Rainbow Electronics MAX7425 User Manual

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General Description

The MAX7418–MAX7425 5th-order, low-pass, switchedcapacitor filters (SCFs) operate from a single +5V (MAX7418–MAX7421) or +3V (MAX7422–MAX7425) supply. These devices draw only 3mA of supply current and allow corner frequencies from 1Hz to 45kHz, making them ideal for low-power post-DAC filtering and antialiasing applications. They feature a shutdown mode that reduces supply current to 0.2µA.

Two clocking options are available: self-clocking (through the use of an external capacitor), or external clocking for tighter corner-frequency control. An offset adjust pin allows for adjustment of the DC output level.

The MAX7418/MAX7422 deliver 53dB of stopband rejection and a sharp rolloff with a 1.6 transition ratio. The MAX7421/MAX7425 achieve a sharper rolloff with a

1.25 transition ratio while still providing 37dB of stopband rejection. The MAX7419/MAX7423 Bessel filters provide low overshoot and fast settling, and the MAX7420/MAX7424 Butterworth filters provide a maximally flat passband response. Their fixed response simplifies the design task of selecting a clock frequency.

Applications

ADC Anti-Aliasing CT2 Base Stations

DAC Postfiltering Speech Processing

Features

♦ 5th-Order, Lowpass Filters

Elliptic Response (MAX7418/MAX7421/ MAX7422/MAX7425) Bessel Response (MAX7419/MAX7423) Butterworth Response (MAX7420/MAX7424)

♦ Clock-Turnable Corner Frequency (1Hz to 45kHz)

♦ Single-Supply Operation

+5V (MAX7418–MAX7421) +3V (MAX7422–MAX7425)

♦ Low Power

3mA (Operating Mode)

0.2µA (Shutdown Mode)

♦ Available in 8-Pin µMAX Package

♦ Low Output Offset: ±4mV

MAX7418–MAX7425

5th-Order, Lowpass,

Switched-Capacitor Filters

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-1821; Rev 0; 11/00

Pin Configuration

Ordering Information

Selector Guide

PART

MAX7418EUA -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

8 µMAX

Selector Guide continued at end of data sheet.

Ordering Information continued at end of data sheet.

MAX7418CUA

0°C to +70°C 8 µMAX

MAX7419CUA

0°C to +70°C 8 µMAX

MAX7419EUA -40°C to +85°C 8 µMAX

MAX7420CUA

0°C to +70°C 8 µMAX

MAX7420EUA -40°C to +85°C 8 µMAX

MAX7421CUA

0°C to +70°C 8 µMAX

MAX7421EUA -40°C to +85°C 8 µMAX

PART FILTER RESPONSE

OPERATING

VOLTAGE (V)

MAX7418 r = 1.6 +5

MAX7419 Bessel +5

MAX7420 Butterworth +5

MAX7421 r = 1.25 +5

87CLK

SHDNIN

OUTV

TOP VIEW

COM

GND

MAX7418–

MAX7425

SUPPLY

0.1µF

SHDN

INPUT

CLOCK

MAX7418–

MAX7425

CLK

GND

OUT

COM

OUTPUT

0.1µF

µMAX

MAX7418–MAX7425

5th-Order, Lowpass, Switched-Capacitor Filters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS—MAX7418–MAX7421

(VDD= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = V

, f

CLK

= 2.2MHz, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

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.

VDDto GND..............................................................-0.3V to +6V

IN, OUT, COM, OS, CLK, SHDN ................-0.3V to (V

+ 0.3V)

OUT Short-Circuit Duration.......................................................1s

Continuous Power Dissipation (T

= +70°C)

8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW

Operating Temperature Ranges

MAX74 _ _C_A ...................................................0°C to +70°C

MAX74 _ _E_A ................................................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +160°C

Lead Temperature (soldering, 10s) .................................+300°C

CLOCK

FILTER CHARACTERISTICS

86 110 135

±50 ±75

MAX7419/MAX7420

MAX7418/MAX7421

MAX7419/MAX7420

MAX7418/MAX7421

-0.2 0 +0.2MAX7419/MAX7420

MAX7418/MAX7421

0.001 to 30VIN= 4Vp-p (Note 1)

Input Voltage Range at OS

2.0 2.5 3.0

COM Voltage Range

Maximum Capacitive Output Load Drive

UNITS

kHz

ppm/°C

V/V

kΩ

mVp-p

kΩ

µA

kHz

µA

Clock Output Current (Internal Oscillator Mode)

CLK

±40 ±60

Clock Input High V

4.5

Clock Input Low V

0.5

CLK

= 0 or 5V

PARAMETER SYMBOL MIN TYP MAX

DC Insertion Gain with Output Offset Removed

0 0.2 0.4

Output Offset Voltage V

OFFSET

±4 ±25

Output Voltage Range 0.25 V

0.25

Clock-to-Corner Tempco 10

Offset Voltage Gain A

COM

Corner Frequency f

Clock-to-Corner Ratio f

CLK/fC

100:1

2.3 2.5 2.7

COM

±0.1

Input Resistance at COM R

COM

100 140

Clock Feedthrough 5

Resistive Output Load Drive R

10 1

50 500

Input Leakage Current at COM ±0.1 ±10

Input Leakage Current at OS ±0.1 ±10

Internal Oscillator Frequency f

OSC

68 87 106

CONDITIONS

Output, COM unconnected

COM

= V

/ 2

(Note 2)

VIN= V

COM

= V

/ 2

Input, OS externally driven

OS to OUT

Input, COM externally driven

SHDN = GND, V

COM

= 0 to V

VOS= 0 to V

OSC

= 1000pF

(Note 3)

-78MAX7419

MAX7418 -76

-78MAX7421

MAX7420

Total Harmonic Distortion plus Noise

THD+N

-67

fIN= 2kHz, VIN= 4Vp-p, measurement bandwidth = 80kHz

FILTER CHARACTERISTICS

CLOCK

MAX7418–MAX7425

5th-Order, Lowpass,

Switched-Capacitor Filters

_______________________________________________________________________________________ 3

Corner-Frequency Range

0.001 to 45

5th-Order, Lowpass,

Switched-Capacitor Filters

ELECTRICAL CHARACTERISTICS—MAX7418–MAX7421 (continued)

(VDD= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = V

, f

CLK

= 2.2MHz, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS—MAX7422–MAX7425

(VDD= +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = V

, f

CLK

= 2.2MHz, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

FILTER CHARACTERISTICS

0.001 to 45

MAX7423/MAX7424

MAX7422/MAX7425

-0.2 0 +0.2MAX7423/MAX7424

MAX7422/MAX7425

UNITS

kHz

ppm/°C

V/V

kΩ

mVp-p

kΩ

µA

PARAMETER SYMBOL MIN TYP MAX

DC Insertion Gain with Output Offset Removed

0 0.2 0.4

Output Offset Voltage V

OFFSET

±4 ±25

Output Voltage Range 0.25 VDD- 0.25

Clock-to-Corner Tempco 10

Offset Voltage Gain A

COM

Clock-to-Corner Ratio f

CLK/fC

100:1

Input Voltage Range at OS V

COM

±0.1

Input Resistance at COM R

COM

100 140

Clock Feedthrough 3

Resistive Output Load Drive R

10 1

50 500

Input Leakage Current at COM ±0.1 ±10

Input Leakage Current at OS ±0.1 ±10

CONDITIONS

COM

= V

/ 2

(Note 2)

VIN= V

COM

= V

/ 2

Measured with respect to COM

OS to OUT

VIN= 2.5Vp-p (Note 1)

SHDN = GND, V

COM

= 0 to V

VOS= 0 to V

Maximum Capacitive Load at OUT

-81MAX7423

MAX7422 -80

-80MAX7425

MAX7424

Total Harmonic Distortion plus Noise

THD+N

-70

fIN= 2kHz, VIN= 2.5Vp-p, measurement bandwidth = 80kHz

1.4 1.5 1.6Input, COM externally driven VCOM Voltage Range

1.4 1.5 1.6Output, COM internally driven

FILTER CHARACTERISTICS

SHUTDOWN

POWER REQUIREMENTS

3.4 4.1MAX7419/MAX7420

MAX7418/MAX7421

µA±0.2 ±10

SHDN

= 0 to V

SHDN Input Leakage Current

UNITS

µA

Supply Voltage V

4.5 5.5

Supply Current

2.9 3.6

Shutdown Current I

SHDN

0.2 1

Power-Supply Rejection Ratio PSRR 70

SHDN Input High

SDH

4.5

SHDN Input Low

SDL

0.5

Operating mode, no load

SHDN = GND

IN = COM (Note 4)

PARAMETER SYMBOL MIN TYP MAXCONDITIONS

MAX7418–MAX7425

5th-Order, Lowpass, Switched-Capacitor Filters

4 _______________________________________________________________________________________

FILTER CHARACTERISTICS

(VDD= +5V for MAX7418–MAX7421, VDD= +3V for MAX7422–MAX7425 filter output measured at OUT, 10kΩ

|| 50pF load to GND at

OUT, SHDN = V

, f

CLK

= 2.2MHz, TA = T

MIN

to T

MAX

, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS—MAX7422–MAX7425 (continued)

(VDD= +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = V

, f

CLK

= 2.2MHz, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

CONDITIONS MIN TYP MAXSYMBOLPARAMETER

Measured at DC

SHDN = GND

0.5V

SDL

SHDN Input Low

2.5V

SDH

SHDN Input High

70PSRRPower-Supply Rejection Ratio

0.2 1I

SHDN

Shutdown Current

2.6 3.4

2.7 3.6V

Supply Voltage

µA

UNITS

SHDN Input Leakage Current

SHDN

= 0 to V

±0.2 ±10 µA

OSC

= 1000pF

(Note 3)

68 87 106

OSC

Internal Oscillator Frequency kHz

0.5V

Clock Input Low V

2.5V

Clock Input High V

68 87 106

CLK

Clock Output Current (Internal Oscillator Mode)

kHz

MAX7422/MAX7425

MAX7423/MAX7424 86 110 135

MAX7422/MAX7425

MAX7423/MAX7424 86 110 135

Operating mode, no load

3.0 3.8

Supply Current I

MAX7422/MAX7425

MAX7423/MAX7424

MIN TYP MAXCONDITIONSPARAMETER

-0.4 ±0.2 0.4fIN= 0.38f

UNITS

Insertion Gain with DC Gain Error Removed (Note 4)

fIN= 0.68f

-0.4 ±0.2 0.4

-0.4 ±0.2 0.4fIN= 0.87f

-36 -33fIN= 1.25f

fIN= 0.97f

-0.4 ±0.2 0.4

-0.7 ±0.2 0.2fIN= f

fIN= 1.43f

-37.2 -35

-1 -0.74fIN= 0.5f

fIN= 3.25f

-37.2 -35

Insertion Gain Relative to DC Gain

fIN= f

-3.6 -3.0 -2.4

fIN= 4f

-41.0 -35

-67 -60fIN= 7f

CLOCK

POWER REQUIREMENTS

ELLIPTIC, r = 1.2—MAX7421/MAX7425

BESSEL FILTERS—MAX7419/MAX7423

SHUTDOWN

MAX7418–MAX7425

5th-Order, Lowpass,

Switched-Capacitor Filters

_______________________________________________________________________________________ 5

Note 1: The maximum fCis defined as the clock frequency f

CLK

= 100 x fCat which the peak S / (THD+N) drops to 68dB with a

sinusoidal input at 0.2f

. Maximum fC increases as VINsignal amplitude decreases.

Note 2: DC insertion gain is defined as ∆V

OUT

/ ∆VIN.

Note 3: MAX7418/MAX7421/MAX7422/MAX7425: f

OSC

(kHz) ≅ 87x103/ C

OSC

(pF).

MAX7419/MAX7420/MAX7423/MAX7424: f

OSC

(kHz) ≅ 110x103/ C

OSC

(pF).

Note 4: PSRR is the change in output voltage from a V

of 4.5V and a VDDof 5.5V.

-70 -65fIN= 5f

-47.5 -43

-3.6 -3.0 -2.4fIN= f

fIN= 3f

-0.3 0

fIN= 0.5f

PARAMETER MIN TYP MAX UNITSCONDITIONS

BUTTERWORTH FILTERS—MAX7420/MAX7424BUTTERWORTH FILTERS—MAX7420/MAX7424

FILTER CHARACTERISTICS

(VDD= +5V for MAX7418–MAX7421, VDD= +3V for MAX7422–MAX7425 filter output measured at OUT, 10kΩ

|| 50pF load to GND at

OUT, SHDN = V

, f

CLK

= 2.2MHz, TA = T

MIN

to T

MAX

, unless otherwise noted.)

__________________________________________Typical Operating Characteristics

(VDD= +5V for MAX7418–MAX7421, VDD= +3V for MAX7422–MAX7425, f

CLK

= 2.2MHz, SHDN = VDD, V

COM

= VOS= VDD/ 2,

= +25°C, unless otherwise noted.)

-90

-60

-70

-80

-50

-40

-30

-20

-10

04020 60 80 100

MAX7418/MAX7422

FREQUENCY RESPONSE (ELLIPTIC, r = 1.6)

MAX7418 toc01

INPUT FREQUENCY (kHz)

GAIN (dB)

-60

-40

-50

-20

-30

-10

04020 60 80 100

MAX7419/MAX7423

FREQUENCY RESPONSE (BESSEL)

MAX7418 toc02

INPUT FREQUENCY (kHz)

GAIN (dB)

-80

-60

-70

-30

-40

-50

-10

-20

04020 60 80 100

MAX7420/MAX7424

FREQUENCY RESPONSE (BUTTERWORTH)

MAX7418 toc03

INPUT FREQUENCY (kHz)

GAIN (dB)

Insertion Gain Relative to DC Gain

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