LMK04828 datasheet(86/102 Pages) TI

86 / 102 page

0.1 PF

50 : Trace

LMK04828-

EP Input

Clock Source

CLKinX

CLKinX*

0.1 PF

50 : Trace

50 :

LMK04828-

EP Input

Clock Source

CLKinX/

OSCin

CLKinX*/

OSCin*

LMK04828-EP

SNAS703 – APRIL 2017

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Product Folder Links: LMK04828-EP

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10.1.2.2 Driving CLKin or OSCin Pins With a Single-Ended Source

The CLKin or OSCin pins of the LMK04828-EP can be driven using a single-ended reference clock source, for

example, either a sine wave source or an LVCMOS/LVTTL source. Either AC coupling or DC coupling may be

used for CLKin. OSCin requires AC coupling. In the case of the sine wave source that is expecting a 50 Ω load,

TI recommends using AC coupling as shown in the circuit below with a 50-Ω termination. It may be required to

add a series resistor to create a voltage divider to keep the input voltage within specification.

NOTE

The signal level must conform to the requirements for the CLKin pins listed in Electrical

Characteristics. CLKinX_BUF_TYPE is recommended to be set to bipolar mode

(CLKinX_BUF_TYPE = 0).

Figure 18. CLKinX/X* or OSCin Single-Ended Termination

If the CLKin pins are being driven with a single-ended LVCMOS/LVTTL source, either DC coupling or AC

coupling may be used. If DC coupling is used, the CLKinX_BUF_TYPE should be set to MOS buffer mode

(CLKinX_BUF_TYPE = 1) and the voltage swing of the source must meet the specifications for DC-coupled,

MOS-mode clock inputs given in Electrical Characteristics. If AC coupling is used, the CLKinX_BUF_TYPE

should be set to the bipolar buffer mode (CLKinX_BUF_TYPE = 0). The voltage swing at the input pins must

meet the specifications for AC-coupled, bipolar mode clock inputs given in Electrical Characteristics . In this

case, some attenuation of the clock input level may be required. A simple resistive divider circuit before the AC-

coupling capacitor is sufficient.

Figure 19. DC-Coupled LVCMOS/LVTTL Reference Clock

10.1.3 Using AC-Coupled Clock Outputs

When using LVDS or HSDS output modes and AC coupling, place shunt a 560 Ω across the outputs close to the

IC to provide a DC path to the driver.

LMK04828 Datasheet(PDF) 86 Page - Texas Instruments

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