SERDESUB-21USB/NOPB - NATIONAL SEMICONDUCTOR

LMX2541 Family

Ultra Low Noise Frequency Synthesizer with

Integrated VCO

Evaluation Board Operating Instructions

National Semiconductor Corporation

High Speed Signal Path Division

Precision Timing Devices

12-4-2009

TABLE OF CONTENTS

LOOP FILTER VALUES ...................................................................................6

CODELOADER SETUP....................................................................................7

SPURS.......................................................................................................10

LMX2541SQ2060E DEFAULT SETUP AND MEASURED PERFORMANCE..........13

LMX2541SQ2380E DEFAULT SETUP AND MEASURED PERFORMANCE..........16

LMX2541SQ2690E DEFAULT SETUP AND MEASURED PERFORMANCE..........19

LMX2541SQ3030E DEFAULT SETUP AND MEASURED PERFORMANCE..........22

LMX2541SQ3030E VCO PHASE NOISE.....................................................24

LMX2541SQ3320E DEFAULT SETUP AND MEASURED PERFORMANCE..........25

LMX2541S3320E SPURS FOR WORST CASE CHANNELS..........................26

LMX2541SQ3320E VCO PHASE NOISE.....................................................27

LMX2541SQ3740E DEFAULT SETUP AND MEASURED PERFORMANCE..........28

LMX2541S3740E SPURS FOR WORST CASE CHANNELS..........................29

LMX2541SQ3740E VCO PHASE NOISE.....................................................30

BILL OF MATERIALS.....................................................................................31

NO COMPONENTS ARE ASSEMBLED ON THE BOTTOM LAYER IN THE DEFAULT

SETUP.SCHEMATIC ......................................................................................33

SCHEMATIC ................................................................................................34

BOARD LAYER STACKUP .............................................................................35

QUICK SETUP

Laptop or PC

RFout uWire

3.4 V

Phase

Noise

Analyzer

LMX2541

Do Not Connect

RFout

Connect to a spectrum analyzer or phase noise analyzer. The Agilent E5052A was used for these

instructions.

Vcc

Connect to a 3.4 volt low noise power supply

uWire

Connect to a computer with CodeLoad er software

ExtVCOin

This is not used in the default setup, but is included to support the use of a n external VCO.

In Full Chip Mode, this device h as an on-chip VC O.

Ftest/LD

The LED is to ensure that the part is locked. T his output can be very useful for diagno stic purposes

OSCin/OSCin*

This is not used in the default setup, but is included to support the use of an external OSCin signal.

The board includes a 100 MHz TCXO, which has two varieties. The OSCin signal is absolutely critical

for the phase noise and spur per formance of the L MX2541.

Manufacturer Model Frequency Comments

Connor

Winfield CWX-813 100 MHz • Good phase noise

• Low Cost

• Drifts a lot.

Crystek CVPD920 100 MHz

• Good Phase Noise

• Drifts much less

• High Cost

National

Semiconductor

LMK01000

LMK02000

LMK03000

LMK04000

Any • Eliminate drift issues

• Potentially the best phase noise

• Best for fractional spurs

Be very aware of the TCXO drift and the contribution that it can have to phase noise. Termination of

the TCXO has a large im pact on f ractional spurs a s well. The best resu lts can be achiev ed by driving

this board with an LMK01000 LVPECL output. Doing so results in about a 4 dB spur improvement.

Loop Filter Values

Parameter LMX2541

SQ2060E LMX2541

SQ2380E LMX2541

SQ2690E LMX2541

SQ3030E LMX2541

SQ3320E LMX2541

SQ3470E

VCO Frequency

(MHz) 1990 –

2240 2200 -

2530 2490 –

2865 2810 -

3230 3130 -

3600 3480 -

4000

VCO Gain

(MHz/V) 13-23 16-30 17-32 20-37 21-37 27 - 42

Charge Pump

Gain (mA) 3.2 3.2 3.2 3.2 3.2 3.2

Phase Detector

Frequency (MHz) 25 25 25 25 25 25

OSCin Frequency

(MHz) 100 100 100 100 100 100

Loop Bandwidth

(kHz) 37.3 –

54.6 40.8 –

61.7 38.7 –

58.6 40.0 –

59.9 38.1 –

54.7 43.1 –

55.7

Phase Margin

(deg) 52.7 –

52.8 53.1-

52 52.9 –

52.4 53.0 –

52.2 52.8 –

52.8 53.2 –

52.7

C1_LF (nF) 2.2 2.2 2.2 2.2 2.2 2.2

C2_LF (nF) 22 22 22 22 22 22

R2_LF (Kohm) 0.47 0.47 0.47 0.47 0.47 0.47

C3_LF (Internal)

(nF) 0.02 0.02 0.02 0.02 0.02 0.02

C4_LF (Internal)

(nF) 0.1 0.1 0.1 0.1 0.1 0.1

R3_LF (Internal)

(Kohm) 1 1 1 1 1 1

R4_LF (Internal)

(Kohm) 0.2 0.2 0.2 0.2 0.2 0.2

* Note that the VCO gai n do es change a fair am ount. Althou gh n ot demonst rated i n these instructi ons, the charge p ump

gain could be adj usted to a ccount for this v ariation.

CodeLoader Setup

Select the part. In this case, it is the LMX2 541SQ3320E.

Choose the correct startup mode. This is determined by the part option.

Load the part. You can load it from the menu or also pre ss Cntrl + L.

On the Port Setup tab, the user may select the type of communication port (USB or Parallel) that will be

used to program the device on the evaluation board. If parallel port is selected, the user should ensure

that the correct port address is entered.

The Pin Configuration field is hardware dependent and normally SHOULD NOT be changed by the user.

The evaluation board is typically shipped with a parallel port cable that is used to interconnect the board

to a PC LPT port, enabling the board to be programmed.

Separately available is a USB2UWIRE-IFACE board which simplifies evaluation by enabling the user to

establish a USB connection from the Codeloader 4 software to the evaluation board.

http://www.national.com/store/view_item/index.html?nsid=USB2UWIRE-IFACE

To view the function of any bit on the CodeLoader configuration tabs, place the cursor over the desired

bit register label and click the right mouse button on it for a description. This Bits/Pins configuration is

common to all options of the LMX2541 evaluation board.

S purs

Oscillator Spurs

Oscillator spurs occur at the oscillator frequency (100 MHz) offset from the carrier. They can be largely

impacted by the board layout. These were taken in 25 MHz increments.

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

-70

1975

2000

2025

2050

2075

2100

2125

2150

2175

2200

2225

2250

2275

2300

2325

2350

2375

2400

2425

2450

2475

2500

2525

2550

2575

2600

2625

2650

2675

2700

2725

2750

2775

2800

2825

2850

2875

2900

2925

2950

2975

3000

3025

3050

3075

3100

3125

3150

3175

3200

3225

3250

3275

3300

3325

3350

3375

3400

3425

3450

3475

3500

3525

3550

3575

3600

3625

3650

3675

3700

3725

3750

3775

3800

3825

3850

3875

3900

3925

3950

3975

4000

2060E

2380E

2690E

3030E

3320E

3740E

Frequency

Option

Reference (Phase Detector) Spurs

Reference spurs occur at a multiple of the p hase detector frequ ency (25 MHz) from the carrier

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

-70

1975

2000

2025

2050

2075

2100

2125

2150

2175

2200

2225

2250

2275

2300

2325

2350

2375

2400

2425

2450

2475

2500

2525

2550

2575

2600

2625

2650

2675

2700

2725

2750

2775

2800

2825

2850

2875

2900

2925

2950

2975

3000

3025

3050

3075

3100

3125

3150

3175

3200

3225

3250

3275

3300

3325

3350

3375

3400

3425

3450

3475

3500

3525

3550

3575

3600

3625

3650

3675

3700

3725

3750

3775

3800

3825

3850

3875

3900

3925

3950

3975

4000

2060E

2380E

2690E

3030E

3320E

3740E

Frequency

Option

Fractional Spurs

In-band spurs occur inside the loop bandwidth. These spurs were measured with a WORST CASE fraction

of 1/5000. The primary fractional spurs are at 5 kHz and the sub-fractional spurs are at 2.5 kHz. The actual

frequency is the frequency in the chart plus 5 kHz.

-70

-65

-60

-55

-50

-45

-40

-35

-30

1975

2000

2025

2050

2075

2100

2125

2150

2175

2200

2225

2250

2275

2300

2325

2350

2375

2400

2425

2450

2475

2500

2525

2550

2575

2600

2625

2650

2675

2700

2725

2750

2775

2800

2825

2850

2875

2900

2925

2950

2975

3000

3025

3050

3075

3100

3125

3150

3175

3200

3225

3250

3275

3300

3325

3350

3375

3400

3425

3450

3475

3500

3525

3550

3575

3600

3625

3650

3675

3700

3725

3750

3775

3800

3825

3850

3875

3900

3925

3950

3975

4000

2060E - Primary

2060E - SubFractional

2380E - Primary

2380E - SubFractional

2690E - Primary

2690E - SubFractional

3030E - Primary

3030E - SubFractional

3320E - Primary

3320E - SubFractional

3740E - Primary

3740E - SubFractional

Frequency

Option

Spur Order

Out-band spurs occur inside the loop bandwidth. These spurs were measured with a WORST CASE

fraction of 1/100. The primary fractional spurs are at 250 kHz and the sub-fractional spurs are at 125 kHz.

The actual frequency is the frequency in t he chart plus 250 kHz.

-70

-65

-60

-55

-50

-45

-40

-35

-30

1975

2000

2025

2050

2075

2100

2125

2150

2175

2200

2225

2250

2275

2300

2325

2350

2375

2400

2425

2450

2475

2500

2525

2550

2575

2600

2625

2650

2675

2700

2725

2750

2775

2800

2825

2850

2875

2900

2925

2950

2975

3000

3025

3050

3075

3100

3125

3150

3175

3200

3225

3250

3275

3300

3325

3350

3375

3400

3425

3450

3475

3500

3525

3550

3575

3600

3625

3650

3675

3700

3725

3750

3775

3800

3825

3850

3875

3900

3925

3950

3975

4000

2060E - Prim ary

2060E - SubFrac tional

2380E - Prim ary

2380E - SubFrac tional

2690E - Prim ary

2690E - SubFrac tional

3030E - Prim ary

3030E - SubFrac tional

3320E - Prim ary

3320E - SubFrac tional

3740E - Prim ary

3740E - SubFrac tional

Frequency

Option

Spur Order

Minimizing Fractional Spurs

• Both fractional and sub-fractional spurs are highly sensitive to the OSCin signal. Higher slew rates

are desired. Also, the termination makes a big difference. For this evaluation board, a series 120

ohm resistor had a large impact.

• The best results have been achieved when driving the part differentially with an LVPECL output of

the LMK01000/2000/3000/400 series of clock conditioner d evices from National Semicon ductor.

• The spurs on this evaluation board are relatively high because the loop bandwidth is very wide. This

wide loop bandwidth takes advantage of the close-in phase noise, but it does expose the fractional

spurs more. The fractional spurs can be reduced by orders of magnitude by reducing the loop

bandwidth. This requires a re-design of the loo p filter.

• To eliminate the SubFractional spurs entirely, choose a fractional denominator with no factors of 2 or

3. For this 100 MHz TCXO and 250 kHz channel spacing, a phase detector frequency of 6.25 MHz

and a fractional denominator of 25 would work. However, the higher N value does degrade the

phase noise. An ideal scenario would be to use a TCXO frequency of something like 125 MHz.

Then the sub-fractional spurs are e liminate d if the phase detector is ch osen to b e 3 0.25 MHz and the

fractional denominator is chosen to be 125.

In the plot below, one was taken with the default 100 MHz TCXO and another was taken with a 125

MHz signal. The phase detector frequency was changed to 31.25 MHz, but the charge pump gain

was reduced to 26X to compensate for this. This is the same part, board, and frequency (3030.25

MHz). Although the fraction is different, notice that the fractional denominator of 125 has no sub

fractional spurs at 125 kHz, 375 kHz, and so on. An LMK01000 evaluation board driven by a 1250

MHz signal was used to produce th is 125 MHz signal.

-160

-140

-120

-100

-80

-60

1.E+04 1.E+05 1.E+06 1.E+07 1.E+08

Of f s e t ( H z)

Phase Noise (dBc/Hz )

F DE N = 125 FDEN = 100

LMX2541SQ2060E Default Setup and Measured Performance

LMX2541SQ2060E Spurs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset fr o m Carr ier (kHz)

Power (dBm)

1975. 25 M Hz

2000. 25 M Hz

2025. 25 M Hz

2050. 25 M Hz

2075. 25 M Hz

2100. 25 M Hz

2125. 25 M Hz

2150. 25 M Hz

2175. 25 M Hz

2200. 25 M Hz

2225. 25 M Hz

2250. 25 M Hz

This graph has been normalized to the average carrier power.

LMX2541SQ2060E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

LMX2541SQ2380E Default Setup and Measured Performance

LMX2541SQ2380E Spurs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset fr o m Carr ier (kHz)

Power (dBm)

2200. 25 M Hz

2225. 25 M Hz

2250. 25 M Hz

2275. 25 M Hz

2300. 25 M Hz

2325. 25 M Hz

2350. 25 M Hz

2375. 25 M Hz

2400. 25 M Hz

2425. 25 M Hz

2450. 25 M Hz

2475. 25 M Hz

2500. 25 M Hz

2525. 25 M Hz

2550. 25 M Hz

This graph has been normalized to the average carrier power.

LMX2541SQ2380E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

LMX2541SQ2690E Default Setup and Measured Performance

LMX2541SQ2690E Spurs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset (kHz)

Power (dBm)

2475. 25 M Hz

2500. 25 M Hz

2525. 25 M Hz

2550. 25 M Hz

2575. 25 M Hz

2600. 25 M Hz

2625. 25 M Hz

2650. 25 M Hz

2675. 25 M Hz

2700. 25 M Hz

2725. 25 M Hz

2750. 25 M Hz

2775. 25 M Hz

2800. 25 M Hz

2825. 25 M Hz

2850. 25 M Hz

2875. 25 M Hz

This graph has been normalized to the average carrier power.

LMX2541SQ2690E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

LMX2541SQ3030E Default Setup and Measured Performance

LMX2541S3030E Spurs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset (kHz )

Power (dBm)

2800. 25 M Hz

2825. 25 M Hz

2850. 25 M Hz

2875. 25 M Hz

2900. 25 M Hz

2925. 25 M Hz

2950. 25 M Hz

2975. 25 M Hz

3000. 25 M Hz

3025. 25 M Hz

3050. 25 M Hz

3075. 25 M Hz

3100. 25 M Hz

3125. 25 M Hz

3150. 25 M Hz

3175. 25 M Hz

3200. 25 M Hz

3225. 25 M Hz

3250. 25 M Hz

This graph ha s been normal ized the average carrier power.

LMX2541SQ3030E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

LMX2541SQ3320E Default Setup and Measured Performance

LMX2541S3320E S purs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset (kHz)

Power (dBm)

3125. 25 M Hz

3150. 25 M Hz

3175. 25 M Hz

3200. 25 M Hz

3225. 25 M Hz

3250. 25 M Hz

3275. 25 M Hz

3300. 25 M Hz

3325. 25 M Hz

3350. 25 M Hz

3375. 25 M Hz

3400. 25 M Hz

3425. 25 M Hz

3450. 25 M Hz

3475. 25 M Hz

3500. 25 M Hz

3525. 25 M Hz

3550. 25 M Hz

3575. 25 M Hz

3600. 25 M Hz

Note that the grap hs have all be en normalize d the average ca rrier power.

LMX2541SQ3320E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

LMX2541SQ3740E Default Setup and Measured Performance

LMX2541S3740E S purs for WORST CASE Channels

(Fraction = 1/100)

-90

-80

-70

-60

-50

-40

-30

-20

-10

-300

-250

-200

-150

-100

-50

100

150

200

250

300

Offset (kHz )

Power (dBm)

3475. 25 M Hz

3500. 25 M Hz

3525. 25 M Hz

3550. 25 M Hz

3575. 25 M Hz

3600. 25 M Hz

3625. 25 M Hz

3650. 25 M Hz

3675. 25 M Hz

3700. 25 M Hz

3725. 25 M Hz

3750. 25 M Hz

3775. 25 M Hz

3800. 25 M Hz

3825. 25 M Hz

3850. 25 M Hz

3875. 25 M Hz

3900. 25 M Hz

3925. 25 M Hz

3950. 25 M Hz

3975. 25 M Hz

4000. 25 M Hz

Note that the grap hs have all be en normalize d the average ca rrier power.

LMX2541SQ3740E VCO Phase Noise

The plots show the VCO phase noise at low,

middle, and high freq uency.

To measure the VCO phase noise, a simple

technique is to lock the PLL to the desired

frequency and set the charge pump state to

“Tri-State”, by clicking this on the PLL tab on

Codeloader. If the phase noise analyzer can

track the signal, a reasonable measurement

can be made. To ensure that this

measurement is of the VCO noise, omit the the

spurs and disconnect the microwire

programming cable .

Bill of Materials

Revision 9/30/2009

Part Manufacturer Part Number Qty Identifier

Capacitors

100 pF Kemet C0603C101J5GAC 4 C1, C5, C33, C35

2.2 nF Kemet C0603C222J5GAC 1 C3_LF

22 nF Kemet C0603C223K5RAC 1 C2_LF

0.1 uF Kemet C0603C104K5RAC 19 C2, C6, C9, C10, C11, C12, C13, C17, C18, C21, C24, C25,

C26, C27, C28, C32, C36, C40, C49

1 uF Kemet C0603C105K8VAC 10 C3, C7, C16, C19, C31, C37, C41, C42, C43, C50

4.7 uF Kemet C0603C475K9PAC 4 C14, C15, C20, C34

10 uF Kemet C0805C106K9PAC 6 C4, C8, C30, C38, C39, C48

Resistors

0 ohm Vishay/Dale CRCW06030000Z0EA 7 R3_LF, R12, R21, R39, R41, R42, R46

4.7 ohm Vishay/Dale CRCW06034R7JNEA 2 R49, R50

10 ohm Vishay/Dale CRCW060310R0JNEA 3 R6, R47, R48

18 ohm Vishay/Dale CRCW060318R0JNEA 1 R2

51 ohm Vishay/Dale CRCW060351R0JNEA 2 R10, R14

120 ohm Vishay/Dale CRCW0603120RJNEA 3 R7, R8, R51

180 ohm Vishay/Dale CRCW0603180RJNEA 1 R36

330 ohm Vishay/Dale CRCW0603330RJNEA 2 R1, R3

470 ohm Vishay/Dale CRCW0603470RJNEA 1 R2_LF

2.2 k Vishay/Dale CRCW06032K20JNEA 1 R35

15 k Vishay/Dale CRCW060315K0JNEA 3 R30, R32, R34

27 k Vishay/Dale CRCW060327K0JNEA 5 R29, R31, R33, R37, R38

100 k Vishay/Dale CRCW0603100KJNEA 2 R4, R5

Other

Ferrite Digikey 490-1015-1-ND 7 L1, L2, L3, L4, L5, L6, L7

3.3 V zener Comchip CZRU52C3V3 1 D2

HEADER_2X5

(POLARIZED) FCI Electronics 52601-S10-8 1 uWire

Green LED Lumex SML-LX2832GC-TR 1 D1

POWER_SMALL Weidmuller 1594540000.0 1 P1

SMA Johnson

Components 142-0701-851 4 OSCin, OSCin*, RFout, Vcc

TCXO - 100

MHz Connor-Winfield CWX813 - 100 MHz 1 Y1

NFET Fairchild BSS138 1 U5

VCXO - 100

MHz CRYSTEK CVPD-920 – 100 MHz 1 U4

LMX2541 National

Semiconductor LMX2541SQxxxx 1 U1

Standoffs SPC Technology SPCS-6 4 Place in Holes at the corners of the board.

Open

Open - Open Capacitor 14 C1_LF, C2pLF, C4_LF, C22, C23, C29, C44, C45, C46, C47

Open Open Capacitor 6 C100, C101, C102, C103, C104, C105

Open - Open Resistor 22

R2pLF,R4_LF, R9, R11, R13, R15, R16, R17, R18, R19,

R20, R22, R23, R24, R25, R26, R27, R28, R40, R43, R44,

R45

Open - Open Resistor 9

R100, R101, R102, R103, R104, R105, R106, R107, R108,

R109

Open - Open Crystal 1 Y100

Open - Open IC 3 U2, U3, U100

Open - Open SMA 3 ExtVCOin, Ftest/LD, VccAux

Top Assembly Diagram

234

Bottom Assembly Diagram

No Components are assembled on the bottom layer in the default setup.

Schematic

Vcc

SMA

C33

100 pF

1 2

3 4

5 6

7 8

910

uWire

HEADER_2X5(POLARIZED)

R35

2.2 k

R36

180 ohm

R33

27 k

R32

15 k

R30

15 k R34

15 k

C32

0.1 uF

C31

1 uF

C30

10 uF

VccPlane

R42

0 ohm

R29

27 k

R43

Open

C22

Open

C29

Open

C15

4.7 uF

C12

0.1 uF

C42

1 uF

R28

Open

R26

Open

R22

Open

R14

51 ohm

R2pLF

Open

R21

0 ohm

R27

Open

ExtVCOin

Open

C1_LF

Open

C2_LF

22 nF

C3_LF

2.2 nF

C4_LF

Open

R3_LF

0 ohm

R2_LF

470 ohm

R4_LF

Open

VccPlane

OSCin

SMA

R10

51 ohm

OSCin*

SMA

Readback

R20

Open

Readback

VccAux

0.1 uF

1 uF

100 pF

1 uF

100 pF

C35

100 pF C36

0.1 uF

GND

VccPlane

RFout

SMA

330 ohm

0.1 uF

18 ohm

10 uF

R101

Open

C20

4.7 uF

C21

0.1 uF

C18

0.1 uF

EN_RFOUT

CECLK

R37

27 k

R38

27 k

EN_RFOUT

CLK

DATA

VccPlane VccPlane

VccPlane

C16

1 uF

VccPlane2

C28

0.1 uF

VccPlane2

C19

1 uF

C25

0.1 uF

C24

0.1 uF

C26

0.1 uF

VccPlane

VccPlane2

VccAux

R41

0 ohm

VccAux

FRAME

SMA_FRAME

VccPlane

R23

Open

R24

Open R25

Open

3.3 V zener

Y100

Open

C100

Open C101

Open

VccAux

R19

Open C34

4.7 uF

C23

Open

R49

4.7 ohm

R50

4.7 ohm

R48

10 ohm

C27

0.1 uF

C17

0.1 uF

Ftest/LD

Open

R40

Open

R45

Open

C47

open

VccDig

VccBias

Bypass

VccDiv

DATA

CLK

RFout

GND

VregRFout

VccRFout

Lmid

VccVCO

VregVCO

VrefVCO

GND 10

CE 11

ExtVCOin 12

VccPLL1 13

VccCP1 14

Vtune 15

CPout 16

FLout 17

VccCP2 18

VccFRAC 25

Ftest/LD 20

OSCin 21

OSCin* 22

VccOSCin 23

RFoutEN 24

VregFRAC 26

GND 27

VccPLL2 19

DAP

LMX2541

VccAux

Open

POWER_SMALL

Green LED

R51

120 ohm

R46

0 ohm

C2pLF

Open

Out

3GND 2

Vcont 1

Vcc

TCXO

R17

Open

R18

Open

R104

Open

R105

Open

DATA

Vtune

R100

Open

GND 0

Bypass 1

NC 2

GND 3

INPUT 4

OUTPUT

ADJ

SHUTDOWN

Open

C44

Open

R44

Open

R31

27 k

C46

Open

R47

10 ohm

CLK

DATA

RFoutEN

Vout

V-

IN+

3IN- 4

V+ 5

U100

Open

R102

Open

R108

Open

R103

Open

R109

Open

R107

Open

C104

Open

VccAux

VccPlane

Series resistance on VregRFout improv es the noise floor

when used in divided m ode.

To use w ith a VCO, use 3 components to mak e a T-splitter and

don't use the Pi-Pad. For sensitivity testing, put components in

the Pi-Pad and zero out resistors in the T-Pad. Also, for

fractional spurs outside the loop bandw idth w ith the external

VCO option, there is some ev idence that putting a resistive pad

can im prov e fractional spurs outside the loop bandw idth.

- Monitor the Ftest/LD pin

- Provisions for Analog Lock Detect

- Supply power for an op-am p for an active filter

- Allow the user to apply FSK modulation

- Monitor CPout Pin

- Monitor or Drive the Vtune pin

1 . Inte rna l V C O

D o n ot use an y b o tto m co mp o n e nts fo r th is.

2 . E x te rn a l VC O with P a s siv e Filter

Disconnecting Vtune isolates Vtune. Might not be necessary

3. Ex ternal VCO with Active Filter

Use the com ponents on the back.

Op AMP can be supplied with Ftest/LD pin or with VccAux voltage.

Use C1 _ LF a nd b ack side resisto rs fo r slow slew rate d esign.

3rd Pole is form ed with C3_LF and resistor back to top of board.

4th Pole is already on top of board.

4. Monitor CPout through Ftest/LD

Discon ne ct V tun e p in for m o re a ccurate results.

5. Monitor or Drive Vtune

Use test point or Ftest/LD SMA and back layer resistors.

Rem ove R3_LF or Tri-state charge pump to drive v oltage.

CPout_Net

C103

Open

C105

Open

C102 Open

R106

Open

GND 3

Vtune 2

GND 1

GND

7Mod

6GND

GND

GND 4

GND

Fout

GND

GND 13

Vcc 14

GND 15

GND 16

Open

VccAuxTP

VregRFout

Pad and External VCO O p tion s

Loop Filter Options

Ftest/LD Pin Options

1. TCXO Mode

Terminate OSCin* if this is done

2. VCXO Mode

Connect VCXO and tie pow er dupply to Vcc/2.

Drive and terminate differentially.

3. Differential Mode

Use 100 ohm or 2x 51 ohm resistors for term ination.

4. Ex ternal Crystal Mode

Use back side of board. May hav e to bend leads of crystal to fit.

5. Use external signal source like LMK04000 evaluation board to drive OSCin/OSCin*

6. Special provisions on GND plane

GND plane isolated below OSCin and connected by a single trace on the bottom layer.

Cut this trace toexperiment further withOSCin isolation

OSCin/OSCin* Options

Vtune 1

NC 2

GND 3

RF*

VCXO - 100 MHz

120 ohm

10 ohm

100 k

C11

0.1 uF

VccAux

Ferrite

VccPlane2

Gate 1

Drain

Source 3

NFET

VccAux

R39

0 ohm

C49

0.1 uF

C50

1 uF C48

10 uF

VccPlane2

Open R12

0 ohm

R11

Open R13

Open

R16

Open

C10

0.1 uF R15

Open

C13

0.1 uF

C14

4.7 uF

C37

1 uF C38

10 uF

C39

10 uF

C40

0.1 uF

C41

1 uF

C45

Open

C43

1 uF

VccPlane

Additional Comments

- Any part w ith designator 100 or higher is on the bottom layer and not assem bled by default.

Board Layer S tackup

Board Material Rogers RO4003

Number of Layers 6

Board Thickness 0.062”

Copper Weight 1 oz Finished

Finish Immersion Gold

Solder Mask Color Green/Gloss

Testing 100% Electrical

Testing

RO4003 (εr = 3.38, Tand = 0.0022)

CONTROLLED THICKNESS of

16 mils thick

Top Layer 1oz thick

GND1 Layer

FR4 (εr = ~4.6)

?? mils thick, but thinner is

referable

VccPlane Layer

FR4

?? mils thick

62 mils thick total

Mid Layer 1

FR4 (εr = ~4.6)

?? mils thick, but thinner is

referable

GND2 Layer

FR4 (εr = ~4.6) = ~4.6)

?? mils thick

Bottom Layer

Top Layer and Silkscreen

GND1 Layer

Beneath the TCXO, the ground plane is separated. It is believed that this may improve spurs, especially at offset frequencies

equal to the TCXO frequency. These planes are connected on the bottom layer by a small trace.

VccPlane Layer

Beneath the TCXO, the power plane is removed to minimize the chance of any noise getting onto this plane.

MidLayer 1

Certain pins like VccFRAC and the TCXO supply pins could potentially be sources of noise. These traces were put on this

separate layer to try to isolate them more from the

GND2 Layer

Beneath the TCXO, the ground plane is separated. It is believed that this may improve spurs, especially at offset frequencies

equal to the TCXO frequency. These planes are connected on the bottom layer by a small trace.

Bottom Layer and Silkscreen

This layer has the small trace that connects the grounded pieces in the GND1 layer. It has options for an active filter and crystal as

well.