SNOSB31J July   2009  – December 2014 LMX2541

PRODUCTION DATA.  

  1. 1 Features
  2. 2  Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
      1. 7.7.1 Not Ensured Characteristics
      2. 7.7.2 Output Power in Bypass Mode
      3. 7.7.3 Output Power in Divided Mode
      4. 7.7.4 RFout Output Impedance
        1. 7.7.4.1 OSCin and Fin Sensitivity
  8. 8 Parameter Measurement Information
    1. 8.1 Bench Test Setups
      1. 8.1.1 Charge Pump Current Measurements
      2. 8.1.2 Charge Pump Current Definitions
        1. 8.1.2.1 Charge Pump Current Definitions
        2. 8.1.2.2 Variation of Charge Pump Current Magnitude vs. Charge Pump Voltage
        3. 8.1.2.3 Variation of Charge Pump Current Magnitude vs. Temperature
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Feature Description
      1. 9.3.1  PLL Reference Oscillator Input Pins
      2. 9.3.2  PLL R Divider
      3. 9.3.3  PLL Phase Detector and Charge Pump
      4. 9.3.4  PLL N Divider and Fractional Circuitry
      5. 9.3.5  Partially Integrated Loop Filter
      6. 9.3.6  Low Noise, Fully Integrated VCO
      7. 9.3.7  Programmable VCO Divider
      8. 9.3.8  Programmable RF Output Buffer
      9. 9.3.9  Powerdown Modes
      10. 9.3.10 Fastlock
      11. 9.3.11 Lock Detect
      12. 9.3.12 Current Consumption
      13. 9.3.13 Fractional Spurs
        1. 9.3.13.1 Primary Fractional Spurs
        2. 9.3.13.2 Sub-Fractional Spurs
      14. 9.3.14 Impact of VCO_DIV on Fractional Spurs
      15. 9.3.15 PLL Phase Noise
        1. 9.3.15.1 , LMX2541SQ3740E Raw Phase Noise Measurement Plot Description
        2. 9.3.15.2 , LMX2541SQ2690 System Phase Noise Plot Description
        3. 9.3.15.3 Phase Noise of PLL
      16. 9.3.16 Impact of Modulator Order, Dithering, and Larger Equivalent Fractions on Spurs and Phase Noise
      17. 9.3.17 Modulator Order
      18. 9.3.18 Programmable Output Power with On/Off
      19. 9.3.19 Loop Filter
      20. 9.3.20 Internal VCO Digital Calibration Time
    4. 9.4 Device Functional Modes
      1. 9.4.1 External VCO Mode
      2. 9.4.2 Digital FSK Mode
    5. 9.5 Programming
      1. 9.5.1 General Programming Information
    6. 9.6 Register Maps
      1. 9.6.1 Register R7
        1. 9.6.1.1  Register R13
          1. 9.6.1.1.1 VCO_DIV_OPT[2:0]
        2. 9.6.1.2  Register R12
        3. 9.6.1.3  Register R9
        4. 9.6.1.4  Register R8
          1. 9.6.1.4.1 AC_TEMP_COMP[4:0]
        5. 9.6.1.5  Register R6
          1. 9.6.1.5.1 RFOUT[1:0] - RFout enable pin
          2. 9.6.1.5.2 DIVGAIN[3:0], VCOGAIN[3:0], and OUTTERM[3:0] - Power Controls for RFout
        6. 9.6.1.6  Register R5
          1. 9.6.1.6.1 FL_TOC[13:0] -- Time Out Counter for FastLock
          2. 9.6.1.6.2 FL_R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3 During Fastlock
          3. 9.6.1.6.3 FL_R4_LF[2:0] -- Value for Internal Loop Filter Resistor R4 During Fastlock
          4. 9.6.1.6.4 FL_CPG[4:0] -- Charge Pump Current for Fastlock
        7. 9.6.1.7  Register R4
          1. 9.6.1.7.1 OSC_FREQ [7:0] -- OSCin Frequency for VCO Calibration Clocking
          2. 9.6.1.7.2 VCO_DIV[5:0] - VCO Divider
          3. 9.6.1.7.3 R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3
          4. 9.6.1.7.4 R4_LF[2:0] -- Value for Internal Loop Filter Resistor R4
          5. 9.6.1.7.5 C3_LF[3:0] -- Value for C3 in the Internal Loop Filter
          6. 9.6.1.7.6 C4_LF[3:0] -- Value for C4 in the Internal Loop Filter
        8. 9.6.1.8  Register R3
          1. 9.6.1.8.1  MODE[1:0] -- Operational Mode
          2. 9.6.1.8.2  Powerdown -- Powerdown Bit
          3. 9.6.1.8.3  XO - Crystal Oscillator Mode Select
          4. 9.6.1.8.4  CPG[4:0] -- Charge Pump Current
          5. 9.6.1.8.5  MUX[3:0] -- Multiplexed Output for Ftest/LD Pin
          6. 9.6.1.8.6  CPP - Charge Pump Polarity
          7. 9.6.1.8.7  OSC2X-- OSCin Frequency Doubler
          8. 9.6.1.8.8  FDM - Extended Fractional Denominator Mode Enable
          9. 9.6.1.8.9  ORDER[2:0] -- Delta-Sigma Modulator Order
          10. 9.6.1.8.10 DITH[1:0] -- Dithering
          11. 9.6.1.8.11 CPT - Charge Pump TRI-STATE
          12. 9.6.1.8.12 DLOCK[2:0] - Controls for Digital Lock Detect
          13. 9.6.1.8.13 FSK - Frequency Shift Keying
        9. 9.6.1.9  Register R2
          1. 9.6.1.9.1 PLL_DEN[21:0] -- Fractional Denominator
        10. 9.6.1.10 Registers R1 and R0
          1. 9.6.1.10.1 PLL_R[11:0] -- PLL R Divider Value
          2. 9.6.1.10.2 PLL_N[17:0] PLL N Divider Value
          3. 9.6.1.10.3 PLL_NUM[21:0] -- Fractional Numerator
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Determining the Best Frequency Option of the LMX2541 to Use
      2. 10.1.2 RFout Output Power Test Setup
      3. 10.1.3 Phase Noise Measurement Test Setup
        1. 10.1.3.1 PLL Phase Noise Measurement
          1. 10.1.3.1.1 PLL Phase Noise Measurement - 1/f Noise
          2. 10.1.3.1.2 PLL Phase Noise Measurement - Flat Noise
        2. 10.1.3.2 VCO Phase Noise Measurement
        3. 10.1.3.3 Divider Phase Noise Measurement
      4. 10.1.4 Input and Output Impedance Test Setup
        1. 10.1.4.1 OSCin Input Impedance Measurement
        2. 10.1.4.2 ExtVCOin Input Impedance Measurement
        3. 10.1.4.3 RFout Output Impedance Measurement
      5. 10.1.5 ExtVCOin (NOT OSCin) Input Sensitivity Test Setup
      6. 10.1.6 OSCin Input Sensitivity Test Setup
        1. 10.1.6.1 Input Sensitivity Test Procedure
        2. 10.1.6.2 OSCin Slew Rate Tests
      7. 10.1.7 Typical Connections
        1. 10.1.7.1 Full Chip Mode, Differential OSCin
        2. 10.1.7.2 External VCO Mode, Single-Ended OSCin, RFout Pin not Used
        3. 10.1.7.3 OSCin/OSCin* Connections
          1. 10.1.7.3.1 Single-Ended Operation
          2. 10.1.7.3.2 Differential Operation
          3. 10.1.7.3.3 Crystal Mode Operation
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Configuring the LMX2541 for Optimal Performance
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

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7 Specifications

7.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) (1)(2)
MIN MAX UNIT
Vcc Power Supply Voltage –0.3 3.6 V
VIN Input Voltage to pins other than Vcc Pins
(3)		 –0.3 (Vcc + 0.3) V
TL Lead Temperature (solder 4 sec.) 260 °C
Tstg Storage Temperature –65 150 °C
(1) 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.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications.
(3) Never to exceed 3.6 V.

7.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2500 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±1750
Machine model (MM) ±400
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

7.3 Recommended Operating Conditions

MIN NOM MAX UNIT
Vcc Power Supply Voltage (All Vcc Pins) 3.15 3.3 3.45 V
TA Ambient Temperature –40 85 °C

7.4 Thermal Information

THERMAL METRIC(1) LMX2541
SQ2060E		 LMX2541
SQ2060E		 LMX2541
SQ2060E		 UNIT
9 Thermal Vias(2) 13 Thermal Vias(3) 16 Thermal Vias(4)
RθJA Junction-to-ambient thermal resistance 31.7 30.3 29.8 °C/W
ψJT Junction-to-top characterization parameter 7.3 7.3 7.3
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
(2) Recommended for Most Reliable Solderability.
(3) Compromise Between Solderability, Heat Dissipation, and Fractional Spurs.
(4) Recommended for Optimal Heat Dissipation and Fractional Spurs.

7.5 Electrical Characteristics

(3.15 V ≤ VCC ≤ 3.45 V, -40°C ≤ TA ≤ 85 °C; except as specified. Typical values are at Vcc = 3.3 V, 25 C.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
CURRENT CONSUMPTION
ICC Entire Chip Supply Current with all blocks enabled Default Power Mode
(1)		 VCO_DIV>1 170 204 mA
VCO_DIV=1 130 156
IPLL Current for External VCO Mode RFoutEN = LOW 72 94 mA
IDIV Current for Divider Only Mode VCO_DIV >1
Default Power Mode
(1)		 84 110 mA
ICCPD Power Down Current CE = 0 V, Device Initialized 100 250 µA
OSCILLATOR (NORMAL MODE OPERATION WITH XO=0)
IIHOSC in Oscillator Input High Current for OSCin and OSCin* VIH = 2.75 V 300 µA
IILOSCin Oscillator Input Low Current for OSCin and OSCin* pins VIL = 0 –100 µA
fOSCin OSCin Frequency Range
(2)		 OSC_2X = 1 5 52 MHz
OSC_2X = 0 MODE = 0 5 700
MODE = 1 5 900
dvOSCin Slew Rate  (2) 150 V/µs
vOSCin Oscillator Sensitivity dvOSCin ≥ 150 V/µs Single-Ended 0.2 2.0 Vpp
Differential 0.4 3.1
OSCILLATOR (CRYSTAL MODE WITH XO=1)
fXTAL Crystal Frequency Range VIH = 2.75 V 5 20 MHz
ESRXTAL Crystal Equivalent Series Resistance This a requirement for the crystal, not a characteristic of the LMX2541. 100 Ω
PXTAL Power Dissipation in Crystal This requirement is for the crystal, not a characteristic of the LMX2541. 200 µW
COSCin Input Capacitance of OSCin 6 pF
PLL
fPD Phase Detector Frequency 104 MHz
ICPout Charge Pump
Output Current Magnitude		 CPG = 1X 100 µA
CPG = 2X 200
CPG = 3X 300
... ...
CPG=32X 3200
ICPoutTRI CP TRI-STATE Current 0.4 V < VCPout < Vcc - 0.4 1 5 nA
ICPoutMM Charge Pump
Sink vs. Source Mismatch		 VCPout = Vcc / 2
TA = 25°C		 3% 10%
ICPoutV Charge Pump
Current vs. CP Voltage Variation		 0.4 V < VCPout < Vcc - 0.4
TA = 25°C		 4%
ICPoutT CP Current vs. Temperature Variation VCPout = Vcc / 2 8%
LN(f)
(3)		 Normalized PLL 1/f Noise
LNPLL_flicker(10 kHz)		 CPG = 1X –116 dBc/Hz
CPG = 32X –124.5
Normalized PLL Noise Floor
LNPLL_flat(1 Hz)		 CPG = 1X –220.8 dBc/Hz
CPG = 32X –225.4
fExtVCOin PLL Input Frequency RFout Buffer Enabled and VCO_DIV > 1 400 4000 MHz
RFout Buffer Disabled and VCO_DIV = 1 400 6000
pExtVCOin PLL Input Sensitivity
((2) applies to Max Limit Only)		 fExtVCOin ≤ 4 GHz –15 10 dBm
fExtVCOin > 4 GHz –5 10
VCO SPECIFICATIONS
fVCO Internal VCO Frequency Range Mode = Full Chip Mode
This is the frequency before the VCO divider.		 2060E 1990 2240 MHz
2380E 2200 2530
2690E 2490 2865
3030E 2810 3230
3320E 3130 3600
3740E 3480 4000
ΔTCL Maximum Allowable Temperature Drift for Continuous Lock (2),(4) 125 °C
pRFout RF Output Power
 Maximum Frequency
Default Power Mode
VCO_DIV=1		 2060E 3.5 dBm
2380E 2.8
2690E 1.6
3030E 1.2
3320E 0.2
3740E –0.3
ΔPRFout Change in Output Power Fixed Temperature with 100 MHz frequency change at the output 0.3 dB
Fixed frequency with a change over the entire temperature range 0.4
KVtune Fine Tuning Sensitivity The lower number in the range applies when the VCO is at its lowest frequency and the higher number applies when the VCO is at its highest frequency. A linear approximation can be used for frequencies between these two cases. 2060E 13 - 23 MHz/V
2380E 16 - 30
2690E 17 - 32
3030E 20 - 37
3320E 21 - 37
3740E 24 - 42
HSRFout Second Harmonic
(6)		 Default Power Mode
(1)
50 Ω Load 		VCO_DIV = 2 –20 dBc
VCO_DIV = 3 –20
DERFout Duty Cycle Error
(6)		 Default Power Mode
(1)
50 Ω Load 		VCO_DIV = 2 3%
VCO_DIV = 3 3%
PSHVCO VCO Frequency Pushing CVregVCO = 4.7 µF, Open Loop 600 kHz/V
PULVCO VCO Frequency Pulling VSWR 1.7 to 1
(6 dB Pad)		 VCO_DIV = 1 ±800 kHz
VCO_DIV > 1 ±60
σΦ RMS Phase Error Integration Bandwidth
= 100 Hz to 20 MHz

Middle VCO Frequency
100 MHz Wenzel Crystal Reference
Integer Mode
Optimized Loop Bandwidth		 2060E 1.6 mRad
2380E 1.8
2690E 2.1
3030E 2.1
3320E 2.3
3740E 2.6
VCO PHASE NOISE(5)
L(f)Fout Phase Noise
2060E		 fRFout =
Min VCO Frequency		 10-kHz Offset –89.7 dBc/Hz
100-kHz Offset –113.7
1-MHz Offset –134.9
10-MHz Offset –155.4
20-MHz Offset –160.3
fRFout =
Max VCO Frequency		 10-kHz Offset –86.5
100-kHz Offset –111.4
1-MHz Offset –132.8
10-MHz Offset –153.4
20-MHz Offset –158.5
L(f)Fout Phase Noise
2380E		 fRFout =
Min VCO Frequency		 10-kHz Offset –87.9 dBc/Hz
100-kHz Offset –112.7
1-MHz Offset –133.8
10-MHz Offset –154.2
20-MHz Offset –159.5
fRFout =
Max VCO Frequency		 10-kHz Offset –83.4
100-kHz Offset –109.1
1-MHz Offset –130.8
10-MHz Offset –151.8
20-MHz Offset –157.5
L(f)Fout Phase Noise
2690E		 fRFout =
Min VCO Frequency		 10-kHz Offset –86.9 dBc/Hz
100-kHz Offset –111.8
1-MHz Offset –133.3
10-MHz Offset –154.2
20-MHz Offset –159.4
fRFout =
Max VCO Frequency		 10-kHz Offset –82.3
100-kHz Offset –108.4
1-MHz Offset –130.3
10-MHz Offset –151.1
20-MHz Offset –156.7
L(f)Fout Phase Noise
3030E		 fRFout =
Min VCO Frequency		 10-kHz Offset –86.1 dBc/Hz
100-kHz Offset –110.5
1-MHz Offset –132.0
10-MHz Offset –152.2
20-MHz Offset –157.1
fRFout =
Max VCO Frequency		 10-kHz Offset –82.2
100-kHz Offset –107.7
1-MHz Offset –129.4
10-MHz Offset –150.5
20-MHz Offset –156.1
L(f)Fout Phase Noise
3320E		 fRFout =
Min VCO Frequency		 10-kHz Offset –84.1 dBc/Hz
100-kHz Offset –109.1
1-MHz Offset –130.7
10-MHz Offset –151.6
20-MHz Offset –156.9
fRFout =
Max VCO Frequency		 10-kHz Offset –82.0
100-kHz Offset –107.0
1-MHz Offset –128.5
10-MHz Offset –149.6
20-MHz Offset –155.2
L(f)Fout Phase Noise
3740E		 fRFout =
Min VCO Frequency		 10-kHz Offset –83.9 dBc/Hz
100-kHz Offset –108.3
1-MHz Offset –129.9
10-MHz offset –150.6
20-MHz Offset –156.5
fRFout =
Max VCO Frequency		 10-kHz Offset –81.6
100-kHz Offset –106.5
1-MHz Offset –127.7
10-MHz Offset –148.6
20-MHz Offset –154.2
DIGITAL INTERFACE (DATA, CLK, LE, CE, Ftest/LD, FLout,RFoutEN)
VIH High-Level Input Voltage 1.6 Vcc V
VIL Low-Level Input Voltage 0.4 V
IIH High-Level Input Current VIH = 1.75, XO = 0 –5 5 µA
IIL Low-Level Input Current VIL = 0 V , XO = 0 –5 5 µA
VOH High-Level Output Voltage IOH = 500 µA 2 V
VOL Low-Level Output Voltage IOL = -500 µA 0 0.4 V
ILeak Leakage Current Ftest/LD and FLout Pins Only –5 5 µA
(1) The LMX2541 RFout power level is programmable with the program words of VCOGAIN, OUTTERM, and DIVGAIN. Changing these words can change the output power of the VCO as well as the current consumption of the output buffer. For the purpose of consistency in electrical specifications, "Default Power Mode" is defined to be the settings of VCOGAIN = OUTTERM = DIVGAIN = 12.
(2) Not tested in production. Specified by characterization. OSCin is tested only to 400 MHz.
(3) See Application and Implementation for more details on these parameters.
(4) 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 device stay in lock. The action of programming the R0 register, even to the same value, activates a frequency calibration routine. This implies that the device 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 device was initially programmed at, the temperature can never drift outside the frequency range of -40°C ≤TA≤ 85°C without violating specifications.
(5) The VCO phase noise is measured assuming that the loop bandwidth is sufficiently narrow that the VCO noise dominates. The phase noise is measured with AC_TEMP_COMP = 5 and the device is reloaded at each test frequency. The typical performance characteristics section shows how the VCO phase noise varies over temperature and frequency.
(6) The duty cycle error (DE) and second harmonic (HS) are theoretically related by the equation HS = 10·log| 2π·DE | - 6 dB. A square wave with 3% duty cycle theoretically has a second harmonic of -20 dBc.

7.6 Timing Requirements

MIN NOM MAX UNIT
tCE Clock to Enable Low Time See Figure 1 25 ns
tCS Data to Clock Set Up Time See Figure 1 25 ns
tCH Data to Clock Hold Time See Figure 1 20 ns
tCWH Clock Pulse Width High See Figure 1 25 ns
tCWL Clock Pulse Width Low See Figure 1 25 ns
tCES Enable to Clock Set Up Time See Figure 1 25 ns
tEWH Enable Pulse Width High See Figure 1 25 ns
LMX2541 30073303.gifFigure 1. Serial Data Timing Diagram

7.7 Typical Characteristics

7.7.1 Not Ensured Characteristics

LMX2541 30073308.gifFigure 2. PLL Normalized Noise Floor vs OSCin Slew Rate (KPD = 32X)
LMX2541 30073309.gifFigure 4. PLL Normalized 1/f Noise vs OSCin Slew Rate (KPD = 32X)
LMX2541 tc05_PLL_NoiseMetricExample.gif Figure 6. PLL 1/f and Noise Floor Measurement of the LMX2541SQ3740E
LMX2541 30073346.gifFigure 3. PLL Normalized Noise Floor vs Charge Pump Gain (Slew Rate = 2000 V/μs)
LMX2541 30073347.gifFigure 5. PLL Normalized 1/f Noise vs Charge Pump Gain (Slew Rate = 2000 V/μs)
LMX2541 tc10_DividerNoiseExample.gif
1. Engaging the divider reduces the phase noise by 20 × log(VCO_DIV) except at far offsets where it adds noise.
Figure 7. Divider Noise Floor vs Divider Value (fVCO = 3700 MHz, Various Values for VCO_DIV)
LMX2541 tc11_DividerNoiseVsFreq.gif
1. Provided the VCO divider is not bypassed, the actual value of it does not impact the divider noise floor; it is the frequency at the RFout pin that impacts the divider noise floor.
2. The above plot shows how this noise floor changes as a function of the frequency of the RFout pin.
Figure 8. Divider Noise Floor vs Frequency

Table 1. Relative VCO Phase Noise Over Temperature Drift
(AC_TEMP_COMP = 24, Vcc = 3.3 V)(1)

TEMPERATURE PHASE NOISE CHANGE IN CELSIUS FOR VARIOUS OFFSETS
LOCK CURRENT 10 kHz 100 kHz 1 MHz 10 MHz 20 MHz
–40 –40 +0.4 –2.0 –1.6 –1.8 –1.6
–40 25 +0.3 +0.5 +0.5 +0.5 +0.4
–40 85 +0.9 +2.0 +2.4 +2.5 +2.3
25 –40 +0.2 –2.2 –1.7 –2.0 –1.8
25 25 This is the default condition to which these other numbers are normalized to.
25 85 +0.6 +1.5 +2.0 +2.0 +1.9
85 –40 +0.2 –2.2 –1.7 –1.9 –1.8
85 25 +0.2 +0.2 +0.3 +0.2 +0.2
85 85 +0.6 +1.8 +2.2 +2.3 +2.1
(1) The table shows the typical degradation for VCO phase noise when the VCO is locked at one temperature and the temperature is allowed to drift to another temperature. A negative value indicates a phase noise improvement.

7.7.2 Output Power in Bypass Mode

The following plots show the trends in output power as a function of temperature, voltage, and frequency. For states where VCOGAIN and OUTTERM are not 12, the table below shows how the output power is modified based on these programmable settings. The measurement of the output power is sensitive to the test circuit. All the numbers in the electrical specifications and typical performance curves were obtained from a characterization setup that accommodate temperature testing and changing of parts. In a more optimized setup the measured RF output power is typically on the order of 1.5 to 2.4 dB higher.

LMX2541 30073316.gifFigure 9. Output Power vs Voltage (VCO_DIV = 1, VCOGAIN = 12, OUTTERM = 12, TA = 25°C)
LMX2541 30073317.gifFigure 11. Output Power vs Temperature (VCO_DIV = 1, VCOGAIN = 12, OUTTERM = 12, Vcc = 3.3 V)
LMX2541 30073315.gifFigure 10. Output Power vs OUTTERM and FREQUENCY (VCO_DIV = 1, TA = 25 °C, Vcc = 3.3 V, VCOGAIN = 12)
LMX2541 30073314.gifFigure 12. Output Power vs VCOGAIN and FREQUENCY (VCO_DIV = 1, TA = 25 °C, Vcc = 3.3 V, OUTTERM = 12)

Table 2. Change in Output Power in Bypass Mode as a Function of VCOGAIN and OUTTERM

VCOGAIN
3 6 9 12 15
OUTTERM 3 –9.7 –8.4 –7.9 –7.8 –7.9
6 –6.6 –4.5 –3.6 –3.4 –3.6
9 –5.7 –3.1 –1.7 –1.3 –1.3
12 –5.4 –2.5 –0.8 +0.0 +0.1
15 –5.3 –2.2 –0.3 +0.8 +1.1

7.7.3 Output Power in Divided Mode

The measurement of the output power is sensitive to the test circuit. All the numbers in the electrical specifications and typical performance curves were obtained from a characterization setup that accommodate temperature testing and changing of parts. In a more optimized setup the measured RF output power is typically on the order of 1.5 to 2.4 dB higher.

LMX2541 30073320.gif
Figure 13. Output Power vs Voltage (VCO_DIV > 1, DIVGAIN = 12, OUTTERM = 12, TA = 25°C)
LMX2541 30073321.gif
Figure 15. Output Power vs Temperature ( VCO_DIV > 1, DIVGAIN = OUTTERM = 12, Vcc = 3.3 V)
LMX2541 30073319.gif
Figure 14. Output Power vs OUTTERM and FREQUENCY (VCO_DIV > 1, TA = 25 °C, Vcc = 3.3 V, DIVGAIN = 12)
LMX2541 30073318.gif
Figure 16. Output Power vs DIVGAIN and FREQUENCY(VCO_DIV > 1, TA = 25 °C, Vcc = 3.3 V, OUTTERM = 12)

Table 3. Change in Output Power in Divided Mode as a Function of DIVGAIN and OUTTERM(1)

DIVGAIN
3 6 9 12 15
OUTTERM 3 –10.2 –6.1 –5.7 –5.5 –5.5
6 –9.8 –4.4 –2.4 –2.1 –2.0
9 –9.8 –4.3 –1.5 –0.7 –0.5
12 –9.9 –4.3 –1.4 +0.0 +0.2
15 –9.9 –4.4 –1.4 +0.3 +0.7
(1) The table shows the RELATIVE output power to the case of VCOGAIN = OUTTERM = 12.

7.7.4 RFout Output Impedance

LMX2541 30073345.gif
The impedance of the RFout pin varies as a function of frequency, VCO_DIV, OUTTERM, VCOGAIN, DIVGAIN, and frequency. When in bypass mode (VCO_DIV = 1), the DIVGAIN word has no impact on the output impedance. When in divided mode (VCO_DIV>1), the VCOGAIN has no impact on the output impedance. This graphic shows how the input impedance varies as a function of frequency for both the bypass and divided cases.
Figure 17. RFout Output Impedance

Table 4. RFout Output Impedance vs. VCOGAIN (Bypass Mode)(1)

Freq. (MHz) VCOGAIN=3 VCOGAIN=6 VCOGAIN=9 VCOGAIN=12 VCOGAIN=15
REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY
50 3.8 2.1 5.5 1.9 7.3 1.8 9.5 1.7 10.1 1.7
100 4.8 4.1 6.1 3.9 7.8 3.7 9.8 3.6 10.3 3.6
200 5.4 5.7 6.8 6.0 8.7 6.3 10.9 6.5 11.4 6.6
400 5.5 9.4 7.5 10.0 9.8 10.6 12.4 11.0 13.1 11.0
600 5.8 15.1 8.1 15.4 10.7 15.7 13.7 15.7 14.5 15.6
800 7.0 20.7 9.6 20.8 12.6 20.8 15.8 20.3 16.7 20.1
1000 9.2 26.3 12.1 26.1 15.4 25.6 19.0 24.6 19.8 24.1
1200 10.7 28.6 13.4 27.9 16.3 26.9 19.3 25.5 20.0 25.0
1400 12.2 30.9 14.7 29.7 17.1 28.2 19.7 26.4 20.2 25.9
1600 13.7 33.2 15.9 31.5 18.0 29.5 20.1 27.4 20.5 26.8
1800 15.2 35.5 17.2 33.3 18.8 30.8 20.5 28.3 20.7 27.7
2000 14.5 39.5 16.4 37.4 17.9 35.0 19.6 32.5 19.8 31.9
2200 15.6 42.9 17.4 40.7 18.7 38.2 20.3 35.6 20.4 35.0
2400 14.2 47.6 16.0 45.3 17.4 42.8 19.0 40.1 19.2 39.4
2600 12.2 51.3 14.1 48.7 15.6 46.5 17.2 43.5 17.3 42.5
2800 11.5 57.9 13.7 55.3 15.3 52.4 17.0 49.0 17.1 48.3
3000 10.6 67.1 13.1 64.0 14.8 60.5 16.3 56.5 16.4 55.7
3200 13.1 77.3 15.7 73.2 17.3 69.0 18.4 64.2 18.4 63.3
3400 17.6 88.1 20.0 82.8 21.1 77.4 21.7 71.8 21.5 70.8
3600 29.0 96.0 30.6 90.2 30.9 83.6 30.2 76.7 29.8 75.6
3800 38.2 99.4 38.0 94.4 36.4 87.3 34.1 80.5 33.4 79.4
4000 43.5 106.0 41.6 99.0 38.9 92.0 35.5 85.1 34.8 83.7
4200 48.0 119.3 45.9 109.8 43.1 101.9 37.2 94.2 36.0 93.0
4400 62.4 137.9 56.4 126.6 49.8 117.6 42.3 109.5 40.8 108.3
4600 87.0 149.4 76.0 138.1 65.4 129.5 54.3 122.2 52.3 121.2
4800 128.1 153.7 109.7 145.6 93.0 140.1 76.7 135.9 74.0 135.5
5000 168.1 134.7 145.4 135.5 124.9 138.0 105.4 141.1 102.4 141.9
(1) This is for the VCO divider in bypass mode (VCO_DIV=1) and the RFout pin powered up. OUTTERM was set to 12.

Table 5. RFout Output Impedance vs. OUTTERM (Bypass Mode)(1)

Freq. (MHz) OUTTERM=3 OUTTERM=6 OUTTERM=9 OUTTERM=12 TERM=15
REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY
50 27.9 1.6 16.2 1.9 12.3 1.8 9.5 1.7 7.8 1.7
100 28.5 2.8 16.7 3.6 12.7 3.6 9.8 3.6 8.0 3.5
200 29.2 3.8 18.1 5.9 14.0 6.3 10.9 6.5 9.0 6.6
400 28.8 5.7 19.2 9.5 15.3 10.3 12.4 11.0 10.6 11.2
600 28.8 8.8 20.4 13.7 16.5 14.9 13.7 15.7 11.9 16.0
800 29.1 11.7 22.5 17.5 18.7 19.2 15.8 20.3 14.0 20.8
1000 28.6 13.4 22.8 19.2 19.3 21.2 16.5 22.5 14.6 23.1
1200 28.0 15.0 23.1 20.9 19.8 23.2 17.1 24.7 15.2 25.4
1400 27.5 16.7 23.3 22.7 20.4 25.2 17.7 26.9 15.8 27.7
1600 27.0 18.4 23.6 24.4 20.9 27.2 18.4 29.0 16.5 30.0
1800 26.4 20.1 23.9 26.1 21.4 29.2 19.0 31.2 17.1 32.3
2000 25.9 21.8 24.1 27.9 22.0 31.1 19.6 33.4 17.7 34.6
2200 25.3 23.5 24.4 29.6 22.5 33.1 20.3 35.6 18.3 36.9
2400 23.1 26.9 22.9 33.2 21.3 37.1 19.0 40.1 17.0 41.8
2600 20.1 29.3 20.5 35.4 19.3 39.6 17.2 42.9 15.1 44.9
2800 18.5 34.2 19.6 40.4 18.8 45.0 17.0 49.0 14.8 51.6
3000 16.6 40.6 18.1 46.9 17.8 51.9 16.3 56.5 14.3 59.7
3200 16.5 47.0 18.9 53.4 19.3 58.9 18.4 64.2 16.7 68.2
3400 17.1 53.8 20.4 60.1 21.8 65.8 21.7 71.8 20.4 76.6
3600 20.8 59.4 25.4 65.0 28.3 70.5 30.2 76.8 30.3 82.5
3800 22.0 64.9 27.3 69.7 31.1 74.6 34.1 80.5 35.4 86.1
4000 23.0 70.0 28.1 74.9 32.1 80.0 35.5 86.4 37.6 92.0
4200 23.7 77.9 28.6 82.8 32.8 87.7 37.0 94.2 39.9 100.9
4400 23.7 93.2 30.1 98.0 35.4 102.9 42.3 109.4 47.8 116.6
4600 27.3 107.4 36.6 112.0 44.8 116.3 54.3 122.2 62.6 128.9
4800 40.1 126.6 52.2 129.8 63.3 132.3 76.7 135.9 89.3 140.5
5000 61.4 142.8 76.2 143.3 89.5 142.3 105.5 141.0 121.0 140.5
(1) The VCO divider was bypassed (VCO_DIV = 1) and the RFout pin was enabled. The VCOGAIN word was set to 12.

Table 6. RFout Output Impedance vs. DIVGAIN (Divided Mode)(1)

Freq. (MHz) DIVGAIN=3 DIVGAIN=6 DIVGAIN=9 DIVGAIN=12 DIVGAIN=15
REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY
50 3.2 2.2 3.6 2.1 5.8 2.0 13.9 1.9 22.3 1.6
100 4.5 4.1 4.6 4.0 6.6 3.8 14.7 3.2 23.2 2.3
200 5.7 5.3 6.4 5.7 7.0 5.9 15.0 4.7 23.0 2.7
400 5.0 9.2 5.6 9.4 7.7 9.5 15.6 7.7 22.8 4.4
600 5.2 14.6 5.7 14.6 7.8 14.6 15.9 12.1 22.2 7.9
800 6.0 20.2 6.5 20.2 8.7 20.2 16.9 16.5 22.3 11.4
1000 7.9 25.7 8.4 25.7 10.7 25.5 18.7 20.5 22.9 14.6
1200 11.0 29.9 11.6 30.0 13.9 29.5 21.4 23.1 24.3 16.8
1400 13.2 32.3 13.9 32.3 16.1 31.7 22.5 24.3 23.9 18.2
1600 14.2 34.4 15.0 34.3 17.1 33.5 22.5 25.8 23.1 20.1
1800 13.9 37.2 14.6 37.0 16.7 36.2 21.6 28.2 21.7 22.9
2000 13.5 41.1 14.3 40.9 16.4 39.9 20.9 31.4 20.6 26.4
2200 14.8 45.1 15.6 44.7 17.8 43.6 21.7 34.5 20.9 29.7
2400 14.1 49.4 14.9 49.0 17.1 47.7 20.4 38.1 19.3 33.5
2600 12.4 52.1 13.2 51.6 15.5 50.1 18.2 40.4 16.8 36.2
2800 11.8 59.3 12.5 58.7 15.0 56.8 17.0 46.2 15.3 42.0
3000 10.7 68.3 11.5 67.6 14.0 65.2 15.2 53.4 13.0 49.2
3200 13.1 78.6 14.0 77.6 16.7 74.5 16.5 61.1 13.8 56.9
3400 18.1 89.6 18.9 88.4 21.6 84.4 19.4 69.2 16.0 65.1
3600 29.2 98.6 29.8 96.9 31.9 91.6 26.1 75.4 21.7 71.6
3800 36.0 105.8 36.5 103.9 37.8 97.5 28.9 81.1 24.0 77.8
4000 43.6 101.4 43.7 99.5 43.7 92.9 32.3 78.8 27.1 76.3
4200 40.6 122.9 40.8 120.3 40.6 111.8 26.6 94.7 20.7 91.8
4400 63.6 143.0 62.9 139.6 59.9 128.6 37.8 111.4 30.0 109.2
4600 90.9 155.3 88.8 151.4 81.1 139.6 49.9 125.8 40.3 124.9
4800 135.8 159.1 131.2 155.7 116.3 145.5 73.7 142.1 61.7 144.0
5000 179.4 135.1 173.2 133.9 153.3 131.4 107.1 147.7 94.5 155.2
(1) This was done with RFout buffer powered up and with OUTTERM=12. VCO_DIV was set to 50.

Table 7. RFout Output Impedance vs. OUTTERM (Divided Mode)(1)

Freq.(MHz) OUTTERM=3 OUTTERM=6 OUTTERM=9 OUTTERM=12 OUTTERM=15
REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY
50 44.1 –0.3 31.8 1.0 21.2 1.7 14.0 1.9 9.3 2.0
100 44.9 –2.2 32.8 0.7 22.1 2.5 14.8 3.2 10.0 3.5
200 43.2 –7.2 33.2 –1.2 23.3 2.8 16.1 4.7 11.3 5.6
400 33.2 –8.1 28.5 –1.5 21.9 4.5 15.7 7.7 11.2 9.1
600 28.0 –3.8 25.7 1.8 21.4 8.0 15.9 12.1 11.4 13.9
800 25.1 1.1 24.0 5.6 21.7 11.5 16.9 16.5 12.5 19.0
1000 23.7 5.8 23.3 9.6 22.4 14.7 18.7 20.5 14.6 23.8
1200 23.5 9.3 23.7 12.4 23.8 16.7 21.4 23.1 17.7 27.2
1400 22.6 12.3 22.9 14.8 23.5 18.1 22.5 24.3 19.5 28.9
1600 21.5 15.3 21.8 17.4 22.6 20.0 22.5 25.8 20.2 30.5
1800 20.2 18.8 20.5 20.7 21.3 22.8 21.6 28.2 19.7 33.0
2000 19.1 22.9 19.4 24.5 20.1 26.3 20.9 31.4 19.3 36.4
2200 19.4 26.4 19.7 28.0 20.5 29.6 21.7 34.5 20.6 39.8
2400 17.9 30.4 18.2 32.0 18.9 33.4 20.4 38.1 19.8 43.6
2600 15.7 33.3 15.9 34.9 16.5 36.1 18.2 40.4 17.9 45.7
2800 14.5 39.0 14.5 40.7 15.1 42.0 17.0 46.2 17.2 51.9
3000 12.7 46.1 12.6 47.9 12.9 49.2 15.2 53.4 15.8 59.5
3200 13.5 53.5 13.3 55.5 13.8 56.9 16.5 61.1 18.0 67.8
3400 15.5 61.3 15.4 63.5 15.9 65.0 19.4 69.2 22.0 76.5
3600 20.9 67.5 21.1 70.0 21.7 71.5 26.1 75.4 30.5 82.8
3800 22.7 73.3 23.1 76.0 23.9 77.6 28.9 81.1 34.7 88.2
4000 25.4 71.7 26.2 74.5 27.1 76.1 32.3 78.8 39.0 84.7
4200 19.0 86.1 19.8 89.5 20.7 91.4 26.6 94.7 34.6 101.8
4400 26.6 102.0 28.3 106.3 29.9 108.7 37.8 111.4 49.4 118.0
4600 34.9 116.4 37.8 121.5 40.1 124.1 49.8 125.9 65.3 130.6
4800 52.1 134.8 57.4 140.3 61.1 143.1 73.7 141.9 93.8 141.8
5000 78.5 147.4 87.4 152.0 93.3 154.0 107.2 148.0 129.0 138.6
(1) This was done in divided mode (VCO_DIV=50) with VCOGAIN=12.

7.7.4.1 OSCin and Fin Sensitivity

LMX2541 OSCinSensitivity.eps
This chart shows the typical sensitivity for a sine wave. Note that at lower frequencies, there is a constant slope that suggests that the part fails when the slew rate falls below 27 V/us. The electrical specifications call for a minimum of 150 V/us to ensure margin. Also, as some of the other performance graphs show, the OSCin slew rate has an impact on fractional spurs and phase noise as well. It is recommended to design to the electrical specifications, not the typical performance plots.
Variation over voltage and temperature is typically very small and on the order than less ±1 dB.
Figure 18. OSCin Sensitivity for Single-Ended SINE Wave
LMX2541 30073331.gif
This plot shows the ExtVCOin sensitivity which applies only when the device is being used in External VCO mode.
Variation over voltage is typically very small and on the order of less than ± 1 dB.
Figure 19. SINE wave ExtVCOin Sensitivity
LMX2541 30073338.gif
Figure 20. OSCin Input Impedance

Table 8. OSCin Frequency

FREQUENCY (MHz) OSCin (NORMAL MODE) OSCin (XO MODE) OSCin# (NORMAL MODE)
REAL IMAGINARY REAL IMAGINARY REAL IMAGINARY
1 3945.3 2261.6 9452.3 2182.1 3975.5 2287.0
5 4846.0 –189.6 2397.9 –916.7 4890.1 –150.1
10 4253.4 –1850.1 428.2 –1105.7 4297.4 –1886.7
20 2295.3 –2366.9 248.4 –591.8 2288.6 –2383.8
30 1290.0 –2087.0 187.1 –410.1 1304.3 –2079.1
40 847.9 –1716.1 163.5 –313.3 855.5 –1718.0
50 581.3 –1464.9 147.9 –257.1 590.7 –1471.6
60 439.2 –1254.1 138.3 –219.0 449.4 –1264.2
70 337.9 –1105.7 131.1 –192.0 349.0 –1115.4
80 269.4 –983.6 127.0 –171.8 276.3 –989.1
90 223.4 –869.9 119.7 –158.0 231.9 –876.2
100 179.2 –776.8 114.5 –143.9 186.9 –783.9
200 52.4 –379.8 93.9 –85.1 54.3 –382.5
300 31.2 –247.0 80.9 –68.9 31.9 –247.4
400 23.5 –181.7 72.3 –58.1 23.8 –180.5
500 20.4 –140.5 65.1 –49.4 20.4 –138.4
600 18.4 –110.2 58.1 –42.1 18.2 –107.6
700 17.0 –88.0 51.9 –35.6 16.7 –85.3
800 15.8 –71.2 47.4 –29.5 15.7 –68.4
900 15.2 –57.6 43.6 –23.4 14.7 –56.3
1000 15.1 –45.2 40.9 –17.2 14.3 –44.7
LMX2541 30073339.gif
Figure 21. ExtVCOin Input Impedance

Table 9. ExtVCOin Frequency

FREQUENCY REAL IMAGINARY
100 627.9 –1532.3
200 193.8 –852.6
400 56.4 –434.5
600 31.3 –287.4
800 23.2 –212.9
1000 17.8 –167.0
1200 15.4 –134.9
1400 14.0 –111.4
1600 12.8 –93.7
1800 11.8 –79.5
2000 11.2 –67.5
2200 10.7 –57.4
2400 10.2 –48.6
2600 10.5 –42.0
2800 9.1 –35.5
3000 7.8 –29.0
3200 7.2 –23.4
3400 6.6 –18.3
3600 5.9 –13.3
3800 5.3 –8.5
4000 5.0 –3.7
4200 4.5 –1.4
4400 4.0 0.9
4600 3.5 3.1
4800 2.6 7.7
5000 1.7 12.1
6000 0.9 26.7
7000 2.3 51.9