SNAS236G October   2005  – January 2016 LMX2485 , LMX2485E

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Typical Characteristics
      1. 6.7.1 Sensitivity
      2. 6.7.2 FinRF Input Impedance
      3. 6.7.3 FinIF Input Impedance
      4. 6.7.4 OSCin Input Impedance
      5. 6.7.5 Currents
  7. 7 Parameter Measurement Information
    1. 7.1 Bench Test Set-Ups
      1. 7.1.1 Charge Pump Current Measurement
      2. 7.1.2 Charge Pump Current Specification Definitions
        1. 7.1.2.1 Charge Pump Output Current Magnitude Variation vs Charge Pump Output Voltage
        2. 7.1.2.2 Charge Pump Sink Current vs Charge Pump Output Source Current Mismatch
        3. 7.1.2.3 Charge Pump Output Current Magnitude Variation vs Temperature
      3. 7.1.3 Sensitivity Measurement Procedure
      4. 7.1.4 Input Impedance Measurement
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 TCXO, Oscillator Buffer, and R Counter
      2. 8.3.2 Phase Detector
      3. 8.3.3 Charge Pump
      4. 8.3.4 Loop Filter
      5. 8.3.5 N Counters and High Frequency Input Pins
        1. 8.3.5.1 High Frequency Input Pins, FinRF and FinIF
        2. 8.3.5.2 Complementary High Frequency Pin, FinRF*
      6. 8.3.6 Digital Lock Detect Operation
      7. 8.3.7 Cycle Slip Reduction and Fastlock
        1. 8.3.7.1 Cycle Slip Reduction (CSR)
        2. 8.3.7.2 Fastlock
        3. 8.3.7.3 Using Cycle Slip Reduction (CSR) to Avoid Cycle Slipping
          1. 8.3.7.3.1 (Fastlock Charge Pump Current) / (Steady-State Charge Pump Current) = CSR
        4. 8.3.7.4 Using Fastlock to Improve Lock Times
        5. 8.3.7.5 Capacitor Dielectric Considerations for Lock Time
      8. 8.3.8 Fractional Spur and Phase Noise Controls
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power Pins, Power-Down, and Power-Up Modes
    5. 8.5 Programming
      1. 8.5.1 General Programming Information
        1. 8.5.1.1 Register Location Truth Table
        2. 8.5.1.2 Control Register Content Map
        3. 8.5.1.3 Quick Start Register Map
        4. 8.5.1.4 Complete Register Map
    6. 8.6 Register Maps
      1. 8.6.1 R0 Register
        1. 8.6.1.1 RF_FN[11:0]—Fractional Numerator for RF PLL
        2. 8.6.1.2 RF_N[10:0]—RF N Counter Value
      2. 8.6.2 R1 Register
        1. 8.6.2.1 RF_FD[11:0]—RF PLL Fractional Denominator
        2. 8.6.2.2 RF_R [5:0]—RF R Divider Value
        3. 8.6.2.3 RF_P—RF Prescaler Bit
        4. 8.6.2.4 RF_PD—RF Power-Down Control Bit
      3. 8.6.3 R2 Register
        1. 8.6.3.1 IF_N[18:0]—IF N Divider Value
        2. 8.6.3.2 IF_PD—IF Power Down Bit
      4. 8.6.4 R3 Register
        1. 8.6.4.1 IF_R[11:0]—IF R Divider Value
        2. 8.6.4.2 RF_CPG—RF PLL Charge Pump Gain
        3. 8.6.4.3 ACCESS—Register Access Word
      5. 8.6.5 R4 Register
        1. 8.6.5.1 MUX[3:0] Frequency Out and Lock Detect MUX
        2. 8.6.5.2 IF_P—IF Prescaler
        3. 8.6.5.3 RF_CPP—RF PLL Charge Pump Polarity
        4. 8.6.5.4 IF_CPP—IF PLL Charge Pump Polarity
        5. 8.6.5.5 OSC_OUT Oscillator Output Buffer Enable
        6. 8.6.5.6 OSC2X—Oscillator Doubler Enable
        7. 8.6.5.7 FM[1:0]—Fractional Mode
        8. 8.6.5.8 DITH[1:0]—Dithering Control
        9. 8.6.5.9 ATPU—PLL Automatic Power Up
      6. 8.6.6 R5 Register
        1. 8.6.6.1 Fractional Numerator Determination [ RF_FN[21:12], RF_FN[11:0], Access[1] ]
        2. 8.6.6.2 Fractional Denominator Determination [ RF_FD[21:12], RF_FD[11:0], Access[1]]
      7. 8.6.7 R6 Register
        1. 8.6.7.1 RF_TOC—RF Time Out Counter and Control for FLoutRF Pin
        2. 8.6.7.2 RF_CPF—RF PLL Fastlock Charge Pump Current
        3. 8.6.7.3 CSR[1:0]—RF Cycle Slip Reduction
      8. 8.6.8 R7 Register
        1. 8.6.8.1 DIV4—RF Digital Lock Detect Divide By 4
        2. 8.6.8.2 IF_RST—IF PLL Counter Reset
        3. 8.6.8.3 RF_RST—RF PLL Counter Reset
        4. 8.6.8.4 RF_TRI—RF Charge Pump Tri-State
        5. 8.6.8.5 IF_TRI—IF Charge Pump Tri-State
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) (1)(2).
MIN MAX UNIT
VCC Power supply voltage –0.3 4.25 V
Vi Voltage on any pin with GND = 0 V –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) For ensured specifications and test conditions, see the Electrical Characteristics. The ensured specifications apply only for the test conditions listed. The voltage at all the power supply pins of VddRF1, VddRF2, VddRF3, VddRF4, VddRF5, VddIF1 and VddIF2 must be the same. VCC will be used to refer to the voltage at these pins and ICC will be used to refer to the sum of all currents through all these power pins.

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge(1) Human-body model (HBM) ±2000 V
Charged-device model (CDM) ±750
Machine model (MM) ±200
(1) This is a high performance RF device is ESD-sensitive. Handling and assembly of this device should be done at an ESD free workstation.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN NOM MAX UNIT
VCC Power supply voltage(1) 2.5 3 3.6 V
TA Operating temperature –40 25 85 °C
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Recommended Operating Conditions indicate conditions for which the device is intended to be functional, but does not ensure specific performance limits. For ensured specifications and test conditions, see the Electrical Characteristics. The ensured specifications apply only for the test conditions listed. The voltage at all the power supply pins of VddRF1, VddRF2, VddRF3, VddRF4, VddRF5, VddIF1 and VddIF2 must be the same. VCC will be used to refer to the voltage at these pins and ICC will be used to refer to the sum of all currents through all these power pins.

6.4 Thermal Information

THERMAL METRIC(1) LMX2485, LMX2485E UNIT
RTW (WQFN)
24 PINS
RθJA Junction-to-ambient thermal resistance 47.2 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 43 °C/W
RθJB Junction-to-board thermal resistance 24 °C/W
ψJT Junction-to-top characterization parameter 0.8 °C/W
ψJB Junction-to-board characterization parameter 24 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance 7 °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics

(VCC = 3.0V; -40°C ≤ TA ≤ +85°C unless otherwise specified)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
ICC PARAMETERS
ICCRF Power supply current,
RF synthesizer		 IF PLL OFF
RF PLL ON
Charge Pump TRI-STATE		 3.3 mA
ICCIF Power supply current,
IF synthesizer		 IF PLL ON
RF PLL OFF
Charge Pump TRI-STATE		 1.7 mA
ICCTOTAL Power supply current, entire synthesizer IF PLL ON
RF PLL ON
Charge Pump TRI-STATE		 5 mA
ICCPD Powerdown current CE = ENOSC = 0 V
CLK, DATA, LE = 0 V		 1 10 µA
RF SYNTHESIZER PARAMETERS
fFinRF Operating frequency(1) LMX2485 RF_P = 8 500 2000 MHz
RF_P = 16 500 3000
LMX2485E RF_P = 8 50 2000
RF_P = 16 50 3000
pFinRF Input sensitivity 500 - 3000 MHz -15 0 dBm
50 - 500 MHz (LMX2485E only) -8 8
fCOMP Phase detector frequency(2) 50 MHz
ICPoutRFSRCE RF charge pump source current(3) RF_CPG = 0
VCPoutRF = VCC/2		 95 µA
RF_CPG = 1
VCPoutRF = VCC/2		 190 µA
RF_CPG = 15
VCPoutRF = VCC/2		 1520 µA
ICPoutRFSINK RF charge pump sink current(3) RF_CPG = 0
VCPoutRF = VCC/2		 –95 µA
RF_CPG = 1
VCPoutRF = VCC/2		 –190 µA
RF_CPG = 15
VCPoutRF = VCC/2		 –1520 µA
ICPoutRFTRI RF charge pump TRI-STATE current magnitude 0.5 ≤ VCPoutRF ≤ VCC -0.5 2 10 nA
| ICPoutRF%MIS | Magnitude of RF CP sink vs. CP source mismatch VCPoutRF = VCC/2
TA = 25°C		 RF_CPG > 2 3% 10%
RF_CPG ≤ 2 3% 13%
| ICPoutRF%V | Magnitude of RF CP current vs. CP voltage 0.5 ≤ VCPoutRF ≤ VCC -0.5
TA = 25°C		 2% 8%
| ICPoutRF%T | Magnitude of RF CP current vs. temperature VCPoutRF = VCC/2 4%
IF SYNTHESIZER PARAMETERS
fFinIF Operating frequency 75 800 MHz
pFinIF IF input sensitivity –10 5 dBm
fCOMP Phase detector frequency 10 MHz
ICPoutIFSRCE IF charge pump source current VCPoutIF = VCC/2 3.5 mA
ICPoutIFSINK IF charge pump sink current VCPoutIF = VCC/2 –3.5 mA
ICPoutIFTRI IF charge pump TRI-STATE current magnitude 0.5 ≤ VCPoutIF ≤ VCC RF -0.5 2 10 nA
| ICPoutIF%MIS | Magnitude of IF CP sink vs CP source mismatch VCPoutIF = VCC/2
TA = 25°C		 1% 8%
| ICPoutIF%V | Magnitude of IF CP current vs CP voltage 0.5 ≤ VCPoutIF ≤ VCC -0.5
TA = 25°C		 4% 10%
| ICPoutIF%TEMP Magnitude of IF CP current vs temperature VCPoutIF = VCC/2 4%
OSCILLATOR PARAMETERS
fOSCin Oscillator operating frequency OSC2X = 0 5 110 MHz
OSC2X = 1 5 20 MHz
vOSCin Oscillator input sensitivity 0.5 VCC VP-P
IOSCin Oscillator input current –100 100 µA
SPURS
Spurs in band See (4) –55 dBc
PHASE NOISE
LF1HzRF RF synthesizer normalized phase noise contribution(5) RF_CPG = 0 –202 dBc/Hz
RF_CPG = 1 –202
RF_CPG = 3 –206
RF_CPG = 7 –208
RF_CPG = 15 –210
LF1HzIF IF synthesizer normalized phase noise contribution –209 dBc/Hz
DIGITAL INTERFACE (DATA, CLK, LE, ENOSC, CE, Ftest/LD, FLoutRF)
VIH High-level input voltage 1.6 VCC V
VIL Low-level input voltage 0.4 V
IIH High-level input current VIH = VCC –1 1 µA
IIL Low-level input current VIL = 0 V –1 1 µA
VOH High-level output voltage IOH = –500 µA VCC - 0.4 V
VOL Low-level output voltage IOL = 500 µA 0.4 V
(1) A slew rate of at least 100 V/uS is recommended for frequencies less than 500 MHz for optimal performance.
(2) For Phase Detector Frequencies greater than 20 MHz, Cycle Slip Reduction (CSR) may be required. Legal divide ratios are also required.
(3) Refer to table in RF_CPG—RF PLL Charge Pump Gain for complete listing of charge pump currents.
(4) To measure the in-band spur, the fractional word is chosen such that when reduced to lowest terms, the fractional numerator is one. The spur offset frequency is chosen to be the comparison frequency divided by the reduced fractional denominator. The loop bandwidth must be sufficiently wide to negate the impact of the loop filter. Measurement conditions are: Spur Offset Frequency = 10 kHz, Loop Bandwidth = 100 kHz, Fraction = 1/2000, Comparison Frequency = 20 MHz, RF_CPG = 7, DITH = 0, and a 4th Order Modulator (FM = 0). These are relatively consistent over tuning range.
(5) Normalized Phase Noise Contribution is defined as: LN(f) = L(f) – 20log(N) – 10log(fCOMP) where L(f) is defined as the single side band phase noise measured at an offset frequency, f, in a 1 Hz Bandwidth. The offset frequency, f, must be chosen sufficiently smaller than the PLL loop bandwidth, yet large enough to avoid substantial phase noise contribution from the reference source. Measurement conditions are: Offset Frequency = 11 kHz, Loop Bandwidth = 100 kHz for RF_CPG = 7, Fraction = 1/2000, Comparison Frequency = 20 MHz, FM = 0, DITH = 0.

6.6 Timing Requirements

MIN NOM MAX UNIT
MICROWIRE INTERFACE TIMING
tCS Data to clock set-up time See Figure 1 25 ns
tCH Data to clock hold time See Figure 1 8 ns
tCWH Clock pulse width high See Figure 1 25 ns
tCWL Clock pulse width low See Figure 1 25 ns
tES Clock to load enable set-up time See Figure 1 25 ns
tEW Load enable pulse width See Figure 1 25 ns
LMX2485 LMX2485E 20087775.gif Figure 1. Microwire Input Timing Diagram

6.7 Typical Characteristics

Typical characteristics do not imply any sort of ensured specification. Ensured specifications are in the Electrical Characteristics section.

6.7.1 Sensitivity

LMX2485 LMX2485E 20087745.gif
TA = 25°C, RF_P = 16
Figure 2. RF PLL Fin Sensitivity
LMX2485 LMX2485E 20087747.gif
TA = 25°C, IF_P = 16
Figure 4. IF PLL Fin Sensitivity
LMX2485 LMX2485E 20087749.gif
TA = 25°C, OSC_2X = 0
Figure 6. OSCin Sensitivity
LMX2485 LMX2485E 20087773.gif
TA = 25°C, OSC_2X = 1
Figure 8. OSCin Sensitivity
LMX2485 LMX2485E 20087746.gif
VCC = 3 V, RF_P = 16
Figure 3. RF PLL Fin Sensitivity
LMX2485 LMX2485E 20087748.gif
VCC = 3 V, IF_P = 16
Figure 5. IF PLL Fin Sensitivity
LMX2485 LMX2485E 20087756.gif
VCC = 3 V, OSC_2X = 0
Figure 7. OSCin Sensitivity
LMX2485 LMX2485E 20087774.gif
VCC = 3 V, OSC_2X = 1
Figure 9. OSCin Sensitivity

6.7.2 FinRF Input Impedance

LMX2485 LMX2485E 20087768.gif Figure 10. FinRF Input Impedance

Table 1. FinRF Input Impedance

FREQUENCY (MHz) REAL (Ω) IMAGINARY (Ω)
50 670 –276
100 531 –247
200 452 –209
300 408 –212
400 373 –222
500 337 –231
600 302 –237
700 270 –239
800 241 –236
900 215 –231
1000 192 –221
1100 172 –218
1200 154 –209
1300 139 –200
1400 127 –192
1500 114 –184
1600 104 –175
1700 96 –168
1800 88 –160
1900 80 –153
2000 74 –147
2200 64 –134
2400 56 –123
2600 50 –113
2800 45 –103
3000 39 –94
3200 37 –86
3400 33 –78
3600 30 –72
3800 28 –69
4000 26 –66

6.7.3 FinIF Input Impedance

LMX2485 LMX2485E 20087754.gif Figure 11. FinIF Input Impedance

Table 2. IF PLL Input Impedance

FinIF INPUT IMPEDANCE
FREQUENCY (MHZ) REAL (Ω) IMAGINARY (Ω)
50 583 –286
75 530 –256
100 499 –241
200 426 –209
300 384 –209
400 347 –219
500 310 –224
600 276 –228
700 244 –228
800 216 –223
900 192 –218
1000 173 –208

6.7.4 OSCin Input Impedance

LMX2485 LMX2485E 20087755.gif Figure 12. OSCin Input Impedance

Table 3. OSCin Input Impedance

FREQUENCY (MHz) POWERED-UP POWERED-DOWN
REAL IMAGINARY MAGNITUDE REAL IMAGINARY MAGNITUDE
5 1730 -3779 4157 392 -8137 8146
10 846 -2236 2391 155 -4487 4490
20 466 -1196 1284 107 -2215 2217
30 351 -863 932 166 -1495 -1504
40 316 -672 742 182 -1144 1158
50 278 -566 631 155 -912 925
60 261 -481 547 153 -758 774
70 252 -425 494 154 -652 669
80 239 -388 456 147 -576 595
90 234 -358 428 145 -518 538
100 230 -337 407 140 -471 492
110 225 -321 392 138 -436 458
120 219 -309 379 133 -402 123
130 214 -295 364 133 -374 397
140 208 -285 353 132 -349 373
150 207 -279 348 133 -329 355

6.7.5 Currents

LMX2485 LMX2485E 20087759.gif
CE = High
Figure 13. Power Supply Current
LMX2485 LMX2485E 20087767.gif
VCC = 3 V
Figure 15. RF PLL Charge Pump Current
LMX2485 LMX2485E 20087764.gif
VCC = 3 V
Figure 17. Charge Pump Leakage RF PLL
LMX2485 LMX2485E 20087761.gif
CE = LOW
Figure 14. Power Supply Current
LMX2485 LMX2485E 20087765.gif
VCC = 3 V
Figure 16. IF PLL Charge Pump Current
LMX2485 LMX2485E 20087763.gif
VCC = 3 V
Figure 18. Charge Pump Leakage IF PLL