LMF100CIWM datasheet(9/28 Pages) NSC

9 / 28 page

1.0 Definitions of Terms

CLK: the frequency of the external clock signal applied to pin

10 or 11.

0: center frequency of the second order function complex

pole pair. f

0 is measured at the bandpass outputs of the

LMF100, and is the frequency of maximum bandpass gain.

(

Figure 1).

notch: the frequency of minimum (ideally zero) gain at the

notch outputs.

z: the center frequency of the second order complex zero

pair, if any. If f

z is different from f0 and if Qz is high, it can be

observed as the frequency of a notch at the allpass output.

(

Figure 13).

Q: “quality factor” of the 2nd order filter. Q is measured at the

bandpass outputs of the LMF100 and is equal to f

0 divided

by the −3 dB bandwidth of the 2nd order bandpass filter (

Fig-

ure 1). The value of Q determines the shape of the 2nd order

filter responses as shown in

Figure 6.

z: the quality factor of the second order complex zero pair,

if any. Q

Z is related to the allpass characteristic, which is

written:

where Q

Z = Q for an all-pass response.

OBP: the gain (in V/V) of the bandpass output at f = f0.

OLP: the gain (in V/V) of the lowpass output as f → 0Hz

(

Figure 2).

OHP: the gain (in V/V) of the highpass output as f → fCLK/2

(

Figure 3).

ON: the gain (in V/V) of the notch output as f → 0 Hz and as

f → f

CLK/2, when the notch filter has equal gain above and

below

the

center

frequency

(

Figure

4).

When

the

low-frequency gain differs from the high-frequency gain, as

in modes 2 and 3a (

Figure 10 and Figure 12), the two quan-

tities below are used in place of H

ON.

ON1: the gain (in V/V) of the notch output as f → 0 Hz.

ON2: the gain (in V/V) of the notch output as f → fCLK/2.

DS005645-19

(a)

DS005645-20

(b)

FIGURE 1. 2nd-Order Bandpass Response

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