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LMK03328: Loss of signal status doesn't appear to work

Part Number: LMK03328

Tool/software:

Hi,

I have a design with the LMK03328 which has an LVDS 20MHz primary input and a 10MHz crystal secondary input.

I have found that the "loss of signal" bits do not seem to do much, they are always 0 - the reference input detector is enabled and the device produces an output clock.

My program writes the registers from the hex file except for the following: 12, 14, 15, 17, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 117, 118, 119, 120, 131, 132, 133, 134

(I believe these are all read only or undefined)

After setting the registers I toggle RESETN_SW in DEV_CTL (R12) to recalibrate the VCO etc. then poll R13 & R18. I can see the CAL1 bit in R13 go high and then low, but all other bits are 0, even if I disconnect the LVDS clock.

Does anyone have an idea?

Thanks.

PLCO02A-pri-20MHz.tcs

R0	0x0010
R1	0x010B
R2	0x0232
R3	0x0302
R4	0x0401
R5	0x0500
R6	0x0600
R7	0x0700
R8	0x0883
R9	0x0940
R10	0x0AA8
R11	0x0B00
R12	0x0CDF
R13	0x0DC0
R14	0x0E00
R15	0x0F00
R16	0x1000
R17	0x1100
R18	0x1210
R19	0x1300
R20	0x14FF
R21	0x15FF
R22	0x16FF
R23	0x1702
R24	0x1800
R25	0x19F1
R26	0x1A30
R27	0x1B00
R28	0x1C10
R29	0x1D14
R30	0x1E20
R31	0x1F20
R32	0x2020
R33	0x2106
R34	0x2220
R35	0x2320
R36	0x248B
R37	0x2510
R38	0x2609
R39	0x2710
R40	0x2853
R41	0x2910
R42	0x2A29
R43	0x2B00
R44	0x2C05
R45	0x2D0A
R46	0x2E00
R47	0x2F00
R48	0x30FF
R49	0x3100
R50	0x3290
R51	0x3303
R52	0x3400
R53	0x3500
R54	0x3600
R55	0x3700
R56	0x3816
R57	0x3908
R58	0x3A00
R59	0x3BFC
R60	0x3C00
R61	0x3D00
R62	0x3E00
R63	0x3F00
R64	0x4000
R65	0x4101
R66	0x420C
R67	0x4320
R68	0x4401
R69	0x4504
R70	0x4607
R71	0x471F
R72	0x4818
R73	0x4900
R74	0x4AF0
R75	0x4B00
R76	0x4C00
R77	0x4D00
R78	0x4E00
R79	0x4F00
R80	0x5000
R81	0x510C
R82	0x5220
R83	0x5301
R84	0x5404
R85	0x5507
R86	0x5600
R87	0x5700
R88	0x5800
R89	0x59DE
R90	0x5A01
R91	0x5B18
R92	0x5C01
R93	0x5D4B
R94	0x5E01
R95	0x5F86
R96	0x6001
R97	0x61BE
R98	0x6201
R99	0x63FE
R100	0x6402
R101	0x6547
R102	0x6602
R103	0x679E
R104	0x6800
R105	0x6900
R106	0x6A05
R107	0x6B0F
R108	0x6C0F
R109	0x6D0F
R110	0x6E0F
R111	0x6F00
R112	0x7000
R113	0x7100
R114	0x7200
R115	0x7308
R116	0x7419
R117	0x7580
R118	0x7607
R119	0x7705
R120	0x7800
R121	0x790F
R122	0x7A0F
R123	0x7B0F
R124	0x7C0F
R125	0x7D00
R126	0x7E00
R127	0x7F00
R128	0x8000
R129	0x8108
R130	0x8219
R131	0x8300
R132	0x8407
R133	0x8505
R134	0x8600
R135	0x8700
R136	0x8800
R137	0x8910
R138	0x8A00
R139	0x8B00
R140	0x8C00
R141	0x8D00
R142	0x8E00
R143	0x8F00
R144	0x9000
R145	0x9100
R169	0xA940
R172	0xAC24
R173	0xAD00

  • Darius,

    Some things I want to note about input detection:

    - The LOS bit assumes that a valid reference clock was provided when the device was powered on. If the device is powered on with no reference, then the LOS bit will not be activated.

    - The LOS bit does not apply to XTAL inputs. 

    Does the LOS bit perform as expected when using the Slew Rate detect instead of the Vih/Vil level detect?:

    Best,

    Cris

  • Hi Cris,

    When you say ".. when the device was powered on" does that mean only when it was powered up, or is toggling RESETN_SW sufficient?

    Thanks for the help.

  • Darius,

    Toggling RESETN_SW will also cause the LOS bit to behave that way. So: remove PRIREF -> toggle RESETN_SW -> LOS=0 -> apply PRIREF -> remove PRIREF -> LOS=1

    Best,

    Cris

  • Hi Cris,

    I just can get the LOS or LOL bits to turn on at all when reading R13.

    If I connect LOL to a status pin then it works (goes active with the input disconnected, inactive when I reconnect it) but the R13 LOL1 bit does not change as I expected.

    Also, if I connect LOS to a status pin does nothing at all - the output does not change (and I see nothing in R13)

    R18 is also 0 all the time, although after reading the datasheet in more detail perhaps this is expected as it does imply that only has status for the single ended detectors (there don't appear to be status bit for the LVDS detectors..)

  • Darius,

    When testing on the bench with your config, the LOS bit worked as expected. We tested with both differential and single-ended inputs.

    In general, I recommend using the STAT0/1 LOL output instead of R13 as the STAT output is more reliable. 

    How are you connecting/disconnecting the input? Are you using an EVM or your own board?

    Best,

    Cris