–9

–8

–7

–6

–5

–4

–3

–2

–1

0

0.1

1

10

100

1000

Frequency (MHz)

LSF0204, LSF0204D

SLVSCP5D – JULY 2014 – REVISED DECEMBER 2015

www.ti.com

PULLUP RESISTOR VALUE (

Ω)

15 mA

10 mA

3 mA

NOMINAL

NOMINAL

NOMINAL

5 V

310

341

465

512

1550

1705

3.3 V

197

217

295

325

983

1082

2.5 V

143

158

215

237

717

788

1.8 V

97

106

145

160

483

532

1.5 V

77

85

115

127

383

422

1.2 V

57

63

85

94

283

312

(1)

(2)

(3)

11.2.1.2.2

LS Family Bandwidth

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

>100MHz 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 10 shows a bandwidth measurement of the LSF family using a two-port network analyzer.

Figure 10. 3-dB Bandwidth

The 3-dB point of the LSF family is

≈600MHz; 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 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 may 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 pullup resistor is needed on the host side (3.3 V) if the LSF family is being

driven by standard CMOS totem pole output driver. Best practice is 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.

14

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