LMK03806: LMK03806 can't output Clock in crystal Mode

TONG TONG

Prodigy 80 points

Part Number: LMK03806

In our application，We use LMK03806BISEQ in crystal mode and the lmk03806 clock can't output. The crystal is 20 MHZ.

When we use LMK03806BISEQ in external clock mode, lmk03806 clock can output.

Attached is our schematic and configuration file。 Please help up check it.

Thanks

LMK03806.pdf

Fullscreen 03806_A2_5down.txt Download

R0 (INIT)	0x80020140
R0	0x00000960
R1	0x80000201
R2	0x80000202
R3	0x00000323
R4	0x00000284
R5	0x80000205
R6	0x00010006
R7	0x81000007
R8	0x00100008
R9	0x55555549
R10	0x9002400A
R11	0x3401202B
R12	0x130C006C
R13	0x3B03826D
R14	0x0300000E
R16	0xC1550410
R24	0x00000018
R26	0x8FA4E21A
R28	0x0010001C
R29	0x0080033D
R30	0x0500033E
R31	0x001F001F

over 3 years ago

0 Julian Hagedorn over 3 years ago

TI__Mastermind 20900 points

Hello,

please check if the Crystal fulfills this requirements on ESR and CL.

regards,

Julian

0 TONG TONG over 3 years ago in reply to Julian Hagedorn

Prodigy 80 points

Hello

Attached is our crystal specification. ESR is 60Ω, Which is more than 40Ω.

We have tested that the crystal has been oscillated. Attached picture are the test data.

We find that LMK03806 Clock probabilistic not output.

0 TONG TONG over 3 years ago in reply to TONG TONG

Prodigy 80 points

Hello

We add one experiment. When LMK03806 clock output, the frequency that we test（97Mhz）doesn't consistent with set value(100Mhz).

Thanks.

0 Julian Hagedorn over 3 years ago in reply to TONG TONG

TI__Mastermind 20900 points

Hi,

the crystal ESR should be below 40 Ohms for 16 to 20.5MHz.

If the frequency is off, then the VCO seems to be unlocked. Was that test done with the XO or the Crystal?

Please check the loop filter again. PLLatinum Sim can help to calculate the correct values.

Regards,

Julian

0 TONG TONG over 3 years ago in reply to Julian Hagedorn

Prodigy 80 points

Hello

That test was in Crystal mode.

We will check the loop filter.

Thanks

0 Julian Hagedorn over 3 years ago in reply to TONG TONG

TI__Mastermind 20900 points

Hello,

thanks for the update. Please let me know if loop filter adjustments helps with locking the VCO and correcting the frequency.

If the outputs are not always visible then it maybe caused by the crystal not always oscillating. That could be due to the high ESR.

regards,

Julian

0 TONG TONG over 3 years ago in reply to Julian Hagedorn

Prodigy 80 points

Hello

I adjust loop filter, but the frequency of clock that LMK03806 output was 97M which wasn't consistent with set value(100Mhz).

I select one 12M crystal which is 50 Ohms ESR. I test the frequency of clock that LMK03806 output was 97M. In my opinion, It is an unreasonable phenomenon. I suspect the config file is wrong in somewhere, Please help us check it.

Thanks

R0 (INIT) 0x80020140
R0 0x00000960
R1 0x80000201
R2 0x80000202
R3 0x00000323
R4 0x00000284
R5 0x80000205
R6 0x00010006
R7 0x81000007
R8 0x00100008
R9 0x55555549
R10 0x9002400A
R11 0x3401202B
R12 0x130C006C
R13 0x3B03826D
R14 0x0300000E
R16 0xC1550410
R24 0x00000018
R26 0xAFA8001A
R28 0x0020001C
R29 0x0080055D
R30 0x0500055E
R31 0x001F001F