MAXIM MAX7401, MAX7405 User Manual

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General Description

The MAX7401/MAX7405 8th-order, lowpass, Bessel,
switched-capacitor filters (SCFs) operate from a single
+5V (MAX7401) or +3V (MAX7405) supply. These
devices draw only 2mA of supply current and allow cor­ner frequencies from 1Hz to 5kHz, making them ideal
for low-power post-DAC filtering and anti-aliasing appli­cations. They feature a shutdown mode that reduces
supply current to 0.2µA.

Two clocking options are available on these devices:
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 MAX7401/MAX7405 Bessel filters provide low over­shoot and fast settling. Their fixed response simplifies
the design task to selecting a clock frequency.

Applications

ADC Anti-Aliasing CT2 Base Stations
Post-DAC Filtering Speech Processing
Air-Bag Electronics

Features

♦ 8th-Order, Lowpass Bessel Filters
♦ Low Noise and Distortion: -82dB THD + Noise
♦ Clock-Tunable Corner Frequency (1Hz to 5kHz)
♦ 100:1 Clock-to-Corner Ratio
♦ Single-Supply Operation

+5V (MAX7401)
+3V (MAX7405)

♦ Low Power

2mA (Operating Mode)

0.2µA (Shutdown Mode)

♦ Available in 8-Pin SO/DIP Packages
♦ Low Output Offset: ±5mV

MAX7401/MAX7405

8th-Order, Lowpass, Bessel,

Switched-Capacitor Filters

________________________________________________________________

Maxim Integrated Products

1

OS

OUTV

DD

1
2

87CLK

SHDNIN

GND

COM

SO/DIP

TOP VIEW

3

4

6

5

MAX7401
MAX7405

V

DD

IN

CLK

OUT

GND

INPUT

0.1µF

0.1µF

CLOCK

SHDN

OUTPUT

V

SUPPLY

COM

OS

MAX7401
MAX7405

Typical Operating Circuit

19-4788; Rev 1; 6/99

Pin Configuration

Ordering Information

PART

MAX7401CPA
MAX7401ESA
MAX7401EPA -40°C to +85°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

8 Plastic DIP
8 SO

8 Plastic DIP
MAX7405CSA
MAX7405CPA
MAX7405ESA
MAX7405EPA -40°C to +85°C

-40°C to +85°C

0°C to +70°C

0°C to +70°C 8 SO

8 Plastic DIP

8 SO

8 Plastic DIP

MAX7401CSA

0°C to +70°C 8 SO

MAX7401/MAX7405

8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS—MAX7401

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

SHDN = VDD, f

CLK

= 100kHz, 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

MAX7401..............................................................-0.3V to +6V

MAX7405..............................................................-0.3V to +4V

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

DD

+ 0.3V)

SHDN........................................................................-0.3V to +6V

OUT Short-Circuit Duration...................................................1sec

Continuous Power Dissipation (T

A

= +70°C)

8-Pin SO (derate 5.88mW/°C above +70°C)................471mW

8-Pin DIP (derate 9.09mW/°C above +70°C)...............727mW

Operating Temperature Ranges

MAX740 _C_A ....................................................0°C to +70°C

MAX740 _E_A .................................................-40°C to +85°C

Storage Temperature Range.............................-65°C to +150°C

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

C

OSC

= 1000pF (Note 4)

VOS= 0 to (VDD- 1V) (Note 3)

SHDN = GND, V

COM

= 0 to V

DD

(Note 1)

Input, COM externally driven

fIN= 200Hz, VIN= 4Vp-p,
measurement bandwidth = 22kHz

VIN= V

COM

= V

DD

/ 2

V

COM

= V

DD

/ 2 (Note 2)

CONDITIONS

29 38 48f

OSC

Internal Oscillator Frequency

±0.1 ±10Input Leakage Current at OS

±0.1 ±10Input Leakage Current at COM

50 500C

L

10 1R

L

Resistive Output Load Drive

10Clock Feedthrough

75 125R

COM

Input Resistance at COM

100:1f

CLK

/f

C

Clock-to-Corner Ratio

0.001 to 5f

C

Corner Frequency

V

COM

1A

OS

OS Voltage Gain to OUT

-82THD+N

Total Harmonic Distortion
plus Noise

10Clock-to-Corner Tempco

0.25 V

DD

-

0.25Output Voltage Range

±5 ±25V

OFFSET

Output Offset Voltage

-0.1 0.15 0.3

DC Insertion Gain with
Output Offset Removed

MIN TYP MAX

SYMBOLPARAMETER

V

CLK

= 0 or 5V

0.5V

IL

Clock Input Low

V

DD

- 0.5V

IH

Clock Input High

±15 ±30I

CLK

Clock Input Current

V

V

µA

kHz

µA

µA

pF

kΩ

mVp-p

kΩ

V

V/V

dB

dB

mV

V

ppm/°C

kHz

UNITS

Maximum Capacitive Load at
OUT

COM Voltage Range

V

DD

/ 2

V

DD

/ 2

V

DD

/ 2

- 0.5 + 0.5

V

COM

±0.1V

OS

Input Voltage Range at OS V

V

DD

/ 2

V

DD

/ 2

V

DD

/ 2

- 0.2 + 0.2

FILTER CHARACTERISTICS

CLOCK

Output, COM internally biased

MAX7401/MAX7405

8th-Order, Lowpass, Bessel,

Switched-Capacitor Filters

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS—MAX7401 (continued)

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

DD

, f

CLK

= 100kHz, TA= T

MIN

to T

MAX

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

ELECTRICAL CHARACTERISTICS—MAX7405

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

DD

, f

CLK

= 100kHz, TA= T

MIN

to T

MAX

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

CONDITIONS

MIN TYP MAX

SYMBOLPARAMETER

Measured at DC

SHDN = GND, CLK driven from 0 to V

DD

Operating mode, no load, IN = OS = COM

0.5V

SDL

SHDN Input Low

V

DD

- 0.5V

SDH

SHDN Input High

60PSRRPower-Supply Rejection Ratio

0.2 1I

SHDN

Shutdown Current

2 3.5Supply Current I

DD

4.5 5.5V

DD

Supply Voltage

V

V

dB

µA

mA

V

UNITS

SHDN Input Leakage Current V

SHDN

= 0 to V

DD

±0.1 ±10 µA

POWER REQUIREMENTS

SHUTDOWN

µA±0.1 ±10VOS= 0 to (V

DD

- 1V) (Note 3)Input Leakage Current at OS

µA±0.1 ±10

SHDN = GND, V

COM

= 0 to V

DD

Input Leakage Current at COM

Maximum Capacitive
Load at OUT

UNITS

kHz

ppm/°C

V

mV
dB

dB

V/V

V

mVp-p

kΩ

pF

PARAMETER SYMBOL

MIN TYP MAX

DC Insertion Gain with
Output Offset Removed

-0.1 0.03 0.3

Output Offset Voltage V

OFFSET

±5 ±25

Output Voltage Range 0.25 V

DD

-

0.25

Clock-to-Corner Tempco 10

Total Harmonic Distortion
plus Noise

THD+N -84

OS Voltage Gain to OUT A

OS

1

Corner Frequency f

C

0.001 to 5

Clock-to-Corner Ratio f

CLK

/

f

C

100:1

COM Voltage Range V

COM

V

DD

/ 2

V

DD

/ 2

V

DD

/ 2

- 0.1 + 0.1

Clock Feedthrough 10
Resistance Output Load Drive R

L

10 1

C

L

50 500

CONDITIONS

V

COM

= V

DD

/ 2 (Note 2)

VIN= V

COM

= V

DD

/ 2

fIN= 200Hz, VIN= 2.5Vp-p,
measurement bandwidth = 22kHz

(Note 1)

kΩInput Resistance at COM R

COM

75 125

COM internally biased or externally driven

VInput Voltage Range at OS V

OS

V

COM

±0.1

FILTER CHARACTERISTICS

MAX7401/MAX7405

8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters

4 _______________________________________________________________________________________

C

OSC

= 1000pF (Note 4)

CONDITIONS

26 34 43f

OSC

Internal Oscillator Frequency

MIN TYP MAX

SYMBOLPARAMETER

Measured at DC

SHDN = GND, CLK driven from 0 to V

DD

Operating mode, no load, IN = OS = COM

V

CLK

= 0 or 3V

0.5V

SDL

SHDN Input Low

V

DD

- 0.5V

SDH

SHDN Input High

60PSRRPower-Supply Rejection Ratio

0.2 1I

SHDN

Shutdown Current

2 3.5

2.7 3.6V

DD

Supply Voltage

0.5V

IL

Clock Input Low

V

DD

- 0.5V

IH

Clock Input High

±15 ±30I

CLK

Clock Input Current

V

V

dB

µA

V

V

V

µA

kHz

UNITS

SHDN Input Leakage Current

V

SHDN

= 0 to V

DD

±0.1 ±10 µA

FILTER CHARACTERISTICS—MAX7401/MAX7405

(VDD= +5V for MAX7401, VDD= +3V for MAX7405; filter output measured at OUT; 10kΩ || 50pF load to GND at OUT; SHDN = VDD;
V

COM = VOS = VDD

/2; f

CLK

= 100kHz; TA = T

MIN

to T

MAX

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

Note 1: The maximum f

C

is defined as the clock frequency, f

CLK

= 100 · fC,at which the peak SINAD drops to 68dB with a sinu-

soidal input at 0.2f

C

.

Note 2: DC insertion gain is defined as ∆V

OUT

/ ∆VIN.

Note 3: OS voltages above V

DD

- 1V saturate the input and result in a 75µA typical input leakage current.

Note 4: For MAX7401, f

OSC

(kHz) ≅ 38 · 103/ C

OSC

(pF). For MAX7405, f

OSC

(kHz) ≅ 34 · 103/ C

OSC

(pF).

CLOCK

POWER REQUIREMENTS

SHUTDOWN

CONDITIONS UNITS

MIN TYP MAX

PARAMETER

mAI

DD

Supply Current

ELECTRICAL CHARACTERISTICS—MAX7405 (continued)

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

DD

, f

CLK

= 100kHz, TA= T

MIN

to T

MAX

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

fIN= 0.5f

C

-1.0 -0.8 -0.6

fIN= f

C

-3.3 -3.0 -2.7

fIN= 3f

C

-33 -29

fIN= 6f

C

dB

-79 -74

Insertion Gain Relative to
DC Gain