CLC446AMC datasheet(9/12 Pages) NSC

9 / 12 page

http://www.national.com

high frequency performance, maintain low parasitic

capacitance from the diodes D1 and D2 to ground, and

from the input of the CLC522 to ground.

Figure 11: Full-Wave Rectifier

Elliptic Low-pass, Anti-aliasing Filter

Elliptic filters are often used in anti-aliasing applications.

If there is noise or undesired signals at frequencies

above 1/2 the sampling rate of an A/D converter, then

these signals are aliased down into the operating

frequency range, degrading the signal of interest. To

filter out these undesired signal components, place a low

pass filter in front of the A/D converter.

The

Typical Application depicted on the front page is a

10MHz, third-order elliptic filter. It has a voltage-

controlled, voltage source (VCVS) topology using a

CLC446. To calculate the component values for this

filter, do the following:

1. Select the filter approximation function for your

application (see References [1-2]). For this design

we chose:

Filter type = Elliptic

Filter order (n) = 3

Passband ripple = 0.18dB

Mininimum stopband attenuation (Amin) =

37.44dB

Cuttoff frequency = 10MHz (at 0.18dB

attenuation)

These choices produce the following results:

-3dB frequency = 12.7MHz

Stopband corner frequency = 29.3MHz

2. Find the pole and zero locations. Reference [1]

gave the following for our filter:

Pole 1:

α = 0.38621

Pole 2:

o = 0.88668

Zero 1:

β = 1.13897

Zero 2:

ω∞ = 3.3505

3. Denormalize the frequency by multiplying by

the cutoff frequency (

o) in radians/second.

For our filter we have:

Cutoff frequency:

o = 2π(10MHz) =

62.832 x 106rad/s

Pole 1:

α' = ω

oα = 24.266 x 10

6rad/s

Pole 2:

' =

oαo = 55.712 x 10

6rad/s

Zero 1:

β' = ω

oβ = 21.052 x 10

6rad/s

Zero 2:

ω∞' = ωoω∞ = 71.564 x 106rad/s

4. Calculate these intermediate coefficients used

in Reference [2].

For this design, a = 0.64226, b = 7.7612 and

c = 75.556 x 106.

5. Set the following resistance and capacitance

scaling factors:

R = an arbitrary value

C = an arbitrary value

We chose C = 47pF and R = 1.00k

Ω.

6. Calculate the capacitor, resistor and gain (K)

values using these equations:

For this design, the calculated values are:

C1 = 47pF, C2 = 91pF, C3 = C4 = 23.5pF,

C5 = 17.95pF, R1 = R2 = 202.1Ω, R3 = 101.1Ω,

R4 = 3190Ω, R5 = 1000Ω and K = 4.928.

7. Select the feedback resistor (Rf) and gain-

setting resistor (Rg) values to obtain a non-

inverting voltage gain of Av = K. See the DC

Gain (non-inverting) sub-section for details

on selecting these values.

CLC446

500

Ω

CLC522

250

Ω

250

Ω

250

Ω

162

Ω

800

Ω

Rin

Ω

Vin

() +

()

== 





∞

αβ

αω

Cb 1

cC b

cC 1 b

4cC

≥

−

()

−

() +

−

⋅

−









CLC446AMC Datenblatt(PDF) 9 Page - National Semiconductor (TI)

CLC446AMC Datenblatt(HTML) 9 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12

Datenblatt Download

Link URL