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LMH1982 - PLL Lock Detection
I understand the "LOCK_CTRL" (Register 01h) programs the maximum phase error between PLL1's Phase Detector inputs.
Is the allowable phase error set by LOCK_CTRL based on (Hsync input / reference divider) or (VCXO clock / feedback divider) ?
I am thinking the allowable phase error is based on (Hsync input / reference divider).
If the (VCXO clock / feedback divider) timing is inside +/- allowable phase error, PLL1 is locked.
Again, answers to these questions can be found in the following E2E forum post:http://e2e.ti.com/support/interface/high_speed_interface/int-high_speed_interface/f/140/p/178827/691492.aspx#691492
Thanks for your comment, but I could not find the page which you had told me.
When I jump to the URL, the page shows,
Sorry, the link I sent was for an internal website. Here are some answers to your questions:
Lock Detection for PLL1 The phase differences between phase detector (PD) inputs produce different up/down output pulses to drive the charge pump and servo the loop filter / VCXO control voltage. When the PLL is in a "locked" state, the up/down pulses will present equal pulses with minimum width to the charge pump inputs. For PLL1, the up/down pulse width is compared against the time window (delay circuit) programmed via LOCK_CTRL register. When the pulse width is within the window for 3 consecutive PD cycles, then valid lock is indicated (SD_LOCK = 1). When the pulse width is outside the window for 3 consecutive PD cycles, then loss of lock is indicated (SD_LOCK = 0).
Lock Detection for PLLs 2/3/4The phase differences between the PD inputs produce different up/down output pulses to drive the charge pump and servo the internal loop filter/VCO control voltage. When the PLL is in a "locked" state, the up/down pulses should be equal with minimal width to charge pump inputs. For PLLs 2/3/4, the time window is based on 2 inverter delays (~50 ps window, default), but this can be programmed to 6 inverter delays (~150 ps window) via a Reserved register 0x1Ch[bit 2]. Valid register values are 0x00h (2 inverter delays) or 0x04h (6 inverter delays). When the pulse width is within the window for 3 consecutive PD cycles, then valid lock is indicated (SD_LOCK = 1 for PLL4, or HD_LOCK = 1 for PLLs 2/3). When the pulse width is outside the window for 3 consecutive PD cycles, then loss of lock is indicated (SD_LOCK = 0 for PLL4, or HD_LOCK = 0 for PLLs 2/3).
Thank you for the answer.
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