LTC1164MJ 查看數據表（PDF） - Linear Technology

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LTC1164MJ

Low Power, Low Noise, Quad Universal Filter Building Block

Linear Technology 

U

ODES OF OPERATIO

Mode 3A

This is an extension of Mode 3 where the highpass and

lowpass output are summed through two external resis-

tors RH and RL to create a notch. This is shown in Figure

10. Mode 3A is more versatile than Mode 2 because the

notch frequency can be higher or lower than the center

frequency of the 2nd order section. The external op amp of

Figure 10 is not always required. When cascading the

sections of the LTC1164, the highpass and lowpass

LTC1164

outputs can be summed directly into the inverting input of

the next section. The topology of Mode 3A is useful for

elliptic highpass and notch filters with clock to cutoff

frequency ratios higher than 100:1. This is often required

to extend the allowed input signal frequency range and to

avoid premature aliasing.

When the internal clock-to-center frequency ratio is set at

50:1, the design equations for Q and bandpass gain are

different from the 100:1 case.

R1

VIN

R4

R3

R2

–

+

N

S

+–

Σ∫

1/4 LTC1164

MODE 2 (100:1):

fo

=

fCLK

100

1 + R2

R4

;

fn

=

fCLK

50

;Q=

R3

R2

1

+ R2

R4

;

HOLP

=

1

– R2/R1

+ (R2/R4)

( ) HOBP =

–R3/R1; HON1 (f →

0)

=

1

– R2/R1

+ (R2/R4)

;

HON2

f

→

fCLK

2

= – R2/R1

BP

LP MODE 2 (50:1):

fo

=

fCLK

50

1 + R2

R4

;

fn

=

fCLK

50

;Q=

1.005 (√1 + R2/R4)

(R2/R3) – (R2/16R4)

;

HOLP

=

– R2/R1

1 + (R2/R4)

∫

HOBP

=

–

1

–

(RR33//R116R4);

HON1(f

→

0)

=

1

– R2/R1

+ (R2/R4)

( ) HON2

f

→

fCLK

2

= – R2/R1

NOTE: THE 50:1 EQUATIONS FOR MODE 2 ARE DIFFERENT FROM THE EQUATIONS

FOR MODE 2 OPERATION OF THE LTC1059, LTC1060 AND LTC1061. START WITH

fo, CALCULATE R2/R4, SET R4; FROM THE Q VALUE, CALCULATE R3:

R3 = 1.005

Q

R2

; THEN CALCULATE R1 TO SET THE DESIRED GAIN

1 + R2 + R2

R4 16R4

LTC1164 • MOO04

Figure 9. Mode 2: 2nd Order Filter Providing Notch, Bandpass, Lowpass

R1

VIN

R4

R3

R2

–

+

AGND

CC

HP S

BP

+–

Σ∫

∫

1/4 LTC1164

RH

MODE 3A (100:1):

fo

=

fCLK

100

R2

R4

;

fn

=

fCLK

100

RRHL ; HOHP = – R2/R1; HOBP = – R3/R1

( ) HOLP

=

– R4/R1; HON1(f

→

0)

=

RG

RL

×

R4;

R1

HON2

f → fCLK

2

=

RG

RH

×

R2

R1

( ) HON (f = fo) = Q

RG

RL

HOLP

–

RG

RH

HOHP

;

Q

=

R3

R2

R2

R4

LP

MODE 3A (50:1):

fo

=

fCLK

50

R2

R4

;

fn

=

fCLK

50

( ) RH;

RL

HOHP

f → fCLK

2

= –R2/R1

HOBP = –

1 – (RR33//R116R4); HOLP(f = 0) = – R4/R1; Q =

1.005 (√R2/R4)

(R2/R3) – (R2/16R4)

RG

RL

–

NOTE: THE 50:1 EQUATIONS FOR MODE 3A ARE DIFFERENT FROM THE EQUATIONS

FOR MODE 3A OPERATION OF THE LTC1059, LTC1060 AND LTC1061. START WITH

fo, CALCULATE R2/R4, SET R4; FROM THE Q VALUE, CALCULATE R3:

R3 = 1.005

NOTCH Q

R2

; THEN CALCULATE R1 TO SET

R2 + R2 THE DESIRED GAIN

R4 16R4

+

EXTERNAL OP AMP OR

INPUT OP AMP OF THE

LTC1164, SIDE A, B, C, D

LTC1164 • MOO05

Figure 10. Mode 3A: 2nd Order Filter Providing Highpass, Bandpass, Lowpass, Notch

1164fa

11

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