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LMX2571: Which Power pin is dedicated to the RFOUTTX/RX driver?

user4779049
Expert 2375 points
Part Number: LMX2571


Hi Team,

Please advise me on my question bellow:

Q1. There are total seven pins for the power. 

    can you let me know which power pin is dedicated to the output driver for the RFOUT TX/RX.

I  am experiencing a loss of lock trouble using LMH2571 in Push-Pull output mode.

I programmed the output power at maximum (31h), the device showed loss of lock.

When I reduced the output power as low as (03h), the device kept lock.

I suspect that large output power interferes the PLL resulting loss of lock.

In doer to isolate the output driver from the lest of circuit inside the device, I want to know

which power pin is dedicated or connected to the driver.

Mita  

  • 0
    TI__Guru** 112150 points

    Hi Mita,

    Could you provide your software configuration? What are the input and output frequencies?

  • +1 in reply to Noel Fung
    Expert 2375 points

    Noel-san,

    Thank you for your feedback.

    Please find code bellows: It is one of an example of my configuration.

      Input:  56.64 MHz

      PDF:  99.12 MHz

      VCO: 5008.952687931 MHz

      Output:  500.8952687931 MHz

    BTW:  Can you give me the answer to my question?

    [SETUP]
ADDRESS=888
CLOCK=8
DATA=4
LE=2
PART=LMX2571
IFACE=SPI
ADDRESS_I2C=0x0

[PINS]
PINNAME00=TrCtl
LOCATION00=7
PINVALUE00=True
PINNAME01=CE
LOCATION01=0
PINVALUE01=True

[MODES]
NAME00=R60
VALUE00=3973120
NAME01=R58
VALUE01=3836928
NAME02=R53
VALUE02=3504134
NAME03=R47
VALUE03=3096576
NAME04=R46
VALUE04=3014681
NAME05=R42
VALUE05=2753040
NAME06=R41
VALUE06=2689048
NAME07=R40
VALUE07=2627612
NAME08=R39
VALUE08=2560507
NAME09=R35
VALUE09=2296967
NAME10=R34
VALUE10=2281473
NAME11=R33
VALUE11=2162688
NAME12=R32
VALUE12=2097152
NAME13=R31
VALUE13=2031616
NAME14=R30
VALUE14=1966080
NAME15=R29
VALUE15=1900544
NAME16=R28
VALUE16=1835008
NAME17=R27
VALUE17=1769472
NAME18=R26
VALUE18=1703936
NAME19=R25
VALUE19=1638400
NAME20=R24
VALUE20=1572895
NAME21=R23
VALUE21=1515332
NAME22=R22
VALUE22=1475975
NAME23=R21
VALUE23=1376516
NAME24=R20
VALUE24=1323033
NAME25=R19
VALUE25=1245184
NAME26=R18
VALUE26=1204630
NAME27=R17
VALUE27=1114180
NAME28=R16
VALUE28=1048576
NAME29=R15
VALUE29=983040
NAME30=R14
VALUE30=917504
NAME31=R13
VALUE31=851968
NAME32=R12
VALUE32=786432
NAME33=R11
VALUE33=720896
NAME34=R10
VALUE34=655360
NAME35=R9
VALUE35=589824
NAME36=R8
VALUE36=524319
NAME37=R7
VALUE37=466692
NAME38=R6
VALUE38=427399
NAME39=R5
VALUE39=327940
NAME40=R4
VALUE40=266262
NAME41=R3
VALUE41=196608
NAME42=R2
VALUE42=149797
NAME43=R1
VALUE43=65618
NAME44=R0
VALUE44=579

[FLEX]
Fosc_F1_FREQ=57.6
Fosc_F2_FREQ=56.64
Fosc_FREQ=56.64
Fout_F1_FREQ=450.000000515
Fout_F2_FREQ=500.8952687931
Fout_FREQ=500.8952687931
Fpd_F1_FREQ=100.8
Fpd_F2_FREQ=99.12
Fpd_FREQ=99.12
Fvco_F1_FREQ=4500.0000051498
Fvco_F2_FREQ=5008.952687931
Fvco_FREQ=5008.952687931
TrCtl_Pin=1
btn_SimplifyFraction=Simplify Fraction
btn_SpurBGone=Spur-b-Gone
flexCHDIV1=5
flexCHDIV2=1
flexCurrent=53.7
flexEXTVCO_CHDIV=0
flexExtVCO_FREQ=480
flexFRAC_ORDER=3
flexIntVCO_FREQ=5008.952687931
flexKpd=2.5
flexKvco=62.26858099241
flexMULT=7
flexOUTBUF_RX_EN=1
flexOUTBUF_RX_PWR=31
flexOUTBUF_TX_EN=0
flexOUTBUF_TX_PWR=31
flexOutputDivide=10
flexPFD_DELAY=4
flexPLL_DEN=0
flexPLL_N=25
flexPLL_NUM=4481430
flexPLL_N_PRE=0
flexPLL_R=1
flexPLL_R_PRE=4

    Mita

  • 0 in reply to user4779049
    TI__Guru** 112150 points

    Hi Mita-san,

    Pin15 is the power supply pin for the output buffer.

    Your software configuration is basically ok, except that MULT_WAIT should be increased to 1132 in order to meet the 20µs requirement.

    When you say loss lock, did you simply mean MUXout is LOW? Could you check the Vtune voltage (pin 25) and also the output signal with a spectrum analyzer? You'd better make OUTBUF_AUTOMUTE = 0 so that the output buffer will not mute even if it is unlock. 

  • 0 in reply to Noel Fung
    Expert 2375 points

    Noel-san,

    Thank you for the answer as well as your advise.

    I will try it with MULT_WAIT=1132.

    Mita

  • 0 in reply to Noel Fung
    Guru 27585 points

    Noel san

    Thank you for your LMX2571's support and cooperation always!
    We work on it with Mita san.

    We tried it with MULT_WAIT=1152(@OSCin=57.6MHz).
    However, it didn't solve.
    Furthermore, we configured Loop filter setting to gain enough phase margin.

    When we reduced the output power(OUTBUF_RX_POW) as low as (03h～04h), the device kept lock.

    We would like to confirm that we suspect that large output power interferes the PLL resulting loss of lock again.
    (For example, it affects to internal power line via output amp stage of large power level.)

    Especially, we also would like to confirm whether it depends on board layout.


    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru** 112150 points

    Hi Matsumoto-san,

    03h-04h are very low output power setting, I have never encountered this problem before.

    How many LMX2571 has this problem? If every LMX2571 has this problem, then I believe it may be an application issue, like layout problem or wrong schematic or wrong component values. 

    If only one LMX2571 has this problem, can they try if making the output frequency = 495.6 MHz (this is an integer channel with NUM=0) can resolve the problem? 

  • 0 in reply to Noel Fung
    Guru 27585 points

    Noel san

    Thank you for your reply!

    How many LMX2571 has this problem?
    ->20 devices (20/170), therefore we think we believe it may be an application issue, like layout problem or wrong schematic or wrong component values also.   
       We will check the board layout and circuit.

    Kind regards,

    Hirotaka Matsumoto