Hi
I would like to use the LMK03318 in our design and I have a few questions:
SECREF/PRIMREF connectivity: the input signal to the PLL is differential (LVPECL input).
In the data sheet the pins above state to have internal capacitors for AC couple mode.
Also Figure 45. Differential Input Buffer Termination Options on Primary and Secondary Reference demonstrate the above.
But on Table 4. Input Buffer Configuration Matrix on Primary and/or Secondary Reference, the statement for LVPECL IO standard is to use external capacitors.
(Also in the LMK03318 EVB there are external capacitors) hence as I understand it is mandatory to use the external capacitors for AC couple mode?
Also Figure 52. AC-Coupling LMK03318 Inputs With LVPECL Signal (Internal Biasing Enabled) demonstrate it.
Hence the best way (please approve) is to implement the connectivity as in the EVB (JP16 to GND).
Note:
SECREF: the input is GXO-E31L oscillator
An additional question is regarding the GPIO pin configurations:
The use is HW_SW_CTRL = 0 (soft pin mode).
GPIO0 need to be connected to VDD_DIG (Normal output driver/divider operation as configured)
GPIO1 is the I2C address lower bits.
GPIO[3:2]: the defaults of the EEPROM are not as I need and I will need either to program it before first use or via registers write
And this is the question I have - when they are floating the register defaults are loaded.
Is there a recommended way (fast and secure) to program the PLL ?
GPIO[3:2] are a select for 1 of 6 EEPROM pages, is the page definition is according to register R8[6:4] PINMODE_SW Register[GPIO32_SW_MODE]?
GPIO4 pin: Frequency margining enable how to configure it?.
GPIO5 pin : Frequency margining offset select, how to configure it?
Regards
Omer