AFE5801 datasheet(34/46 Pages) TI

34 / 46 page

AFE5851

0.1

CLKP

CLKM

AFE5801

DifferentialSine-Wave

orPECL orLVDSClockInput

AFE5851

CLKP

CLKM

AFE5801

CMOSClockInput

AFE5801

SLOS591D – SEPTEMBER 2008 – REVISED MAY 2010

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For single ended sinusoidal clocks or for differential clocks (differential sinewave, LVPECL, LVDS…), the clock

amplifier should be enabled. For that, the connection scheme of Figure 40 should be used. The common-mode

voltage of the clock source should match one of the clock inputs of the AFE5801 (VCM) which is set internally

using 5k

Ω resistors, as shown in Figure 39. The easiest way to ensure this is to AC couple the inputs as shown

in Figure 40. The same scheme applies to the case where the clock is single ended but its amplitude is small or

its edges are not sharp (for instance, with a sinusoidal single-ended clock). In this case, the input clock signal

can be connected with a capacitor to CLKINP (as in Figure 40) and the CLKINM should be connected to ground

also through a capacitor, i.e., AC coupled to AVSS.

Figure 40. Differential Clock Driving Circuit

If a transformer is used with the secondary floating (for instance, to pass from single-ended to differential) , it can

then obviously be connected directly to the clock inputs, without the need of the 100nF series capacitors.

Figure 41. Single-Ended Clock Driving Circuit

Finally, on the differential clock configurations, Figure 42 shows the use of the CDCM7005 to generate the

AFE5801 clock signals.

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AFE5801 Datasheet(PDF) 34 Page - Texas Instruments