19-1768; Rev 0; 7/00
Dual Universal Switched-Capacitor Filters
General Description
The MAX7490/MAX7491 consist of two identical low-
power, low-voltage, wide dynamic range, Rail-to-Rail
®
,
2nd-order switched-capacitor building blocks. Each of
the two filter sections, together with two to four external
resistors, can generate all standard 2nd-order func-
tions: bandpass, lowpass, highpass, and notch (band
reject). Three of these functions are simultaneously
available. Fourth-order filters can be obtained by cas-
cading the two 2nd-order filter sections. Similarly, high-
er order filters can easily be created by cascading
multiple MAX7490/MAX7491s.
Two clocking options are available: self-clocking
(through the use of an external capacitor) or external
clocking for tighter cutoff frequency control. The clock-
to-center frequency ratio is 100:1. Sampling is done at
twice the clock frequency, further separating the cutoff
frequency and Nyquist frequency.
The MAX7490/MAX7491 have an internal rail splitter
that establishes a precise common voltage needed for
single-supply operation. The MAX7490 operates from a
single +5V supply and the MAX7491 operates from a
single +3V supply. Both devices feature a low-power
shutdown mode and come in a 16-pin QSOP package.
Features
o
Dual 2nd-Order Filter in a 16-Pin QSOP Package
o
High Accuracy
Q Accuracy: ±0.2%
Clock-to-Center Frequency Error: ±0.2%
o
Rail-to-Rail Input and Output Operation
o
Single-Supply Operation: +5V (MAX7490)
or +3V (MAX7491)
o
Internal or External Clock
o
Highpass, Lowpass, Bandpass, and Notch Filters
o
Clock-to-Center Frequency Ratio of 100:1
o
Internal Sampling-to-Center Frequency Ratio
of 200:1
o
Center Frequency up to 40kHz
o
Easily Cascaded for Multipole Filters
o
Low-Power Shutdown: <1µA Supply Current
MAX7490/MAX7491
Ordering Information
PART
MAX7490CEE
MAX7490EEE
MAX7491CEE
MAX7491EEE
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
SUPPLY
PIN-
VOLTAGE
PACKAGE
(+V)
16 QSOP
16 QSOP
16 QSOP
16 QSOP
5
5
3
3
________________________Applications
Tunable Active Filters
Multipole Filters
ADC Anti-Aliasing
Post-DAC Filtering
Adaptive Filtering
Phase-Locked Loops (PLLs)
Set-Top Boxes
Pin Configuration
TOP VIEW
LPA 1
BPA 2
NA/HPA 3
16 LPB
15 BPB
14 NB/HPB
Typical Application Circuit appears at end of data sheet.
INVA 4
SA 5
SHDN 6
GND 7
V
DD
8
MAX7490
MAX7491
13 INVB
12 SB
11 COM
10 EXTCLK
9
CLK
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
QSOP
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Dual Universal Switched-Capacitor Filters
MAX7490/MAX7491
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND ..............................................................-0.3V to +6V
EXTCLK,
SHDN
to GND ...........................................-0.3V to +6V
INV_, LP_, BP_, N_/HP_, S_, COM,
CLK to GND............................................-0.3V to (V
DD
+ 0.3V)
Maximum Current into Any Pin ...........................................50mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.30mW/°C above +70°C).........667mW
Operating Temperature Range
MAX749_CEE ....................................................0°C to +70°C
MAX749_EEE ..................................................-40°C to +85°C
Die Temperature ..............................................................+150°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°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.
ELECTRICAL CHARACTERISTICS—MAX7490
(V
DD
= EXTCLK = +5V, f
CLK
= 625kHz, T
A
= T
MIN
to T
MAX
, 10kΩ || 50pF load to V
DD
/2 at LP_, BP_, and N_/HP_,
SHDN
= V
DD
, 0.1µF
from COM to GND, 50% duty-cycle clock input, COM = V
DD
/2. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
FILTER
Center Frequency Range
Clock-to-Center Frequency
Accuracy
Q Accuracy
f
O
Temperature Coefficient
Q Temperature Coefficient
DC Lowpass Gain Accuracy
V
OS1
DC Offset Voltage (Figure 8)
Crosstalk (Note 2)
V
OS2
V
OS3
Mode 1, R1 = R2 = 10kΩ
DC offset of input inverter
DC offset of 1st integrator
DC offset of 2nd integrator
f
IN
= 10kHz
Input: COM externally driven
COM Voltage Range
V
COM
Output: COM internally driven
Input Resistance at COM
Clock Feedthrough
Noise (Note 3)
Output Voltage Swing
Input Leakage Current at COM
CLOCK
Maximum Clock Frequency
Internal Oscillator Frequency
(Note 4)
Clock Input High
f
CLK
f
OSC
EXTCLK = GND, C
OSC
= 1000pF
EXTCLK = GND, C
OSC
= 100pF
V
DD
- 0.5
95
4
135
1.35
175
MHz
kHz
MHz
V
SHDN
= GND, V
COM
= 0 to V
DD
R
COM
Up to 5th harmonic of f
CLK
Mode 1, R1 = R2 = R3 =10kΩ, LP output,
Q=1
0.2
±0.1
V
DD
/2
- 0.5
V
DD
/2
- 0.2
140
f
O
f
CLK
/f
O
Mode 1
Mode 1, R1 = R3 = 50kΩ , R2 = 10kΩ,
Q = 5, deviation from 100:1
Mode 1, R1 = R3 = 50kΩ, R2 = 10kΩ, Q = 5
0.001 to
40
±0.2
±0.2
±1
±5
±0.1
±3
±4
±4
-60
V
DD
/2
V
DD
/2
250
200
60
V
DD
- 0.2
±10
V
DD
/2
+ 0.5
V
V
DD
/2
+ 0.2
325
kΩ
µV
RMS
µV
RMS
V
µA
±0.5
±12.5
±15
±30
dB
mV
±0.7
±2
kHz
%
%
ppm/°C
ppm/°C
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Dual Universal Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS—MAX7490 (continued)
(V
DD
= EXTCLK = +5V, f
CLK
= 625kHz, T
A
= T
MIN
to T
MAX
, 10kΩ || 50pF load to V
DD
/2 at LP_, BP_, and N_/HP_,
SHDN
= V
DD
, 0.1µF
from COM to GND, 50% duty-cycle clock input, COM = V
DD
/2. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Clock Input Low
Clock Duty Cycle
SHDN
AND EXTCLK
Input High
Input Low
Input Leakage Current
POWER REQUIREMENTS
Supply Voltage
Power-Supply Current
Shutdown Current
V
DD
I
DD
I
SHDN
No external load, mode 1, R1 = R3 = 50kΩ,
R2 = 10kΩ, Q = 5
SHDN
= GND
±18
R
L
≥
10kΩ, C
L
≤
50pF
GBW
SR
R
L
≥
10kΩ, C
L
≤
50pF
R
L
≥
10kΩ, C
L
≤
50pF
130
7
6.4
4.5
3.5
5.5
4.0
1
V
mA
µA
mA
dB
MHz
V/µs
V
IH
V
IL
V
INPUT
= 0 to V
DD
±0.4
V
DD
- 0.5
0.5
±10
V
V
µA
50
±
5
SYMBOL
CONDITIONS
MIN
TYP
MAX
0.5
UNITS
V
%
MAX7490/MAX7491
INTERNAL OP AMPS CHARACTERISTICS
Output Short-Circuit Current
DC Open-Loop Gain
Gain Bandwidth Product
Slew Rate
_______________________________________________________________________________________
3
Dual Universal Switched-Capacitor Filters
MAX7490/MAX7491
ELECTRICAL CHARACTERISTICS—MAX7491
(V
DD
= EXTCLK = +3V, f
CLK
= 625kHz, T
A
= T
MIN
to T
MAX
, 10kΩ || 50pF load to V
DD
/2 at LP_, BP_, and N_/HP_,
SHDN
= V
DD
, 0.1µF
from COM to GND, 50% duty-cycle clock input, COM = V
DD
/2. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
FILTER
Center Frequency Range
Clock-to-Center Frequency
Accuracy
Q Accuracy
f
O
Temperature Coefficient
Q Temperature Coefficient
DC Lowpass Gain Accuracy
DC Offset Voltage
(Figure 8)
Crosstalk (Note 2)
V
OS1
V
OS2
V
OS3
Mode 1, R1 = R2 = 10kΩ
DC offset of input inverter
DC offset of 1st integrator
DC offset of 2nd integrator
f
IN
= 10kHz
Input: COM externally driven
COM Voltage Range
V
COM
Output: COM internally driven
Input Resistance at COM
Clock Feedthrough
Noise (Note 3)
Output Voltage Swing
Input Leakage Current at COM
CLOCK
Maximum Clock Frequency
Internal Oscillator Frequency
(Note 4)
Clock Input High
Clock Input Low
Clock Duty Cycle
SHDN
AND EXTCLK
Input High
Input Low
Input Leakage Current
V
IH
V
IL
V
INPUT
= 0 to V
DD
±0.4
V
DD
- 0.5
0.5
±10
V
V
µA
50
±5
f
CLK
f
OSC
EXTCLK = GND, C
OSC
= 1000pF
EXTCLK = GND, C
OSC
= 100pF
V
DD
- 0.5
0.5
95
4
135
1.35
175
MHz
kHz
MHz
V
V
%
SHDN
= GND, V
COM
= 0 to V
DD
R
COM
Up to 5th harmonic of f
CLK
Mode 1, R1= R2 = R3 = 10kΩ,
LP output, Q = 1
0.2
±0.1
V
DD
/2
- 0.1
V
DD
/2
- 0.1
60
f
O
f
CLK
/f
O
Mode 1
Mode 1, R1 = R3 = 50kΩ , R2 = 10kΩ,
Q = 5, deviation from 100:1
Mode 1, R1 = R3 = 50kΩ, R2 = 10kΩ,
Q=5
0.001 to
40
±0.2
±0.2
±1
±5
±0.1
±3
±4
±4
-60
V
DD
/2
V
DD
/2
80
200
60
V
DD
- 0.2
±10
V
DD
/2
+ 0.1
V
V
DD
/2
+ 0.1
120
kΩ
µV
RMS
µV
RMS
V
µA
±0.5
±12.5
±15
±25
dB
mV
±0.7
±2
kHz
%
%
ppm/°C
ppm/°C
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
Dual Universal Switched-Capacitor Filters
MAX7490/MAX7491
ELECTRICAL CHARACTERISTICS—MAX7491 (continued)
(V
DD
= EXTCLK = +3V, f
CLK
= 625kHz, T
A
= T
MIN
to T
MAX
, 10kΩ || 50pF load to V
DD
/2 at LP_, BP_, and N_/HP_,
SHDN
= V
DD
, 0.1µF
from COM to GND, 50% duty-cycle clock input, COM = V
DD
/2. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
POWER REQUIREMENTS
Supply Voltage
Power-Supply Current
Shutdown Current
Output Short-Circuit Current
DC Open-Loop Gain
Gain Bandwidth Product
Slew Rate
GBW
SR
R
L
≥
10kΩ, C
L
≤
50pF
R
L
≥
10kΩ, C
L
≤
50pF
R
L
≥
10kΩ, C
L
≤
50pF
V
DD
I
DD
I
SHDN
No load, mode 1, R1 = R3 = 50kΩ,
R2 = 10kΩ, Q = 5
SHDN
= GND
±11
130
7
6
2.7
3.5
3.6
4.0
1
V
mA
µA
mA
dB
MHz
V/µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INTERNAL OP AMPS CHARACTERISTICS
Note 1:
Resistive loading of the N_/HP_, LP_, BP_ outputs includes the resistors used for the filter implementation.
Note 2:
Crosstalk between internal filter sections is measured by applying a 1V
RMS
10kHz signal to one bandpass filter section input
and grounding the input of the other bandpass filter section. The crosstalk is the ratio between the output of the grounded
filter section and the 1V
RMS
input signal of the other section.
Note 3:
Bandwidth of noise measurement is 80kHz.
Note 4:
f
OSC
(kHz) = 135 x 10
3
/ C
OSC
(C
OSC
in pF)
Typical Operating Characteristics
(V
DD
= +5V for MAX7490, V
DD
= +3V for MAX7491, f
CLK
= 625kHz,
SHDN
= EXTCLK = V
DD
, COM = V
DD
/2, Mode 1, R3 = R1 = 50kΩ,
R2 = 10kΩ, Q = 5, T
A
= +25°C, unless otherwise noted.)
2ND-ORDER BANDPASS FILTER
FREQUENCY RESPONSE
MAX7490-01
2ND-ORDER BANDPASS FILTER
PHASE RESPONSE
MAX7490-02
f
CLK
/f
O
DEVIATION vs. f
CLK
-0.1
f
CLK
/f
O
DEVIATION (%)
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
V
DD
= 5V
V
DD
= 3V
MAX7490-03
10
0
-10
-20
-30
-40
-50
-60
1
10
FREQUENCY (kHz)
300
250
200
PHASE (%)
150
100
50
0
V
DD
= +5V
f
CLK
= 625kHz
Q=5
1
10
FREQUENCY (kHz)
0
GAIN (dB)
100
100
100
1000
f
CLK
(kHz)
10,000
_______________________________________________________________________________________
5
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