ML2111CIP View Datasheet(PDF) - Micro Linear Corporation

Part Name

Description

Manufacturer

ML2111CIP

Universal Dual High Frequency Filter

Micro Linear Corporation 

ML2111

OPERATION MODES (Continued)

The clock to center frequency ratio range is:

500

1

˜

fCLK

f0

˜ 100 or 50

11

(mode 1c)

(6)

100 or 50

11

˜

fCLK

f0

˜ 100 or

2

50

2

(mode 1b)

(7)

The input impedance of the S1 pin is clock dependent,

and in general R5 should not be larger than 5kW for fCLK <

2.5MHz and 2kW for fCLK > 2.5MHz. Mode 1c can be

used to increase the clock-to-center-frequency ratio

beyond 100:1. The limit for the (fCLK/f0) ratio is 500:1 for

this mode. The filter will exhibit large output offsets with

larger ratios. Mode 1d (Figure 19) is the fastest mode of

operation: center frequencies beyond 20kHz can easily

be achieved at a 50:1 ratio.

Modes 2, 2a, and 2b (Figures 20, 21, and 22) have notch

outputs whose frequency, fn, can be tuned independently

from the center frequency, f0. However, for all cases fn <

f0. These modes are useful when cascading second order

functions to create an overall elliptic highpass, bandpass

or notch response. The input amplifier and its feedback

resistors R2 and R4 are now part of the resonant loop.

Because of this, mode 2 and its derivatives are slower

than mode 1 and its derivatives.

In Mode 3 (Figure 23) a single resistor ratio, R2/R4, can

tune the center frequency below or above the fCLK/100 (or

fCLK/50) ratio. Mode 3 is a state variable configuration

since it provides a highpass, bandpass, lowpass output

through progressive integration. Notches are acquired by

summing the highpass and lowpass outputs (mode 3a,

Figure 24). The notch frequency can be tuned below or

R4

R3

R2

R1

VIN

4 (17) +

HP

S1A

3 (18) 5 (16)

+Σ

BP

2 (19)

LP

1 (20)

f0

=

fCLK

100(50)

™

R2 ;Q = R3 ™

R4 R2

R2 ;

R4

HOHP

=

-

R2

R1

;HOLP

=

-

R4

R1

;

HOBP

=

-

R3

R1

SA/B

6

15

V-

Figure 23. Mode 3: 2nd Order Filter Providing Highpass, Bandpass, Lowpass — ½ ML2111

Q = R2 ™ R3

R4 R2

R4

R3

f0

=

fCLK

100(50)

™

R2

R4

; fn

=

fCLK

100(50)

™

Rh ;

Rl

R2

R1

VIN

4 (17) +

HP

S1A

3 (18) 5 (16)

+Σ

BP

2 (19)

SA/B

6

15

Rh

V-

LP

HOHP

=

-

R2

R1

;HOBP

=

-

R3

R1

;HOLP

=

- R4 ;

R1

1 (20)

1 6   HON f = f0

  Rg

=Q™

Rg

Rl

™ HOLP

- Rg

Rh

™ HOHP

;

External

Rl

Op Amp

  HON2

f “ fCLK

2

= Rg ™ R2 ;

Rh R1

+

NOTCH

1 6 HON1 f “ 0

= Rg

Rl

™ R4

R1

Figure 24. Mode 3a: 2nd Order Filter Providing Highpass, Bandpass, Lowpass, Notch — ½ ML2111

18

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