MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

General Description

The MAX270/MAX271 are digitally-programmed, dual

second-order continuous-time lowpass filters. Their typi-

cal dynamic range of 96dB surpasses most switched

capacitor filters which require additional filtering to

remove clock noise. The MAX270/MAX271 are ideal for

anti-aliasing and DAC smoothing applications and can

be cascaded for higher-order responses.

The two filter sections are independently programmable

by either microprocessor (FP) control or pin strapping.

Cutoff frequencies in the 1kHz to 25kHz range can be

selected.

The MAX270 has an on-board, uncommitted op amp,

while the MAX271 has an internal track-and-hold (T/H).

Features

S

Continuous-Time Filtering - No Clock Required

S

Dual 2nd-Order Lowpass Filters

S

Sections Independently Programmable: 1kHz to

25kHz

S

96dB Dynamic Range

S

No External Components

S

Cascadable for Higher Order

S

Low-Power Shutdown Mode

S

Track-and-Hold (MAX271)

Ordering Information

PART

MAX270CPP

MAX270CWP

MAX270EPP

MAX270EWP

MAX271CNG

MAX271CWG

MAX271ENG

MAX271EWG

TEMP RANGE

0NC to +70NC

-40NC to +85NC

0NC to +70NC

-40NC to +85NC

PIN-PACKAGE

20 PDIP

20 Wide SO

20 PDIP

20 Wide SO

20 PDIP

20 Wide SO

20 PDIP

20 Wide SO

Applications

Lowpass Filtering

Anti-Aliasing Filter

Output Smoothing

Low-Noise Applications

Anti-Aliasing and Track-and-Hold (MAX271)

Devices are available in a lead(Pb)-free/RoHS-compliant package.

Specify lead-free by adding a plus (+) to the part number when

ordering.

Typical Operating Circuit

+5V

-5V

Pin Configurations

TOP VIEW

1

OP OUT

V+

OUTA

SHDN

INA

V-

INB

OUTB

GND

WR

OP IN

D6

D5

D4

D3

D2

D1

D0

A0

CS

20

19

18

17

16

15

14

13

12

11

V+

IN INA

GND

FILTER A

ANTI-ALIASING

V-

2

OUTA

A/D WITH

T/H

3

4

DSB

MAX270

OUT OUTB

FILTER B

ANTI-ALIASING

AO

D0-D6

CS

WR

INB

DAC

5

6

7

8

9

Pin Configurations

continued at end

of data sheet

.

MAX270

10

µP OR PIN-STRAP CONTROL

PDIP/SO(W)

For pricing, delivery, and ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

19-3701; Rev 2; 1/12

MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

ABSOLUTE MAXIMUM RATINGS

V+ to V- .................................................................-0.3V to +17V

V+ to GND ............................................................-0.3V to +8.5V

V- to GND .............................................................. -0.3V to -8.5V

Input Voltage to GND, Any Input Pin ....(V- - 0.3V) to (V+ + 0.3V)

Duration of Output Short Circuit to GND...................Continuous

Continuous Power Dissipation (T

A

= +70NC)

MAX270

PDIP (derate 11.1mW/NC above +70NC) .....................889mW

SO (W) (derate 10mW/NC above +70NC ......................800mW

MAX271

PDIP (derate 13.3mW/NC above +70NC) ...................1067mW

SO (W) (derate 11.7mW/NC above +70NC) .................. 941mw

Operating Temperature Ranges:

MAX27_C_ _....................................................... 0NC to +70NC

MAX27_E_ _ .................................................... -40NC to +85NC

Storage Temperature Range............................ -65NC to +165NC

Lead Temperature (soldering, 10s) ................................+300NC

Soldering Temperature (reflow)

Lead(Pb)-free ...............................................................+260NC

Containing lead(Pb) .....................................................+240NC

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V+ = +5V, V- = -5V; T

A

= +25NC, unless otherwise noted.)

PARAMETER

FILTER CHARACTERISTICS

Operating Frequency Range

Programmed Cutoff Frequency (f

C

)

Range

Programmed Cutoff Frequency

Error

f

C

code = 53 (2.536kHz typ)

f

C

code = 127 (25kHz typ)

f

C

code = 0 (1kHz typ),

T

A

= T

MIN

to T

MAX

f

C

code = 127 (25kHz typ),

T

A

= T

MIN

to T

MAX

f

C

code = 0 (1kHz typ)

f

C

code = 127 (25kHz typ)

f

C

code = 0

(1kHz typ)

f

C

code = 127

(25kHz typ)

0.15

12

FV

RMS

38

f

IN

= 1kHz

f

IN

= 8kHz

f

IN

= 25kHz

f

IN

= 200kHz

-6

-34

0.15

dB

-3.6

(Note 1)

2

1 to 25

Q2.9

Q9.5

-2.4

-33

-0.5

dB

MHz

kHz

%

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Filter Gain

Maximum Gain (Peaking)

Wideband Noise

50Hz to 50kHz bandwidth

DC CHARACTERISTICS

DC Output Signal Swing

OUTA, OUTB, OP OUT (MAX270)

OUTA, OUTB, T/H OUT (MAX271)

Offset Voltage at Outputs

OUTA, OUTB, OP OUT (MAX270)

OUTA, OUTB, T/H OUT (MAX271)

DC Input Leakage Current

INA, INB (MAX270)

INA, INB (MAX271)

T

A

= T

MIN

to T

MAX

R

LOAD

= 5kI, T

A

= T

MIN

to T

MAX

-3

+3

V

-2

+2

mV

-1

+1

FA

2

Maxim Integrated

MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

ELECTRICAL CHARACTERISTICS (continued)

(V+ = +5V, V- = -5V; T

A

= +25NC, unless otherwise noted.)

PARAMETER

SYMBOL

DYNAMIC FILTER CHARACTERISTICS (MAX270)

Total Harmonic Distortion

Signal Noise Plus Distortion

Spurious-Free Dynamic Range

Slew Rate

Bandwidth

TRACK AND HOLD (MAX271)

Hold Settling Time

Acquisition Time

Hold Step

Droop Rate

Offset Voltage at T/H OUT

T/H OUT Disabled Output Leakage

Current

Total Harmonic Distortion

Spurious-Free Dynamic Range

DIGITAL INPUTS

Digital Input High Voltage

Digital Input Low Voltage

Digital Input Current

POWER REQUIREMENTS

Supply Voltage Range

Supply Current

Shutdown Supply Current

Power-Supply Rejection Ratio at

1kHz

Note 1:

Note 2:

Note 3:

Note 4:

Note 5:

Note 6:

Note 7:

Note 8:

PSRR

T

A

= T

MIN

to T

MAX

(Note 9)

T

A

= T

MIN

to T

MAX

(Note 10)

f

C

code = 0 (1kHz typ), V

+

= 5V

DC

+

10mV

P-P

at 1kHz

30

Q2.375

to

Q8

6.5

15

V

mA

FA

dB

T

A

= T

MIN

to T

MAX

, digital input held at

Q5V,

includes MODE (MAX271)(Note 8)

-1

T

A

= T

MIN

to T

MAX

(Note 8)

2.4

0.8

+1

V

FA

THD

SFDR

T

A

= T

MIN

to T

MAX

Includes filter offset

T

A

= T

MIN

to T

MAX

, V

T/H

= 0V (Track Mode)

f

C

code = 44 (2.01kHz typ), V

IN

= 3.5V

P-P

at

390.625Hz, sampling rate = 50kHz

(Notes 2, 6, 7)

-6

-10

To 0.1% (Note 4)

To 0.1% (Note 5)

500

1.8

1

30

+6

+10

-70

70

dB

ns

Fs

mV

FV/Fs

mV

FA

THD

SINAD

SFDR

f

C

code = 44 (2.01kHz typ), V

IN

= 3.5V

P-P

at

390.625Hz (Notes 2 and 3)

-70

73

70

1.2

2

V/Fs

MHz

dB

CONDITIONS

MIN

TYP

MAX

UNITS

UNCOMMITTED AMPLIFIER (MAX270)

All internal amplifiers limited to 2MHz bandwidth.

Only filter A tested for these parameters.

Spurious-Free Dynamic Range is the ratio of the fundamental to the largest of any harmonic or noise spur in dB.

Includes T/H propagation delays. With 5kω, parallel 100pF load.

±2V input step settling 0.1% with 5kω parallel 100pF load.

T/H

pin toggled at sampling rate, 50% duty cycle.

THD and SFDR specifications for T/H include contributions from filter.

Digital pins include

SHDN, WR, CS,

A0, D0–D6 (MAX270) and

SHDN,

T/H, A/B,

WR,

T/H EN,

CS,

A0, A1, D0–D6,

T/H

(MAX271).

Note 9:

Input of uncommitted op amp disconnected with a 5kω feedback resistor from input to output.

Note 10:

WR, CS,

A0, D0–D6 held at +5V; V

SHDN

= 0V (MAX270).

WR, CS,

A0, A1, D0–D6,

T/H,

T/H, A/B, T/H, MODE held at

+5V; V

SHDN

= 0V (MAX271).

Maxim Integrated

3

MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

TIMING CHARACTERISTICS (Figure 2)

(V+ = +5V, V- = -5V; T

A

= +25NC, unless otherwise noted.)

PARAMETER

CS

to

WR

Setup

CS

to

WR

Hold

WR

Pulse Width

Address-Setup Time

Address-Hold Time

Data-Setup Time

Data-Hold time

SYMBOL

t

WS

t

WH

t

SV

t

AS

t

AH

t

DS

t

DH

100

30

10

30

10

CONDITIONS

MIN

TYP

MAX

0

UNITS

ns

Note 11:

All input control signals specified with t

r

= t

f

= 5ns (10% to 90% of +5V) and timed from a +1.6V voltage level.

Typical Operating Characteristics

FILTER GAIN vs. FREQUENCY

MAX270 toc01

0

FILTER GAIN vs. FREQUENCY

(NORMALIZED TO CUTOFF FREQUENCY)

MAX270 toc02

PASSBAND FILTER GAIN

vs. FREQUENCY

0

MAX270 toc03

0

0.5

-20

GAIN (dB)

-20

GAIN (dB)

-1

T

A

= +125˚C

T

A

= +25˚C

T

A

= -55˚C

-40

-60

V+ = +5V

V- = -5V

f

C

CODE = 127 (25kHz TYP)

T

A

= +25˚C

-2

-60

-80

1k

10k

f

IN

(Hz)

100k

1M

V+ = +5V

V- = -5V

f

C

CODE = 0-127 (1-25kHz TYP)

T

A

= +25˚C

0.1

1.0

f

IN/

f

C

10

100

V+ = +5V

V- = -5V

f

C

CODE = 0 (1kHz TYP)

-3

1

10

f

IN/

f

C

100

1k

-80

PASSBAND FILTER GAIN

vs. FREQUENCY

MAX270 toc04

PASSBAND FILTER GAIN vs. FREQUENCY

(NORMALIZED TO CUTOFF FREQUENCY)

MAX270 toc05

FILTER PHASE SHIFT vs. FREQUENCY

(NORMALIZED TO CUTOFF FREQUENCY)

MAX270 toc06

0.5

0

+0.5

0

GAIN (dB)

-1

V+ = +5V

V- = -5V

f

C

CODE = 0-127 (1-25kHz TYP)

T

A

= +25˚C

PHASE SHIFT (DEGREES)

T

A

= +125˚C

T

A

= +25˚C

T

A

= -55˚C

-45

-90

-2

V+ = +5V

V- = -5V

f

C

CODE = 127 (25kHz TYP)

-2

-135

V+ = +5V

V- = -5V

f

C

CODE = 0-127

(1-25kHz TYP)

T

A

= +25˚C

-3

25

100

f

IN

(Hz)

1k

10k

25k

-3

-180

0.001

0.01

f

IN/

f

C

0.1

1.0

0.01

0.1

f

IN/

f

C

1.0

10

4

Maxim Integrated

MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

Typical Operating Characteristics (continued)

CASCADED FILTER GAIN vs. FREQUENCY

(NORMALIZED TO CUTOFF FREQUENCY)

MAX270 toc07

CASCADED FILTER GAIN vs. FREQUENCY

(NORMALIZED TO CUTOFF FREQUENCY)

MAX270 toc08

FILTER HARMONIC DISTORTION

MAX270 toc09

+0.5

-0.5

-1.5

GAIN (dB)

0

-20

-40

-20

GAIN (dB)

-2.5

-3.5

-4.5

-5.5

-6.5

-7.5

0.01

V+ = +5V

V- = -5V

f

C

(FILTER A) = f

C

(FILTER B) =

0-127 (1-25kHz TYP)

FILTERS A AND B CASCADED

FIGURE 5

T

A

= +25˚C

0.1

f

IN/

f

C

1.0

-40

-60

-80

0.01

V+ = +5V

V- = -5V

f

C

(FILTER A) = f

C

(FILTER B) =

0-127 (1-25kHz TYP)

FILTERS A AND B CASCADED

FIGURE 5

T

A

= +25˚C

1.0

f

IN/

f

C

10

-60

-80

-100

-120

0

1k

V+ = +5V

V- = -5V

f

C

CODE = 44 (2.01kHz TYP)

f

TEST

= 390.625Hz

T

A

= +25˚C

V

IN

= 3.5V

P-P

2k

F (Hz)

3k

4k

FILTER TOTAL HARMONIC DISTORTION

PLUS NOISE vs.INPUT FREQUENCY

MAX270 toc10

FILTER TOTAL HARMONIC DISTORTION

PLUS NOISE vs. INPUT AMPLITUDE

MAX270 toc11

MAX271 FILTER PLUS TRACK-AND-HOLD

SPURIOUS-FREE DYNAMIC RANGE

vs. INPUT FREQUENCY

f

IN

(Hz)

195

781

f

C

CODE

0

72

105

124

f

C

(Hz)

(TYP)

1k

4.01k

8.08k

19.4k

SFDR

(dB)

73.5

69.5

66

61.5

MAX270 toc12

f

IN

(Hz)

190

390

1367

4875

f

C

CODE

0

44

100

127

f

C

(Hz)

(TYP)

1k

2.01k

7.01k

25k

THD PLUS

NOISE

(TYP)

-78

-73

-67

-60

-65

-70

-75

GAIN (dB)

V+ = +5V

V- = -5V

f

IN

= 390.625Hz

f

C

CODE = 44 (2.01kHz TYP)

T

A

= +25˚C

1562.5

-80

-66

-85

0.2

1.0

V

IN

(V

P-P)

8.0

3906

V+ = 5V, V- = -5V; V

IN

= 3.5V

P-P

; T

A

= +25˚C

V+ = 5V, V- = -5V; V

IN

= 3.5V

P-P

;

T/H SWITCHED AT 50kHz, 50% DUTY CYCLE; T

A

= +25˚C

MAX271 FILTER PLUS TRACK-AND-HOLD

SPURIOUS-FREE DYNAMIC RANGE

vs. INPUT AMPLITUDE

MAX270 toc13

MAX271 FILTER PLUS TRACK-AND-HOLD

SPURIOUS-FREE DYNAMIC RANGE

vs. SAMPLING FREQUENCY

f

SAMPLE

(Hz)

f

IN

(Hz)

f

C

CODE

f

C

(Hz)

SFDR

(dB)

MAX270 toc14

55

SFDR (dB)

65

V+ = +5V

V- = -5V

f

IN

= 390Hz

f

C

CODE = 44 (2.01kHz TYP)

T

A

= +25˚C

100k

781

72

4.01k

72

200k

75

1562

105

8.08k

72

500k

-85

0.5

1.0

8.0

3906

124

19.4k

64

V

IN

(V

P-P)

V+ = 5V, V- = -5V; V

IN

= 3.5V

P-P

;

T/H SWITCHED AT 50kHz, 50% DUTY CYCLE; T

A

= +25˚C

Maxim Integrated

5

参数名称	属性值
状态	ACTIVE
有源滤波器类型	CONTINUOUS TIME FILTER

	MAX271	MAX270
描述	CONTINUOUS TIME FILTER	CONTINUOUS TIME FILTER
状态	ACTIVE	ACTIVE
有源滤波器类型	CONTINUOUS TIME FILTER	CONTINUOUS TIME FILTER

MAX271

MAX271概述

MAX271规格参数

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