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Replies: 2
Views: 52
Part Number: LMK04208
Hi allWould you mind if we ask LMK04208?<Question1>Our customer uses LMK04208 with following condtions;-Input : sinwave 10MHz 0.5Vrms -Output : 30MHz LVCMOS 3.3VIs it possible?<Question2>If <Question1> is possible, should we select on TICSPRO at input?Biploar??<Question3>We would like to simulate of phase noise.PLLatinum doesn't correspond for this device.How should we simulate?Kind regards,Hirotaka Matsumoto
Hi Hirotaka,
We will get back to you the next business day.
Regards,Hao
Clock and Timing Systems & Applications
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More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html
Hello Matsumoto-san,
Q1: The limiting factor with sinewave input at low frequency is typically slew rate. The slew rate of a sine wave is given by:
Slew (V/s) = 2π * Vpk (V) * Freq (Hz)
= 2π * (sqrt(2) * 0.5Vrms) * (10e6 Hz) = 44.4e6 V/s = 0.044V/ns
The datasheet for LMK04208 lists the minimum slew rate for CLKinX as 0.1V/ns, so the 10MHz sine wave does not meet the minimum slew rate requirements at that amplitude. The amplitude would need to be increased (0.1/0.44) * 0.5Vrms = 1.125Vrms, or about 3.2Vpp to meet the datasheet minimum specifications. This is higher than the maximum single-ended signal swing of 2.4Vpp. Therefore, single-ended 10MHz sinewave cannot not meet datasheet requirements.
On the other hand, a 3.1Vpp sinewave into a balun, or a differential sinewave with half the amplitude (1.55Vpp) at each pin would be close enough to meeting datasheet minimum requirements at 10MHz (0.097V/ns), without exceeding the maximum differential signal swing limits. So if they use a 10MHz sinewave, they should couple it differentially to yield the highest signal amplitude.
Q2: I recommend AC-coupling and using bipolar mode for sinewave input.
Q3: LMK04208 is the same die as LMK04808, so you can use LMK04808 to simulate LMK04208 performance.
Regards,
Derek Payne
Texas Instruments