–9

–8

–7

–6

–5

–4

–3

–2

–1

0

0.1

1

10

100

1000

Frequency (MHz)

14

LSF0101, LSF0102, LSF0108

SDLS966G – DECEMBER 2013 – REVISED FEBRUAURY 2016

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Product Folder Links: LSF0101 LSF0102 LSF0108

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Copyright © 2013–2016, Texas Instruments Incorporated

9.2.1.2.3

LSF Family Bandwidth

The maximum frequency of the LSF family is dependent on the application. The device can operate at speeds of

>100 MHz gave the correct conditions. The maximum frequency is dependent upon the loading of the

application. The LSF family behaves like a standard switch where the bandwidth of the device is dictated by the

on resistance and on capacitance of the device.

Figure 7 shows a bandwidth measurement of the LSF family using a two-port network analyzer.

Figure 7. 3-dB Bandwidth

The 3-dB point of the LSF family is

≈ 600 MHz; however, this measurement is an analog type of measurement.

For digital applications the signal should not degrade up to the fifth harmonic of the digital signal. The frequency

bandwidth should be at least five times the maximum digital clock rate. This component of the signal is very

important in determining the overall shape of the digital signal. In the case of the LSF family, a digital clock

frequency of greater than 100 MHz can be achieved.

The LSF family does not provide any drive capability. Therefore higher frequency applications will require higher

drive strength from the host side. No pull-up resistor is needed on the host side (3.3 V) if the LSF family is being

driven by standard CMOS totem pole output driver. Ideally, it is best to minimize the trace length from the LSF

family on the sink side (1.8 V) to minimize signal degradation.

All fast edges have an infinite spectrum of frequency components; however, there is an inflection (or knee) in the

the shape of the signal.

equations:

(2)

(3)

time of the signal. For signals with rise time characteristics based on 20% to 80% thresholds, which is very

Some guidelines to follow that will help maximize the performance of the device:

•

•

The trace length should be less than half the time of flight to reduce ringing and line reflections or non-

monotonic behavior in the switching region.

•

To reduce overshoots, a pull-up resistor can be added on the 1.8 V side; be aware that a slower fall time is to

be expected.