LMH1983 Lock time difference

hisakichi kobayashi

Other Parts Discussed in Thread: LMH1983

Hi all,

LMH1983 is used by my customer. When a 44.4-kHz WORD clock is put in, the phenomenon in which lock time becomes long strangely has occurred.

7457.Presentation.pdf

Please let me know the cause and measure which become slow to a word clock.

Best regards,

Hisakichi Kobayashi.

over 11 years ago

0 Michael Peffers over 11 years ago

TI__Mastermind 20820 points

Hi Hisakichi,

Sorry for the delay in response, someone is looking into this and will reply shortly.

Regards,

Michael Peffers

Analog Applications Engineer

0 Nasser Mohammadi over 11 years ago in reply to Michael Peffers

TI__Guru* 93670 points

Greetings Kobayashi-San,

Please note table 1 of the LMH1983 data sheet. 32KHx or 44KHz reference is not supported, in default mode, by LMH1983. Has the customer tired 48KHz or 96 KHz instead?

Regards,,nasser

0 hisakichi kobayashi over 11 years ago in reply to Nasser Mohammadi

Intellectual 950 points

Hi nasser,

I have 48KHz data. Look at file as follows 2 page.

8585.Presentation1.pdf

It is except a setup of table1. Isn't there any USER mode which can be set up?

Regards,, Hisakichi Kobayashi.

0 Nasser Mohammadi over 11 years ago in reply to hisakichi kobayashi

TI__Guru* 93670 points

Kobayashi-San,

I was epecting perhaps a lock time of 1 second or so since PLL1 loop bandwidth is very low, about 3Hz, but 6 seconds is longer than what i was expecting. Can you please send us the customer LMH1983 schematic?

Regards,,nasser

0 hisakichi kobayashi over 11 years ago in reply to Nasser Mohammadi

Intellectual 950 points

Hi Nasser,

The customer LMH1983 schematics is not open. If the phase comparison frequency of various zones is used, the zone which becomes disadvantageous in characteristic will also generate a loop filter part. For this reason, we changed the frequency inputted into HIN and decided to cope with it so that phase comparison frequency may not become low too much.

Thanks,

Regards,, Hisakichi Kobayashi.

0 Nasser Mohammadi over 11 years ago in reply to hisakichi kobayashi

TI__Guru* 93670 points

Hi Hisakichi-San,

It is possible to get a long lock time when using audio clocks as the reference. There are a couple of reasons, when using audio clocks our loop bandwidth has to be very low so we divide down the audio clock. On top of this, we have to also divide down the reference clock(i.e 27MHz) as well. So these cause us to have a long lock time(i.e 6 seconds) for the audio clocks.

Regards,,nasser

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LMH1983 Lock time difference