LMK04832PAPSLASHEM datasheet(84/102 Pages) TI

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9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

Texas Instruments provides the TICSPRO software to assist with device setup, frequency divider calculations,

and general device programming as well as the PLLatinum™ simulation software for loop filter design and phase

noise/jitter simulation on ti.com.

9.1.1 Treatment of Unused Pins

Not all pins are needed for every application. In general, power down the unused feature in software. The

unused pin may be left floating or grounded through a 1-kΩ resistor.

Table 9-1. Treatment of Unused Pins

PINS

TREATMENT IF UNUSED

CLKOUTx_P/CLKOUTx_N

1 kΩ to GND or float pin

RESET/GPO

1 kΩ to GND or float pin

SYNC/SYSREF_REQ

1 kΩ to GND or float pin

FIN0_P/FIN0_N

1 kΩ to GND or float pin

STATUS_LD1,STATUS_LD2

1 kΩ to GND or float pin

CPOUT1,CPOUT2

1 kΩ to GND or float pin

OSCOUT_P/CLKIN2_P

1 kΩ to GND or float pin

OSCOUT_N/CLKIN2_N

1 kΩ to GND or float pin

9.1.2 Frequency Planning and Spur Minimization

Frequency planning refers to strategically assigning frequencies to outputs for the purposes of spur minimization.

Spurs vary as a function of output frequency, output format, and output assignments. Spurs can be directly

coupling from one output to the next or be caused by a mixing product. For instance, if one output is at 3 GHz

and another output is at 750 MHz, one can see a 750 MHz-spur coupling through the 3-GHz output. In some

situations, it is also possible to have a spur that occurs at the greatest common divisor of the two frequencies

(250 MHz in this case). In either case, the choice of which outputs the 3-GHz and 750-MHz frequencies are

assigned to can have an impact on spurs.

Table 9-2. Factors Impacting Spurs

Factor

General Guidelines and Tips

Output Frequency

To a point, higher frequencies tend to couple stronger to other outputs, but bypassing impacts this.

Output Format

Stronger signals and single-ended signals tend to couple stronger to other outputs. LVDS tends to couple

less than LVPECL as well. For LVCMOS, consider using both sides of the output with one side inverted to

the other (Norm/Inv) to minimize crosstalk.

Frequency Assignment to

Output

(Frequency Planning)

Outputs that are physically closer and that share the same power supply tend to have stronger crosstalk.

Outputs are grouped by supply in the following manner: Clock Group 0: (CLK0,CLK1,CLK12,CLK13),

Clock Group 1: (CLK2, CLK3), Clock Group 2 (CLK4, CLK5, CLK6, CLK7), Clock Group 3 (CLK8, CLK9,

CLK10, CLK11). Use frequency planning to minimize spur levels to the most critical outputs.

Frequency planning involves trial and error, but there is some strategy in planning. Try to ensure that the same

frequencies are placed on outputs that have the strongest crosstalk and that different frequencies are placed on

outputs that have weaker crosstalk

LMK04832-SEP

SNAS838A – OCTOBER 2022 – REVISED NOVEMBER 2022

www.ti.com

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