LMK03318: Current consumption

Shu,

You can load a configuration into TICS Pro and get the output current if an EVM is connected, per this thread: https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/1171337/lmk03318-power-consumption-calculation/4412228?tisearch=e2e-sitesearch&keymatch=LMK03318%25252520current#4412228

This functionality is not supported if not connected to an actual device, as it is a read of the device's ADC measurement.

In the example from the above thread, when the device has all outputs set to AC-CML (the configuration file can be uploaded in the Raw Registers page), the measured current is 63-64mA. Note that the value in the table in the datasheet is larger - it fully depends on the settings for the inputs, PLL, and outputs. If, for example, if OUT4 through OUT7 are unused, then their currents would not be present in the overall current.

The easiest way to determine current consumption is to create the configuration in TICS Pro, load it onto an LMK03318EVM, provide the supply voltages, and read the ADC currents from the device.

Thanks,

Kadeem

Shu,

The pin is able to be pulled up to either 3.3 V or 1.8 V. The PDN pin is rated for maximum 3.6 V, and recognizes a logical low at 0.6 V (with logical high at 1.2 V)  You can connect this to either VDDO_01 or VDD_R (the core voltage) in your design.

The EVM designer chose to use the VDDO_01 voltage exclusively for the supply for OUT0 and OUT1, with all of the buttons connected to the core voltage.

Thanks,

Kadeem

Shu,

I have the following responses:

• the primary input is an LVPECL clock, the secondary input is a LVCMOS clock from an active oscillator. Both frequency is 100MHz. Do I need to transfer the LVCMOS clock to LVPECL to secondary input? But use the auto switch function to change reference input, would it be better to use same type input?
  • The two inputs are independent, and can be different clock formats. The important details for using the auto switching functionality are below
  • 
  • 
• The oscillator is 1.8V power supply. The VIH min is only 1.4V, looks like I can connect it directly to second input. but how about I connect to negative pin of second input to a 0.9V reference voltage that is a regular way to drive single-end single to differential input, the swing could be 0.9V. I fell it is better than the way to connect 1.8V oscillator to second input. But I don’t find such modes in the datasheet, does the LMK03318 support this way? which way is better?
  •  If using a single-ended input, pull the XO_N pin to GND, per the datasheet. No other configuration of the SECREF_N pin for single-ended inputs is supported. The input buffer of this pin supports single-ended inputs
  • 
  • 
• The LMK05318B has to use a XO or other reference to the XO pin. Then another clock go to reference input to synchronize. How about I use one source and separate it to two clocks using a buffer, then connect them to the reference input and XO input of LMK05318B, will that work?
  • Technically speaking, the LMK03318 supports XO as an input clock to the SECREF pins as well, per this thread: https://e2e.ti.com/support/clock-timing-group/clock-timing-internal/f/clock-timing---internal-forum/1093966/lmk03328-does-lmk03328-support-xo-input/4051811?tisearch=e2e-sitesearch&keymatch=lmk03328%2520xo#4051811. Therefore, it stands to reason that this would work.
  • I have also seen designs where SECREF is just completely unused. In this case, the SECREF buffer is disabled and the SECREF pins are floating, see this thread: https://e2e.ti.com/support/clock-timing-group/clock-timing-internal/f/clock-timing---internal-forum/1119436/lmk03318-lmk03318-schematic/4152148?tisearch=e2e-sitesearch&keymatch=lmk03318%2520secref#4152148

Thanks,

Kadeem

Shu,

Using an LVCMOS clock instead of an XO will work here.

Thanks,

Kadeem