power Supply for the VCO Buffer circuitry. Input may range from 2.8 — 3.2 V. Bypass
capacitors should be placed as close as possible to this pin and ground.
VccDIG
1
—
Power Supply for digital LDO circuitry. Input may range from 2.8 — 3.2 V. Bypass
capacitors should be placed as close as possible to this pin and ground.
VccPLL
27
—
Power Supply for the PLL. Input may range from 2.8 — 3.2 V. Bypass capacitors should be
placed as close as possible to this pin and ground.
VccVCO
16
—
Power Supply for VCO regulator circuitry. Input may range from 2.8 — 3.2 V. Bypass
capacitors should be placed as close as possible to this pin and ground.
VrefVCO
18
—
Internal reference voltage for VCO LDO. Not intended to drive an external load. Connect to
ground with a capacitor.
VregBUF
6
—
Internally regulated voltage for the VCO buffer circuitry. Connect to ground with a
capacitor.
VregDIG
36
—
Internally regulated voltage for LDO digital circuitry.
VregPLL1
26
—
Internally regulated voltage for PLL charge pump. Not intended to drive an external load.
Connect to ground with a capacitor.
VregPLL2
28
—
Internally regulated voltage for RF digital circuitry. Not intended to drive an external load.
Connect to ground with a capacitor.
VregVCO
17
—
Internally regulated voltage for VCO circuitry. Not intended to drive an external load.
Connect to ground with a capacitor and some series resistance.
Vtune
23
Input
NAME
NO.
CE
MICROWIRE Latch Enable input. High impedance CMOS input. This pin must not exceed
2.75 V. Data stored in the shift register is loaded into the selected latch register when LE
goes HIGH.
This pin is for test purposes and should be grounded for normal operation.
Tuning voltage input for the VCO. For connection to the CPout pin through an external
passive loop filter.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2)
MIN
MAX
UNIT
Power Supply Voltage
–0.3
3.5
V
All other pins
(Except Ground)
Power Supply Voltage
–0.3
3.0
V
TL
Lead Temperature (solder 4 sec.)
260
°C
TJ
Junction Temperature
125
°C
Tstg
Storage temperature
150
°C
VCC
(VccDIG, VccVCO,
VccBUF, VccPLL)
(1)
(2)
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±500
Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
±250
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 500-V HBM is possible with the necessary precautions.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 250-V CDM is possible with the necessary precautions.
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
VCC
Power Supply Voltage
(VccDig, VccVCO, VccBUF)
Vi
Serial Interface and Power Control Voltage
TA
Ambient Temperature (1)
(1)
MIN
NOM
MAX
2.8
3.0
3.2
UNIT
V
0
2.75
V
–40
85
°C
Maximum Allowable Temperature Drift for Continuous Lock is how far the temperature can drift in either direction from the value it was
at the time that the R0 register was last programmed, and still have the part stay in lock. The action of programming the R0 register,
even to the same value, activates a frequency calibration routine. This implies that the part will work over the entire frequency range, but
if the temperature drifts more than the maximum allowable drift for continuous lock, then it will be necessary to reload the R0 register to
ensure that it stays in lock. Regardless of what temperature the part was initially programmed at, the temperature can never drift outside
the frequency range of –40°C ≤ TA ≤ 85°C without violating specifications.
7.4 Thermal Information
THERMAL METRIC (1)
LMX2531
LMX2531
NJH0036D
NJG0036A
36 PINS
36 PINS
RθJA
Junction-to-ambient thermal resistance
35.5
35.5
ψJB
Junction-to-board characterization parameter
9.1
9.1
(1)
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report (SPRA953).
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
5
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
7.5 Electrical Characteristics
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
LMX2531LQ2265E/
2570E
38
44
LMX2531LQ2820E/
3010E
38
46
All Other Options
34
41
LMX2531LQ2265E/
2570E
41
49
LMX2531LQ2820E/
3010E
44
52
All Other Options
37
46
UNIT
CURRENT CONSUMPTION
Divider Disabled
Power Supply Current Power
Supply Current
ICC
Divider Enabled
ICCPD
Power Down Current
CE = 0 V, Part Initialized
7
mA
µA
OSCILLATOR
IIHOSC
Oscillator Input High Current
VIH = 2.75 V
100
µA
IILOSC
Oscillator Input Low Current
VIL = 0
–100
fOSCin
Frequency Range
See (1)
5
80
MHz
vOSCin
Oscillator Sensitivity
0.5
2.0
Vpp
32
MHz
µA
PLL
fPD
Phase Detector Frequency
Charge Pump
Output Current Magnitude
ICPout
ICP = 0
90
µA
ICP = 1
180
µA
ICP = 3
360
µA
ICP = 15
1440
ICPoutTRI
CP TRI-STATE Current
0.4 V < VCPout < 2.0 V
ICPoutMM
Charge Pump
Sink vs Source Mismatch
ICPoutV
ICPoutT
LN(f)
(1)
(2)
(3)
6
µA
2
10
VCPout = 1.2 V
TA = 25°C
2%
8%
Charge Pump
Current vs CP Voltage Variation
0.4 V < VCPout < 2.0 V
TA = 25°C
4%
CP Current vs Temperature
Variation
VCPout = 1.2 V
8%
Normalized PLL 1/f Noise
LNPLL_flicker(10 kHz)
See (2)
ICP = 1X Charge Pump Gain
–94
ICP = 16X Charge Pump Gain
–104
Normalized PLL Noise Floor
LNPLL_flat
See (3)
ICP = 1X Charge Pump Gain
–202
ICP = 16X Charge Pump Gain
–212
nA
dBc/Hz
dBc/Hz
There are program bits that need to be set based on the OSCin frequency. Refer to the following sections: XTLSEL[2:0] -- OSCin
Select, XTLDIV[1:0] -- Division Ratio for the OSCin Frequency, XTLMAN[11:0] -- Manual OSCin Mode, XTLMAN2 -- Manual Crystal
Mode Second Adjustment, and LOCKMODE -- Frequency Calibration Mode. Not all bit settings can be used for all frequency choices of
OSCin. For instance, automatic modes described in XTLSEL[2:0] -- OSCin Select do not work below 8 MHz.
One of the specifications for modeling PLL in-band phase noise is the PLL 1/f noise normalized to 1 GHz carrier frequency and 10 kHz
offset, LPLL_flicker(10 kHz). From this normalized index of PLL 1/f noise, the PLL 1/f noise can be calculated for any carrier and offset
frequency as: LNPLL_flicker(f) = LPLL_flicker(10 kHz) – 10 × log (10 kHz / f) + 20 × log ( Fout / 1 GHz ). Flicker noise can dominate at low
offsets from the carrier and has a 10 dB/decade slope and improves with higher charge pump currents and at higher offset frequencies .
To accurately measure LPLL_flicker(10 kHz) it is important to use a high phase detector frequency and a clean reference to make it such
that this measurement is on the 10 dB/decade slope close to the carrier. LPLL_flicker(f) can be masked by the reference oscillator
performance if a low power or noisy source is used. The total PLL in-band phase noise performance is the sum of LPLL_flicker(f) and
LPLL_flat. In other words,LPLL(f) = 10 × log (10 (LNPLL_flat / 10 ) + 10(LNPLL_flicker (f) / 10 )
A specification used for modeling PLL in-band phase noise floor is the Normalized PLL noise floor, LNPLL_flat, and is defined as:
LNPLL_flat = L(f) – 20 × log (N) – 10 × log(fPD). LPLL_flat is the single side band phase noise in a 1 Hz Bandwidth and fPD is the phase
detector frequency of the synthesizer. LPLL_flat contributes to the total noise, L(f). To measure LPLL_flat the offset frequency must be
chosen sufficiently smaller then the loop bandwidth of the PLL, and yet large enough to avoid a substantial noise contribution from the
reference and PLL flicker noise. LPLL_flat can be masked by the reference oscillator performance if a low power or noisy source is used.
The total PLL in-band phase noise performance is the sum of LPLL_flicker(f) and LPLL_flat. In other words, LPLL(f) = 10 × log (10 (LNPLL_flat / 10 )
+ 10 (LNPLL_flicker (f) / 10 )
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VCO FREQUENCIES
Operating Frequency Range
(All options have a frequency
divider, this applies before the
divider. The frequency after the
divider is half of what is shown)
fFout
LMX2531LQ1146E
1106
1184
LMX2531LQ1226E
1184
1268
LMX2531LQ1312E
1268
1360
LMX2531LQ1415E
1360
1470
LMX2531LQ1500E
1499
1510
LMX2531LQ1515E
1450
1580
LMX2531LQ1570E
1530
1636
LMX2531LQ1650E
1590
1700
LMX2531LQ1700E
1662
1770
LMX2531LQ1742
1760
1866
LMX2531LQ1778E
1726
1840
LMX2531LQ1910E
1834
2028
LMX2531LQ2080E
1904
2274
LMX2531LQ2265E
2178
2400
LMX2531LQ2570E
2336
2790
LMX2531LQ2820E
2710
2925
LMX2531LQ3010E
2910
3132
MHz
OTHER VCO SPECIFICATIONS
ΔTCL
(4)
Maximum Allowable Temperature
Drift for Continuous Lock
See (4)
LMX2531LQ1742
65
LMX2531LQ1500E/1570E/1650E/
1146E/1226/1312E/1415E/1515E
90
LMX2531LQ1700E/1778E/1910E/
2080E/2265E/2570E/2820E/3010E
125
°C
Maximum Allowable Temperature Drift for Continuous Lock is how far the temperature can drift in either direction from the value it was
at the time that the R0 register was last programmed, and still have the part stay in lock. The action of programming the R0 register,
even to the same value, activates a frequency calibration routine. This implies that the part will work over the entire frequency range, but
if the temperature drifts more than the maximum allowable drift for continuous lock, then it will be necessary to reload the R0 register to
ensure that it stays in lock. Regardless of what temperature the part was initially programmed at, the temperature can never drift outside
the frequency range of –40°C ≤TA≤ 85°C without violating specifications.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
7
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
Divider Disabled
pFout
Output Power to a 50-Ω Load
(Applies across entire tuning range.)
Divider Enabled
8
MIN
TYP
MAX
LMX2531LQ1146E
1
4.0
7
LMX2531LQ1226E
1
3.5
7
LMX2531LQ1312E
1
3.5
7
LMX2531LQ1415E
0
3.0
6
LMX2531LQ1500E
1
3.5
7.0
LMX2531LQ1515E
–1
2.5
5
LMX2531LQ1570E
2
4.5
8
LMX2531LQ1650E
2
4.5
8
LMX2531LQ1700E
1
3.5
7
LMX2531LQ1742
1
3.5
7
LMX2531LQ1778E
1
3.5
7
LMX2531LQ1910E
1
3.5
7
LMX2531LQ2080E
1
3.5
7
LMX2531LQ2265E
1
3.5
7
LMX2531LQ2570E
0
3.0
6
LMX2531LQ2820E
–0.5
2.5
5.5
LMX2531LQ3010E
–1.5
1.5
4.5
LMX2531LQ1146E
–1
2.0
5
LMX2531LQ1226E
–1
2.0
5
LMX2531LQ1312E
–1
1.5
4
LMX2531LQ1415E
–2
0.5
3
LMX2531LQ1500E
1
3.0
6.0
LMX2531LQ1515E
–2
0.5
3
LMX2531LQ1570E
1
3.0
6
LMX2531LQ1650E
1
3.0
6
LMX2531LQ1700E
1
3.0
6
LMX2531LQ1742
1
3.0
6
LMX2531LQ1778E
1
3.0
6
LMX2531LQ1910E
1
3.0
6
LMX2531LQ2080E
0
2.5
5
LMX2531LQ2265E
0
2.5
5
LMX2531LQ2570E
–1
1.5
4
LMX2531LQ2820E
–2.5
0
2.5
LMX2531LQ3010E
–3
–0.5
2
Submit Documentation Feedback
UNIT
dBm
dBm
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
KVtune
Fine Tuning Sensitivity
(When a range is displayed in the
typical column, indicates the lower
sensitivity is typical at the lower end
of the tuning range, and the higher
tuning sensitivity is typical at the
higher end of the tuning range.)
TEST CONDITIONS
TYP
2.5 — 5.5
LMX2531LQ1226E
3—6
LMX2531LQ1312E
3—6
LMX2531LQ1415E
3.5 — 6.5
LMX2531LQ1500E
4—7
LMX2531LQ1515E
4—7
LMX2531LQ1570E
4—7
LMX2531LQ1650E
4—7
LMX2531LQ1700E
6 — 10
LMX2531LQ1742
MAX
UNIT
MHz/V
4—7
LMX2531LQ1778E
6 — 10
LMX2531LQ1910E
8 — 14
LMX2531LQ2080E
9 — 20
LMX2531LQ2265E
10 — 16
LMX2531LQ2570E
10 — 23
LMX2531LQ2820E
12 — 28
LMX2531LQ3010E
13 — 29
Divider
Disabled
Second Harmonic
50 Ω Load
Divider
Enabled
HSFout
MIN
LMX2531LQ1146E
Harmonic Suppression
(Applies Across Entire Tuning
Range)
Divider
Disabled
Third Harmonic
50 Ω Load
Divider
Enabled
LMX2531LQ1146E
/1226E/1312E
/1415E/1515E
–35
LMX2531LQ2820E
/3010E
–40
All Other Options
–30
–25
LMX2531LQ1146E
/1226E/1312E
/1415E/1515E
–30
–20
LMX2531LQ2820E
/3010E
–30
–15
All Other Options
–20
–15
LMX2531LQ1146E
/1226E/1312E
–35
–30
LMX2531LQ2820E
/3010E
–50
All Other Options
–40
–35
LMX2531LQ1146E
/1226E/1312E
/1570E/1650E
–20
–15
LMX2531LQ2820E
/3010E
–40
–20
All Other Options
–25
–20
PUSHFout
Frequency Pushing
Creg = 0.1 µF, VDD ± 100 mV, Open Loop
PULLFout
Frequency Pulling
VSWR = 2:1, Open Loop
ZFout
Output Impedance
–25
300
kHz/V
±600
50
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
dBc
kHz
Ω
9
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
VCO PHASE NOISE
TEST CONDITIONS
fFout = 1146 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1146E)
fFout = 573 MHz
DIV2 = 1
fFout = 1226 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1226E)
fFout = 613 MHz
DIV2 = 1
fFout = 1314 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1312E)
fFout = 657 MHz
DIV2 = 1
fFout = 1415 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1415E)
fFout = 707.5 MHz
DIV2 = 1
fFout = 1500 MHz
DIV2 = 1
Phase Noise
(LMX2531LQ1500E)
fFout = 750 MHz
DIV2 = 1
(5)
10
TYP
10-kHz Offset
–96
100-kHz Offset
–121
1-MHz Offset
–142
5-MHz Offset
–156
10-kHz Offset
–101
100-kHz Offset
–126
1-MHz Offset
–147
5-MHz Offset
–156
10-kHz Offset
–95
100-kHz Offset
–121
1-MHz Offset
–142
5-MHz Offset
–155
10-kHz Offset
–101
100-kHz Offset
–126
1-MHz Offset
–147
5-MHz Offset
–155
10-kHz Offset
–95
100-kHz Offset
–121
1-MHz Offset
–140
5-MHz Offset
–154
10-kHz Offset
–101
100-kHz Offset
–126
1-MHz Offset
–146
5-MHz Offset
–154
10-kHz Offset
–95
100-kHz Offset
–121
1-MHz Offset
–141
5-MHz Offset
–154
10-kHz Offset
–100
100-kHz Offset
–126
1-MHz Offset
–146
5-MHz Offset
–154
10-kHz Offset
L(f)Fout
MIN
MAX
UNIT
(5)
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
–97
100-KHz Offset
–120
1-MHz Offset
–142
5-MHz Offset
–155
10-kHz Offset
–103
100-kHz Offset
–126
1-MHz Offset
–131
5-MHz Offset
–155
dBc/Hz
The VCO phase noise is measured assuming that the loop bandwidth is sufficiently narrow that the VCO noise dominates. The
maximum limits apply only at center frequency and over temperature, assuming that the part is reloaded at each test frequency. Over
frequency, the phase noise can vary 1 to 2 dB, with the worst case performance typically occurring at the highest frequency. Over
temperature, the phase noise typically varies 1 to 2 dB, assuming the part is reloaded.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
fFout = 1515 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1515E)
fFout = 757.5 MHz
DIV2 = 1
fFout = 1583 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1570E)
fFout = 791.5 MHz
DIV2 = 1
fFout = 1645 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1650E)
fFout = 822.5 MHz
DIV2 = 1
fFout = 1716 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1700E)
fFout = 858 MHz
DIV2 = 1
fFout= 1813 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1742)
fFout = 906.5 MHz
DIV2 = 1
fFout = 1783 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1778E)
fFout = 891.5 MHz
DIV2 = 1
MIN
TYP
10-kHz Offset
–96
100-kHz Offset
–122
1-MHz Offset
–142
5-MHz Offset
–153
10-kHz Offset
–99
100-kHz Offset
–125
1-MHz Offset
–145
5-MHz Offset
–154
10-kHz Offset
–93
100-kHz Offset
–118
1-MHz Offset
–140
5-MHz Offset
–154
10-kHz Offset
–99
100-kHz Offset
–122
1-MHz Offset
–144
5-MHz Offset
–155
10-kHz Offset
–93
100-kHz Offset
–118
1-MHz Offset
–140
5-MHz Offset
–154
10-kHz Offset
–99
100-kHz Offset
–122
1-MHz Offset
–144
5-MHz Offset
–155
10-kHz Offset
–92
100-kHz Offset
–117
1-MHz Offset
–139
5-MHz Offset
–153
10-kHz Offset
–98
100-kHz Offset
–122
1-MHz Offset
–144
5-MHz Offset
–154
10-kHz Offset
–92
100-kHz Offset
–117
1-MHz Offset
–140
5-MHz Offset
–152
10-kHz Offset
–99
100-kHz Offset
–122
1-MHz Offset
–143
5-MHz Offset
–152
10-kHz Offset
–92
100-kHz Offset
–117
1-MHz Offset
–139
5-MHz Offset
–152
10-kHz Offset
–97
100-kHz Offset
–122
1-MHz Offset
–144
5-MHz Offset
–154
MAX
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
UNIT
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
11
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
fFout = 1931 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ1910E)
fFout = 965.5 MHz
DIV2 = 1
fFout = 2089 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ2080E)
fFout = 1044.5 MHz
DIV2 = 1
fFout = 2264 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ2265E)
fFout = 1132 MHz
DIV2 = 1
fFout = 2563 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ2570E)
fFout = 1281.5 MHz
DIV2 = 1
fFout = 2818 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ2820E)
fFout = 1409 MHz
DIV2 = 1
fFout = 3021 MHz
DIV2 = 0
L(f)Fout
Phase Noise
(LMX2531LQ3010E)
fFout = 1510.5 MHz
DIV2 = 1
12
MIN
TYP
10-kHz Offset
–89
100-kHz Offset
–115
1-MHz Offset
–138
5-MHz Offset
–151
10-kHz Offset
–95
100-kHz Offset
–121
1-MHz Offset
–143
5-MHz Offset
–155
10-kHz Offset
–87
100-kHz Offset
–113
1-MHz Offset
–136
5-MHz Offset
–150
10-kHz Offset
–93
100-kHz Offset
–119
1-MHz Offset
–142
5-MHz Offset
–154
10-kHz Offset
–88
100-kHz Offset
–113
1-MHz Offset
–136
5-MHz Offset
–150
10-kHz Offset
–94
100-kHz Offset
–118
1-MHz Offset
–141
5-MHz Offset
–154
10-kHz Offset
–86
100-kHz Offset
–112
1-MHz Offset
–135
5-MHz Offset
–149
10-kHz Offset
–91
100-kHz Offset
–117
1-MHz Offset
–139
5-MHz Offset
–152
10-kHz Offset
–84
100-kHz Offset
–111
1-MHz Offset
–133
5-MHz Offset
–148
10-kHz Offset
–90
100-kHz Offset
–117
1-MHz Offset
–138
5-MHz Offset
–150
10-kHz Offset
–83
100-kHz Offset
–110
1-MHz Offset
–132
5-MHz Offset
–147
10-kHz Offset
–88
100-kHz Offset
–116
1-MHz Offset
–137
5-MHz Offset
–148
Submit Documentation Feedback
MAX
UNIT
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
Electrical Characteristics (continued)
(VCC = 3.0 V, –40°C ≤ TA ≤ 85 °C; except as specified.)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2.75
V
DIGITAL INTERFACE (DATA, CLK, LE, CE, Ftest/LD, FLout)
VIH
High-Level Input Voltage
VIL
Low-Level Input Voltage
1.6
IIH
High-Level Input Current
VIH = 1.75
–3.0
IIL
Low-Level Input Current
VIL = 0 V
–3.0
VOH
High-Level Output Voltage
IOH = 500 µA
VOL
Low-Level Output Voltage
IOL = –500 µA
2.0
0.4
V
3.0
µA
3.0
µA
2.65
0.0
V
0.4
V
7.6 MICROWIRE Timing Requirements
See Figure 2 and Serial Data Timing Requirements.
MIN
NOM
MAX
UNIT
tCS
Data to Clock Set-Up Time
25
ns
tCH
Data to Clock Hold Time
20
ns
tCWH
Clock Pulse Width High
25
ns
tCWL
Clock Pulse Width Low
25
ns
tES
Clock to Enable Set-Up Time
25
ns
tCES
Enable to Clock Set-Up Time
25
ns
tEWH
Enable Pulse Width High
25
ns
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
13
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
7.7 Typical Performance Characteristics
See Table 1.
MAGNITUDE OF INPUT IMPEDANCE (k:)
6
5
4
Powered
Down
3
2
Powered
Up
1
0
0
25
50
75
100
125
150
FREQUENCY (MHz)
Figure 1. OSCin Input Impedance
14
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
8 Detailed Description
8.1 Overview
The LMX2531 is a low-power, high-performance frequency synthesizer system which includes the PLL, VCO,
and partially integrated loop filter. Feature Description gives a discussion of the various blocks of this device.
8.2 Functional Block Diagram
Vtune
Charge
Pump
CPout
Fast
Lock
FLout
VregVCO
VCO
VREG
VrefVCO
Prescaler
N
Divider
I
Fout
1/2
Comp
MUX
Ftest/ LD
OSCin
R
Divider
OSCin*
DIG
VREG
DATA
CLK
PLL
VREG1
Serial Interface
Control
LE
CE
PLL
VREG2
8.3 Feature Description
8.3.1 Reference Oscillator Input
Because the VCO frequency calibration algorithm is based on clocks from the OSCin pin, there are certain bits
that need to be set depending on the OSCin frequency. XTLSEL (R6[22:20]) and XTLDIV (R7[9:8]) are both
need to be set based on the OSCin frequency, fOSCin. For some options and for low OSCin frequencies, the
XTLMAN (R7[21:10]) and XTLMAN2 (R8[4]) words need to be set to the correct value.
Table 1. OSCin Input Impedance (See Figure 1)
FREQUENCY
POWERED UP (kΩ)
POWERED DOWN (kΩ)
(MHz)
REAL
IMAGINARY
MAGNITUDE
REAL
IMAGINARY
MAGNITUDE
1
4.98
–2.70
5.66
6.77
–8.14
10.59
5
3.44
–3.04
4.63
5.73
–6.72
9.03
10
1.42
–2.67
3.02
1.72
–5.24
5.51
20
0.52
–1.63
1.71
0.53
–2.94
2.98
30
0.29
–1.22
1.25
0.26
–2.12
2.14
40
0.18
–0.92
0.94
0.17
–1.58
1.59
50
0.13
–0.74
0.75
0.14
–1.24
1.25
60
0.10
–0.63
0.64
0.10
–1.06
1.06
70
0.09
–0.56
0.56
0.09
–0.95
0.95
80
0.07
–0.50
0.50
0.08
–0.86
0.87
90
0.07
–0.46
0.46
0.07
–0.80
0.80
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
15
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Feature Description (continued)
Table 1. OSCin Input Impedance (See Figure 1) (continued)
FREQUENCY
POWERED UP (kΩ)
POWERED DOWN (kΩ)
(MHz)
REAL
IMAGINARY
MAGNITUDE
REAL
IMAGINARY
MAGNITUDE
100
0.06
–0.41
0.42
0.07
–0.72
0.72
110
0.06
–0.37
0.38
0.07
–0.65
0.65
120
0.05
–0.34
0.34
0.06
–0.59
0.59
130
0.05
–0.32
0.32
0.06
–0.55
0.55
140
0.04
–0.29
0.30
0.05
–0.50
0.50
150
0.04
–0.27
0.28
0.05
–0.47
0.47
8.3.2 R Divider
The R divider divides the OSCin frequency down to the phase detector frequency. The R divider value, R, is
restricted to the values of 1, 2, 4, 8, 16, and 32. If R is greater than 8, then this also puts restrictions on the
fractional denominator, FDEN, than can be used. This is discussed in greater depth in later sections.
8.3.3 Phase Detector and Charge Pump
The phase detector compares the outputs of the R and N dividers and puts out a correction current
corresponding to the phase error. The phase detector frequency, fPD, can be calculated as shown in Equation 1.
fPD = fOSCin / R
(1)
Choosing R = 1 yields the highest possible phase detector frequency and is optimum for phase noise, although
there are restrictions on the maximum phase detector frequency which could force the R value to be larger. The
far out PLL noise improves 3 dB for every doubling of the phase detector frequency, but at lower offsets, this
effect is much less due to the PLL 1 / f noise. Aside from getting the best PLL phase noise, higher phase
detector frequencies also make it easier to filter the noise that the delta-sigma modulator produces, which peaks
at an offset frequency of fPD / 2 from the carrier. The LMX2531 also has 16 levels of charge pump currents and a
highly flexible fractional modulus. Increasing the charge pump current improves the phase noise about 3 dB per
doubling of the charge pump current, although there are small diminishing returns as the charge pump current
increases.
From a loop filter design and PLL phase noise perspective, one might think to always design with the highest
possible phase detector frequency and charge pump current. However, if one considers the worst case fractional
spurs that occur at an output frequency equal to 1 channel spacing away from a multiple of the fOSCin, then this
gives reason to reconsider. If the phase detector frequency or charge pump currents are too high, then these
spurs could be degraded, and the loop filter may not be able to filter these spurs as well as theoretically
predicted. For optimal spur performance, a phase detector frequency around 2.5 MHz and a charge pump
current of 1X are recommended.
8.3.4 N Divider and Fractional Circuitry
The N divider in the LMX2531 includes fractional compensation and can achieve any fractional denominator
between 1 and 4,194,303. The integer portion, NInteger, is the whole part of the N divider value and the fractional
portion, NFractional, is the remaining fraction. So in general, the total N divider value, N, is determined by
Equation 2.
N = NInteger + NFractional
(2)
For example, if the phase detector frequency (fPD) was 10 MHz and the VCO frequency (fVCO) was 1736.1 MHz,
then N would be 173.61. This would imply that NInteger is 173 and NFractional is 61/100. NInteger has some minimum
value restrictions that are arise due to the architecture of this divider. The first restrictions arise because the N
divider value is actually formed by a quadruple modulus 16/17/20/21 prescaler, which creates minimum divide
values. NInteger is further restricted because the LMX2531 due to the fractional engine of the N divider.
16
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
The fractional word, NFractional , is a fraction formed with the NUM and DEN words. In the example used here with
the fraction of 61/100, NUM = 61 and DEN = 100. The fractional denominator value, DEN, can be set from 2 to
4,194,303. The case of DEN = 0 makes no sense, because this would cause an infinite N value; the case of 1
makes no sense either (but could be done), because integer mode should be used in these applications. All
other values in this range, like 10, 32, 42, 734, or 4,000,000 are all valid. Once the fractional denominator, DEN,
is determined, the fractional numerator, NUM, is intended to be varied from 0 to DEN-1.
In general, the fractional denominator, DEN, can be calculated by dividing the phase detector frequency by the
greatest common divisor (GCD) of the channel spacing (fCH) and the phase detector frequency. If the channel
spacing is not obvious, then it can be calculated as the greatest common divisor of all the desired VCO
frequencies.
FDEN = k × fPD / GCD (fPD , fCH) k = 1, 2, 3 ..
(3)
For example, consider the case of a 10 MHz phase detector frequency and a 200 kHz channel spacing at the
VCO output. The greatest common divisor of 10 MHz and 200 kHz is just 200 kHz. If one takes 10 MHz divided
by 200 kHz, the result is 50. So a fractional denominator of 50, or any multiple of 50 would work in this example.
Now consider a case with a 10 MHz phase detector frequency and a 30 kHz channel spacing. The greatest
common divisor of 10 MHz and 30 kHz is 10 kHz. The fractional denominator therefore must be a multiple 1000,
because this is 10 MHz divided by 10 kHz. For a final example, consider an application with a fixed output
frequency of 2110.8 MHz and a OSCin frequency of 19.68 MHz. If the phase detector frequency is chosen to be
19.68 MHz, then the channel spacing can be calculated as the greatest common multiple of 19.68 MHz and
2110.8 MHz, which is 240 kHz. The fractional denominator is therefore a multiple of 41, which is 19.68 MHz /
240 kHz. Refer to AN-1865 Frequency Synthesis and Planning for PLL Architectures (SNAA061) for more details
on frequency planning.
To achieve a fractional N value, an integer N divider is modulated between different values. This gives rise to
three main degrees of freedom with the LMX2531 delta-sigma engine including the modulator order, dithering,
and the way that the fractional portion is expressed. The first degree of freedom is the modulator order, which
gives the user the ability to optimize for a particular application. The modulator order can be selected as zero
(integer mode), two, three, or four. One simple technique to better understand the impact of the delta-sigma
fractional engine on noise and spurs is to tune the VCO to an integer channel and observe the impact of
changing the modulator order from integer mode to a higher order. The higher the fractional modulator order is,
the lower the spurs theoretically are. However, this is not always the case, and the higher order fractional
modulator can sometimes give rise to additional spurious tones, but this is dependent on the application. The
second degree of freedom with the LMX2531 delta-sigma engine is dithering. Dithering is often effective in
reducing these additional spurious tones, but can add phase noise in some situations. The third degree of
freedom is the way that the fraction is expressed. For example, 1/10 can be expressed as 100000/1000000.
Expressing the fraction in higher order terms sometimes improves the performance, particularly when dithering is
used. In conclusion, there are some guidelines to getting the optimum choice of settings, but these optimum
settings are application specific. Refer to AN-1879 Fractional N Frequency Synthesis (SNAA062) for a much
more detailed discussion on fractional PLLs and fractional spurs.
8.3.5 Partially Integrated Loop Filter
The LMX2531 integrates the third pole (formed by R3 and C3) and fourth pole (formed by R4 and C4) of the loop
filter. The values for C3, C4, R3, and R4 can also be programmed independently through the MICROWIRE
interface and also R3 and R4 can be changed during FastLock, for minimum lock time. The larger the values of
these components, the stronger the attenuation of the internal loop filter. The maximum attenuation can be
achieved by setting R3 = R4 = 40 kΩ and C3 = C4 = 100 pF while the minimum attenuation is achieved by
disabling the loop filter by setting EN_LPFLTR (R6[15]) to zero. Note that when the internal loop filter is disabled,
there is still a small amount of input capacitance on front of the VCO on the order of 200 pF.
Because that the internal loop filter is on-chip, it is more effective at reducing certain spurs than the external loop
filter. The higher order poles formed by the integrated loop filter are also helpful for attenuating noise due to the
delta-sigma modulator. This noise produced by the delta-sigma modulator is outside the loop bandwidth and
dependent on the modulator order. Although setting the filtering for maximum attenuation gives the best filtering,
it puts increased restrictions on how wide the loop bandwidth of the system can be, which corresponds to the
case where the shunt loop filter capacitor, C1, is zero. Increasing the charge pump current and/or the phase
detector frequency increases the maximum attainable loop bandwidth when designing with the integrated filter. It
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
17
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
is recommended to set the internal loop filter as high as possible without restricting the loop bandwidth of the
system more than desired. If some setting between the minimum and maximum value is desired, it is preferable
to reduce the resistor values before reducing the capacitor values because this will reduce the thermal noise
contribution of the loop filter resistors. For design tools and more information on partially integrated loop filters,
go to the Clock Design Tool on www.ti.com.
8.3.6 Low Noise, Fully Integrated VCO
The LMX2531 includes a fully integrated VCO, including the inductors. For optimum phase noise performance,
this VCO has frequency and phase noise calibration algorithms. The frequency calibration algorithm is necessary
because the VCO internally divides up the frequency range into several bands, to achieve a lower tuning gain,
and therefore better phase noise performance. The frequency calibration routine is activated any time that the R0
register is programmed. There are several bits including LOCKMODE and XTLSEL that need to be set properly
for this calibration to be performed in a reliable fashion. If the temperature shifts considerably and the R0 register
is not programmed, then it cannot drift more than the maximum allowable drift for continuous lock, ΔTCL, or else
the VCO is not ensured to stay in lock. The phase noise calibration algorithm is necessary to achieve the lowest
possible phase noise. Each version of the LMX2531, the VCO_ACI_SEL bit (R6[19:16]) needs to be set to the
correct value to ensure the best possible phase noise.
The gain of the VCO can change considerably over frequency. It is lowest at the minimum frequency and highest
at the maximum frequency. This range is specified in Electrical Characteristics of the data sheet. When designing
the loop filter, the following method is recommended to determine what VCO gain to design to. First, take the
geometric mean of the minimum and maximum frequencies that are to be used. Then use a linear approximation
to extrapolate the VCO gain. Suppose the application requires the LMX2531LQ2080E PLL to tune from 2100 to
2150 MHz. The geometric mean of these frequencies is sqrt (2100 × 2150) MHz = 2125 MHz. The VCO gain is
specified as 9 MHz/V at 1904 MHz and 20 MHz/V at 2274 MHz. Over this range of 370 MHz, the VCO gain
changes 11 MHz/V. Therefore, at 2125 MHz, the VCO gain would be approximately 9 + (2125 – 1904) × 11 / 370
= 15.6 MHz/V. Although the VCO gain can change from part to part, this variation is small compared to how
much the VCO gain can change over frequency.
The VCO frequency is related to the other frequencies and divider values as shown in Equation 4.
fVCO = fPD × N = fOSCin × N / R
(4)
8.3.7 Programmable VCO Divider
All options of the LMX2531 offer the option of dividing the VCO output by two to get half of the VCO frequency at
the Fout pin. The channel spacing at the Fout pin is also divided by two as well. Because this divide by two is
outside feedback path between the VCO and the PLL, enabling does require one to change the N divider, R
divider, or loop filter values. When this divider is enabled, there will be some far-out phase noise contribution to
the VCO noise. Note that the R0 register should be reprogrammed the first time after the DIV2 bit is enabled or
disabled for optimal phase noise performance. The frequency at the Fout pin is related to the VCO frequency
and divider value, D, as shown in Equation 5.
fFout = fVCO / D
18
(5)
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
8.3.8 Serial Data Timing Requirements
See MICROWIRE Timing Requirements.
MSB
DATA
D19
LSB
D18
D17
D16
D15
D0
C3
C2
C1
C0
CLK
tCES
tCS
tCWH
tCH
tCWL
tES
LE
tEWH
Figure 2. Serial Data Timing Diagram
The DATA is clocked into a shift register on each rising edge of the CLK signal. On the rising edge of the LE
signal, the data is sent from the shift registers to an actual counter. There are several other considerations as
well:
• A slew rate of at least 30 V/μs is recommended for the CLK, DATA, and LE signals.
• After the programming is complete, the CLK, DATA, and LE signals should be returned to a low state.
• It is recommended to put a small delay between the falling edge of the last CLK pulse and the rising edge of
the LE pulse for optimal noise immunity and the most reliable programming.
• Although it is strongly recommended to keep LE low after programming, LE can be kept high if bit R5[23] is
changed to 0 (from its default value of 1). If this bit is changed, then the operation of the part is not ensured
because it is not tested under these conditions.
• If the CLK and DATA lines are toggled while the in VCO is in lock, as is sometimes the case when these lines
are shared with other parts, the phase noise may be degraded during the time of this programming.
• If the part is not programmed, the values of the registers in this part have to be assumed to be random.
Therefore, the current consumption and spurs generated by this part can be random. If this is an issue, the
CE pin can be held low for more consistent behavior.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
19
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
8.4 Device Functional Modes
The LMX2531 operates mainly in the active mode. The other two modes are reset and powerdown modes. The
powerdown mode can be achieved by taking the CE pin to 0 V. The reset mode is achieved if the REG_RST bit
is set to 1.
8.5 Programming
The LMX2531 is programmed using 11 24-bit registers used to control the LMX2531 operation. A 24-bit shift
register is used as a temporary register to indirectly program the on-chip registers. The shift register consists of a
data field and an address field. The last 4 register bits, CTRL[3:0] form the address field, which is used to
decode the internal register address. The remaining 20 bits form the data field DATA[19:0]. While LE is low,
serial data is clocked into the shift register upon the rising edge of clock (data is programmed MSB first). When
LE goes high, data is transferred from the data field into the selected register bank. Although there are actually
14 registers in this part, only a portion of them should be programmed, because the state of the other hidden
registers (R13, R11, and R10) are set during the initialization sequence. Although it is possible to program these
hidden registers, as well as a lot of bits that are defined to either 1 or 0, the user should not experiment with
these hidden registers and bits, because the parts are not tested under these conditions and doing so will most
likely degrade performance.
Table 2. Register Location Truth Table
20
C3
C2
C1
C0
Data Address
1
1
0
0
R12
1
0
0
1
R9
1
0
0
0
R8
0
1
1
1
R7
0
1
1
0
R6
0
1
0
1
R5
0
1
0
0
R4
0
0
1
1
R3
0
0
1
0
R2
0
0
0
1
R1
0
0
0
0
R0
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
8.6 Register Maps
8.6.1 General Programming Information
Table 3. Programming Register Structure
DATA[19:0]
CONTROL[3:0]
MSB
D19
LSB
D18
D17
D16
D15
D14
D13
D12
D11
D10
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
C
3
C
2
C
1
C0
8.6.1.1 Initialization Sequence
The initial loading sequence from a cold start is described in Table 4. The registers must be programmed in order
shown. There must be a minimum of 10 ms between the time when R5 is last loaded and R1 is loaded to ensure
time for the LDOs to power up properly.
Table 4. Initialization Sequence
REG.
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
DATA[19:0]
3
2
1
0
C3
C2
C1
C0
R5
INIT1
1
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
R5
INIT2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
R5
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
1
0
1
Program R12 as shown in the complete register map.
1
1
0
0
R9
Program R9 as shown in the complete register map.
1
0
0
1
R8
See individual section for Register R8 programming information.
Programming of this register is necessary under specific circumstances.
1
0
0
0
R7
See individual section for Register R7 programming information.
0
1
1
1
R6
See individual section for Register R6 programming information.
0
1
1
0
R4
See individual section for Register R4 programming information.
Register R4 only needs to be programmed if FastLock is used.
0
1
0
0
R3
See individual section for Register R3 programming information.
0
0
1
1
R2
See individual section for Register R2 programming information.
0
0
1
0
R1
See individual section for Register R1 programming information.
0
0
0
1
R0
See individual section for Register R0 programming information.
0
0
0
0
R12
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
21
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
8.6.1.2 Complete Register Content Map
Table 5 shows all the programmable bits for the LMX2531. No programming order or initialization sequence is implied by Table 5, only the location of the
programming information.
REGISTER
Table 5. Complete Register Content Map
23
22
21
20
18
17
16
14
13
12
11
10
N
[7:0]
R1
0
0
R2
0
1
9
8
7
6
5
4
DIV2 FDM
NUM
[11:0]
ICP
[3:0]
1
N
[10:8]
NUM
[21:12]
DEN
[11:0]
DITHER
[1:0]
ORDER
[1:0]
R
[5:0]
FoLD
[3:0]
DEN
[21:12]
ICPFL
[3:0]
TOC
[13:0]
R4
0
0
R5
1
0
R6
0
R7
0
0
R8
0
0
0
0
0
0
1
R9
0
0
0
0
0
0
0
0
R12
0
0
0
0
0
0
0
1
22
15
DATA[19:0]
R0
R3
19
0
0
0
XTLSEL
[2:0]
REG
_RS
T
0
0
0
EN_
LPF
LTR
VCO_ACI_SEL
[3:0]
0
0
R4_ADJ
[1:0]
0
0
R4_ADJ_F
L
[1:0]
EN_
DIG
LDO
EN_
PLL
LDO
2
R3_ADJ
[1:0]
XTLMAN
[11:0]
EN_
PLL
LDO
1
EN_
EN_ EN_
VCO
OSC VCO
LD
R3_ADJ_F
L
[1:0]
EN_
PLL
C3_4_ADJ
[2:0]
3
2
1
0
C3
C2
C1
C0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
XTLDIV
[1:0]
0
0
0
0
0
1
1
1
0
0
0
0
0
0
0
0
0
0
XTL
MAN
2
1
0
0
0
0
0
0
0
1
0
1
1
1
0
1
0
1
0
0
1
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
0
LOCK
MODE
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
8.6.1.3 Register R0
The action of programming the R0 register activates a frequency calibration routine for the VCO. This calibration
is necessary to get the VCO to center the tuning voltage for optimal performance. If the temperature drifts
considerably, then the PLL should stay in lock, provided that the temperature drift specification is not violated.
8.6.1.3.1 NUM[10:0] and NUM[21:12] -- Fractional Numerator
The NUM word is split between the R0 register and R1 register. The Numerator bits determine the fractional
numerator for the delta-sigma PLL. This value can go from 0 to 4095 when the FDM bit (R3[22]) is 0 (the other
bits in this register are ignored), or 0 to 4194303 when the FDM bit is 1.
Table 6. Fractional Numerator
FRACTIONAL
NUMERATOR
NUM[21:12]
0
NUM[11:0]
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
409503
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4096
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
...
...
4194303
Note that there are restrictions on the fractional numerator value depending on the R divider value if it is 16 or
32.
8.6.1.3.2 N[7:0] and N[10:8]
The N counter is 11 bits. 8 of these bits are located in the R0 register, and the remaining 3 (MSB bits) are
located in the R1 register. The LMX2531 consists of an A, B, and C counter, which work in conjunction with the
16/17/20/21 prescaler to form the final N counter value.
Table 7. N Divider Value
N[10:8]
N[7:0]
N Value
C
B
40 MHz
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
8.6.1.10.2 XTLMAN[11:0] -- Manual OSCin Mode
XTLMAN must be programmed if word XTLSEL (XTLSEL[2:0] -- OSCin Select) is set to manual OSCin mode. In
the table below, the proper value for XTLMAN is shown based on some common OSCin frequencies (fOSCin) and
various LMX2531 options. For any OSCin frequency XTLMAN can be calculated as 16 × fOSCin / Kbit. fOSCin is
expressed in MHz and Kbit values for the LMX2531 frequency options can be found in Table 28.
Table 27. XTLMAN Values for Common OSCin Frequencies
DEVICE
fOSCin
5 MHz
10 MHz
20 MHz
30.72 MHz
61.44 MHz
76.8 MHz
LMX2531LQ1146E
53
107
213
327
655
819
LMX2531LQ1226E
53
107
213
327
655
819
LMX2531LQ1312E
47
94
188
289
578
722
LMX2531LQ1415E
47
94
188
289
578
722
LMX2531LQ1500E
40
80
160
246
492
614
LMX1531LQ1515E
40
80
160
246
492
614
LMX2531LQ1570E
38
76
152
234
468
585
LMX2531LQ1650E
38
76
152
234
468
585
LMX2531LQ1700E
35
70
139
214
427
534
LMX2531LQ1742
32
64
128
197
393
492
LMX2531LQ1778E
31
62
123
189
378
473
LMX2531LQ1910E
27
53
107
164
328
410
LMX2531LQ2265E
20
40
80
123
246
307
LMX2531LQ2080E
18
36
71
109
218
273
LMX2531LQ2570E
13
27
53
82
164
205
LMX2531LQ2820E
11
23
46
70
140
178
LMX2531LQ3010E
10
20
40
61
123
154
Table 28. Kbit Values for Various LMX2531 Options
DEVICE
Kbit
LMX2531LQ1146E
1.5
LMX2531LQ1226E
1.5
LMX2531LQ1312E
1.7
LMX2531LQ1415E
1.7
LMX2531LQ1500E
2
LMX2531LQ1515E
2
LMX2531LQ1570E
2.1
LMX2531LQ1650E
2.1
LMX2531LQ1700E
2.3
LMX25311742
2.5
LMX2531LQ1778E
2.6
LMX2531LQ1910E
3
LMX2531LQ2265E
4
LMX2531LQ2080E
4.5
LMX2531LQ2570E
6
LMX2531LQ2820E
7
LMX2531LQ3010E
8
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
31
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
8.6.1.11 Register R8
8.6.1.11.1 XTLMAN2 -- Manual Crystal Mode Second Adjustment
This bit also adjusts the calibration timing for lock time. In the case that manual mode for XTLSEL is selected
and the OSCin frequency is greater than 40 MHz, this bit should be enabled, otherwise it should be 0.
8.6.1.11.2 LOCKMODE -- Frequency Calibration Mode
This bit controls the method for which the VCO frequency calibration is done. The two valid modes are linear
mode and mixed mode. Linear mode works by searching through the VCO frequency bands in a consecutive
manner. Mixed mode works by initially using a divide and conquer approach and then using a linear approach.
For small frequency changes, linear mode is faster and for large frequency changes, mixed mode is faster.
Linear mode can always be used, but there are restrictions for when Mixed Mode can be used.
Table 29. Lockmode Settings
LOCKMODE
DESCRIPTION
CONDITIONS on OSCin
FREQUENCY
CONDITIONS on OPTIONS
0
Reserved
Never use this mode
1
Linear Mode
Works over all options and all valid OSCin Frequencies
2
Mixed Mode
3
Reserved
All but the following options
LMX2531LQ1146E/1226E/1312E/1415E/1515E
fOSCin ≥ 8 MHz
Never use this mode
8.6.1.12 Register R9
All the bits in this register should be programmed as shown in Complete Register Content Map.
8.6.1.13 Register R12
Even though this register does not have user-selectable bits, it still needs to be programmed. This register should
be loaded as shown in Complete Register Content Map.
32
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The LMX2531 can be used in a broad class of applications. In general, they tend to fall in the categories where
the output frequency is a nicely related input frequency and those that require fractional mode. The following
schematic generally applies to most applications.
9.2 Typical Application
TCXO
C2_LF
100 nF
C1_LF
OSCin
100 nF
OSCin*
1 PF
FLout
VccDIG
R2pLF
CPout
10:
Vtune
R2_LF
10 nF
VregDIG
3.3:
VccVCO
Power
Supply
4.7 PF
VregVCO
10:
10 nF
1 PF
VrefVCO
LMX2531
10 nF
10:
VregBUF
VccBUF
0.22:
470 nF
0.22:
470 nF
1 PF
Fout
Test
1 PF
CE
VccPLL
10 PF
CLK
DATA
LE
10:
Ftest/LD
VregPLL2
VregPLL1
100 pF
Microcontroller
Circuit
Table 30. Typical Connection Diagram
PIN(S)
Vcc, Vreg, and Vref
Pins
APPLICATION INFORMATION
Consult the power supply recommendations for these pins.
CLK
DATA
LE
Because the maximum voltage on these pins is less than the minimum Vcc voltage, level shifting may be required if
the output voltage of the microcontroller is too high. This can be accomplished with a resistive divider.
CE
As with the CLK, DATA, and LE pins, level shifting may be required if the output voltage of the microcontroller is too
high. A resistive divider or a series diode are two ways to accomplish this. The diode has the advantage that no
current flows through it when the chip is powered down.
Ftest/LD
It is an option to use the lock detect information from this pin.
Fout
This is the high frequency output. This needs to be AC coupled, and matching may also be required. The value of
the DC blocking capacitor may be changed, depending on the output frequency.
CPout
Vtune
In most cases, it is sufficient to short these together, although there always the option of adding additional poles.
C1_LF, C2_LF, and R2_LF are used in conjunction with the internal loop filter to make a fourth order loop filter.
R2pLF
This is the fastlock resistor, which can be useful in many cases, because the spurs are often better with low charge
pump currents, and the internal loop filter can be adjusted during fastlock.
OSCin
This is the reference oscillator input pin. It needs to be AC coupled.
OSCin*
If the device is being driven single-ended, this pin needs to be shunted to ground with a capacitor.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
33
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Typical Application (continued)
9.2.1 Design Requirements
Consider generating 1500-MHz fixed frequency from a fixed 10-MHz input frequency. This is the situation similar
that was used for the LMX2531LQ1500E evaluation board.
For this design example, use the parameters listed in Table 31 as the user-input parameters.
Table 31. Design Procedure
PARAMETER
VALUE
REASON FOR CHOOSING
Fout
1500 MHz
This value was given.
Fosc
10 MHz
This value was given.
Fpd
10 MHz
This maximized for the best phase noise performance. This is an integer PLL design, so
it makes sense to maximize this. If Fpd 10 MHz it was a fractional design, then
sometimes lowering this frequency can improve fractional spurs.
Loop Bandwidth
11.5 kHz
This is wider for better jitter, but it is also restricted by the internal loop filter
Phase Margin
76.8 deg
Choosing a high phase margin is good for better jitter.
Kpd
16x
C3_LF
50 pF
Higher charge pump gains are better for better PLL phase noise
C4_LF
50 pF
R3_LF
10 kΩ
R4_LF
10 kΩ
C1_LF
Open
The internal loop filter restricts the loop bandwidth. By making C1_LF=open, this
maximizes the achievable bandwidth for a particular setup condition.
C2_LF
82 nF
These can be calculated with the Clock Architect.
R2_LF
1.5 kΩ
These can be calculated with the Clock Architect.
ORDER
"Reset Modulator"
DITHER
"Disabled"
XTLMAN
80
In general, the internal loop filter restricts how wide the loop bandwidth can be. Although
a wider loop bandwidth could be obtained by switching out the internal loop filter
altogether, it is nice to have some internal poles to filter some unwanted spurs. So this is
the minimum setting for the internal loop filter.
The device should be set to integer mode.
Dithering does not help in integer mode.
This is a setting for the LMX2531LQ1500E for a 10 MHz input.
9.2.2 Detailed Design Procedure
Use the WEBENCH® Clock Architect to calculate the values of C2_LF and R2_LF.
Set the device to integer mode and DITHER to disabled.
9.2.3 Application Curves
Figure 3. Closed Loop Phase Noise
34
Submit Documentation Feedback
Figure 4. Open Loop VCO Noise
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
9.3 Do's and Don'ts
Category
Don't
Why
Loop Filter Design
For integer Designs:
Maximize charge pump current
and phase detector frequency.
For Fractional Designs:
Blindly maximize charge pump
current and phase detector
frequency.
Maximizing the charge pump current and
phase detector frequency give the best PLL
phase noise and also allow a wider
bandwidth with the internal filter engaged.
However, increasing these also increase the
integer boundary spur. So for a fractional
design, these need to be balanced against
fractional spurs.
Partially Integrated
Loop Filter
Be aware that engaging this can
restrict the loop filter bandwidth.
Use TI simulation tools to see
how wide the bandwidth can be.
Design for the widest possible
bandwidth with the integrated
filter engaged and be surprised
when the bandwidth is smaller.
Enabling the internal loop filter poles
provides useful filtering, but also restricts
how wide the loop bandwidth can be.
Ground the "No Connect" Pins
where the pin description says
"Do Not Ground".
The DAP is grounded and used. However, if
the terminal description says "Do not
ground" this is for a reason. Some of these
pins are for the VCO tank circuit. There are
other no connect pins that are true no
connect, but there is no advantage to
grounding them. Note that the pad labeled
"NC" above pins 14 and 15 should NOT be
grounded.
"No Connect" and
DAP Pins
Do
Ground the DAP Pin
10 Power Supply Recommendations
The device is designed to operate within a recommended supply voltage range of 2.8 V to 3.2 V. Do not exceed
the values listed in the Absolute Maximum Ratings table. If the supply is not available, ensure that the CLK,
DATA, LE, and CE pins are held low. A power-on reset (POR) feature is not available for this device.
11 Layout
11.1 Layout Guidelines
For the layout of the LMX2531, perhaps the most important factor is to be aware of the package footprint. The
asymmetrical land pattern can cause issues if not correctly done.
11.1.1 Typical Connection Diagram
11.1.1.1 VccDIG, VccVCO, VccBUF, and VccPLL
These pins are inputs to voltage regulators. Because the LMX2531 contains internal regulators, the power supply
noise rejection is very good and capacitors at this pin are not critical. An RC filter can be used to reduce supply
noise, but if the capacitor is too large and is placed too close to these pins, they can sometimes cause phase
noise degradation in the 100 — 300 kHz offset range. Recommended values are from open to 1 μF. The 10 Ω
series resistors serve to filter power supply noise and isolate these pins from large capacitances.
11.1.1.2 VregDIG
A bypass capacitor of 10 nF is recommended.
11.1.1.3 VrefVCO
If the VrefVCO capacitor is changed, it is recommended to keep this capacitor between 1/100 and 1/1000 of the
value of the VregVCO capacitor.
11.1.1.4 VregVCO
Because this pin is the output of a regulator, there are stability concerns if there is not sufficient series
resistance. For ceramic capacitors, the ESR (Equivalent Series Resistance) is too low, and it is recommended
that a series resistance of 1 — 3.3 Ω is necessary. If there is insufficient ESR, then there may be degradation in
the phase noise, especially in the 100 — 300 kHz offset. Recommended values are from 1 μF to 10 μF.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
35
LMX2531
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
www.ti.com
Layout Guidelines (continued)
11.1.1.5 VregPLL1VregPLL2
The choice of the capacitor value at this pin involves a trade-off between integer spurs and phase noise in the
100 — 300 kHz offset range. Using a series resistor of about 220 mΩ in series with a capacitance that has an
impedance of about 150 mΩ at the phase detector frequency seems to give an optimal trade-off. For instance, if
the phase detector frequency is 2.5 MHz, then make this series capacitor 470 nF. If the phase detector
frequency is 10 MHz, make this capacitance about 100 nF.
11.2 Layout Example
36
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
LMX2531
www.ti.com
SNAS252S – OCTOBER 2005 – REVISED DECEMBER 2014
12 Device and Documentation Support
12.1 Device Support
For the Clock Architect tool, go to http://www.ti.com/lsds/ti/analog/webench/clock-architect.page
12.2 Trademarks
All trademarks are the property of their respective owners.
12.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
12.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
Submit Documentation Feedback
Copyright © 2005–2014, Texas Instruments Incorporated
Product Folder Links: LMX2531
37
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LMX2531LQ1146E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311146E
LMX2531LQ1226E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311226E
LMX2531LQ1312E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311312E
LMX2531LQ1415E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311415E
LMX2531LQ1500E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311500EB
LMX2531LQ1515E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311515E
LMX2531LQ1570E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311570EB
LMX2531LQ1650E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311650EA
LMX2531LQ1700E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311700EB
LMX2531LQ1742/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311742A
LMX2531LQ1778E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311778EA
LMX2531LQ1910E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311910EB
LMX2531LQ2080E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312080EB
LMX2531LQ2265E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312265ED
LMX2531LQ2570E/NOPB
ACTIVE
WQFN
NJG
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312570EC
LMX2531LQ2820E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312820E
LMX2531LQ3010E/NOPB
ACTIVE
WQFN
NJH
36
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
313010E
LMX2531LQE1226E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311226E
LMX2531LQE1312E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311312E
LMX2531LQE1415E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311415E
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
10-Dec-2020
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LMX2531LQE1515E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311515E
LMX2531LQE2820E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312820E
LMX2531LQE3010E/NOPB
ACTIVE
WQFN
NJH
36
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
313010E
LMX2531LQX1226E/NOPB
ACTIVE
WQFN
NJH
36
2500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311226E
LMX2531LQX1650E/NOPB
ACTIVE
WQFN
NJG
36
2500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311650EA
LMX2531LQX1742/NOPB
ACTIVE
WQFN
NJG
36
2500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
311742A
LMX2531LQX2570E/NOPB
ACTIVE
WQFN
NJG
36
2500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
312570EC
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
工商网监
湘ICP备2023018690号
